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Show Area Forecast Discussion - Charleston, SC (Charleston, SC Area) Selection: |
| #515441 (Received by flhurricane at: 9:44 PM 01.Jun.2012) AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 937 PM EDT FRI JUN 1 2012 .SYNOPSIS... A COLD FRONT WILL CROSS THE REGION TONIGHT...AND DRY HIGH PRESSURE WILL PREVAIL INTO SUNDAY. ANOTHER COLD FRONT WILL GRADUALLY ADVANCE INTO THE SOUTHEAST THROUGH THE FIRST HALF OF NEXT WEEK...AND HIGH PRESSURE COULD BUILD INTO THE REGION AGAIN AROUND MIDWEEK. && .NEAR TERM /THROUGH SATURDAY/... CONVECTION ASSOCIATED WITH A PRE-FRONTAL TROUGH CONTINUES TO DISSIPATE ALONG MUCH OF THE COAST...BUT COULD LINGER A BIT LONGER IN THE EVENING ACROSS NORTH COASTAL GEORGIA. THERE IS ANOTHER LINE OF CONVECTION UPSTREAM ALONG THE ACTUAL COLD FRONT...BUT IT SHOULD GRADUALLY WEAKEN WITH THE LOSS OF DIURNAL HEATING AND AS IT APPROACHES...WITH THE BULK OF IT PASSING TO THE NORTH. WILL MAINTAIN A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS INTO THE EARLY OVERNIGHT HOURS BEHIND THE PRE-FRONTAL TROUGH UNTIL THE MAIN FRONT CLEARS THE COAST. THE THREAT FOR SEVERE THUNDERSTORMS HAS GREATLY DIMINISHED AND ALL WATCHES HAVE BEEN DISCONTINUED. LOWS AWAY FROM THE IMMEDIATE COAST ARE FORECAST TO REACH THE MID TO UPPER 60S...WITH SOME LOWER 60S POSSIBLE WELL INLAND. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... SATURDAY...A SOMEWHAT REFRESHING AIR MASS WILL FOLLOW IN WAKE OF THE COLD FRONT THAT MOVES AWAY FROM THE AREA OVER THE ATLANTIC IN THE MORNING. A BROAD TROUGH UPSTAIRS WILL COVER THE EASTERN THIRD OF THE NATION...WHILE WEAK SURFACE HIGH PRESSURE BUILDS IN FROM THE NORTHERN GULF COAST REGION. ALTHOUGH 850 MB TEMPS WILL DROP TO AROUND 11-12C...THIS WILL BE OFFSET BY PLENTIFUL SUNSHINE AND A DOWNSLOPE FLOW TO PRODUCE MAX TEMPS IN THE MID AND UPPER 80S. WHEN COMBINED WITH DEW POINTS IN THE AFTERNOON DOWN INTO THE LOWER AND MIDDLE 50S...RH LEVELS WILL BE DOWN IN THE 30-40 PERCENT RANGE...RATHER LOW FOR EARLY JUNE. SATURDAY NIGHT...THE SET UP LOOKS GOOD FOR DECENT RADIATIONAL COOLING...WITH MAINLY CLEAR SKIES AND A LIGHT WIND REGIME AS HIGH PRESSURE CONTINUES TO MOVE IN FROM THE WEST. THIS WILL ALLOW FOR TEMPS TO FALL TO THE UPPER 50S FAR INLAND TO THE LOWER AND MIDDLE 60S MOST ELSEWHERE. THESE VALUES ARE ABOUT 5-8 DEGREES BELOW SEASONAL NORMS. SUNDAY THROUGH SUNDAY NIGHT...THE TROUGH IN THE EAST WILL SHIFT INTO THE ATLANTIC BY LATE SUNDAY AND HEIGHTS SLOWLY BEGIN TO BUILD IN RESPONSE. THE SURFACE HIGH OVER THE SE PART OF THE COUNTRY WILL SPLIT IN TWO...WITH ONE PORTION SHIFTING SOUTH INTO THE GULF AND ACROSS FLORIDA...WITH THE SECOND AND WEAKER PORTION FOUND NEAR THE SOUTHERN APPALACHIANS. IN BETWEEN A WEAK COLD FRONT WILL TRY AND SNEAK IN FROM THE NW BY LATE SUNDAY AND SUNDAY NIGHT. THE LACK OF MOISTURE...LITTLE FORCING IN THE LOW LEVELS AND NO SUPPORT ALOFT SUGGESTS THAT WE/LL BE HARD PRESSED TO RECEIVED ANY PRECIP. WE/LL MAINTAIN POPS UNDER 15 PERCENT...ALTHOUGH WE CANNOT ENTIRELY RULE OUT A FEW SHOWERS FOR SUNDAY NIGHT AS WEAK ISENTROPIC LIFT BEGINS TO DEVELOP ON THE 295/300K SURFACES. WESTERLY FLOW AND COMPRESSIONAL HEATING IN ADVANCE OF THE COLD FRONT SUNDAY...ALONG WITH 850 MB TEMPS THAT CLIMB TO 14-15C...WILL SUPPORT MAX TEMPS IN THE UPPER 80S AND LOWER 90S AWAY FROM THE COAST. WARM ADVECTION SUNDAY NIGHT AND AN INCREASE IN CLOUD COVER WILL LIMIT TEMPS TO NO LOWER THAN THE MID AND UPPER 60S MOST LOCALES SUNDAY NIGHT. MONDAY...THE FORECAST AREA WILL LIE WITHIN A NW FLOW ALOFT BETWEEN THE TROUGH IN THE ATLANTIC...AND A RIDGE BUILDING OVER THE ROCKIES. FURTHER WEST IN ANOTHER TROUGH IN THE PACIFIC...WITH A RESULTING OMEGA BLOCKING PATTERN TO TAKE SHAPE. MEANWHILE...THE COLD FRONT WILL BECOME LESS DEFINED BUT DOES APPEAR TO STALL OUT OVER OR NEAR THE FORECAST AREA. THERE IS STILL THE LACK OF SUPPORT IN THE MID AND UPPER LEVELS...BUT LOW LEVEL CONVERGENCE AND AN INCREASE IN MOISTURE SUPPORTS AT LEAST SMALL POPS ACROSS THE ENTIRE FORECAST AREA. 850 MB TEMPS RISE ANOTHER DEGREE OR TWO...AND WITH A CONTINUED DEEP OFFSHORE FLOW IT/LL BE ANOTHER HOT DAY WITH HIGHS 88-94 AWAY FROM THE SHORELINE. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... A REINFORCING COLD FRONT LOOKS TO PUSH THROUGH MONDAY NIGHT AS LOW PRESSURE MOVES OFF THE SOUTHERN NEW ENGLAND COAST. ONCE AGAIN THE FRONT WILL STALL OUT OVER OR JUST SOUTH OF THE AREA TUESDAY THROUGH MID WEEK BEFORE LIFTING BACK NORTH LATE IN THE WEEK. RAIN CHANCES LOOK TO BE MAINLY DIURNALLY-DRIVEN WITH THE BEST CHANCES OVERALL COMING THURSDAY INTO FRIDAY AS DEEPER MOISTURE MOVES BACK INTO THE AREA. TEMPERATURES WILL BE LARGELY DEPENDENT UPON THE POSITION OF THE FRONT AND RAIN COVERAGE BUT KEPT THEM AT OR ABOVE NORMAL THROUGH TUESDAY BEFORE DROPPING BELOW NORMAL WEDNESDAY. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... SHOWERS AND A FEW THUNDERSTORMS COULD IMPACT THE TERMINALS INTO THE EARLY OVERNIGHT HOURS AHEAD OF A COLD FRONT APPROACHING FROM THE WEST. THE COLD FRONT SHOULD MOVE THROUGH THE TERMINALS PRIOR TO DAYBREAK...WITH WINDS SHIFTING WEST-NORTHWEST IN ITS WAKE. ALTHOUGH ADDITIONAL SHOWERS/THUNDERSTORMS ARE CERTAINLY POSSIBLE...COVERAGE AND TIMING UNCERTAINTY HAS PREVENTED ANY MENTION IN THE FORECAST AT THIS TIME. OTHERWISE...VFR CONDITIONS WILL PREVAIL THROUGH 00Z SUNDAY. EXTENDED AVIATION OUTLOOK...VFR THROUGH THE WEEKEND WITH INCREASING CHANCES OF SUB-VFR CONDITIONS EARLY NEXT WEEK AS A BACKDOOR COLD FRONT MOVES INTO THE AREA AND STALLS OVER/SOUTH OF THE AREA THROUGH MID WEEK. && .MARINE... SOUTH-SOUTHWEST WINDS WILL PREVAIL INTO THE OVERNIGHT HOURS AHEAD OF AN APPROACHING COLD FRONT FROM THE WEST. THE FRONT SHOULD MOVE OFFSHORE PRIOR TO DAYBREAK WITH WINDS SHIFTING WESTERLY IN ITS WAKE. WIND SPEEDS WILL REMAIN UPWARDS OF AROUND 15 KT AHEAD OF THE FRONT...AND ONLY DIMINISH SLIGHTLY BY LATE TONIGHT ONCE IT PASSES THROUGH. SEAS WILL REMAIN IN THE 2-4 FT RANGE. ALL SMALL CRAFT ADVISORIES HAVE BEEN DISCONTINUED. SATURDAY AND SATURDAY NIGHT...AN OFFSHORE FLOW WILL PREVAIL IN WAKE OF THE COLD FRONT...AS WEAK HIGH PRESSURE BUILDS FROM THE WEST. THE END RESULT WILL BE FOR DECENT BOATING CONDITIONS FOR THE START OF THE WEEKEND. SUNDAY AND SUNDAY NIGHT...THE PRESSURE GRADIENT WILL BEGIN TO TIGHTEN BETWEEN HIGH PRESSURE TO THE SOUTH AND A COLD FRONT THAT BEGINS TO APPROACH FROM THE NW SUNDAY NIGHT. THAT ALONG WITH SOME ENHANCEMENT DUE TO THE AFTERNOON/EVENING SEA BREEZE AND A LOW LEVEL NOCTURNAL JET WILL GENERATE SLIGHTLY HIGHER WIND AND SEA CONDITIONS. HOWEVER...SMALL CRAFT ADVISORIES DO NOT LOOK TO BE A REQUIREMENT. MONDAY...THE COLD FRONT WILL STALL OVER OR NEAR THE COASTAL WATERS...AND IT/S EXACT PLACEMENT AND ORIENTATION WILL DETERMINE WHAT EXACTLY HAPPENS IN REGARDS TO WINDS AND THE RESULTING SEAS. LATEST INDICATIONS ARE HOWEVER THAT AN OFFSHORE FLOW WILL PREVAIL...AND CONDITIONS WILL REMAIN BELOW ANY SMALL CRAFT ADVISORY CRITERIA. TUESDAY THROUGH WEDNESDAY...A LOW CONFIDENCE FORECAST WITH TOO MUCH UNCERTAINTY AS TO WHETHER OR NOT THE STATIONARY FRONT LINGERS OVER OR NEAR THE WATERS...OR DOES IT TRANSITION OVER INTO A WARM FRONT AND LIFT NORTH. EITHER WAY...SUB-SCA CONDITIONS APPEAR LIKELY. && .TIDES/COASTAL FLOODING... THE UPCOMING FULL MOON AND LUNAR PERIGEE WILL CREATE PERIGEAN SPRING TIDES...WHICH COULD BE HIGH ENOUGH TO PRODUCE MINOR COASTAL FLOODING DURING THE HIGH TIDE EACH EVENING INTO AT LEAST EARLY NEXT WEEK. GUIDANCE SHOWS THAT THE EVENING HIGH TIDE WILL APPROACH SHALLOW COASTAL FLOODING CRITERIA IN THE CHARLESTON HARBOR...BUT IS EXPECTED TO REMAIN JUST BELOW. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...NONE. && $$ |
| #515427 (Received by flhurricane at: 8:26 PM 01.Jun.2012) AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 820 PM EDT FRI JUN 1 2012 .SYNOPSIS... A COLD FRONT WILL CROSS THE REGION TONIGHT...AND DRY HIGH PRESSURE WILL PREVAIL INTO SUNDAY. ANOTHER COLD FRONT WILL GRADUALLY ADVANCE INTO THE SOUTHEAST THROUGH THE FIRST HALF OF NEXT WEEK...AND HIGH PRESSURE COULD BUILD INTO THE REGION AGAIN AROUND MIDWEEK. && .NEAR TERM /THROUGH SATURDAY/... CONVECTION ASSOCIATED WITH A PRE-FRONTAL TROUGH CONTINUES TO SHIFT TOWARD THE COAST AND SHOULD PUSH OFFSHORE DURING THE MID-EVENING HOURS. THE SEVERE WEATHER THREAT HAS DIMINISHED SIGNIFICANTLY...AND THE SEVERE THUNDERSTORM WATCH FOR PARTS OF EASTERN SOUTH CAROLINA WILL LIKELY BE CANCELLED ONCE THE CONVECTION MOVES OFFSHORE. THERE IS ANOTHER LINE OF CONVECTION DEVELOPING UPSTREAM ALONG THE ACTUAL COLD FRONT...BUT IT SHOULD GRADUALLY WEAKEN WITH THE LOSS OF DIURNAL HEATING AS IT APPROACHES FROM THE WEST. WILL MAINTAIN A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS INTO THE EARLY OVERNIGHT HOURS BEHIND THE PRE-FRONTAL TROUGH UNTIL THE MAIN FRONT CLEARS THE COAST. LOWS MAY DIP INTO THE LOW 60S FAR INLAND...WITH LOW 70S STILL RIGHT ALONG THE COAST. && .SHORT TERM /SATURDAY NIGHT/... SATURDAY...A SOMEWHAT REFRESHING AIR MASS WILL FOLLOW IN WAKE OF THE COLD FRONT THAT MOVES AWAY FROM THE AREA OVER THE ATLANTIC IN THE MORNING. A BROAD TROUGH UPSTAIRS WILL COVER THE EASTERN THIRD OF THE NATION...WHILE WEAK SURFACE HIGH PRESSURE BUILDS IN FROM THE NORTHERN GULF COAST REGION. ALTHOUGH 850 MB TEMPS WILL DROP TO AROUND 11-12C...THIS WILL BE OFFSET BY PLENTIFUL SUNSHINE AND A DOWNSLOPE FLOW TO PRODUCE MAX TEMPS IN THE MID AND UPPER 80S. WHEN COMBINED WITH DEW POINTS IN THE AFTERNOON DOWN INTO THE LOWER AND MIDDLE 50S...RH LEVELS WILL BE DOWN IN THE 30-40 PERCENT RANGE...RATHER LOW FOR EARLY JUNE. SATURDAY NIGHT...THE SET UP LOOKS GOOD FOR DECENT RADIATIONAL COOLING...WITH MAINLY CLEAR SKIES AND A LIGHT WIND REGIME AS HIGH PRESSURE CONTINUES TO MOVE IN FROM THE WEST. THIS WILL ALLOW FOR TEMPS TO FALL TO THE UPPER 50S FAR INLAND TO THE LOWER AND MIDDLE 60S MOST ELSEWHERE. THESE VALUES ARE ABOUT 5-8 DEGREES BELOW SEASONAL NORMS. SUNDAY THROUGH SUNDAY NIGHT...THE TROUGH IN THE EAST WILL SHIFT INTO THE ATLANTIC BY LATE SUNDAY AND HEIGHTS SLOWLY BEGIN TO BUILD IN RESPONSE. THE SURFACE HIGH OVER THE SE PART OF THE COUNTRY WILL SPLIT IN TWO...WITH ONE PORTION SHIFTING SOUTH INTO THE GULF AND ACROSS FLORIDA...WITH THE SECOND AND WEAKER PORTION FOUND NEAR THE SOUTHERN APPALACHIANS. IN BETWEEN A WEAK COLD FRONT WILL TRY AND SNEAK IN FROM THE NW BY LATE SUNDAY AND SUNDAY NIGHT. THE LACK OF MOISTURE...LITTLE FORCING IN THE LOW LEVELS AND NO SUPPORT ALOFT SUGGESTS THAT WE/LL BE HARD PRESSED TO RECEIVED ANY PRECIP. WE/LL MAINTAIN POPS UNDER 15 PERCENT...ALTHOUGH WE CANNOT ENTIRELY RULE OUT A FEW SHOWERS FOR SUNDAY NIGHT AS WEAK ISENTROPIC LIFT BEGINS TO DEVELOP ON THE 295/300K SURFACES. WESTERLY FLOW AND COMPRESSIONAL HEATING IN ADVANCE OF THE COLD FRONT SUNDAY...ALONG WITH 850 MB TEMPS THAT CLIMB TO 14-15C...WILL SUPPORT MAX TEMPS IN THE UPPER 80S AND LOWER 90S AWAY FROM THE COAST. WARM ADVECTION SUNDAY NIGHT AND AN INCREASE IN CLOUD COVER WILL LIMIT TEMPS TO NO LOWER THAN THE MID AND UPPER 60S MOST LOCALES SUNDAY NIGHT. MONDAY...THE FORECAST AREA WILL LIE WITHIN A NW FLOW ALOFT BETWEEN THE TROUGH IN THE ATLANTIC...AND A RIDGE BUILDING OVER THE ROCKIES. FURTHER WEST IN ANOTHER TROUGH IN THE PACIFIC...WITH A RESULTING OMEGA BLOCKING PATTERN TO TAKE SHAPE. MEANWHILE...THE COLD FRONT WILL BECOME LESS DEFINED BUT DOES APPEAR TO STALL OUT OVER OR NEAR THE FORECAST AREA. THERE IS STILL THE LACK OF SUPPORT IN THE MID AND UPPER LEVELS...BUT LOW LEVEL CONVERGENCE AND AN INCREASE IN MOISTURE SUPPORTS AT LEAST SMALL POPS ACROSS THE ENTIRE FORECAST AREA. 850 MB TEMPS RISE ANOTHER DEGREE OR TWO...AND WITH A CONTINUED DEEP OFFSHORE FLOW IT/LL BE ANOTHER HOT DAY WITH HIGHS 88-94 AWAY FROM THE SHORELINE. && .LONG TERM /SUNDAY THROUGH FRIDAY/... A REINFORCING COLD FRONT LOOKS TO PUSH THROUGH MONDAY NIGHT AS LOW PRESSURE MOVES OFF THE SOUTHERN NEW ENGLAND COAST. ONCE AGAIN THE FRONT WILL STALL OUT OVER OR JUST SOUTH OF THE AREA TUESDAY THROUGH MID WEEK BEFORE LIFTING BACK NORTH LATE IN THE WEEK. RAIN CHANCES LOOK TO BE MAINLY DIURNALLY-DRIVEN WITH THE BEST CHANCES OVERALL COMING THURSDAY INTO FRIDAY AS DEEPER MOISTURE MOVES BACK INTO THE AREA. TEMPERATURES WILL BE LARGELY DEPENDENT UPON THE POSITION OF THE FRONT AND RAIN COVERAGE BUT KEPT THEM AT OR ABOVE NORMAL THROUGH TUESDAY BEFORE DROPPING BELOW NORMAL WEDNESDAY. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... SHOWERS AND A FEW THUNDERSTORMS COULD IMPACT THE TERMINALS THIS EVENING AHEAD OF A COLD FRONT APPROACHING FROM THE WEST. THE COLD FRONT SHOULD MOVE THROUGH THE TERMINALS PRIOR TO DAYBREAK...WITH WINDS SHIFTING WEST-NORTHWEST IN ITS WAKE. ALTHOUGH ADDITIONAL SHOWERS/THUNDERSTORMS ARE CERTAINLY POSSIBLE...COVERAGE AND TIMING UNCERTAINTY HAS PREVENTED ANY MENTION IN THE FORECAST OUTSIDE OF ANY ONGOING THUNDERSTORM/VICINITY THUNDERSTORMS. VFR CONDITIONS WILL PREVAIL OUTSIDE OF ANY CONVECTION THROUGH 00Z SUNDAY. EXTENDED AVIATION OUTLOOK...VFR THROUGH THE WEEKEND WITH INCREASING CHANCES OF SUB-VFR CONDITIONS EARLY NEXT WEEK AS A BACKDOOR COLD FRONT MOVES INTO THE AREA AND STALLS OVER/SOUTH OF THE AREA THROUGH MID WEEK. && .MARINE... SOUTH-SOUTHWEST WINDS WILL PREVAIL INTO THE OVERNIGHT HOURS AHEAD OF AN APPROACHING COLD FRONT FROM THE WEST. THE FRONT SHOULD MOVE OFFSHORE PRIOR TO DAYBREAK WITH WINDS SHIFTING WESTERLY IN ITS WAKE. WIND SPEEDS WILL REMAIN UPWARDS OF 15 TO PERHAPS 20 KT AHEAD OF THE FRONT...AND ONLY DIMINISH SLIGHTLY BY LATE TONIGHT ONCE IT PASSES THROUGH. SEAS WILL REMAIN IN THE 2-4 FT RANGE. ALL SMALL CRAFT ADVISORIES HAVE BEEN DISCONTINUED. SATURDAY AND SATURDAY NIGHT...AN OFFSHORE FLOW WILL PREVAIL IN WAKE OF THE COLD FRONT...AS WEAK HIGH PRESSURE BUILDS FROM THE WEST. THE END RESULT WILL BE FOR DECENT BOATING CONDITIONS FOR THE START OF THE WEEKEND. SUNDAY AND SUNDAY NIGHT...THE PRESSURE GRADIENT WILL BEGIN TO TIGHTEN BETWEEN HIGH PRESSURE TO THE SOUTH AND A COLD FRONT THAT BEGINS TO APPROACH FROM THE NW SUNDAY NIGHT. THAT ALONG WITH SOME ENHANCEMENT DUE TO THE AFTERNOON/EVENING SEA BREEZE AND A LOW LEVEL NOCTURNAL JET WILL GENERATE SLIGHTLY HIGHER WIND AND SEA CONDITIONS. HOWEVER...SMALL CRAFT ADVISORIES DO NOT LOOK TO BE A REQUIREMENT. MONDAY...THE COLD FRONT WILL STALL OVER OR NEAR THE COASTAL WATERS...AND IT/S EXACT PLACEMENT AND ORIENTATION WILL DETERMINE WHAT EXACTLY HAPPENS IN REGARDS TO WINDS AND THE RESULTING SEAS. LATEST INDICATIONS ARE HOWEVER THAT AN OFFSHORE FLOW WILL PREVAIL...AND CONDITIONS WILL REMAIN BELOW ANY SMALL CRAFT ADVISORY CRITERIA. TUESDAY THROUGH WEDNESDAY...A LOW CONFIDENCE FORECAST WITH TOO MUCH UNCERTAINTY AS TO WHETHER OR NOT THE STATIONARY FRONT LINGERS OVER OR NEAR THE WATERS...OR DOES IT TRANSITION OVER INTO A WARM FRONT AND LIFT NORTH. EITHER WAY...SUB-SCA CONDITIONS APPEAR LIKELY. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...NONE. && $$ |
| #515303 (Received by flhurricane at: 4:11 PM 01.Jun.2012) AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 404 PM EDT FRI JUN 1 2012 .SYNOPSIS... A COLD FRONT WILL CROSS THE REGION TONIGHT...AND DRY HIGH PRESSURE WILL PREVAIL INTO SUNDAY. ANOTHER COLD FRONT WILL GRADUALLY ADVANCE INTO THE SOUTHEAST THROUGH THE FIRST HALF OF NEXT WEEK...AND HIGH PRESSURE COULD BUILD INTO THE REGION AGAIN AROUND MIDWEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THIS AFTERNOON...CONVECTION OUT AHEAD OF THE APPROACHING COLD FRONT CONTINUES TO FIRE ACROSS PORTIONS OF SE GA...MOVING INTO SOUTHERN SC. SO FAR THE CONVECTION HAS STRUGGLED TO DEVELOP INTO A COHESIVE LINE AND HAS INSTEAD BEEN SOMEWHAT DISORGANIZED SINGLE AND MULTI-CELL STORMS. THE GREATEST THREAT FOR SEVERE STORMS CONTINUES TO BE WITHIN WATCH 334...BUT AN ISOLATED STRONG TO SEVERE STORM WILL BE POSSIBLE IN THE PERIPHERY OF THE ACTUAL WATCH. BASED ON THE STORMS THAT HAVE DEVELOPED SO FAR AND STORM REPORTS FROM ACROSS THE REGION...THE BIGGEST THREAT WILL BE DAMAGING WIND GUSTS. LARGE HAIL IS ALSO POSSIBLE BUT NOT AS LIKELY. TONIGHT...THE ACTUAL COLD FRONT IS PROGGED TO MOVE ACROSS THE FORECAST AREA IN THE 06-12Z SATURDAY TIME FRAME. ANY RESIDUAL CONVECTION AND LINGERING OUTFLOW BOUNDARIES WILL DRIVE POPS INTO THE EARLY PART OF TONIGHT...BUT WITH THE LOSS OF DIURNAL HEATING COVERAGE IS EXPECTED TO BE ON A DECREASING TREND. I HAVE FAVORED AREAS FURTHER TO THE EAST WITH A SHORT TIME OF LIKELY AND THEN DECREASING TO CHANCE THROUGH AROUND MIDNIGHT. WINDS WILL GRADUALLY SHIFT TO W AND THEN NW BEHIND THE FRONT. LOWS MAY DIP INTO THE LOW 60S FAR INLAND...WITH LOW 70S STILL RIGHT ALONG THE COAST. LAKE WINDS...WIND GUSTS SO FAR TODAY HAVE MAXED OUT IN THE 15-20 MPH RANGE OVER THE LAKE...WITH ONLY MARGINALLY HIGHER GUSTS ALONG THE LAKE SHORE. THEREFORE THE LAKE WIND ADVISORY HAS BEEN CANCELED. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... SATURDAY...A SOMEWHAT REFRESHING AIR MASS WILL FOLLOW IN WAKE OF THE COLD FRONT THAT MOVES AWAY FROM THE AREA OVER THE ATLANTIC IN THE MORNING. A BROAD TROUGH UPSTAIRS WILL COVER THE EASTERN THIRD OF THE NATION...WHILE WEAK SURFACE HIGH PRESSURE BUILDS IN FROM THE NORTHERN GULF COAST REGION. ALTHOUGH 850 MB TEMPS WILL DROP TO AROUND 11-12C...THIS WILL BE OFFSET BY PLENTIFUL SUNSHINE AND A DOWNSLOPE FLOW TO PRODUCE MAX TEMPS IN THE MID AND UPPER 80S. WHEN COMBINED WITH DEW POINTS IN THE AFTERNOON DOWN INTO THE LOWER AND MIDDLE 50S...RH LEVELS WILL BE DOWN IN THE 30-40 PERCENT RANGE...RATHER LOW FOR EARLY JUNE. SATURDAY NIGHT...THE SET UP LOOKS GOOD FOR DECENT RADIATIONAL COOLING...WITH MAINLY CLEAR SKIES AND A LIGHT WIND REGIME AS HIGH PRESSURE CONTINUES TO MOVE IN FROM THE WEST. THIS WILL ALLOW FOR TEMPS TO FALL TO THE UPPER 50S FAR INLAND TO THE LOWER AND MIDDLE 60S MOST ELSEWHERE. THESE VALUES ARE ABOUT 5-8 DEGREES BELOW SEASONAL NORMS. SUNDAY THROUGH SUNDAY NIGHT...THE TROUGH IN THE EAST WILL SHIFT INTO THE ATLANTIC BY LATE SUNDAY AND HEIGHTS SLOWLY BEGIN TO BUILD IN RESPONSE. THE SURFACE HIGH OVER THE SE PART OF THE COUNTRY WILL SPLIT IN TWO...WITH ONE PORTION SHIFTING SOUTH INTO THE GULF AND ACROSS FLORIDA...WITH THE SECOND AND WEAKER PORTION FOUND NEAR THE SOUTHERN APPALACHIANS. IN BETWEEN A WEAK COLD FRONT WILL TRY AND SNEAK IN FROM THE NW BY LATE SUNDAY AND SUNDAY NIGHT. THE LACK OF MOISTURE...LITTLE FORCING IN THE LOW LEVELS AND NO SUPPORT ALOFT SUGGESTS THAT WE/LL BE HARD PRESSED TO RECEIVED ANY PRECIP. WE/LL MAINTAIN POPS UNDER 15 PERCENT...ALTHOUGH WE CANNOT ENTIRELY RULE OUT A FEW SHOWERS FOR SUNDAY NIGHT AS WEAK ISENTROPIC LIFT BEGINS TO DEVELOP ON THE 295/300K SURFACES. WESTERLY FLOW AND COMPRESSIONAL HEATING IN ADVANCE OF THE COLD FRONT SUNDAY...ALONG WITH 850 MB TEMPS THAT CLIMB TO 14-15C...WILL SUPPORT MAX TEMPS IN THE UPPER 80S AND LOWER 90S AWAY FROM THE COAST. WARM ADVECTION SUNDAY NIGHT AND AN INCREASE IN CLOUD COVER WILL LIMIT TEMPS TO NO LOWER THAN THE MID AND UPPER 60S MOST LOCALES SUNDAY NIGHT. MONDAY...THE FORECAST AREA WILL LIE WITHIN A NW FLOW ALOFT BETWEEN THE TROUGH IN THE ATLANTIC...AND A RIDGE BUILDING OVER THE ROCKIES. FURTHER WEST IN ANOTHER TROUGH IN THE PACIFIC...WITH A RESULTING OMEGA BLOCKING PATTERN TO TAKE SHAPE. MEANWHILE...THE COLD FRONT WILL BECOME LESS DEFINED BUT DOES APPEAR TO STALL OUT OVER OR NEAR THE FORECAST AREA. THERE IS STILL THE LACK OF SUPPORT IN THE MID AND UPPER LEVELS...BUT LOW LEVEL CONVERGENCE AND AN INCREASE IN MOISTURE SUPPORTS AT LEAST SMALL POPS ACROSS THE ENTIRE FORECAST AREA. 850 MB TEMPS RISE ANOTHER DEGREE OR TWO...AND WITH A CONTINUED DEEP OFFSHORE FLOW IT/LL BE ANOTHER HOT DAY WITH HIGHS 88-94 AWAY FROM THE SHORELINE. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... A REINFORCING COLD FRONT LOOKS TO PUSH THROUGH MONDAY NIGHT AS LOW PRESSURE MOVES OFF THE SOUTHERN NEW ENGLAND COAST. ONCE AGAIN THE FRONT WILL STALL OUT OVER OR JUST SOUTH OF THE AREA TUESDAY THROUGH MID WEEK BEFORE LIFTING BACK NORTH LATE IN THE WEEK. RAIN CHANCES LOOK TO BE MAINLY DIURNALLY-DRIVEN WITH THE BEST CHANCES OVERALL COMING THURSDAY INTO FRIDAY AS DEEPER MOISTURE MOVES BACK INTO THE AREA. TEMPERATURES WILL BE LARGELY DEPENDENT UPON THE POSITION OF THE FRONT AND RAIN COVERAGE BUT KEPT THEM AT OR ABOVE NORMAL THROUGH TUESDAY BEFORE DROPPING BELOW NORMAL WEDNESDAY. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... THE PRIMARY CONCERN OVER THE NEXT 6-12 HOURS IS THE POTENTIAL FOR THUNDERSTORMS AT KCHS AND KSAV. HAVE GONE WITH PREVAILING VCTS TO BEGIN WITH...THEN A TEMPO FOR THUNDER INTO THE EVENING HOURS. GUSTY WINDS INTO THE 20-25 KT RANGE WILL BE POSSIBLE OUTSIDE OF THUNDERSTORMS...WITH STRONGER GUSTS POSSIBLE IF DIRECTLY AFFECTED BY STORMS. OVERALL THUNDERSTORM COVERAGE WILL BEGIN TO DIMINISH IN THE EVENING WITH VARIOUS MODELS HAVING THINGS DRY BY AROUND 00Z. OVERNIGHT THERE ARE NO REAL CONCERNS...WINDS WILL TURN MORE WEST AND THEN NORTHWEST AS THE ACTUAL COLD FRONT GET INTO THE REGION JUST BEFORE SUNRISE. EXTENDED AVIATION OUTLOOK...VFR THROUGH THE WEEKEND WITH INCREASING CHANCES OF SUB-VFR CONDITIONS EARLY NEXT WEEK AS A BACKDOOR COLD FRONT MOVES INTO THE AREA AND STALLS OVER/SOUTH OF THE AREA THROUGH MID WEEK. && .MARINE... HAVE OPTED TO DROP THE SCA/S FOR EVERYWHERE OUTSIDE OF THE CHARLESTON HARBOR. SO FAR WINDS HAVE MAXED OUT IN THE 15-20 KT RANGE WITH ONLY MARGINAL 25 KT GUSTS IN THE HARBOR. EVEN WITH THE ACTUAL PASSAGE OF THE COLD FRONT WINDS ARE EXPECTED TO REMAIN AT OR BELOW 20 KTS. WINDS WILL SHIFT TO SOUTHWESTERLY TO WESTERLY LATE TONIGHT. SEAS WILL REMAIN BELOW CRITERIA OVERNIGHT...BUT WILL BE ON THE INCREASE LATE. EXPECT GENERALLY 2-4 FT WITHIN 20 NM AND 3-5 FT BEYOND. SATURDAY AND SATURDAY NIGHT...AN OFFSHORE FLOW WILL PREVAIL IN WAKE OF THE COLD FRONT...AS WEAK HIGH PRESSURE BUILDS FROM THE WEST. THE END RESULT WILL BE FOR DECENT BOATING CONDITIONS FOR THE START OF THE WEEKEND. SUNDAY AND SUNDAY NIGHT...THE PRESSURE GRADIENT WILL BEGIN TO TIGHTEN BETWEEN HIGH PRESSURE TO THE SOUTH AND A COLD FRONT THAT BEGINS TO APPROACH FROM THE NW SUNDAY NIGHT. THAT ALONG WITH SOME ENHANCEMENT DUE TO THE AFTERNOON/EVENING SEA BREEZE AND A LOW LEVEL NOCTURNAL JET WILL GENERATE SLIGHTLY HIGHER WIND AND SEA CONDITIONS. HOWEVER...SMALL CRAFT ADVISORIES DO NOT LOOK TO BE A REQUIREMENT. MONDAY...THE COLD FRONT WILL STALL OVER OR NEAR THE COASTAL WATERS...AND IT/S EXACT PLACEMENT AND ORIENTATION WILL DETERMINE WHAT EXACTLY HAPPENS IN REGARDS TO WINDS AND THE RESULTING SEAS. LATEST INDICATIONS ARE HOWEVER THAT AN OFFSHORE FLOW WILL PREVAIL...AND CONDITIONS WILL REMAIN BELOW ANY SMALL CRAFT ADVISORY CRITERIA. TUESDAY THROUGH WEDNESDAY...A LOW CONFIDENCE FORECAST WITH TOO MUCH UNCERTAINTY AS TO WHETHER OR NOT THE STATIONARY FRONT LINGERS OVER OR NEAR THE WATERS...OR DOES IT TRANSITION OVER INTO A WARM FRONT AND LIFT NORTH. EITHER WAY...SUB-SCA CONDITIONS APPEAR LIKELY. && .TIDES/COASTAL FLOODING... THE UPCOMING FULL MOON AND LUNAR PERIGEE WILL CREATE PERIGEAN SPRING TIDES...WHICH COULD BE HIGH ENOUGH TO PRODUCE MINOR COASTAL FLOODING DURING THE HIGH TIDE EACH EVENING INTO AT LEAST EARLY NEXT WEEK. GUIDANCE SHOWS THAT THE EVENING HIGH TIDE WILL APPROACH SHALLOW COASTAL FLOODING CRITERIA IN THE CHARLESTON HARBOR...BUT IS EXPECTED TO REMAIN JUST BELOW. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR AMZ330. && $$ |
| #515252 (Received by flhurricane at: 2:41 PM 01.Jun.2012) AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 236 PM EDT FRI JUN 1 2012 .SYNOPSIS... A COLD FRONT WILL APPROACH THE AREA TODAY AND WILL MOVE THROUGH THE REGION TONIGHT. DRY HIGH PRESSURE WILL THEN PREVAIL THROUGH THE WEEKEND. ANOTHER COLD FRONT WILL GRADUALLY ADVANCE INTO THE SOUTHEAST THROUGH THE FIRST HALF OF NEXT WEEK...AND HIGH PRESSURE COULD BUILD INTO THE REGION AGAIN AROUND MIDWEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... EARLY THIS AFTERNOON...A QUICK UPDATE TO INCLUDE THE SEVERE THUNDERSTORM WATCH FOR COLLETON...DORCHESTER...BEKELEY AND CHARLESTON COUNTIES. A BROKEN LINE OF THUNDERSTORMS IS STARTING TO TAKE SHAPE JUST TO THE WEST OF THE AREA AND IS EXPECTED TO PUSH ACROSS THROUGH THE AFTERNOON. DAMAGING WIND GUSTS APPEAR TO BE THE PRIMARY THREAT WITH THE STRONGEST STORMS THAT DEVELOP...BUT LARGE HAIL IS ALSO STILL A POSSIBILITY. OVERALL THE CONVECTION BACK ACROSS MUCH OF NE GA IS WEAKER AND HAVING A HARD TIME DEVELOPING. STILL...ISOLATED STRONG TO SEVERE STORMS WILL BE POSSIBLE IN THIS AREA AS WELL. LAKE WINDS...THE POTENTIAL FOR WIND GUSTS TO 25 KNOTS IS SUFFICIENT TO JUSTIFY A LAKE WIND ADVISORY FROM NOON UNTIL 8 PM. THUNDERSTORMS COULD PRODUCE STRONG WINDS LATER THIS AFTERNOON FOLLOWED BY DIMINISHING WINDS PRIOR TO 8 PM. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... PRECIPITATION COULD COME TO AN ABRUPT END THIS EVENING...BUT LINGERING MOISTURE DEPICTED BY GUIDANCE JUSTIFIES POPS LINGERING BUT DIMINISHING AS THE NIGHT PROGRESSES. OVERNIGHT...THE COLD FRONT WILL PUSH OFFSHORE AND COOLER/DRYER AIR WILL SPREAD INTO THE REGION. THIS PERIOD TO BE DOMINATED BY A MEAN UPPER TROUGH OVER THE EAST COAST. AT THE SURFACE...COOLER/DRIER HIGH PRESSURE WILL BUILD IN FROM THE WEST SATURDAY BEHIND A DEPARTING COLD FRONT. A BACKDOOR COLD FRONT WILL APPROACH THE AREA SUNDAY NIGHT FROM THE NORTH...POSSIBLY PUSHING INTO THE AREA BY MONDAY BEFORE STALLING OUT. THINK RAIN CHANCES ARE TOO LOW TO MENTION SUNDAY NIGHT BUT AT LEAST ISOLATED SHOWERS/THUNDERSTORMS ARE EXPECTED MONDAY AS DEEPER MOISTURE MOVES INTO THE AREA. TEMPERATURES WILL MODERATE THROUGH THE PERIOD...LIKELY BECOMING ABOVE NORMAL MONDAY. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... A REINFORCING COLD FRONT LOOKS TO PUSH THROUGH MONDAY NIGHT AS LOW PRESSURE MOVES OFF THE SOUTHERN NEW ENGLAND COAST. ONCE AGAIN THE FRONT WILL STALL OUT OVER OR JUST SOUTH OF THE AREA TUESDAY THROUGH MID WEEK BEFORE LIFTING BACK NORTH LATE IN THE WEEK. RAIN CHANCES LOOK TO BE MAINLY DIURNALLY-DRIVEN WITH THE BEST CHANCES OVERALL COMING THURSDAY INTO FRIDAY AS DEEPER MOISTURE MOVES BACK INTO THE AREA. TEMPERATURES WILL BE LARGELY DEPENDENT UPON THE POSITION OF THE FRONT AND RAIN COVERAGE BUT KEPT THEM AT OR ABOVE NORMAL THROUGH TUESDAY BEFORE DROPPING BELOW NORMAL WEDNESDAY. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... THE PRIMARY CONCERN OVER THE NEXT 6-12 HOURS IS THE POTENTIAL FOR THUNDERSTORMS AT KCHS AND KSAV. HAVE GONE WITH PREVAILING VCTS TO BEGIN WITH...THEN A TEMPO FOR THUNDER INTO THE EVENING HOURS. GUSTY WINDS INTO THE 20-25 KT RANGE WILL BE POSSIBLE OUTSIDE OF THUNDERSTORMS...WITH STRONGER GUSTS POSSIBLE IF DIRECTLY AFFECTED BY STORMS. OVERALL THUNDERSTORM COVERAGE WILL BEGIN TO DIMINISH IN THE EVENING WITH VARIOUS MODELS HAVING THINGS DRY BY AROUND 00Z. OVERNIGHT THERE ARE NO REAL CONCERNS...WINDS WILL TURN MORE WEST AND THEN NORTHWEST AS THE ACTUAL COLD FRONT GET INTO THE REGION JUST BEFORE SUNRISE. EXTENDED AVIATION OUTLOOK...VFR THROUGH THE WEEKEND WITH INCREASING CHANCES OF SUB-VFR CONDITIONS EARLY NEXT WEEK AS A BACKDOOR COLD FRONT MOVES INTO THE AREA AND STALLS OVER/SOUTH OF THE AREA THROUGH MID WEEK. && .MARINE... TODAY AND TONIGHT...S/SW WINDS AHEAD OF AN APPROACHING COLD FRONT WILL INCREASE...AND THE POTENTIAL FOR WIND GUSTS TO AT LEAST 25 KNOTS JUSTIFIES THE ONGOING SMALL CRAFT ADVISORY FOR ALL MARINE ZONES INCLUDING CHARLESTON HARBOR. THE END TIME FOR SCA CONDITIONS WILL VARY FROM LATE EVENING ON THE HARBOR TO LATE TONIGHT ACROSS THE OUTER GA WATERS...AS WINDS WILL SHIFT TO THE WEST AND DIMINISH IN THE WAKE OF COLD FROPA TONIGHT. MARINERS SHOULD REMAIN ALERT FOR THE POSSIBILITY OF STRONG TO SEVERE T-STORMS IN ADVANCE OF THE COLD FRONT...ESPECIALLY LATE TODAY THROUGH THIS EVENING. SATURDAY AND SUNDAY...WEAK HIGH PRESSURE WILL BUILD FROM THE WEST BEHIND A DEPARTING COLD FRONT OFFSHORE. A LIGHT WIND REGIME WILL PREVAIL...WITH NO MORE THAN A WEAK SEA BREEZE CIRCULATION DEVELOPING EACH AFTERNOON. SUNDAY NIGHT THROUGH WEDNESDAY...A BACKDOOR COLD FRONT IS EXPECTED TO APPROACH THE WATERS FROM THE NORTH SUNDAY NIGHT BEFORE STALLING OUT OVER OR NEAR THE AREA THROUGH MID WEEK. GENERALLY LOW CONFIDENCE THIS PERIOD AS WINDS/SEAS WILL BE HIGHLY DEPENDENT ON THE POSITION OF THE FRONT. KEPT CONDITIONS BELOW ADVISORY LEVELS AT THIS TIME. && .TIDES/COASTAL FLOODING... THE UPCOMING FULL MOON AND LUNAR PERIGEE WILL CREATE PERIGEAN SPRING TIDES WHICH COULD BE HIGH ENOUGH TO PRODUCE MINOR COASTAL FLOODING EACH EVENING DURING THE HIGH TIDES INTO EARLY NEXT WEEK. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...LAKE WIND ADVISORY UNTIL 8 PM EDT THIS EVENING FOR SCZ045. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR AMZ350-352- 354. SMALL CRAFT ADVISORY UNTIL 5 AM EDT SATURDAY FOR AMZ374. SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR AMZ330. && $$ |
| #515219 (Received by flhurricane at: 11:41 AM 01.Jun.2012) AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 1100 AM EDT FRI JUN 1 2012 .SYNOPSIS... A COLD FRONT WILL APPROACH THE AREA TODAY AND WILL MOVE THROUGH THE REGION TONIGHT. DRY HIGH PRESSURE WILL THEN PREVAIL THROUGH THE WEEKEND. ANOTHER COLD FRONT WILL GRADUALLY ADVANCE INTO THE SOUTHEAST THROUGH THE FIRST HALF OF NEXT WEEK...AND HIGH PRESSURE COULD BUILD INTO THE REGION AGAIN AROUND MIDWEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... LATE THIS MORNING...THE FORECAST FOR TODAY REVOLVES AROUND THE COLD FRONT APPROACHING FROM THE WEST AND THE POTENTIAL FOR SEVERE THUNDERSTORMS OUT AHEAD OF IT. WATER VAPOR IMAGERY AND MORNING UPPER AIR ANALYSIS SHOWS THE CLOSED LOW OVER THE GREAT LAKES REGION WITH A LESS AMPLIFIED SHORTWAVE AROUND ITS SOUTHERN PERIPHERY MOVING ACROSS THE FL PANHANDLE. REGIONAL RADAR IMAGERY SHOWS DIMINISHING CONVECTION ALONG THE PANHANDLE OUT AHEAD OF THIS FEATURE WITH MORE SCATTERED STORMS ENTERING SOUTH-CENTRAL GA. THE ACTUAL COLD FRONT IS WELL BACK TO THE WEST...AND THE PRIMARY ACTIVITY TODAY WILL OCCUR AHEAD OF IT DURING MAX DIURNAL HEATING. THE POTENTIAL FOR SURFACE HEATING APPEARS PRETTY GOOD AS VISIBLE SATELLITE IMAGERY DEPICTS MAINLY THIN CIRRUS SPREADING OVER THE AREA WITH MOSTLY CLEAR TO PARTLY CLOUDY SKIES ACROSS MUCH OF SOUTHERN AND EASTERN SC/GA. TEMPS ARE WARMING QUICKLY INTO THE LOW TO MID 80S AND WE SHOULD BE ABLE TO REACH THE UPPER 80S TO NEAR 90 PRIOR TO CONVECTIVE INITIATION AND THE ONSET OF RESULTING CLOUDIER SKIES. THE PRIMARY UPPER FORCING FOR TODAY WILL COME IN THE WAY OF A BROAD AREA OF DIVERGENCE IN THE ENTRANCE REGION OF A 100 KT 250 MB JET ON THE EAST SIDE OF THE CLOSED UPPER LOW. ALTHOUGH THE BEST UPPER FORCING WILL REMAIN TO OUR NORTH CLOSER TO THE UPPER LOW...THE SHORTWAVE CURRENTLY MOVING ACROSS THE FL PANHANDLE WILL CROSS THE AREA THIS AFTERNOON/EVENING. THE BIGGEST LIMITING FACTOR FOR THE COVERAGE AND SEVERITY OF STORMS IS THE FACT THAT THE BEST DEEP FORCING AND SURFACE DESTABILIZATION WILL OCCUR JUST TO OUR NORTH. STILL...GIVEN TEMPS WARMING INTO THE UPPER 80S...WE SHOULD BE ABLE TO GET AT LEAST NUMEROUS COVERAGE OF THUNDERSTORMS CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WINDS. MODIFIED SOUNDINGS RESULT IN CAPE VALUES IN THE 1000-1500 J/KG RANGE THIS AFTERNOON. 500 MB FLOW WILL INCREASE OVER THE AREA THIS AFTERNOON TO AROUND 45 KTS...RESULTING IN 0-6 KM SHEAR UPWARDS OF 25-30 KTS. THERE WILL ALSO STILL BE A GOOD AMOUNT OF MID LEVEL DRY AIR AS EVIDENCED BY UPSTREAM RAOBS...SO DCAPE VALUES APPROACHING 1000 J/KG WILL BE POSSIBLE. FREEZING LEVELS WILL BE AROUND 13 KFT WITH A -20 C OF ABOUT 25 KFT. THESE PARAMETERS ARE A BIT LESS IMPRESSIVE THAN WE HAD OVER SE GA YESTERDAY AFTERNOON...AND THE HIGHER FREEZING LEVEL WILL LIKELY RESULT IN MORE OF A WIND THREAT THAN HAIL. STILL...LARGE HAIL IS POSSIBLE. CURRENT EXPECTATIONS ARE FOR CONVECTION TO INITIATE OVER SE GA AND SPREAD NORTHEASTWARD THROUGH THE AFTERNOON AND INTO THE EVENING. THE PRIMARY TIME PERIOD FOR THE SEVERE THREAT IS 2PM-10PM...WITH THE FAVORED CONVECTIVE MODE BEING MULTI-CELL CLUSTERS. LAKE WINDS...THE POTENTIAL FOR WIND GUSTS TO 25 KNOTS IS SUFFICIENT TO JUSTIFY A LAKE WIND ADVISORY FROM NOON UNTIL 8 PM. THUNDERSTORMS COULD PRODUCE STRONG WINDS LATER THIS AFTERNOON FOLLOWED BY DIMINISHING WINDS PRIOR TO 8 PM. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... PRECIPITATION COULD COME TO AN ABRUPT END THIS EVENING...BUT LINGERING MOISTURE DEPICTED BY GUIDANCE JUSTIFIES POPS LINGERING BUT DIMINISHING AS THE NIGHT PROGRESSES. OVERNIGHT...THE COLD FRONT WILL PUSH OFFSHORE AND COOLER/DRYER AIR WILL SPREAD INTO THE REGION. THIS PERIOD TO BE DOMINATED BY A MEAN UPPER TROUGH OVER THE EAST COAST. AT THE SURFACE...COOLER/DRIER HIGH PRESSURE WILL BUILD IN FROM THE WEST SATURDAY BEHIND A DEPARTING COLD FRONT. A BACKDOOR COLD FRONT WILL APPROACH THE AREA SUNDAY NIGHT FROM THE NORTH...POSSIBLY PUSHING INTO THE AREA BY MONDAY BEFORE STALLING OUT. THINK RAIN CHANCES ARE TOO LOW TO MENTION SUNDAY NIGHT BUT AT LEAST ISOLATED SHOWERS/THUNDERSTORMS ARE EXPECTED MONDAY AS DEEPER MOISTURE MOVES INTO THE AREA. TEMPERATURES WILL MODERATE THROUGH THE PERIOD...LIKELY BECOMING ABOVE NORMAL MONDAY. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... A REINFORCING COLD FRONT LOOKS TO PUSH THROUGH MONDAY NIGHT AS LOW PRESSURE MOVES OFF THE SOUTHERN NEW ENGLAND COAST. ONCE AGAIN THE FRONT WILL STALL OUT OVER OR JUST SOUTH OF THE AREA TUESDAY THROUGH MID WEEK BEFORE LIFTING BACK NORTH LATE IN THE WEEK. RAIN CHANCES LOOK TO BE MAINLY DIURNALLY-DRIVEN WITH THE BEST CHANCES OVERALL COMING THURSDAY INTO FRIDAY AS DEEPER MOISTURE MOVES BACK INTO THE AREA. TEMPERATURES WILL BE LARGELY DEPENDENT UPON THE POSITION OF THE FRONT AND RAIN COVERAGE BUT KEPT THEM AT OR ABOVE NORMAL THROUGH TUESDAY BEFORE DROPPING BELOW NORMAL WEDNESDAY. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... AHEAD OF AN APPROACHING COLD FRONT/WITHIN A PREFRONTAL TROUGH AND ALONG VARIOUS MESOSCALE BOUNDARIES...SCATTERED TO NUMEROUS THUNDERSTORMS WILL DEVELOP THIS AFTERNOON AND EVENING. LATEST MODEL GUIDANCE SUGGESTS THAT THUNDERSTORMS ARE LIKELY AT SOME POINT AT BOTH TERMINALS THIS AFTERNOON INTO EARLY EVENING...BUT CONFIDENT TIMING REMAINS ELUSIVE. 12Z TAFS WILL MAINTAIN CB/VCTS AT BOTH TERMINALS DURING THE 19Z-01Z TIME PERIOD. ANY THUNDERSTORMS COULD BECOME STRONG/SEVERE WITH STRONG/SHIFTING WINDS AND MVFR OR LOWER FLIGHT CONDITIONS DURING A 2-4 HOUR PERIOD WITHIN THIS TIME WINDOW. EVEN OUTSIDE OF CONVECTION...S/SW WINDS WILL INCREASE AT BOTH TERMINALS AND WILL GUST TO 20-25 KT THIS AFTERNOON. EXTENDED AVIATION OUTLOOK...VFR THROUGH THE WEEKEND WITH INCREASING CHANCES OF SUB-VFR CONDITIONS EARLY NEXT WEEK AS A BACKDOOR COLD FRONT MOVES INTO THE AREA AND STALLS OVER/SOUTH OF THE AREA THROUGH MID WEEK. && .MARINE... TODAY AND TONIGHT...S/SW WINDS AHEAD OF AN APPROACHING COLD FRONT WILL INCREASE...AND THE POTENTIAL FOR WIND GUSTS TO AT LEAST 25 KNOTS JUSTIFIES THE ONGOING SMALL CRAFT ADVISORY FOR ALL MARINE ZONES INCLUDING CHARLESTON HARBOR. THE END TIME FOR SCA CONDITIONS WILL VARY FROM LATE EVENING ON THE HARBOR TO LATE TONIGHT ACROSS THE OUTER GA WATERS...AS WINDS WILL SHIFT TO THE WEST AND DIMINISH IN THE WAKE OF COLD FROPA TONIGHT. MARINERS SHOULD REMAIN ALERT FOR THE POSSIBILITY OF STRONG TO SEVERE T-STORMS IN ADVANCE OF THE COLD FRONT...ESPECIALLY LATE TODAY THROUGH THIS EVENING. SATURDAY AND SUNDAY...WEAK HIGH PRESSURE WILL BUILD FROM THE WEST BEHIND A DEPARTING COLD FRONT OFFSHORE. A LIGHT WIND REGIME WILL PREVAIL...WITH NO MORE THAN A WEAK SEA BREEZE CIRCULATION DEVELOPING EACH AFTERNOON. SUNDAY NIGHT THROUGH WEDNESDAY...A BACKDOOR COLD FRONT IS EXPECTED TO APPROACH THE WATERS FROM THE NORTH SUNDAY NIGHT BEFORE STALLING OUT OVER OR NEAR THE AREA THROUGH MID WEEK. GENERALLY LOW CONFIDENCE THIS PERIOD AS WINDS/SEAS WILL BE HIGHLY DEPENDENT ON THE POSITION OF THE FRONT. KEPT CONDITIONS BELOW ADVISORY LEVELS AT THIS TIME. && .TIDES/COASTAL FLOODING... THE UPCOMING FULL MOON AND LUNAR PERIGEE WILL CREATE PERIGEAN SPRING TIDES WHICH COULD BE HIGH ENOUGH TO PRODUCE MINOR COASTAL FLOODING EACH EVENING DURING THE HIGH TIDES INTO EARLY NEXT WEEK. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...LAKE WIND ADVISORY UNTIL 8 PM EDT THIS EVENING FOR SCZ045. MARINE...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO MIDNIGHT EDT TONIGHT FOR AMZ350-352-354. SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 5 AM EDT SATURDAY FOR AMZ374. SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR AMZ330. && $$ |
| #515189 (Received by flhurricane at: 7:26 AM 01.Jun.2012) AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 715 AM EDT FRI JUN 1 2012 .SYNOPSIS... A COLD FRONT WILL APPROACH THE AREA TODAY AND WILL MOVE THROUGH THE REGION TONIGHT. DRY HIGH PRESSURE WILL THEN PREVAIL THROUGH THE WEEKEND. ANOTHER COLD FRONT WILL GRADUALLY ADVANCE INTO THE SOUTHEAST THROUGH THE FIRST HALF OF NEXT WEEK...AND HIGH PRESSURE COULD BUILD INTO THE REGION AGAIN AROUND MIDWEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... LOWERED POPS TO LESS THAN 15 PERCENT FOR THE REMAINDER OF THE MORNING. A CHANCE FOR THUNDERSTORMS SHOULD REDEVELOP PRIMARY FORECAST ATTENTION REMAINS FOCUSED ON POTENTIAL FOR SEVERE WEATHER THIS AFTERNOON/EVENING. A DEEPENING LONGWAVE UPPER TROUGH WILL PUSH AN ELONGATED SHORTWAVE TROUGH AND ASSOCIATED SURFACE COLD FRONT TOWARD THE FORECAST AREA TODAY. INITIALLY...BY EARLY AFTERNOON THUNDERSTORMS WILL FIRE OVER AND UPSTREAM OF THE FORECAST AREA...WELL AHEAD OF THE COLD FRONT ALONG VARIOUS BOUNDARIES INCLUDING A PREFRONTAL SURFACE TROUGH INLAND AND THE SEA BREEZE OVER THE FORECAST AREA. ONCE CONVECTION BEGINS THE COMBINATION OF INSTABILITY...STRENGTHENING LOW/MID LEVEL WIND FIELDS/0-6 KM SHEAR INCREASING TO 25-35 KNOTS...DYNAMIC FORCING FOR ASCENT PROVIDED BY THE LONGWAVE UPPER TROUGH/ASSOCIATED SHORTWAVE TROUGH AND MESOSCALE BOUNDARY INTERACTIONS WILL SUPPORT MULTICELL THUNDERSTORMS AND PERHAPS EVEN BRIEF SUPERCELLS WITH OCCASIONAL DAMAGING WIND GUSTS AND LARGE HAIL. ACCORDINGLY...A MENTION OF SEVERE THUNDERSTORMS IS INCLUDED WITHIN PUBLIC PRODUCTS AND IS ADDRESSED WITHIN THE HAZARDOUS WEATHER OUTLOOK. FURTHER...PWATS APPROACHING 2 INCHES WILL SUPPORT A THREAT FOR LOCALLY EXCESSIVE RAINFALL ESPECIALLY IF/WHERE ECHO TRAINING OCCURS. THIS COMPLEX SCENARIO TRANSLATES TO UNCERTAIN POPS AND PRECIPITATION TIMING. LATEST GUIDANCE CONTINUES TO DIFFER REGARDING POPS AND DETAILS OF THE EVOLVING CONVECTIVE REGIME... BUT ODDS FAVOR MOST AREAS RECEIVING AT LEAST SOME MEASURABLE PRECIPITATION SO A PERIOD OF LIKELY POPS ARE JUSTIFIED THIS AFTERNOON/EARLY EVENING IN MOST LOCATIONS. FURTHER...GIVEN THE POTENTIAL FOR THUNDERSTORM ORGANIZATION THIS FORECAST FAVORS THE SOMEWHAT FASTER NAM SCENARIO...WITH MOST THE SIGNIFICANT THUNDERSTORMS INITIATING BY EARLY THIS AFTERNOON THEN PUSHING OFF THE COAST EARLY THIS EVENING. OF NOTE...A SHIELD OF HIGH CLOUDS STREAMING INTO THE REGION FROM THE SOUTH COULD LIMIT INSOLATION/INSTABILITY TO SOME DEGREE... BUT SYNOPTIC SCALE FORCING FOR ASCENT AND DEEP LAYER SHEAR SHOULD COMPENSATE FOR ANY SUBTLE REDUCTION IN CAPE. LAKE WINDS...THE POTENTIAL FOR WIND GUSTS TO 25 KNOTS IS SUFFICIENT TO JUSTIFY A LAKE WIND ADVISORY FROM NOON UNTIL 8 PM. THUNDERSTORMS COULD PRODUCE STRONG WINDS LATER THIS AFTERNOON FOLLOWED BY DIMINISHING WINDS PRIOR TO 8 PM. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... PRECIPITATION COULD COME TO AN ABRUPT END THIS EVENING...BUT LINGERING MOISTURE DEPICTED BY GUIDANCE JUSTIFIES POPS LINGERING BUT DIMINISHING AS THE NIGHT PROGRESSES. OVERNIGHT...THE COLD FRONT WILL PUSH OFFSHORE AND COOLER/DRYER AIR WILL SPREAD INTO THE REGION. THIS PERIOD TO BE DOMINATED BY A MEAN UPPER TROUGH OVER THE EAST COAST. AT THE SURFACE...COOLER/DRIER HIGH PRESSURE WILL BUILD IN FROM THE WEST SATURDAY BEHIND A DEPARTING COLD FRONT. A BACKDOOR COLD FRONT WILL APPROACH THE AREA SUNDAY NIGHT FROM THE NORTH...POSSIBLY PUSHING INTO THE AREA BY MONDAY BEFORE STALLING OUT. THINK RAIN CHANCES ARE TOO LOW TO MENTION SUNDAY NIGHT BUT AT LEAST ISOLATED SHOWERS/THUNDERSTORMS ARE EXPECTED MONDAY AS DEEPER MOISTURE MOVES INTO THE AREA. TEMPERATURES WILL MODERATE THROUGH THE PERIOD...LIKELY BECOMING ABOVE NORMAL MONDAY. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... A REINFORCING COLD FRONT LOOKS TO PUSH THROUGH MONDAY NIGHT AS LOW PRESSURE MOVES OFF THE SOUTHERN NEW ENGLAND COAST. ONCE AGAIN THE FRONT WILL STALL OUT OVER OR JUST SOUTH OF THE AREA TUESDAY THROUGH MID WEEK BEFORE LIFTING BACK NORTH LATE IN THE WEEK. RAIN CHANCES LOOK TO BE MAINLY DIURNALLY-DRIVEN WITH THE BEST CHANCES OVERALL COMING THURSDAY INTO FRIDAY AS DEEPER MOISTURE MOVES BACK INTO THE AREA. TEMPERATURES WILL BE LARGELY DEPENDENT UPON THE POSITION OF THE FRONT AND RAIN COVERAGE BUT KEPT THEM AT OR ABOVE NORMAL THROUGH TUESDAY BEFORE DROPPING BELOW NORMAL WEDNESDAY. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... LOW LEVEL MOISTURE COULD SUPPORT SCATTERED MVFR/IFR LEVEL CLOUDS EARLY THIS MORNING. OTHERWISE...VFR CONDITIONS SHOULD PREVAIL UNTIL AFTERNOON. AHEAD OF AN APPROACHING COLD FRONT/WITHIN A PREFRONTAL TROUGH AND ALONG VARIOUS MESOSCALE BOUNDARIES...SCATTERED TO NUMEROUS THUNDERSTORMS WILL DEVELOP THIS AFTERNOON AND EVENING. LATEST MODEL GUIDANCE SUGGESTS THAT THUNDERSTORMS ARE LIKELY AT SOME POINT AT BOTH TERMINALS THIS AFTERNOON INTO EARLY EVENING...BUT CONFIDENT TIMING REMAINS ELUSIVE. 12Z TAFS WILL MAINTAIN CB/VCTS AT BOTH TERMINALS DURING THE 19Z-01Z TIME PERIOD. ANY THUNDERSTORMS COULD BECOME STRONG/SEVERE WITH STRONG/SHIFTING WINDS AND MVFR OR LOWER FLIGHT CONDITIONS DURING A 2-4 HOUR PERIOD WITHIN THIS TIME WINDOW. EVEN OUTSIDE OF CONVECTION...S/SW WINDS WILL INCREASE AT BOTH TERMINALS AND WILL GUST TO 20-25 KT THIS AFTERNOON. EXTENDED AVIATION OUTLOOK...VFR THROUGH THE WEEKEND WITH INCREASING CHANCES OF SUB-VFR CONDITIONS EARLY NEXT WEEK AS A BACKDOOR COLD FRONT MOVES INTO THE AREA AND STALLS OVER/SOUTH OF THE AREA THROUGH MID WEEK. && .MARINE... TODAY AND TONIGHT...S/SW WINDS AHEAD OF AN APPROACHING COLD FRONT WILL INCREASE...AND THE POTENTIAL FOR WIND GUSTS TO AT LEAST 25 KNOTS JUSTIFIES THE ONGOING SMALL CRAFT ADVISORY FOR ALL MARINE ZONES INCLUDING CHARLESTON HARBOR. THE END TIME FOR SCA CONDITIONS WILL VARY FROM LATE EVENING ON THE HARBOR TO LATE TONIGHT ACROSS THE OUTER GA WATERS...AS WINDS WILL SHIFT TO THE WEST AND DIMINISH IN THE WAKE OF COLD FROPA TONIGHT. MARINERS SHOULD REMAIN ALERT FOR THE POSSIBILITY OF STRONG TO SEVERE T-STORMS IN ADVANCE OF THE COLD FRONT...ESPECIALLY LATE TODAY THROUGH THIS EVENING. SATURDAY AND SUNDAY...WEAK HIGH PRESSURE WILL BUILD FROM THE WEST BEHIND A DEPARTING COLD FRONT OFFSHORE. A LIGHT WIND REGIME WILL PREVAIL...WITH NO MORE THAN A WEAK SEA BREEZE CIRCULATION DEVELOPING EACH AFTERNOON. SUNDAY NIGHT THROUGH WEDNESDAY...A BACKDOOR COLD FRONT IS EXPECTED TO APPROACH THE WATERS FROM THE NORTH SUNDAY NIGHT BEFORE STALLING OUT OVER OR NEAR THE AREA THROUGH MID WEEK. GENERALLY LOW CONFIDENCE THIS PERIOD AS WINDS/SEAS WILL BE HIGHLY DEPENDENT ON THE POSITION OF THE FRONT. KEPT CONDITIONS BELOW ADVISORY LEVELS AT THIS TIME. && .TIDES/COASTAL FLOODING... THE UPCOMING FULL MOON AND LUNAR PERIGEE WILL CREATE PERIGEAN SPRING TIDES WHICH COULD BE HIGH ENOUGH TO PRODUCE MINOR COASTAL FLOODING EACH EVENING DURING THE HIGH TIDES INTO EARLY NEXT WEEK. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...LAKE WIND ADVISORY FROM NOON TODAY TO 8 PM EDT THIS EVENING FOR SCZ045. MARINE...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO MIDNIGHT EDT TONIGHT FOR AMZ350-352-354. SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 5 AM EDT SATURDAY FOR AMZ374. SMALL CRAFT ADVISORY FROM NOON TODAY TO 10 PM EDT THIS EVENING FOR AMZ330. && $$ |
| #515171 (Received by flhurricane at: 4:42 AM 01.Jun.2012) AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 434 AM EDT FRI JUN 1 2012 .SYNOPSIS... A COLD FRONT WILL APPROACH THE AREA TODAY AND WILL MOVE THROUGH THE REGION TONIGHT. DRY HIGH PRESSURE WILL THEN PREVAIL THROUGH THE WEEKEND. ANOTHER COLD FRONT WILL GRADUALLY ADVANCE INTO THE SOUTHEAST THROUGH THE FIRST HALF OF NEXT WEEK...AND HIGH PRESSURE COULD BUILD INTO THE REGION AGAIN AROUND MIDWEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... WITHIN THE ONGOING WARM ADVECTION REGIME...A FEW SHOWERS/THUNDERSTORMS WILL IMPACT NORTHERN COUNTIES/ADJACENT COASTAL WATERS EARLY THIS MORNING. ALSO...STRATUS COULD DEVELOP AND INCREASE IN COVERAGE AROUND DAYBREAK...ALTHOUGH COVERAGE/PERSISTENCE OF LOW CLOUDS HAS REMAINED LIMITED THUS FAR THROUGH THE PREDAWN HOURS. PRIMARY FORECAST CONCERNS FOCUS ON POTENTIAL FOR SEVERE WEATHER THIS AFTERNOON/EVENING. A DEEPENING LONGWAVE UPPER TROUGH WILL PUSH AN ELONGATED SHORTWAVE TROUGH AND ASSOCIATED SURFACE COLD FRONT TOWARD THE FORECAST AREA TODAY. INITIALLY...THUNDERSTORMS WILL FIRE WELL AHEAD OF THE COLD FRONT ALONG VARIOUS BOUNDARIES INCLUDING A PREFRONTAL SURFACE TROUGH OVER THE FORECAST AREA AND/OR WILL MOVE INTO THE REGION FROM UPSTREAM THIS AFTERNOON. ONCE CONVECTION BEGINS THE COMBINATION OF INSTABILITY...STRENGTHENING LOW/MID LEVEL WIND FIELDS/0-6 KM SHEAR INCREASING TO 25-35 KNOTS...DYNAMIC FORCING FOR ASCENT PROVIDED BY THE LONGWAVE UPPER TROUGH/ASSOCIATED SHORTWAVE TROUGH AND MESOSCALE BOUNDARY INTERACTIONS WILL SUPPORT MULTICELL THUNDERSTORMS AND PERHAPS EVEN BRIEF SUPERCELLS WITH OCCASIONAL DAMAGING WIND GUSTS AND LARGE HAIL. ACCORDINGLY...A MENTION OF SEVERE THUNDERSTORMS IS INCLUDED WITHIN PUBLIC PRODUCTS AND IS ADDRESSED WITHIN THE HAZARDOUS WEATHER OUTLOOK. FURTHER...PWATS APPROACHING 2 INCHES WILL SUPPORT A THREAT FOR LOCALLY EXCESSIVE RAINFALL ESPECIALLY IF/WHERE ECHO TRAINING OCCURS. A COMPLEX SCENARIO TRANSLATES TO UNCERTAIN POPS AND PRECIPITATION TIMING. 01/00Z GUIDANCE CONTINUES TO DIFFER REGARDING POPS...BUT ODDS FAVOR MOST AREAS RECEIVING AT LEAST SOME MEASURABLE PRECIPITATION SO A PERIOD OF LIKELY POPS ARE JUSTIFIED THIS AFTERNOON/EARLY EVENING IN MOST LOCATIONS. FURTHER...GIVEN THE POTENTIAL FOR THUNDERSTORM ORGANIZATION THIS FORECAST FAVORS THE SOMEWHAT FASTER NAM SCENARIO...WITH MOST THE SIGNIFICANT THUNDERSTORMS INITIATING EARLY THIS AFTERNOON THEN PUSHING OFF THE COAST EARLY THIS EVENING. LAKE WINDS...THE POTENTIAL FOR WIND GUSTS TO 25 KNOTS IS SUFFICIENT TO JUSTIFY A LAKE WIND ADVISORY FROM NOON UNTIL 8 PM. THUNDERSTORMS COULD PRODUCE STRONG WINDS LATER THIS AFTERNOON FOLLOWED BY DIMINISHING WINDS PRIOR TO 8 PM. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... PRECIPITATION COULD COME TO AN ABRUPT END THIS EVENING...BUT LINGERING MOISTURE DEPICTED BY GUIDANCE JUSTIFIES POPS LINGERING BUT DIMINISHING AS THE NIGHT PROGRESSES. OVERNIGHT...THE COLD FRONT WILL PUSH OFFSHORE AND COOLER/DRYER AIR WILL SPREAD INTO THE REGION. THIS PERIOD TO BE DOMINATED BY A MEAN UPPER TROUGH OVER THE EAST COAST. AT THE SURFACE...COOLER/DRIER HIGH PRESSURE WILL BUILD IN FROM THE WEST SATURDAY BEHIND A DEPARTING COLD FRONT. A BACKDOOR COLD FRONT WILL APPROACH THE AREA SUNDAY NIGHT FROM THE NORTH...POSSIBLY PUSHING INTO THE AREA BY MONDAY BEFORE STALLING OUT. THINK RAIN CHANCES ARE TOO LOW TO MENTION SUNDAY NIGHT BUT AT LEAST ISOLATED SHOWERS/THUNDERSTORMS ARE EXPECTED MONDAY AS DEEPER MOISTURE MOVES INTO THE AREA. TEMPERATURES WILL MODERATE THROUGH THE PERIOD...LIKELY BECOMING ABOVE NORMAL MONDAY. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... A REINFORCING COLD FRONT LOOKS TO PUSH THROUGH MONDAY NIGHT AS LOW PRESSURE MOVES OFF THE SOUTHERN NEW ENGLAND COAST. ONCE AGAIN THE FRONT WILL STALL OUT OVER OR JUST SOUTH OF THE AREA TUESDAY THROUGH MID WEEK BEFORE LIFTING BACK NORTH LATE IN THE WEEK. RAIN CHANCES LOOK TO BE MAINLY DIURNALLY-DRIVEN WITH THE BEST CHANCES OVERALL COMING THURSDAY INTO FRIDAY AS DEEPER MOISTURE MOVES BACK INTO THE AREA. TEMPERATURES WILL BE LARGELY DEPENDENT UPON THE POSITION OF THE FRONT AND RAIN COVERAGE BUT KEPT THEM AT OR ABOVE NORMAL THROUGH TUESDAY BEFORE DROPPING BELOW NORMAL WEDNESDAY. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... LOW LEVEL MOISTURE COULD SUPPORT MVFR/IFR CEILINGS AT ANY TIME THROUGH THE EARLY MORNING. HOWEVER...TIMING OF SUB-VFR CONDITIONS WILL REMAIN DIFFICULT AS LOW CLOUD COVERAGE WILL REMAIN CHANGEABLE AND LESS THAN WIDESPREAD. SCATTERED TO NUMEROUS THUNDERSTORMS WILL DEVELOP IN ASSOCIATION WITH A PRE-FRONTAL TROUGH AND ALONG VARIOUS MESOSCALE BOUNDARIES FRIDAY AFTERNOON AND EVENING. 01/00Z MODEL GUIDANCE SUGGESTS THAT THUNDERSTORMS ARE LIKELY AT SOME POINT AT BOTH TERMINALS THIS AFTERNOON INTO EARLY EVENING...BUT CONFIDENT TIMING REMAINS ELUSIVE. 06Z TAFS WILL INCLUDE CBS AND VCTS FOR PART OF THE 18Z- 02Z TIME PERIOD...AND THUNDERSTORMS COULD PRODUCE GUSTY/ SHIFTING WINDS AND MVFR OR LOWER FLIGHT CONDITIONS DURING A 2-4 HOUR PERIOD WITHIN THIS TIME WINDOW. EVEN OUTSIDE OF CONVECTION...S/SW WINDS WILL INCREASE AT BOTH TERMINALS AND WILL GUST TO 20-25 KT DURING FRIDAY AFTERNOON. EXTENDED AVIATION OUTLOOK...VFR THROUGH THE WEEKEND WITH INCREASING CHANCES OF SUB-VFR CONDITIONS EARLY NEXT WEEK AS A BACKDOOR COLD FRONT MOVES INTO THE AREA AND STALLS OVER/SOUTH OF THE AREA THROUGH MID WEEK. && .MARINE... TODAY AND TONIGHT...S/SW WINDS AHEAD OF AN APPROACHING COLD FRONT WILL INCREASE...AND THE POTENTIAL FOR WIND GUSTS TO AT LEAST 25 KNOTS JUSTIFIES THE ONGOING SMALL CRAFT ADVISORY FOR CHARLESTON HARBOR AND ALSO JUSTIFIES SMALL CRAFT ADVISORIES FOR ALL OTHER COASTAL ZONES. THE END TIME FOR SCA CONDITIONS WILL VARY FROM LATE EVENING ON THE HARBOR TO LATE TONIGHT ACROSS THE OUTER GA WATERS...AS WINDS WILL SHIFT TO THE WEST AND DIMINISH IN THE WAKE OF COLD FROPA TONIGHT. MARINERS SHOULD REMAIN ALERT FOR THE POSSIBILITY OF STRONG TO SEVERE T-STORMS IN ADVANCE OF THE COLD FRONT...ESPECIALLY LATE TODAY THROUGH THIS EVENING. SATURDAY AND SUNDAY...WEAK HIGH PRESSURE WILL BUILD FROM THE WEST BEHIND A DEPARTING COLD FRONT OFFSHORE. A LIGHT WIND REGIME WILL PREVAIL...WITH NO MORE THAN A WEAK SEA BREEZE CIRCULATION DEVELOPING EACH AFTERNOON. SUNDAY NIGHT THROUGH WEDNESDAY...A BACKDOOR COLD FRONT IS EXPECTED TO APPROACH THE WATERS FROM THE NORTH SUNDAY NIGHT BEFORE STALLING OUT OVER OR NEAR THE AREA THROUGH MID WEEK. GENERALLY LOW CONFIDENCE THIS PERIOD AS WINDS/SEAS WILL BE HIGHLY DEPENDENT ON THE POSITION OF THE FRONT. KEPT CONDITIONS BELOW ADVISORY LEVELS AT THIS TIME. && .TIDES/COASTAL FLOODING... THE UPCOMING FULL MOON AND LUNAR PERIGEE WILL CREATE PERIGEAN SPRING TIDES WHICH COULD BE HIGH ENOUGH TO PRODUCE MINOR COASTAL FLOODING EACH EVENING DURING THE HIGH TIDES INTO EARLY NEXT WEEK. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...LAKE WIND ADVISORY FROM NOON TODAY TO 8 PM EDT THIS EVENING FOR SCZ045. MARINE...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO MIDNIGHT EDT TONIGHT FOR AMZ350-352-354. SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 5 AM EDT SATURDAY FOR AMZ374. SMALL CRAFT ADVISORY FROM NOON TODAY TO 10 PM EDT THIS EVENING FOR AMZ330. && $$ |
| #515124 (Received by flhurricane at: 12:56 AM 01.Jun.2012) AFDCHS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 1256 AM EDT FRI JUN 1 2012 .SYNOPSIS... WEAK ATLANTIC HIGH PRESSURE WILL GIVE WAY TO A COLD FRONT MOVING THROUGH THE AREA FRIDAY NIGHT...FOLLOWED BY HIGH PRESSURE THROUGH THE WEEKEND. ANOTHER COLD FRONT WILL GRADUALLY ADVANCE INTO THE SOUTHEAST THROUGH THE FIRST HALF OF NEXT WEEK...AND HIGH PRESSURE COULD BUILD INTO THE REGION AGAIN AROUND MIDWEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... OVERNIGHT...ISOLATED TO SCATTERED THUNDERSTORMS WILL BRUSH FAR INLAND COUNTIES AND COASTAL WATERS. ANY SHOWERS/THUNDERSTORMS WILL SHIFT INTO NORTHERN COUNTIES LATE. OTHERWISE...EXPECT A WARM AND MUGGY NIGHT WITH TEMPERATURES NOT FALLING BELOW 70F AT MANY LOCATIONS AND HOLDING IN THE MID TO UPPER 70S AT THE COAST. && .SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/... FRIDAY...LOW LEVEL STRATUS WILL KEEP LOW TEMPS MILD IN THE MORNING. IT WILL ALSO SLIGHTLY LIMIT SURFACE HEATING EARLY IN THE DAY. IT WILL NOT BE A DEEP LAYER AND SHOULD MIX OUT MID DAY. MODELS ARE IN PRETTY GOOD AGREEMENT THAT SOME FORM OF LOW LEVEL MOISTURE WILL BE PRESENT WITH THE MAJORITY BEING STRATUS. GROUND FOG IS A POSSIBILITY OVER THE INLAND AREAS WHERE THE WIND SPEEDS ARE LOWER. THE CHANCE OF SEA BREEZE INITIATION WILL BE GREATEST OVER THE SC COAST WITH THE SOUTHERLY FLOW AND THE ORIENTATION OF THE COAST. FRIDAY AFTERNOON INTO FRIDAY NIGHT...AN APPROACHING UPPER TROUGH AND ASSOCIATED SURFACE COLD FRONT WILL SUPPORT SCATTERED TO BROKEN CONVECTION ESPECIALLY DURING THE AFTERNOON/EVENING. THE CONVECTION WILL BE AHEAD OF THE COLD FRONT WHICH GETS HELD UP OVER W. GA. EVEN THOUGH THE KSAV MODEL SOUNDINGS SHOW HIGHER CAPE...EXPECT MOST OF THE THUNDERSTORM ACTIVITY FURTHER NORTH IN THE PROXIMITY OF THE MID AND UPPER LEVEL SUPPORT. MODELS ARE CONSISTENT WITH MOST OF SOUTHEAST SOUTH CAROLINA UNDER THE ENHANCED LIFT OF THE 90KT JET MAX AND 500MB TROUGH/VORT MAX. THERMODYNAMIC/ KINEMATIC PARAMETERS SUPPORT MULTICELL THUNDERSTORMS CAPABLE OF PRODUCING EPISODES OF DAMAGING WIND GUSTS AND LARGE HAIL WITH THE GREATEST CHANCE IN THE VICINITY OF THE ENHANCED CONVERGENCE OF THE SEA BREEZE. ACCORDINGLY...AREAS ALONG AND NORTH OF INTERSTATE 16 REMAIN IN A SLIGHT RISK FOR SEVERE THUNDERSTORMS. POPS REMAIN UNCERTAIN. WHILE THUNDERSTORMS COULD BECOME NUMEROUS...JUSTIFYING LIKELY OR HIGHER POPS...GUIDANCE HAS TRENDED TOWARD LOWER POPS...SUGGESTING THAT BEST COVERAGE OF THUNDERSTORMS WILL REMAIN NORTH OF THE REGION. FOR NOW...CAPPED HIGHEST POPS IN THE 50-60 PERCENT RANGE FRIDAY AFTERNOON INTO FRIDAY EVENING. SATURDAY...IN THE WAKE OF COLD FROPA A DRIER AIR MASS FEATURING DEWPOINTS IN THE MID 50S TO LOWER 60S WILL OVERSPREAD THE REGION. SOME GUIDANCE SUGGESTS THAT SUFFICIENT MOISTURE WILL PERSIST TO SUPPORT ISOLATED SHOWERS/THUNDERSTORMS ESPECIALLY WHERE SEA BREEZE CONVERGENCE DEVELOPS NEAR THE COAST. THIS SCENARIO JUSTIFIES NON-ZERO POPS...BUT GIVEN THE INCREASINGLY DRY/CAPPED ENVIRONMENT HELD POPS BELOW 15 PERCENT WITH NO EXPLICIT MENTION OF PRECIPITATION. TEMPERATURES SHOULD TOP OUT IN THE MID TO UPPER 80S. SATURDAY NIGHT SHOULD FEATURE BELOW NORMAL TEMPERATURES IN THE LOWER TO MID 60S. SUNDAY...HIGH TEMPS LOOK TO CREEP BACK UP NEAR 90 FOR MOST OF THE CWA WITH ENHANCED SOUTHERLY FLOW AND THE REMAINING MOISTURE CLEARING OUT. PRECIP CHANCES ARE NEAR ZERO. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... THE UNSEASONABLY DRY AIR MASS WILL REMAIN IN PLACE SUNDAY. TEMPERATURES WILL RECOVER INTO THE UPPER 80S TO LOWER 90S... BUT DEWPOINTS WILL REMAIN IN THE UPPER 50S/LOWER 60S. POPS ARE ESSENTIALLY ZERO SUNDAY. NEXT WEEK...A BLOCKING PATTERN WILL DEVELOP...ALLOWING A LONGWAVE UPPER TROUGH TO AMPLIFY OVER THE EAST. THIS TROUGH WILL GRADUALLY PUSH A SLOW-MOVING SURFACE COLD FRONT INTO THE SOUTHEAST DURING THE FIRST HALF OF THE WEEK. THUS...INTRODUCED SLIGHT CHANCE POPS DURING THE MONDAY AND TUESDAY TIME FRAME...AND HIGHER POPS COULD EVENTUALLY BE REQUIRED FOR A PORTION OF THAT TIME PERIOD. EVEN AS HIGH PRESSURE EXPANDS FROM THE NORTH AROUND MIDWEEK...STRONG DRYING IS NOT INDICATED...AND LOW CHANCE POPS ARE JUSTIFIED. OVERALL...THIS PATTERN WILL NOT FAVOR ANY HOT/HUMID WEATHER...AND TEMPERATURES SHOULD REMAIN CLOSE TO OR EVEN SLIGHTLY BELOW NORMAL NEXT WEEK. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... LOW LEVEL MOISTURE COULD SUPPORT MVFR/IFR CEILINGS AT ANY TIME THROUGH THE NIGHT. HOWEVER...TIMING OF SUB-VFR CONDITIONS WILL REMAIN DIFFICULT AS LOW CLOUD COVERAGE WILL REMAIN CHANGEABLE AND LESS THAN WIDESPREAD. SCATTERED CONVECTION WILL DEVELOP IN ASSOCIATION WITH A PRE- FRONTAL TROUGH AND ALONG VARIOUS MESOSCALE BOUNDARIES FRIDAY AFTERNOON AND EVENING. 01/00Z MODEL GUIDANCE SUGGESTS THAT THUNDERSTORMS ARE LIKELY AT SOME POINT AT BOTH TERMINALS THIS AFTERNOON INTO EARLY EVENING...BUT CONFIDENT TIMING REMAINS ELUSIVE. 06Z TAFS WILL INCLUDE CBS AND VCTS FOR PART OF THE 18Z-02Z TIME PERIOD...AND THUNDERSTORMS COULD PRODUCE GUSTY/ SHIFTING WINDS AND MVFR OR LOWER FLIGHT CONDITIONS DURING A 2-4 HOUR PERIOD WITHIN THIS TIME WINDOW. EVEN OUTSIDE OF CONVECTION...S/SW WINDS WILL INCREASE AT BOTH TERMINALS AND WILL GUST TO 20-25 KT DURING FRIDAY AFTERNOON. EXTENDED AVIATION OUTLOOK...VFR. && .MARINE... TONIGHT...SOUTHERLY FLOW OUT AHEAD OF A COLD FRONT TO THE WEST WILL BEGIN TO INCREASE. THERE IS A DECENT 20-25 KT LOW LEVEL JET WITHIN THE SOUTHERLY FLOW...BUT LIMITED MIXING OVER THE WATERS WILL PREVENT WINDS FROM BECOMING STRONG ENOUGH TO SUPPORT SCA/S. S TO SSW WINDS WILL GENERALLY AVERAGE 15-20 KTS THROUGH SUNRISE WITH SEAS BUILDING TO 2-3 FT...PERHAPS AS HIGH AS 4 FT BEYOND 20 NM. FRIDAY AND FRIDAY EVENING...A TIGHT SURFACE PRESSURE GRADIENT BETWEEN ATLANTIC HIGH PRESSURE AND AN APPROACHING COLD FRONT FROM THE WEST AND NW WITH SUPPORT S/SW WINDS IN THE 15-20 KT RANGE...CAUSING SEAS TO BUILD TO 3-5 FT. MARGINAL SMALL CRAFT ADVISORY WINDS COULD DEVELOP FRIDAY AFTERNOON INTO FRIDAY EVENING...WENT WITH A SMALL CRAFT ADVISORY FOR THE CHARLESTON HARBOR. MARINERS SHOULD REMAIN ALERT FOR THE POSSIBILITY OF STRONG TO SEVERE T-STORMS IN ADVANCE OF THE COLD FRONT...ESPECIALLY LATE FRIDAY INTO FRIDAY NIGHT. SATURDAY AND SUNDAY...WEAK HIGH PRESSURE WILL BUILD FROM THE WEST AS THE COLD FRONT PULLS FAR AWAY TO THE EAST AND SE. A LIGHT OFFSHORE WIND REGIME WILL PREVAIL...WITH NO MORE THAN WEAK SEA BREEZE CIRCULATION DEVELOPING EACH AFTERNOON. MONDAY AND TUESDAY...A SLOW-MOVING COLD FRONT WILL APPROACH FROM THE NORTH. SOUTH TO SOUTHWEST WINDS WILL PREVAIL. MONDAY...WINDS MAINLY 10 KT OR LESS WILL BE ACCOMPANIED BY 1-2 FT SEAS. TUESDAY...WINDS SHOULD INCREASE AND SEAS WILL BUILD...INTRODUCING A LOW PROBABILITY FOR SMALL CRAFT ADVISORY CONDITIONS. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 10 PM EDT THIS EVENING FOR AMZ330. && $$ |
