AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 120 AM EST SUN FEB 5 2012 .SYNOPSIS... LOW PRESSURE TRACKS EAST ACROSS NORTH CAROLINA TONIGHT...THEN MOVES OFF THE COAST SUNDAY. WEAK HIGH PRESSURE BUILDS INTO THE AREA FROM THE NORTH SUNDAY NIGHT AND MONDAY. LOW PRESSURE MOVES NORTHEAST ALONG THE CAROLINA COAST MONDAY NIGHT. A COLD FRONT MOVES ACROSS THE AREA TUESDAY NIGHT. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... UPDATE...THE WARM FRONT HAS BEEN PUSHED SOUTHWARD AS A LONGWAVE TROUGH (AND ASSOCIATED SHORTWAVE) BEGINS TO SWING INTO THE NORTHEAST CONUS FROM THE EASTERN GREAT LAKES AND AS SURFACE HIGH PRESSURE CREATES A WEDGE OVER THE APPALACHIANS. PRECIPITATION COVERAGE HAS BEEN ALTERED FOR THE REMAINDER OF TONIGHT THROUGH SUNDAY AS BULK OF PRECIP SLIDES SOUTH WITH THE WARM FRONT. SNOW WAS OBSERVED EARLIER THIS EVENING ALONG INTERSTATE 81 CORRIDOR IN NORTHERN VIRGINIA/MARYLAND. HOWEVER LATEST WEATHER ANALYSIS SUGGESTS THAT DENDRITIC GROWTH ZONE (DGZ) WILL REMAIN TOO HIGH THROUGH TONIGHT (AROUND 500 MB)...DESPITE WET BULB ZERO HEIGHTS FALLING TOWARD THE SURFACE BY MORNING OVER EXTREME NORTHERN PORTIONS OF FA. NAM12/RUC80 00Z MODEL RUNS DO SUGGEST THAT THICKNESS HEIGHTS ALSO FALL OVERNIGHT...BUT WILL KEEP MIXED PRECIP OUT OF THE FORECAST BASED ON LOCATION OF THE DGZ. PREVIOUS DISCUSSION (313 PM EST)...MODELS IN AGREEMENT FOR A RATHER WET NIGHT AHEAD AS LOW PRESSURE MOVES EAST ACROSS NC. ASSOCIATED WARM FRONT PROGGED TO SET UP INVOF THE NC/VA BORDER THIS EVENING BEFORE MOVING SOUTH INTO NC. BEST LIFT AND SUPPORT FOR WDSPRD PCPN ACROSS THE SOUTH WHERE HEAVIEST QPF WILL BE (1/2 TO 1 INCH). NE WINDS ACROSS THE NORTH SETS UP AN INSITU WEDGE SCENARIO WITH A COLD RAIN (1/3 TO 1/2 INCH). ADDED SOME MDT RAIN TO THE GRIDS ALONG AND SOUTH OF THE BOUNDARY. POPS 100 PERCENT ALL AREAS. TEMPS DROP INTO THE M-U30S ACROSS NRN COUNTIES (CRITICAL THICKNESS VALUES STAY WARM ENOUGH FOR ALL RAIN)...40-45 ACROSS 40 HALF OF FA. && .SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY/... SUPPORT FOR RAIN CONTINUES ACROSS THE SOUTHERN COUNTIES SUNDAY MORNING THEN SHIFTS OFFSHORE DURING THE AFTERNOON. MODELS THEN DIFFER A BIT ON JUST HOW FAST HIGH PRESSURE TO THE NORTH BEGINS TO DRY OUT COLUMN. GIVEN A NORTHERLY FLOW AND LINGERING LOW LEVEL MOISTURE IN TSCTNS THRU MID AFTERNOON...WILL KEEP LIGHT RAIN AND DRIZZLE IN FORECAST FOR NOW...ALTHOUGH IT MAY END BY LATE IN THE DAY ACROSS THE NORTHERN COUNTIES. TEMPS STEADY IN THE 40S THEN SLOWLY FALLING OFF BY LATE IN THE DAY. DESPITE FALLING THICKNESSES DURING THE AFTERNOON...PRECIP WILL BE TOO LIGHT AND MAY EVEN END BEFORE ENOUGH COLD AIR MOVES IN FOR ANY P-TYPE ISSUES. LATEST MODELS KEEP ENOUGH MOISTURE LINGERING ACROSS NE NC A LOW CHC POP THROUGH 00Z MON. OTW...TSCTNS SHOW A DRYING COLUMN WITH DECREASING CLOUDINESS SUNDAY NIGHT. LOWS 30-35...U30S ACROSS SERN COASTAL AREAS. WEAK HIGH PRESSURE BUILDS INTO RGN EARLY MONDAY...BUT A S/W TROF MOVES ACROSS THE AREA MONDAY AFTRN THAT ACTUALLY SPAWNS A SFC LOW TO DEVELOP OFF THE CAROLINA COAST LATER MON THEN MOVE IT NE ALONG THE GULF STREAM WALL MONDAY NIGHT. THE MODELS DIFFER ON JUST HOW FAR NORTH ANY MOISTURE GETS. 12Z EURO ACTUALLY THROWS PCPN BACK AS FAR WEST AS RIC. GIVEN THE UNCERTAINTY...HAVE ADDED SLIGHT CHC SHWRS TO NE NC MONDAY AFTERNOON AND CHC SHWRS TO SERN VA/NE NC MONDAY EVENING. SYSTEM MOVES FURTHER OFFSHORE LATER MONDAY NIGHT. HIGHS MONDAY 50-55. LOWS MONDAY NITE IN THE 30S. DRY TUESDAY AS WEAK HIGH PRESSURE MOVES OVER THE AREA AHEAD OF NEXT COLD FRONT APPROACHING FROM THE NW. HIGHS IN THE 50S. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... LATEST SUITE OF MODELS ARE NOW IN BETTER AGREEMENT W/ THE EXTENDED TIMEFRAME. THEY ALL SHOW THE DEVELOPMENT OF A +PNA PATTERN...WITH RIDGING OVER THE WESTERN CONUS EXTENDING WELL UP INTO NW CANADA. THIS WILL DRIVE COLD AIR THAT HAD BEEN IN PLACE FOR MUCH OF THE WINTER SEASON OVER ALASKA/NW CANADA INTO ERN CANADA. HOWEVER...WITHOUT DOWNSTREAM RIDGING TOO FAR OFF TO THE EAST (GENLY STAYING E OF GREENLAND)...BULK OF THE COLD AIR WILL REMAIN NORTH OF THE MID ATLC THROUGH THE EXTENDED PERIOD (I.E. NO -NAO). THIS WOULD SUPPORT ONLY A MODEST COOL-DOWN GOING INTO NEXT WEEKEND. WED WILL FEATURE HIGH PRESSURE TO OUR NORTH...EXTENDING FROM THE GREAT LAKES EAST INTO NY STATE...GRADUALLY MOVING OFF INTO NEW ENGLAND WED NIGHT/THU...NOSING SOUTHWARD INTO THE MID ATLC. WITH WEAK MID LEVEL SHORTWAVE ENERGY APPROACHING FROM THE WSW AND BRUSHING THE CWA LATE WED/WED NIGHT...WILL CARRY 20-30% CHANCE FOR -RA ALL ZONES (HIGHEST NORTH). STAYED ON COOL SIDE OF GUIDANCE GIVEN THE SYNOPTIC SETUP FOR AT LEAST WEAK CAD...HIGHS MAINLY 45-50 NW...TO THE MID 50S SE. AFTER THAT...KEPT THE REST OF PERIOD DRY AS POLAR VORTEX AND MAIN UPR TROUGH REMAIN TO OUR NORTH. HIGHS STAY NEAR OR SLIGHTLY ABOVE AVG THU-FRI (HIGHS IN UPR 40S TO MID 50S)...COOLING A FEW DEGREES BY SAT 40S TO LOWER 50S FAR SE). && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... WIDESPREAD IFR CONDITIONS SHOULD CONTINUE OVERNIGHT WITH PERIODS OF LIGHT RAIN AND DRIZZLE CONTINUING MAINLY SOUTH OF RIC. A SLOW IMPROVEMENT IS EXPECTED N-S BEGINNING EARLY THIS MORNING. IFR CONDITIONS SHOULD END FIRST AT SBY AROUND 10Z...AND LINGER TOWARD MIDDAY FOR ORF/ECG. BY AFTERNOON CEILINGS SHOULD CONTINUE TO LIFT...BUT REMAIN MVFR FOR SE LOCATIONS. HIGH PRESSURE BUILDS IN BY TONIGHT WITH CLEARING NORTH AND SCT MID-CLOUDS SOUTH. A LIGHT NNE WIND SHOULD PREVAIL THROUGH EARLY MORNING AND INCREASE TO 8-12KT DURING THE DAY...BEFORE BECOMING LIGHT TONIGHT. A QUICK MOVING LOW PRESSURE SYSTEM OFF THE COAST MAY BRING A PERIOD OF RAIN AND LOWER CEILINGS TO ORF/ECG MONDAY NIGHT. ANOTHER SYSTEM PASSES NORTH OF THE REGION AROUND WEDNESDAY/WEDNESDAY NIGHT. HOWEVER...DRY AND VFR CONDITIONS SHOULD PREVAIL MOST OF THE WEEK. && .MARINE... A WEAK FRONTAL BOUNDARY IS SITUATED ACRS NRN ZONES CURRENTLY...AND WILL SLOWLY DROP N-S ACROSS THE AREA THIS EVENING AND OVERNIGHT. LOW PRESSURE TRACKS ALONG THIS BOUNDARY AND OFF THE COAST SUNDAY...AND DEEPENS WHILE IT DOES SO. THE PRESSURE GRADIENT BRIEFLY TIGHTENS SUNDAY IN THE WAKE OF THE LOW. NAM/WRF BASED GUIDANCE REMAINS STRONGEST ON THE WIND WHILE THE GFS/NON-WRF BASED GUIDANCE GENERALLY SUGGESTS SUB-SCA CONDITIONS. WHILE IT APPEARS MARGINAL...OPTED TO RAISE SCA HEADLINES FOR MOST OF THE MARINE AREA FOR 15-20 KT WINDS AND/OR SEAS BUILDING TO 5 FT. THINKING IS THAT GENLY THE NNE DIRECTION DOES NOT TAKE MUCH TO BUILD SEAS TO 5 FT. ON THE BAY AND SOUND...ONLY NEED 15-20 KT FOR SCA HEADLINES AND THIS APPEARS LIKELY AT LEAST FOR A 3-6 HR PERIOD SOMETIME SUNDAY. SUN NIGHT/MON...END THE HEADLINES DURING THE EVENING EXCEPT KEPT IT GOING INTO EARLY MON AM FOR NC WATERS WHERE GRADIENT STAYS STRONGER CLOSEST TO THE DEPARTING SFC LOW. ALSO..MODELS HAVE TRENDED A BIT STRONGER ON A SECOND WAVE OF LOW PRESSURE MON NIGHT/TUE AM OFF THE NC COAST. BUMPED SEAS UP TO 4 FT FOR THIS ACRS SRN CSTL WATERS...BUT WOULD NOT BE SURPRISED TO SEE ANOTHER SCA NEEDED FOR THE SOUTH. STRONG HIGH PRESSURE APPROACHES FROM THE NW ON TUE...ALTHOUGH WINDS GENLY STAY 15 KT OR LESS...WITH SOME INCREASE POSSIBLE BY TUE NIGHT. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 7 AM THIS MORNING TO 10 PM EST THIS EVENING FOR ANZ631-632-634-650-652-654-656. SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 1 AM EST MONDAY FOR ANZ633-658. && $$ SYNOPSIS...MPR