AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 326 PM EDT FRI JUL 8 2011 .SYNOPSIS... A STATIONARY FRONT OVER OUR AREA WILL CONTINUE TO BRING UNSETTLED WEATHER ACROSS THE REGION THROUGH TONIGHT. A WEAK LOW PRESSURE AREA WILL TRACK ALONG THE FRONT AND PASS THROUGH THE AREA TONIGHT. HIGH PRESSURE WILL BUILD INTO OUR AREA DURING SATURDAY AND BE OVER THE REGION SUNDAY AND INTO MONDAY. ANOTHER FRONT MAY BRING MORE UNSETTLED CONDITIONS TO THE REGION LATER MONDAY INTO TUESDAY. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR THE ENTIRE CWA UNTIL 900 PM. THUNDERSTORMS ARE DEVELOPING ACROSS THE AREA WITH A WIND AND HAIL THREAT BEING THE PRIMARY CONCERNS. THE FLASH FLOOD WATCH WILL ALSO CONTINUE FOR THE CENTRAL AND SOUTHERN AREAS WITH THE HIGHER PRECIPITATION RATES AND TOTALS EXPECTED IN THESE AREAS. THE URBAN AREAS WILL BE MOST SUSCEPTIBLE TO FLOODING...ESPECIALLY ALONG THE I-95 CORRIDOR. RATES OF ONE TO TWO INCHES PER HOUR MAY OCCUR. PATCHY FOG WILL DEVELOP LATE TONIGHT ONCE THE RAINS END AND SKY COVER BEGINS TO BREAK UP A BIT. FOG WAS NOT INCLUDED IN THE GRIDS ATTM...SINCE THERE IS ALREADY PLENTY OF WORDINESS WITH THE SVR/FLOOD WORDING ALREADY IN THERE. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... THE LAST OF THE CLOUDS AND SCATTERED SHOWERS ASSOCIATED WITH THE FRONT AND LOW PRESSURE AREAS FROM THE NEAR TERM WILL BE PASSING OFF THE COAST SAT MORNING. LOW CHC POPS AND A FEW CLOUDS ARE STILL IN THE GRIDS FOR THE MORNING AREAS ACROSS ERN DELAWARE AND THE SRN COASTAL WATERS. HIGH PRESSURE WILL BUILD IN SAT AND REMAIN INTO MONDAY. A DRY FORECAST IS EXPECTED WITH MAINLY CLR SKIES. TEMPERATURES WILL STILL BE VERY WARM...BUT THE LOWER HUMIDITY VALUES WILL MAKE THINGS COMFORTABLE. SAT NIGHT WILL BE COOL WITH LOWS IN 50S ACROSS THE NORTHERN AREAS AND LOW TO MID 60S IN MOST OTHER AREAS. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... THE MODELS HAVE BEEN PRETTY CONSISTENT THAT THE FLAT HEAT RIDGE OVER THE EASTERN CONUS WILL RETROGRADE SLIGHTLY TO THE SOUTHWEST. AFTER THE 500MB TROF PASSES, A CANADIAN HIGH PRESSURE SYSTEM WILL BUILD INTO THE NORTHEASTERN CONUS. THERE REMAINS DIFFERENCES AS TO HOW ROBUST THE CONVECTION WILL BE WITH THE COLD FRONTAL PASSAGE MONDAY NIGHT INTO TUESDAY. TODAY THE TIMING LOOKS SLIGHTLY BETTER FOR A MORE ACTIVE TUESDAY. WE OPTED FOR POPS CLOSER TO THE GFS VS WHAT WOULD BE INFERRED USING THE ECMWF. AFTER THE FRONT CLEARS THE REGION, OUR CWA SHOULD HAVE A COUPLE OF DAYS WITH QUITE PLEASANT DEW POINTS. THERE ARE DIFFERENCES AS TO HOW COOL IT WILL GET, ALTHOUGH THE GAPS ARE SMALLER THAN YESTERDAY. BASED ON HOW ABOVE NORMAL THIS METEOROLOGICAL SUMMER HAS BEEN SO FAR, WE HAVE OPTED TO KEEP MAX TEMPS TOWARD THE WARMER END OF THE ENSEMBLE MEMBERS THROUGHOUT THE LONG TERM. REGARDLESS AFTER A HOT AND HUMID TUESDAY, LOWER TEMPERATURES ARE IN STORE, ESPECIALLY AT NIGHT, FOR THE REST OF THE LONG TERM PERIOD. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. REST OF THIS AFTERNOON...18Z TAFS POSTED FOR BEST CHANCE OF STRONGEST WIND AND IFR CONDS THIS AFTERNOON. WILL UPDATE TAFS AS ANY STRONGER STORMS APPROACH. SEVERE THUNDERSTORM WATCH NUMBER 610 THROUGH 01Z FOR THE ENTIRE PHILADELPHIA TAF AREA IS NOW POSTING AS OF THIS WRITING AT 148 PM. SHOWERS/THUNDERSTORMS...ARE DEVELOPING AND WILL CONCENTRATE THEIR ENERGY EVENTUALLY IN S CENTRAL NJ AND SE PA AROUND 20Z-24Z. SEVERAL STORMS ARE EXPECTED TO PRODUCE BRIEF IFR/LIFR CONDS IN 1/2SM +T+SHRA WLY G50 KT WITH SREF RELATIVELY HIGH PROBS FOR SVR/SUPERCELLS AND POSSIBLY A TOR IN OUR CWA THIS AFTN. WHETHER THEY GO OVER THE TAF LOCATIONS IS UNKNOWN. TONIGHT...MVFR OR IFR CIGS SPREAD S BEHIND THE FRONT WITH HEAVY CONVECTION BECOMING CONCENTRATED FROM KPHL-KACY SOUTHWARD AND EVENTUALLY DRIFTING OFFSHORE TOWARD 07Z. OUTLOOK... SATURDAY...IFR STRATUS IS POSSIBLE ALONG AND SOUTH OF A KILG-KACY LINE THROUGH ABOUT 1400 UTC. AFTER THE SURFACE LOW PULLS AWAY...THE LOW LEVEL INVERSION SHOULD BREAK...AND VFR CONDITIONS ARE EXPECTED EVERYWHERE FOR THE REMAINDER OF THE DAY. CONVECTIVE TEMPERATURES COULD BE MET IN THE AFTERNOON...WHICH SHOULD RESULT IN SCATTERED CUMULUS. HOWEVER...INCREASING STABILITY SHOULD LIMITED ANY CONVECTIVE POTENTIAL. SAT NIGHT AND SUNDAY...WEAK HIGH PRESSURE BUILDING INTO THE REGION SHOULD RESULT IN VFR CONDITIONS. SUN NIGHT...VFR TO START BUT WAA MVFR CIGS MAY DEVELOP IN E PA LATE. MONDAY...WARM AIR ADVECTION AHEAD OF A FRONTAL BOUNDARY COULD MEAN SCATTERED THUNDERSTORMS LATE MONDAY OR MONDAY NIGHT...BUT OVERALL VFR CONDITIONS ARE EXPECTED. && .MARINE... NO HEADLINES EXCEPT THE SEVERE THUNDERSTORM WATCH 610 THROUGH 01Z POSTING AS OF AROUND 148 PM. THE STATIONARY FRONT STRETCHED ACROSS THE NORTHERN OCEAN WATERS THIS MORNING...WITH THE REMAINDER OF THE WATERS REMAINS IN THE SOUTH SOUTHWEST FLOW ON THE WARM SIDE OF THE FRONT. FOR THE MOST PART A 3 FOOT SOUTHERLY SHORT PERIOD SWELL CONTINUES ON THE WATERS. AS THE FRONT OOZES SOUTH TODAY...MORE OF THE OCEAN WATERS ADJACENT TO THE NEW JERSEY COAST WILL SEE WINDS BECOMES POST FRONTAL...AND SHOULD REMAIN BELOW 15 KNOTS. SOUTH OF THE FRONT...THE SOUTH SOUTHWEST FLOW SHOULD GENERALLY REMAIN BELOW 15 KNOTS INTO THIS EVENING. THE MAIN FORECAST PROBLEM COMES LATER TONIGHT AND SATURDAY MORNING. ALL SHORT RANGE MODELS SHOW A WAVE DEVELOPING ON THE FRONT LATE TONIGHT AND MOVING OFF THE NEW JERSEY AND DELAWARE COASTS SATURDAY MORNING. THE 0000 UTC NAM CONTINUES THE TREND THE NAM HAS SHOWN FOR THREE DAYS...AND DEEPENS THE SYSTEM SATURDAY. THE 0000 UTC NAM SOLUTION WOULD RESULT IN STRONG SMALL CRAFT NORTHEAST WINDS (WITH NEAR GALE GUSTS) FOR THE SOUTHERN OCEAN WATERS. THE MODEL CONSENSUS (EXCLUDING THE 0000 UTC NAM) SHOWS A MUCH WEAKER SOLUTION...AND THIS SEEMS TO BE MORE IN LINE WITH LOCAL EXPECTATIONS. WITH THAT IN MIND...WHILE IT WOULD APPEAR AS THOUGH GUSTS TO 20 KNOTS ARE POSSIBLE LATER TONIGHT AND SATURDAY MORNING ACROSS THE SOUTHERN OCEAN WATERS...SMALL CRAFT WINDS APPEAR UNLIKELY. HOWEVER...THE SEAS COULD BE A DIFFERENT MATTER. THE LATEST WNAWAVE GUIDANCE HAS BACKED OFF A TAD WITH REGARD TO SEAS...AND WOULD KEEP ALL OF OUR OCEAN WATERS BELOW 5 FEET LATE TONIGHT AND SATURDAY MORNING. FOR NOW...THIS SOLUTION IS ACCEPTED...AND WE WILL HOLD OFF ON ISSUING A SMALL CRAFT ADVISORY. IF LATER GUIDANCE SUGGEST SEAS WILL BE HIGHER...A SMALL CRAFT ADVISORY FOR THE OCEAN FOR SEAS COULD BE ISSUED LATER TODAY. AFTER THE LOW PULLS AWAY LATE SATURDAY MORNING...WINDS SHOULD DROP BELOW 15 KNOTS. AS WEAK HIGH PRESSURE BUILDS IN FROM THE WEST...THE GRADIENT COULD DROP OFF ENOUGH TO ALLOW LOCAL SEA AND BAY BREEZES TO DEVELOP IN THE MID TO LATE AFTERNOON. AS THE HIGH BUILDS OFF THE MID ATLANTIC COAST SATURDAY NIGHT INTO SUNDAY NIGHT...WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT LEVELS. THE RETURN FLOW AROUND THE HIGH COULD RESULT IN WINDS AND SEAS INCREASING MONDAY INTO TUESDAY. THERE IS A CHANCE FOR WINDS TO GUST TO 25 KNOTS DURING THIS TIME...BUT CONFIDENCE IN THIS IS LOW FOR NOW. && .EQUIPMENT... NWR LEWES IS BACK ON THE AIR. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR PAZ067>071. NJ...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR NJZ009-010-012>027. DE...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR DEZ001>004. MD...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR MDZ008-012-015-019- 020. MARINE...NONE. && $$ SYNOPSIS...O`HARA