Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 281757 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 157 PM EDT THU MAY 28 2015 .SYNOPSIS... A COLD FRONT WILL MOVE ACROSS THE AREA LATE TODAY. HIGH PRESSURE REESTABLISHES ITSELF OFF THE EAST COAST FRIDAY INTO SATURDAY. A COLD FRONT IS FORECAST TO MOVE SLOWLY SOUTHEAST ACROSS THE AREA SATURDAY NIGHT OR SUNDAY. HIGH PRESSURE WILL RETURN TO THE NORTHEAST EARLY NEXT WEEK WHILE THE FRONTAL BOUNDARY STALLS TO OUR SOUTH. && .NEAR TERM /THROUGH TONIGHT/... 145 PM ESTF: WATCH SHOWERS AND TSTMS POP NOW WEST OF PHL AND SINCE 1 PM VCNTY KBLM/KMJX. 1230 PM ESTF: LITTLE CHANGE TO THE MID MORNING UPDATES EXCEPT THE SVR WATCH 233 WORDING FOR NNJ. DRY AIR OVERCOMES POTENTIAL INSTABILITY IN THE POCONOS BY 2 PM AND SO THEN, HOW FAR SOUTH AND WEST DO TSTMS DEVELOP THIS AFTERNOON. FOR NOW...WE THINK THE MOST WIDESPREAD ACTIVITY WILL BE NNJ...ALONG AND N OF I78, BUT THIS IS ADJUSTABLE BASED ON REALITY. 830 AM ESTF UPDATE: MORE CLOUD COVER THIS MORNING, RAISED TEMPS 2 DEGS THIS AFTN AND INCLUDES 90 PHL. FOR PNE THIS WOULD BE A HEAT WAVE SO PARTS OF OUR AREA HAVE BEEN FLIRTING WITH 90F SINCE MEMORIAL DAY. SEE NO REASON THAT IT IS ANY COOLER TODAY THAN YDY, ESPECIALLY WITH THE COLD FRONT STILL NEAR KIPT. ADDED HEAVY RAIN TO PORTIONS OF THE FCST AREA THIS AFTERNOON, ESPECIALLY DELAWARE RIVER EAST. PWAT A BIT LESS THAN YDY. PROBABLY CLOSE TO 1.5 THIS AFTN. STILL PLENTY FOR FOR BRIEF TORRENTIAL SHOWERS. DECENT MODELED MLCAPE OF 1000+J. SHEAR MARGINAL BUT NOT IMPOSSIBLE FOR 1 OR 2 SVR STORMS, ESP MORE FAVORABLE 0-6KM SPEED SHEAR REGION OF NNJ AS PER CONTINUED 1240Z SPC D1 OUTLOOK. TONIGHT... THERE COULD BE LEFTOVER SHOWERS AND ISOLATED TSTMS AFTER 6 PM, ESPECIALLY COASTAL NJ. WIND SHIFTS FROM WEST TO LIGHT NNE. THERE MAY BE SOME PATCHY FOG/ST OVERNIGHT IN THE FRONTAL BOUNDARY WITH CONFIDENCE FOR FOG/STRATUS FORMATION BELOW AVG. WILL INSERT PATCHY FOG INTO THE WEATHER USING THE UPS CROSSOVER TOOL. OTHERWISE A FAIR NIGHT AND MAYBE A FEW DEGREES COOLER UP NORTH DUE TO DRIER ALOFT NOW FILTERING IN AS SEEN VIA THE KMSV 7F DEWPOINT DROP IN 1 HR AT 17Z. FCST TEMPS ARE BASED ON THE WARMER 12Z/28 NAM MOS AND ALL OTHER GUIDANCE IS DERIVED OFF A 50 50 BLEND OF THE 12Z/28 GFS/NAM MOS. && .SHORT TERM /FRIDAY/... A NICER DAY WITH LOWER DEWPOINTS...AN IDEAL SUMMER DAY KPHL NORTHEASTWARD...WARM BUT RELATIVELY COMFORTABLE WITH LIGHT EAST WINDS TURNING SE OR S DURING THE AFTERNOON. COOLER COASTS DUE TO THE UPWELLED COOLER OCEAN WATERS, ESPECIALLY NNJ. WE HAVE POPS IN DURING THE MORNING DELMARVA AND SPREADING NWD THRU E PA IN THE AFTN BUT CONFIDENCE IS BELOW AVG. IT SHOULD BE RAINFREE MOST OF OUR FORECAST AREA ON FRIDAY. FCST TEMPS BASED ON THE WARMER OF THE AVBL 12Z/28 NCEP GUIDANCE. REMAINDER OF THE ELEMENTS DERIVED FROM THE 12Z/28 50 50 BLENDED GFS/NAM MOS. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... HIGH PRESSURE IS FORECAST TO REESTABLISH ITSELF ACROSS THE ATLANTIC ON FRIDAY, WITH OUR AREA ON THE WESTERN EDGE, WHILE THE RIDGE ALOFT BUILDS TO OUR EAST AS WELL. THIS SHOULD HELP KEEP THE WEATHER MOSTLY DRY INTO FRIDAY. HOWEVER, WITH RETURN FLOW ACROSS THE AREA, INSTABILITY IS FORECAST TO DEVELOP ACROSS THE THE AREA, ESPECIALLY FOR WESTERN AREAS. THIS DAYTIME INSTABILITY COULD LEAD TO A FEW ISOLATED SHOWERS/THUNDERSTORMS WITH ANY VORTICITY IMPULSE THAT MOVES ACROSS THE WESTERN EDGE OF THE RIDGE. THE SURFACE HIGH AND RIDGING ALOFT PUSH EASTWARD SLIGHTLY SATURDAY, WITH SOUTHWEST FLOW AT THE SURFACE ALOFT DEVELOPING. THIS WILL ALLOW FOR A COUPLE OF SHORT WAVE/VORTICITY IMPULSES TO MOVE ACROSS THE AREA LATE SATURDAY WHILE DAYTIME INSTABILITY DEVELOPS AS WELL. AN INCREASE IN SHOWER/THUNDERSTORM ACTIVITY IS POSSIBLE, ESPECIALLY FOR THE WESTERN PORTIONS OF THE AREA. A COLD FRONT IS THEN FORECAST TO MOVE ACROSS THE AREA SATURDAY NIGHT INTO SUNDAY. THE LATEST GFS AND ECMWF HAVE PRETTY GOOD AGREEMENT WITH THE TIMING OF THE PRECIPITATION. BOTH AGREE THAT SUNDAY LOOKS TO BE THE PERIOD WITH HIGHEST PROBABILITY FOR PRECIPITATION AS THE FRONT MOVES ACROSS AND SOUTH OF THE AREA. PW VALUES INCREASE TO NEAR 2 INCHES, SO THERE COULD BE A PERIOD OF HEAVY RAINFALL WITH ANY SHOWERS THAT DEVELOP DURING THE TIME PERIOD. THERE REMAINS INSTABILITY FORECAST AHEAD OF THE FRONT, SO WE WILL KEEP THUNDERSTORMS IN THE FORECAST, BUT ONCE THE FRONT PASSES, THUNDERSTORM POTENTIAL DECREASES. HIGH PRESSURE RETURNS TO THE NORTHEAST EARLY NEXT WEEK AS THE FRONTAL BOUNDARY PUSHES SOUTH AND LIKELY STALLS JUST SOUTH OF OUR AREA. WITH THE HIGH TO OUR NORTHEAST, THIS WILL KEEP EASTERLY FLOW ACROSS THE AREA. SOUTHWEST-WESTERLY FLOW ALOFT WILL REMAIN ACROSS THE AREA AS WELL. SEVERAL SHORT WAVE/VORTICITY IMPULSES WILL LIKELY MOVE ACROSS THE AREA EARLY NEXT WEEK, WHICH COULD HELP CREATE PRECIPITATION ACROSS THE AREA. WITH THE EASTERLY FLOW ACROSS THE AREA, THE ATMOSPHERE SHOULD BE STABLE, SO WE HAVE REMOVED THUNDERSTORMS FROM THE FORECAST MONDAY AND TUESDAY DUE TO LACK OF INSTABILITY. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. REMAINDER OF THIS AFTERNOON...VFR SCT-BKN AOA 5000 FT WITH BRIEF IFR CONDS AND WNW WIND GUST 28-38KT IN SCT-BKN SHOWERS/TSTMS DEVELOPING NOW, MAINLY IN NJ. PLEASE SEE TAFS FOR DETAILS ON TIMING ANY SHOWERS/TSTMS THIS AFTERNOON. CFP POCONOS KABE/KRDG ROUGHLY 21Z- 24Z TODAY. CONFIDENCE ON TSTM COVERAGE AND TIMING IS LESS THAN IDEAL. TONIGHT...CFP OCCURS ELSEWHERE WITH WIND SHIFTING TO LIGHT N AND THEN NE. IFR ST/FOG MAY FORM IN THE FRONTAL ZONE OVERNIGHT OTRW PREDICTING GENERALLY VFR. CONFIDENCE: BELOW AVERAGE DUE TO THE UNCERTAINTY REGARDING THE FORMATION OF IFR ST/FOG OVERNIGHT. FRIDAY...VFR WITH ANY LEFTOVER IFR DISSIPATING BY 14Z AND THEN SCT-BKN CLOUDS AOA 4000 FT DURING THE AFTN. LIGHT E WIND DURING THE MORNING BECOMING SE TO S DURING THE AFTERNOON. ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE FOR KILG AND KRDG DURING THE AFTN CONFIDENCE: AVERAGE. OUTLOOK... FRIDAY NIGHT...VFR EARLY, THEN LOWERING CIGS/VSBYS WITH STRATUS/FOG POSSIBLE OVERNIGHT. SATURDAY...LOWER CONDITIONS POSSIBLE EARLY, THEN BECOMING VFR DURING THE DAY. SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE WHICH MAY LOCALLY REDUCE CIGS/VSBYS. GUSTY SOUTH-SOUTHWEST WINDS AROUND 20 KNOTS. SATURDAY NIGHT-MONDAY...AN EXTENDED PERIOD OF MVFR/IFR CONDITIONS POSSIBLE. A CHANCE OF RAIN EACH DAY. BEST POTENTIAL FOR THUNDERSTORMS IS SUNDAY. && .MARINE... OTHER THAN GUSTY WINDS NEAR ANY TSTMS THIS AFTERNOON AND EVENING, WE DO NOT ANTICIPATE SCA CONDITIONS THROUGH TONIGHT. SLY FLOW TODAY SHOULD TURN NE ALONG THE NNE WATERS TONIGHT. STRONGEST TSTM ACTIVITY SHOULD BE MONMOUTH AND NORTHERN OCEAN COUNTIES IN THE 4P-630P TIME FRAME WHERE AN SMW MAY BE NEEDED? OUTLOOK... FRIDAY-FRIDAY NIGHT...SUB-SMALL CRAFT ADVISORY CONDITIONS CURRENTLY EXPECTED, ALTHOUGH WINDS MAY GUST AROUND 20 KNOTS AT TIMES. SATURDAY-MONDAY...SEAS MAY RETURN TO 5 FEET OR GREATER LATE ON SATURDAY AHEAD AHEAD OF AN APPROACHING COLD FRONT. SEAS MAY REMAIN ELEVATED INTO MONDAY, AND WINDS MAY INCREASE TO 25 KNOTS. && .RIP CURRENTS... NEW WEBLINK, WORKS BEST ON FIREFOX. DISPLAYS THE FCST GRAPHIC ETC. WWW.WEATHER.GOV/PHI/SURFRIP4 LOW RISK CONTINUES THROUGH FRIDAY. SUBSTANTIAL UPWELLING OCCURRED YESTERDAY WITH THE SOUTHERLY FLOW, ESPECIALLY NNJ WATERS WHERE 44065 WATER TEMP DROPPED ALMOST 9 DEGREES IN 24 HRS DOWN INTO THE UPPER 40S EARLIER THIS MORNING. CHILLY TO SWIM MOST OF CENTRAL AND NNJ BEACHES DESPITE WELL ABOVE NORMAL LAND TEMPS. && .CLIMATE... MAY 2015...A TOP 5 WARMEST ON RECORD FOR LARGE PORTIONS OF OUR AREA. CONSERVATIVE VALUES LISTED BELOW FROM OUR 5 AM SFT AND COOLING THE NEAR MIDNIGHT SUNDAY NIGHT MAY 31 LOW TEMP DUE TO NLY FLOW CAA SUNDAY EVENING. ALLENTOWN WILL PROBABLY AVERAGE VERY CLOSE TO 65.9 OR 6 DEGREES ABOVE NORMAL. POR BACK TO 1922. AT LEAST 5TH WARMEST ON RECORD. 1991 67.2 2012 66.1 1944 66.0 2004 65.9 PHILADELPHIA WILL PROBABLY AVERAGE CLOSE TO 69.7 DEGREES OR 5.8 DEGREES ABOVE NORMAL. SECOND WARMEST ON RECORD. 1991 70.8 NUMBER 3 WOULD BE 69.2 IN 2004. ATLANTIC CITY MAY 2015 65.9 OR 4.8 ABOVE NORMAL AND PROBABLE #3 POR BACK TO 1874 2004 66.9 1991 66.0 2015 WILMINGTON DE SOLID POR BACK TO 1916 LOCKED INTO #4 WARMEST 1896 70.1 1991 69.1 2004 68.2 2015 NO AVAILABLE MONTHLY HISTORICAL DATA FOR KMPO KGED KTTN AND KRDG. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...ROBERTSON/DRAG 156P NEAR TERM...DRAG 156P SHORT TERM...DRAG 156P LONG TERM...ROBERTSON AVIATION...DRAG/ROBERTSON 156P MARINE...DRAG/ROBERTSON 156P RIP CURRENTS...156P CLIMATE...156P

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