Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 022242 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 642 PM EDT THU JUL 2 2015 .SYNOPSIS... WEAK HIGH PRESSURE WILL BUILD TO OUR NORTH TONIGHT INTO FRIDAY AS ANOTHER WAVE OF LOW PRESSURE MOVES ALONG A STALLED FRONT TO THE SOUTH. ANOTHER AREA OF HIGH PRESSURE WILL THEN MOVE INTO THE REGION THROUGH THE HOLIDAY WEEKEND. A COLD FRONT WILL CROSS THE AREA BY WEDNESDAY. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 630 PM FORECAST UPDATE... TEMPS WERE ADJUSTED DOWNWARD SEVERAL DEGREES. IT FEELS RATHER COOL OUT THERE FOR JULY STANDARDS AS BREAKS IN THE CLOUDS NEVER DEVELOPED DURING THE DAY. THE BULK OF THE SHOWER ACTIVITY THRU SUNSET SHOULD BE CONFINED TO SE PA/C AND S NJ AND THE DELMARVA. THE COLD FRONT RESIDES SOUTH AND EAST OF THE CWA, BUT THERE IS ENOUGH LIFT ON THE COOL SIDE OF THE BOUNDARY FOR THESE SHOWERS TO CONTINUE AS OUR REGION IS POSITIONED IN THE RIGHT ENTRANCE-REGION OF AN UPPER-LEVEL JET STREAK. THERE IS ALSO A SUBTLE MID-LEVEL SHORTWAVE TROUGH SEEN ON WATER VAPOR SATELLITE THAT IS CURRENTLY MOVING THRU THE MID-ATLANTIC STATES. PREVIOUS DISCUSSION... FRONT REMAINS STALLED TO OUR SOUTH, AND WITH AN UPPER LEVEL SHORT WAVE TROUGH LIFTING NE OVER THE REGION, WE COULD CONTINUE TO SEE ISOLATED SCATTERED SHOWERS THROUGH THE DAY TIME HOURS. MODELS CONTINUE TO PAINT QPF OVERNIGHT. HOWEVER, THIS SEEMS A BIT OVERDONE AS THERE CONTINUES TO BE DRY AIR ADVECTION IN THE LOW LEVELS, NOT TO MENTION A LACK OF UPPER LEVEL SUPPORT (SAVE FOR A BRIEF PERIOD UNDER THE RIGHT REAR QUADRANT OF A WEAK UPPER LEVEL JET). MODELS HAVE BACKED OFF ON ANY MID LEVEL SHORT WAVE TROUGHS AS WELL. THEREFORE HAVE DECREASED POPS, EXCEPT IN SOUTHERN DELMARVA AS THERE CONTINUES TO BE THE CHANCE FOR SHOWER DEVELOPMENT ALONG THE FRONT. AS FAR AS FOG POTENTIAL, GIVEN THE LOW LEVEL DRY AIR ADVECTION, IT WILL BE VERY DEPENDENT FIRST ON IF AND WHEN WINDS WILL SHIFT TO MORE OF AN OFF SHORE DIRECTION. IN ADDITION, AREAS IN DELMARVA AND SOUTHERN NJ THAT HAD RAIN TODAY MAY STILL HAVE SOME STANDING WATER TONIGHT WHICH COULD HELP FOG DEVELOPMENT. FOR NOW, HAVE INCLUDED PATCHY FOG GENERALLY ALONG AND SOUTH OF A MIV TO ACY LINE. HOWEVER, WILL NOT MENTION ANY POTENTIAL FOR DENSE FOG AT THIS TIME GIVEN THE UNCERTAINTY IN THE TIMING OF THE WIND SHIFT. && .SHORT TERM /6 AM FRIDAY THROUGH 6 AM FRIDAY/... UPPER LEVEL SHORT WAVE RIDGE MOVES OVER HEAD BRINGING MOSTLY DRY CONDITIONS, ALTHOUGH STILL A FEW SHOWERS MAY DEVELOP ALONG THE OLD FRONTAL BOUNDARY AND MOVE NORTHEAST INTO OUR REGION. EVEN THOUGH THERE SHOULD BE LESS CLOUDS TOMORROW (ESPECIALLY IN THE NORTHWEST), STILL EXPECT TEMPERATURES TO BE SLIGHTLY BELOW NORMAL GIVEN THE RELATIVELY COOL AIR MASS STILL IN PLACE. && .LONG TERM /FRIDAY THROUGH THURSDAY/... FOR THE START OF THE EXTENDD PD, A STALLED FRONT WILL BE LOCATED S OF THE REGION. LOW PRES IS EXPECTED TO MOV ALG THE FRONT AND CUD TRIGGER SOME SHRA/TSRA SAT INTO SAT EVE. THE BEST CHCS ARE OVER SRN AREA. IT STILL APPEARS THAT ANY ACTIVITY SHUD BE SCT AND OVER WITH BY SUNSET OR SHORTLY THEREAFTER. SAT LOOKS TO BE THE WORST OF THE TWO WEEKEND DAYS, IF WE HAD TO PICK ONE. BY SUN, HIGH PRES BEGINS TO BUILD IN AND SUN SHUD BE DRY OVER MOST, IF NOT ALL OF THE AREA, CONTINUING INTO SUN NIGHT. THE MDLS HAVE SOME DISAGREEMENT AS WE MOVE INTO MON. THE GFS IS DRY. THE CMC IS ALSO DRY. THE ECMWF TRIES TO DEVELOP ANOTHER WAVE OF LOW PRES AND IS SUBSEQUENTLY WETTER THAN THE OTHER MDLS. RIGHT NOW, THE ECMWF IS THE OUTLIER. BUT, FELT COMPELLED TO AT LEAST INTRODUCE SOME VERY LOW POPS. HOWEVER, CONFIDENCE IS VERY LOW. THE ECMWF KEEPS THINGS WET INTO TUE WHILE THE OTHER MDLS ARE DRY. THEN, BY WED, MDLS COME INTO BETTER AGREEMENT AGAIN AS A CDFNT APPROACHES FROM THE W, PRECIP WOULD PROB LINGER INTO THU, BUT THERE IS STILL A WEEK FOR THE MDLS TO IRON OUT ANY DIFFS IN FRONTAL TIMING. WITH THE EXCEPTION OF SAT, WHICH LOOKS TO BE ON THE COOL SIDE, TEMPS SHUD BE NR OR SLIGHTLY ABV NRML THRU THE PD. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. LOW CLOUDS ARE STUBBORN TO ERODE ACROSS SOUTHERN NJ WHERE THE MOST PERSISTENT SHOWER ACTIVITY HAS BEEN THIS AFTERNOON. IFR CONDITIONS NOW LOOK TO LINGER AT MIV AND ESPECIALLY ACY THRU AT LEAST 00Z. AT MIV/ACY, CANNOT RULE OUT THE POTENTIAL FOR A BRIEF IMPROVEMENT LATER THIS EVENING ONCE RAIN MOVES OUT BUT THAT OPPURTUNITY IS LOOKING LESS AND LESS LIKELY. ELSEWHERE, MAINLY VFR CONDITIONS THRU THE EVENING. WINDS WILL BE LIGHT AND VARIABLE. AFTER 06Z, BR COULD DEVELOP, BUT THERE IS CONSIDERABLE UNCERTAINTY GIVEN DRIER AIR MOVING INTO THE REGION AND A WIND SHIFT FROM NORTHEASTERLY TO MORE NORTHERLY (WIND SHOULD REMAIN LIGHT, GENERALLY 5 KT OR LESS THROUGH THE TAF PERIOD). FOR NOW HAVE ONLY MENTIONED MVFR CONDITIONS AT KMIV, AND IFR CONDITIONS AT KACY, WHICH HAVE A HIGHER RISK GIVEN SATURATED GROUND. EXPECT TO RETURN TO VFR EVERYWHERE BY 18Z TOMORROW. THERE REMAINS A SMALL CHANCE FOR SHOWERS, BUT TOO SMALL TO MENTION IN ANY TAFS AT THIS TIME. OUTLOOK... FRI NIGHT AND SAT...GENLY VFR. HOWEVER, THERE WILL BE A CHC OF MVFR/IFR CONDS SAT AFTN/EVE IN SCT SHWRS AND PSBL TSRA. BEST CHCS ARE FOR THE SRN TAF SITES. MDT CONFIDENCE. SAT NIGHT THRU TUE...VFR CONDS EXPECTED SUN AND TUE. HIGH CONFIDENCE. LESS CERTAINTY FOR MON, DUE TO MDL DISAGREEMENT. COULD BE A BETTER CHANCE OF SHRA/TSRA, BUT CONFIDENCE IS MUCH LOWER. && .MARINE... WINDS AND SEAS SHOULD STAY BELOW SCA CRITERIA TONIGHT AND TOMORROW. OUTLOOK... FRI NIGHT THROUGH SAT...DEPENDING ON THE STRENGTH AND TRACK OF LOW PRES ALG STALLED FRONT, SCA MAY BE NEEDED, ESPECIALLY ON THE SRN WATERS. HOWEVER, LTST GUID INDICATES BOTH WIND AND SEAS WILL REMAIN BELOW SCA CRITERIA DURG THIS PD. SAT NIGHT THRU TUE...NO MARINE FLAGS ANTICIPATED DURG THIS PD. && .TIDES/COASTAL FLOODING... THE ONSHORE FLOW COMBINING WITH RATHER ROBUST SPRING TIDES FOLLOWING THE FULL MOON (WHICH OCCURRED THIS PAST WEDNESDAY) MIGHT CAUSE MINOR TIDAL FLOODING WITH THE EVENING HIGH TIDE CYCLES ON FRIDAY (THE MORE LIKELY ONE) AND SATURDAY. HOWEVER, LTST GUID INDICATES WE SHUD STAY JUST BELOW MINOR TIDAL FLOODING CRITERIA ATTM. && .RIP CURRENTS... THE COMBINATION OF AN ONSHORE FLOW AND THE FULL MOON IS EXPECTED TO INCREASE THE STRENGTH OF RIP CURRENTS ON FRIDAY AND SATURDAY, BEFORE CONDITIONS IMPROVE ON SUNDAY. WE THINK THAT ONE OR BOTH DAYS COULD REACH MODERATE RISK LEVELS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...NIERENBERG NEAR TERM...JOHNSON/KLEIN SHORT TERM...JOHNSON LONG TERM...NIERENBERG AVIATION...JOHNSON/NIERENBERG/KLEIN MARINE...JOHNSON/NIERENBERG TIDES/COASTAL FLOODING... RIP CURRENTS...

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