Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 272156 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 556 PM EDT WED MAY 27 2015 .SYNOPSIS... HIGH PRESSURE REMAINS OFF THE COAST AND A COLD FRONT WILL MOVE ACROSS THE AREA THURSDAY INTO THURSDAY NIGHT. HIGH PRESSURE REESTABLISHES ITSELF OFF THE EAST COAST FRIDAY INTO SATURDAY. A COLD FRONT IS FORECAST TO MOVE ACROSS THE AREA SATURDAY NIGHT INTO SUNDAY. HIGH PRESSURE WILL RETURN TO THE NORTHEAST EARLY NEXT WEEK WHILE THE FRONT STALLS TO THE SOUTH. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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5:50 PM UPDATE...CANCELLED THE SEVERE THUNDERSTORM WATCH FOR MUCH OF THE AREA. THIS IS FOR AREAS WEST OF THE CONVECTION AND ALSO THE DELMARVA. MUCH OF THE COASTAL COUNTIES WERE ALSO DROPPED FROM THE WATCH DUE TO THE STABILIZING INFLUENCE FROM THE OCEAN. OTHERWISE, AN AREA OF HIGH PRESSURE REMAINS OFF THE EAST COAST AT LATE-DAY, WITH AN ASSOCIATED UPPER RIDGE EXTENDING NEAR OUR REGION AND OUT OVER THE ATLANTIC WATERS. MEANWHILE TO OUR WEST, AN UPPER TROUGH AND ASSOCIATED SURFACE COLD FRONT EXTEND OVER THE GREAT LAKES TO MIDWEST STATES. THERE ALSO LOOKS TO BE A LEAD UPPER SHORTWAVE TROUGH MOVING INTO OUR REGION AS WELL AS A WEAK LEE-SIDE SURFACE TROUGH ALONG THE APPALACHIANS TO OUR WEST, HELPING TO CONTRIBUTE SOME ATMOSPHERIC LIFT FOR SCATTERED CONVECTION. LAPS DATA SHOWED THAT SUFFICIENT DESTABILIZATION OCCURRED, WITH SURFACE-BASED CAPE VALUES RANGING MOSTLY BETWEEN 1000 TO 1500 J/KG ACROSS MOST OF THE FORECAST AREA, EXCEPT ALONG THE COAST. IN ADDITION, MODEST SHEAR EXISTS ALONG WITH AMPLE LOW-LEVEL MOISTURE, WITH DEW POINTS INTO THE UPPER 60S AND EVEN LOW 70S ACROSS THE FORECAST AREA. WITH THESE FACTORS IN MIND, WE WILL CONTINUE TO SEE A BROKEN LINE OF SCATTERED SHOWER AND THUNDERSTORM ACTIVITY GRADUALLY PROGRESSING EASTWARD ACROSS THE FORECAST AREA THROUGH THE REST OF LATE-DAY AND INTO THIS EVENING. ALONG WITH DOWNPOURS, THE MAIN CONCERN WITH ANY STRONGER TO SEVERE STORMS WOULD BE GUSTY TO LOCALLY DAMAGING STRAIGHT-LINE WINDS. A WARM AND MUGGY OVERNIGHT IS EXPECTED, AND WE USED A BLEND OF MET/MAV GUIDANCE FOR MINIMUM TEMPERATURES. OVERNIGHT LOWS WILL MAINLY BE IN THE MIDDLE TO UPPER 60S ACROSS THE FORECAST AREA, AND WITH AMPLE LOW-LEVEL MOISTURE REMAINING ACROSS THE REGION, SOME PATCHY FOG IS POSSIBLE.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... DURING THE DAYTIME THURSDAY, THE PREVIOUSLY MENTIONED SURFACE COLD FRONT IS EXPECTED TO APPROACH OUR FORECAST AREA DURING THE MORNING AND GRADUALLY CROSS THE REGION THROUGH THE AFTERNOON TO EVENING. SIMILAR TO WEDNESDAY, AN INCREASE IN INSTABILITY IS EXPECTED DURING THE DAY, AND WITH THE APPROACHING FRONT AND A SHORTWAVE ALOFT ACTING AS LIFTING MECHANISMS, MORE SCATTERED SHOWER/THUNDERSTORM ACTIVITY IS ANTICIPATED. WE BEGIN POPS A LITTLE EARLIER IN THE DAY, DURING THE MORNING, FOR OUR WESTERN ZONES. HIGHEST CHANCE POPS, THOUGH, ARE FOCUSED INTO THE AFTERNOON, BEFORE DECREASING THEN INTO THE EVENING AS THE FRONT PASSES BY TO THE EAST. MET/MAV GUIDANCE BLENDED WITH CONTINUITY YIELDS HIGH TEMPERATURES MOSTLY INTO THE MIDDLE AND UPPER 80S FOR THE REGION. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... A COLD FRONT WILL BE MOVING ACROSS THE AREA AT THE START OF THE PERIOD AND COULD HAVE SOME SHOWERS AND TSTMS WITH IT. THE PRECIP SHOULD BE WINDING DOWN EARLY IN THE PD. ON FRI, HIGH PRES BUILDS BACK INTO THE REGION, AND DRY CONDS ARE EXPECTED. LOW PRES THEN ADVANCES ACRS QUEBEC ON SAT AND ITS ASSOCD CDFNT WILL APPROACH FROM THE W ON SAT. THERE IS QUITE A BIT OF UNCERTAINTY AS TO PRECIP CHCS ON SAT. THE GFS IS FASTER WITH THE FRONT, AND HAS SOME PRECIP, MAINLY N. THE GFS IS SLOWER AND DRIER. FOR NOW WILL GO WITH LOW POPS. THE GFS HAS CFP SAT NIGHT, WITH THE ECMWF ON SUN. SHWRS/TSTMS WILL ACCOMPANY FROPA, BUT THERE STILL REMAIN QUESTIONS AS TO THE TIMING. THE FRONT THEN STALLS TO THE S OF THE REGION AS HIGH PRES BUILDS OVER QUEBEC. YESTERDAY, THE MDLS HAD DRIED OUT EARLY NEXT WEEK. NOW, THEY ARE MAKING IT WETTER. AGAIN, CONFIDENCE IS LOW AS THE MDLS TRY TO IRON THINGS OUT. LOWERED POPS A BIT YESTERDAY, AND RAISED THEM A BIT TODAY, BUT DON`T WANT TO MAKE ANY WHOLESALE CHANGES. ALSO, SOME QUESTIONS REMAIN AS TO AREAL EXTENT AND PLACEMENT OF THE PRECIP. BY TUE, THE LOW MOVE NEWD OUT TO SEA AND PRECIP CHCS EITHER MOVE NWD (GFS) OR DECREASE (ECMWF). THE FCST IS CONTINGENT ON THE STALLED FRONT AND WHERE IT STALLS, WHETHER IT WASHES OUT AND IF ANY WAVES DEVELOP UPON IT. THE MDLS ARE HAVING A DIFFICULT TIME RESOLVING THE FCST EARLY NEXT WEEK AND AS A RESULT, THE CONFIDENCE IN THIS FCST IS MUCH BELOW AVERAGE. THERE WILL LIKELY BE SOME PRECIP BEYOND SUN, BUT WHERE, WHEN, AND TO WHAT EXTENT REMAIN BIG QUESTIONS. TEMPS LOOK TO START ABV NRML BUT CUD BE BELOW NRML ERLY NEXT WEEK DEPENDING ON HOW THINGS PLAY OUT. && .AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. OVERALL, MAINLY VFR CONDITIONS ARE EXPECTED LATE-DAY AND THIS EVENING, EXCEPT A PERIOD OF SUB-VFR IS POSSIBLE WITH ANY SCATTERED SHOWER/TSTORM ACTIVITY. WE HAVE INCLUDED A MENTION OF THIS IN THE TAFS AS A TEMPO GROUP, 22Z TO 01Z TIMEFRAME IN AND AROUND THE I- 95 CORRIDOR. THEREAFTER, WITH THE LOSS OF DAYTIME HEATING, WE EXPECT ANY LEFTOVER SHWR/TSTORM ACTIVITY TO WANE AND DISSIPATE AS IT APPROACHES THE COASTAL PLAIN, AND WITH STORMS UNLIKELY TO REACH KACY THIS EVENING, NO MENTION WAS INCLUDED IN THE TAF. OUTSIDE OF ANY STRONG WINDS IN TSTORMS, SOUTH-SOUTHWEST WINDS WILL CONTINUE MOSTLY IN THE 10 TO 15 KNOT RANGE WITH SOME GUSTS NEAR 20 KNOTS POSSIBLE THROUGH THIS EVENING. OVERNIGHT...ONCE SHWRS DISSIPATE AND END, AMPLE LOW-LEVEL MOISTURE WILL REMAIN ACROSS THE AREA, AND GUIDANCE INDICATES MOSTLY MVFR CONDITIONS TO DEVELOP WITH SOME LOWER CLOUDS AND PATCHY FOG. THIS HAS BEEN INCLUDED IN THE TAFS, STARTING AROUND THE 08Z/09Z TIMEFRAME. SOUTH-SOUTHWEST WINDS WILL DECREASE TO 5 KNOTS OR LESS. THURSDAY...ANY LOW CLOUDS/FOG SHOULD LIFT, WITH CONDITIONS IMPROVING BACK TO VFR BY MID-MORNING. WHILE SOME SCATTERED SHWRS/TSTORMS ARE POSSIBLE DURING THE DAY WHICH MAY LOCALLY REDUCE CIGS/VSBYS, TIMING AND COVERAGE OF THESE WAS TOO UNCERTAIN AT THIS TIME TO INCLUDE IN THE TAFS. SOUTHWEST WINDS WILL GRADUALLY BECOME MORE WESTERLY AND INCREASE TO AROUND 10 TO 12 KNOTS. OUTLOOK... THU NIGHT...GENERALLY VFR. SCT SHRA/TSRA EARLY. MDT CONFIDENCE. FRI...GENERALLY VFR. ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE FOR WESTERN TAFS. FRI NIGHT...VFR EARLY, THEN LOWERING CIGS/VSBYS POSSIBLE OVERNIGHT. MDT CONFIDENCE. SAT...IFR/MVFR PSBL EARLY, THEN BECOMING VFR DURING THE DAY. SCATTERED SHRA/TSRA PSBL WHICH MAY REDUCE CIGS/VSBYS. GUSTY SOUTH- SOUTHWEST WINDS AROUND 20 KNOTS. LOW TO MDT CONFIDENCE ON TSRA. SAT NIGHT-SUN...SUB-VFR CONDITIONS POSSIBLE, ESPECIALLY WITH SHRA/TSRA. LOW TO MDT CONFIDENCE.
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&& .MARINE...
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THROUGH THIS EVENING AND TONIGHT, SOME WIND GUSTS TO AROUND 25 KNOTS ARE EXPECTED, ALONG WITH SOME WAVE HEIGHTS APPROACHING THE 4 TO 5 FOOT RANGE FOR THE COASTAL WATERS. WE THEREFORE MAINTAIN THE CURRENT SMALL CRAFT ADVISORY THROUGH 10Z THURSDAY. THEREAFTER, WHILE SOME WIND GUSTS TO AROUND 20 KNOTS MAY STILL OCCUR FOR THE COASTAL WATERS, MAINLY SUB-SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED FOR THE COASTAL WATERS AND FOR DELAWARE BAY THROUGH THURSDAY. OUTLOOK... THU-SAT...SUB-SCA CONDS EXPECTED, ALTHOUGH WINDS MAY GUST AROUND 20 KNOTS AT TIMES. SAT NIGHT...SEAS MAY RETURN TO 5 FEET OR GREATER OVERNIGHT AHEAD OF AN APPROACHING CDFNT. SUN...SCA CONDS LIKELY WITH CFP.
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&& .RIP CURRENTS...
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BASED ON OFFICE GUIDANCE, WE CONTINUE A MODERATE RISK OF RIP CURRENTS THROUGH THIS EVENING FOR THE NJ BEACHES UNDER A BREEZY SOUTH WIND.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT THURSDAY FOR ANZ450>455. && $$ SYNOPSIS...NIERENBERG NEAR TERM...GORSE/KLINE SHORT TERM...KLINE LONG TERM...NIERENBERG AVIATION...KLINE/NIERENBERG MARINE...KLINE/NIERENBERG RIP CURRENTS...

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