Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 272008 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 408 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/... 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 SHOWS THAT SUFFICIENT DESTABILIZATION HAS OCCURRED, WITH SURFACE-BASED CAPE VALUES RANGING MOSTLY BETWEEN 1000 TO 1500 J/KG ACROSS MOST OF THE FORECAST AREA, EXCEPT PERHAPS ALONG THE IMMEDIATE COAST. IN ADDITION, MODEST SHEAR EXISTS ALONG WITH AMPLE LOW-LEVEL MOISTURE, WITH DEWPOINTS 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. WE CARRY LIKELY TO HIGH CHANCE POPS TO THE INTERSTATE 95 CORRIDOR AND THEN GRADUALLY DIMINISH POPS FARTHER EAST WITH THE LOSS OF DAYTIME HEATING INTO MID EVENING. 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. && .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 TUESDAY/... 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 /19Z WEDNESDAY THROUGH MONDAY/... 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, WITH THE 19Z TO 21Z TIMEFRAME EXPECTED FOR MUCH OF EASTERN PA AND THE 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. && .MARINE... 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. && .RIP CURRENTS... BASED ON OFFICE REGRESSION GUIDANCE, WE CONTINUE A MODERATE RISK OF RIP CURRENTS THROUGH TODAY FOR THE NJ BEACHES UNDER A BREEZY SOUTH WIND. && .CLIMATE... ************************************************************* HERE IS OUR ANNUAL LOOK AS TO HOW HOT, HOT, HOT THE SUMMER WILL BE BASED ON PAST PERFORMANCES. A FULL FLEDGED EL NINO IS UNDERWAY IN THE TROPICAL PACIFIC. ALL DYNAMICAL AND STATISTICAL MODELS KEEP IT GOING, THE DIFFERENCES THAT EXIST ARE TO ITS STRENGTH THROUGH THIS UPCOMING SUMMER. THE DYNAMICAL AND STATISTICAL MODELS ARE AVERAGING A MODERATE EL NINO FOR THE COMBINED SUMMER MONTHS. SOME MODELS, INCLUDING THE CFS2 AND ECMWF ARE PREDICTING A STRONG EL NINO. IN THE CPC MONITORING EL NINO ERA STARTING SINCE 1950, THE HIGHEST (WARMEST) SUMMER ANOMALY RECORDED WAS +1.5C (NEAR OR AT THE THRESHOLD FOR STRONG EL NINOS) DURING THE SUMMER OF 1997. THIS UPCOMING WEEK WILL REALLY SEAL THE DEAL THAT THIS MAY WILL BE UNSEASONABLY WARM IN PHILADELPHIA. IT "MAY" EVEN BE A TOP THREE WARMEST. THIS FOLLOWS ON THE HEELS OF AN UNSEASONABLY WARM APRIL. SINCE 1872, THE COMBINATION OF BOTH WARM (TOP THIRD OF ALL YEARS) APRILS AND MAYS HAS ONLY OCCURRED TWENTY-THREE TIMES. BUT IT HAS OCCURRED ELEVEN TIMES SINCE 1990 AND SIX OF THE LAST SEVEN SPRINGS. SO WE SCOURED THE CLIMATE RECORDS TO FIND BUDDING OR IN PROGRESS EL NINOS THAT COINCIDED WITH BOTH WARM APRILS AND MAYS LOCALLY IN THE CPC MONITORING ERA. WE FOUND THREE PAST SUMMERS THAT MET THE CRITERIA. THE ONE SIGN IS THAT ALL THREE ANALOG SUMMERS WERE WETTER THAN NORMAL, HOPEFULLY KEEPING DROUGHT CONDITIONS FROM INTENSIFYING FURTHER. THE NORTH AMERICAN MULTI MODEL ENSEMBLE PREDICTIONS FOR THIS UPCOMING SUMMER HAS WARMER AND DRIER THAN NORMAL WEATHER EXPECTED IN OUR AREA. THE INTERNATIONAL MULTI MODEL ENSEMBLE FORECASTS ARE SLIGHTLY MORE OPTIMISTIC PREDICTING NEAR NORMAL TEMPERATURES AND PRECIPITATION. THE ANALOGS FOR PHILADELPHIA ARE: YEAR JUNE AVG JULY AVG AUGUST AVG SUMMER AVG SUMMER PCPN 1969 73.4 75.1 75.2 74.6 18.30 1977 68.6 77.8 76.2 74.2 15.50 1991 75.7 79.0 79.0 77.9 12.01 AVG 72.6 77.3 76.8 75.6 15.27 1981- 2010 73.3 78.1 76.6 76.0 11.28 NORMAL THE OFFICIAL CPC OUTLOOK FOR OUR FORECAST AREA IS FOR EQUAL CHANCES OF ABOVE AND BELOW NORMAL TEMPERATURES AS WELL AS EQUAL CHANCES OF ABOVE AND BELOW NORMAL PRECIPITATION. && .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...KLINE SHORT TERM...KLINE LONG TERM...NIERENBERG AVIATION...KLINE/NIERENBERG MARINE...KLINE/NIERENBERG RIP CURRENTS...KLINE CLIMATE...

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