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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