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000
FXUS61 KPHI 131955
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
355 PM EDT SUN APR 13 2014

.SYNOPSIS...
HIGH PRESSURE CONTINUES TO SLIDE EAST OFF THE SHORE TONIGHT. A COLD
FRONT WILL APPROACH FROM THE WEST TOMORROW NIGHT AND PUSH THROUGH
THE REGION TUESDAY AFTERNOON. IN THE WAKE OF THE COLD FRONT, HIGH
PRESSURE WILL SETTLE IN OVER THE REGION THROUGH THE REMAINDER OF THE
WORK WEEK. AN UPPER LEVEL TROUGH COULD SLIDE OVER OUR REGION EARLY
NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
STRONG WARM AIR ADVECTION AND PLENTY OF SUNSHINE HAVE ALLOWED
TEMPERATURES TO EXCEED EXPECTED HIGHS AND BASICALLY BLEW STAT
GUIDANCE AWAY. THE DEEPER MIXING HAS FINALLY TAPPED INTO SOME OF THE
STRONGER LOW-LEVEL WINDS AND THE GUSTS ARE STARTING TO INCREASE FOR
THE NEXT FEW HOURS BEFORE DROPPING OFF SHORTLY AFTER SUNSET.

MID AND HIGHER LEVEL CLOUDS WILL BE ON THE INCREASE TONIGHT FROM THE
WEST. STILL UNSURE HOW MUCH STRATUS AND OR FOG FORMS LATE TONIGHT
ACROSS THE REGION. DEWPOINTS ARE MUCH HIGHER THAN THEY WERE EARLIER
THIS MORNING BUT THE BOUNDARY LAYER WINDS WERE ALSO MUCH WEAKER
ALLOWING BETTER MOISTURE POOLING TO OCCUR. THINKING THAT TONIGHT THE
BEST CHANCES FOR STRATUS ARE ALONG THE COASTAL AREAS AND POSSIBLY
DOWNWIND OF THE UPPER CHESAPEAKE BAY...SLIGHT BAY ENHANCEMENT
POSSIBLE. EITHER WAY WITH CLOUDS OVERHEAD AND A MUCH WARMER STARTING
POINT TEMPERATURES SHOULD BE SEVERAL DEGREES WARMER THAN THIS MORNING
WITH LOWS IN THE UPPER-50S TO LOW 60S IN SOME SPOTS.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
ANY LOWER CLOUDS AND FOG SHOULD BURN OFF LATE MORNING GIVING WAY TO
THE MID AND HIGHER LEVEL CLOUDS. THE RIDGING OFFSHORE SHOULD
CONTINUE TO PUSH EASTWARD AND SOME LOWER HEIGHTS AND THICKNESSES
ADVECT INTO THE REGION FROM THE WEST. THE GRADIENT FLOW WILL STILL
BE FROM THE SOUTH-SOUTHWEST WHERE THE GUIDANCE IS SHOWING SLIGHTLY
COOLER LOW-LEVEL TEMPERATURES. ALL INDICATIONS SHOW MONDAY BEING A
COUPLE DEGREES COOLER THAN SUNDAY WITH THE NEUTRAL/COOLER AIR
ADVECTION OCCURRING AND MORE CLOUD COVER IN PLACE. THAT BEING SAID
STILL WENT ABOVE GUIDANCE FOR TOMORROW AS THE AIRMASS ON A WHOLE
REMAINS UNCHANGED.

NUMERICAL GUIDANCE AND PROBABILISTIC QPF GUIDANCE SHOW THE MAIN
SHOWERY ACTIVITY WITH THE COLD FRONT, AGAIN WELL TO OUR WEST
TOMORROW, HOLDING OFF THROUGH THE DAYTIME. THEREFORE WE KEEP
TOMORROW DRY.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
THE BIG WEATHER STORY OF THE WEEK IS GOING TO BE THE STRONG COLD
FRONT AND ASSOCIATED PRECIPITATION TO BEGIN THE LONG TERM PERIOD.

OVERVIEW...THERE IS MUCH BETTER MODEL AGREEMENT TODAY WITH THE
TIMING AND TRACK OF THIS COLD FRONT, WITH THE TREND GENERALLY
TOWARDS A MORE PROGRESSIVE SOLUTION. STILL EXPECTING STRONG
SOUTHERLY/SOUTHWESTERLY FLOW TO DEVELOP IN THE WARM SECTOR, AND WITH
THAT WIDESPREAD PRECIPITATION AHEAD OF THE FRONT. THE FRONT IS NOW
EXPECTED TO COMPLETELY PUSH THROUGH THE REGION BETWEEN 18Z TUESDAY
AND 00Z WEDNESDAY. THERE MAY BE A BRIEF PERIOD (LESS THAN 6 HR) OF
PRECIPITATION BEHIND THE FRONT, BUT CONSIDERING THE SOURCE REGION OF
THE POLAR AIR MASS, EXPECT CONSIDERABLE DRY AIR ADVECTION BEHIND THE
FRONT.

HEAVY RAIN...MODELS CONTINUE TO SHOW MAXIMUM PRECIPITABLE WATER
VALUES AROUND 1.5 INCHES...OR ABOUT 2 STANDARD DEVIATIONS ABOVE
NORMAL FOR THIS TIME OF THE YEAR. IN ADDITION, THE 0-6KM MEAN FLOW
TUESDAY NIGHT CONTINUING INTO TUESDAY MORNING IS NEARLY PARALLEL TO
THE APPROACHING FRONT, INCREASING THE RISK FOR TRAINING STORMS.
HOWEVER, WARM CLOUD LAYER IS MARGINAL FOR AN ENHANCED HEAVY RAIN
THREAT, PWAT VALUES ACTUALLY DECREASE BEFORE THE MAXIMUM LIFT
ARRIVES OVER THE REGION, AND WITH THE TREND TOWARDS A FASTER COLD
FRONT THE PERIOD FOR HEAVY RAIN POTENTIAL IS SHORTER THAN PREVIOUSLY
EXPECTED. WILL CONTINUE WITH SIMILAR WORDING IN THE HWO HIGHLIGHTING
THE POTENTIAL FOR HEAVY RAIN.

THUNDERSTORMS...MODELS DEPICT MARGINAL ML CAPE VALUES (<100 J/KG) IN
THE WARM SECTOR. HOWEVER, THERE IS POTENTIAL FOR ELEVATED
INSTABILITY AS WELL THROUGH THE ENTIRE PERIOD THAT THE REGION IS IN
THE WARM SECTION.

WINTRY MIX OF PRECIPITATION BEHIND THE FRONT...AS MENTIONED
PREVIOUSLY, EXPECT THE PERIOD OF PRECIPITATION BEHIND THE FRONT TO
BE RATHER BRIEF. THE HIGHER TERRAIN OF THE POCONOS COULD SEE SOME
WINTRY MIX THROUGH THIS PERIOD, BUT GIVEN HIGH GROUND TEMPERATURES,
DO NOT EXPECT MUCH IN THE WAY OF ACCUMULATION.

EXPECT THE SURFACE RIDGE TO BE THE DOMINANT FEATURE FOR THE REGION
WEDNESDAY AND THURSDAY. EXPECT ONLY A MODEST WARMING TREND THROUGH
THIS PERIOD MAINLY DUE TO AIR MASS MODIFICATION.

BEGINNING THURSDAY, WE`RE WATCHING AN UPPER LEVEL THROUGH DIGGING
SOUTHEAST OVER THE GREAT BASIN REGION. THAT MUCH THE MODELS AGREE
ON. BY FRIDAY MODEL DIFFERENCES AND ENSEMBLE SPREAD INCREASE
CONSIDERABLY. THE GFS SHOWS THE TROUGH CUTTING OFF, DEEPENING AND
INTENSIFYING IN THE THE NORTHERN STREAM, EVENTUALLY PROPAGATING TO
THE GREAT LAKES REGION. WITH THIS SOLUTION, OUR REGION COULD BE IN
THE WARM SECTOR, WITH STEADY RAIN THROUGH THE WEEKEND. THE ECMWF ON
THE OTHER HAND, CUTS OFF THE LOW IN THE SOUTHERN STREAM, AS IT
PROPAGATES OFF THE COAST OF THE CAROLINAS BY SUNDAY. THIS WOULD
RESULT IN COOLER CONDITIONS, AND ONLY A BRIEF PERIOD OF
PRECIPITATION FOR MOST OF OUR REGION. CONSIDERING THE LOW
CONFIDENCE, HAVE STAYED CLOSE TO THE PREVIOUS FORECAST AND WPC
GUIDANCE THROUGH THIS PERIOD.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

THIS EVENING - TONIGHT...MOSTLY VFR. SOUTH-SOUTHWESTERLY WINDS WILL
CONTINUE TO GUST INTO THE LOW-20 KNOTS RANGE THROUGH THE EVENING
HOURS. A SEA-BREEZE FRONT HAS BEEN PUSHING INLAND TODAY NEAR ACY AS
THE WINDS ARE LESS THAN EXPECTED ALOFT BUT SHOULD HAVE HARD TIME
MOVING MUCH FURTHER. SHORTLY AFTER SUNSET WE SHOULD LOSE THE GUSTS
BUT KEEP THE HIGHER SUSTAINED WINDS. THERE IS STILL A QUESTION ABOUT
HOW MUCH STRATUS FORMS TONIGHT. HIGHER CONFIDENCE EXISTS CLOSER TO
THE COAST AT MIV/ACY SO KEPT IT THERE BUT STILL HINTED AT IT
ELSEWHERE...WE BARELY RECEIVED ANY THIS MORNING.

TOMORROW...ANY STRATUS/FOG THAT DOES FORM LATE TONIGHT SHOULD
LIFT/BURN OFF BY LATE MORNING. SOUTHERLY WINDS WILL PICK UP AGAIN
AND BEGIN TO GUST, SLIGHTLY STRONGER, TOMORROW AFTERNOON.

OUTLOOK...

MONDAY NIGHT AND TUESDAY...DETERIORATING CONDITIONS TO WIDESPREAD
MVFR AND POSSIBLY WIDESPREAD IFR. RAIN COULD BE HEAVY AT TIMES, AND
ISOLATED THUNDERSTORMS ARE POSSIBLE DURING THE DAY TUESDAY.

WEDNESDAY THROUGH THURSDAY NIGHT...GENERALLY VFR CONDITIONS EXPECTED.

&&

.MARINE...
SOUTHERLY WINDS WILL CONTINUE TO INCREASE TONIGHT AND TOMORROW SO
EVEN THOUGH WE HAVE NOT MUCH SCA ACTIVITY TODAY WE SHOULD BY LATE
TONIGHT AND TOMORROW. SEAS SHOULD ALSO RESPOND, AS THEY HAVE NOT
YET, TO THE BETTER SOUTHERLY SURGE COMING TOMORROW AHEAD OF THE
APPROACHING COLD FRONT.

OUTLOOK...
TUESDAY...SMALL CRAFT ADVISORY CONDITIONS ARE LIKELY. A COLD FRONT
WILL MOVE THROUGH LATE TUESDAY AFTERNOON BRINGING AN ABRUPT SHIFT
FROM SOUTHERLY TO NORTHWESTERLY WINDS.

WEDNESDAY...SMALL CRAFT ADVISORY CONDITIONS POSSIBLE ESPECIALLY
EARLY IN THE DAY, BUT EXPECT WINDS TO DECREASE WEDNESDAY AFTERNOON.

WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...WINDS NEAR OR JUST BELOW
25KT. HOWEVER, WAVE HEIGHTS COULD BE ABOVE 5 FT THROUGH THE ENTIRE
PERIOD.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT TUESDAY FOR ANZ450>455.
     SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ430-431.

&&

$$
SYNOPSIS...JOHNSON
NEAR TERM...HEAVENER
SHORT TERM...HEAVENER
LONG TERM...JOHNSON
AVIATION...HEAVENER/JOHNSON
MARINE...HEAVENER/JOHNSON