Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 011945
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
345 PM EDT MON SEP 1 2014

.SYNOPSIS...
SIMILAR WEATHER PATTERN WILL BE IN PLACE TOMORROW, LEADING TO
ANOTHER WARM AND MUGGY DAY. A COLD FRONT IS THEN EXPECTED TO MOVE
ACROSS THE AREA LATE TUESDAY AND EARLY WEDNESDAY. HIGH PRESSURE WILL
BUILD IN BEHIND THIS FRONT BEGINNING WEDNESDAY AFTERNOON. ANOTHER
COLD FRONT COULD APPROACH FROM THE WEST EARLY SATURDAY BEFORE
STALLING NEAR OR JUST SOUTH OF OUR REGION BY SUNDAY.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
TEMPERATURES THIS AFTERNOON HAVE WARMED INTO THE MID AND UPPER 80S
AS EXPECTED. HOWEVER WITH DEWPTS REMAINING IN THE LOW 70S THE
APPARENT TEMPS ARE WELL INTO THE 90S...EXCEPT FOR HIGHER ELEVATIONS
IN THE POCONOS AND NW NJ. WITH AFTN HEATING THE AMS HAS BECOME
MODERATELY UNSTABLE WITH LI/S AROUND -5 TO -7 AND SFC-BASED CAPE
1500 TO 3000 J/KG. THE MORE UNSTABLE AIR SEEMS TO BE INVOF CHES BAY
AND DELMARVA. SOME SCT TSTMS HAVE DEVELOPED BUT THEY SEEM TO BE
LOCALLY FORCED E.G. BY LAND/WATER DIFFERENTIAL HEATING. HAVE KEPT
CHC POPS IN THE FCST FOR THIS AFTN/EVE BUT ADJUSTED TO MAKE SMWHAT
HIGHER POPS S OF PHL.

FOR TONIGHT...EXPECT TSTMS TO DIE OFF WITH A COUPLE HOURS OF SUNSET
AS THERE DOES NOT SEEM TO BE ANY LARGER SCALE FORCING INVOLVED ATTM.
POSSIBLE EXCEPTION IS IF SOME MORE ORGANIZED QLCS MOVES IN FROM THE
WEST BUT THAT DOESN`T SEEM LIKELY NOW. OTRW...EXPECT A MILD/MUGGY
NIGHT WITH LOWS UPPER 60S TO LOW 70S AND SOME PATCHY FOG LIKELY
DVLPG AFTER MIDNIGHT.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
FOR TUESDAY...OVERALL CONDS WILL BE SIMILAR TO TODAY...BUT THE
AIRMASS WILL BE SLIGHTLY WARMER WITH 850MB TEMPS A DEGREES OR TWO
HIGHER. THUS AFTN MAX TEMPS ARE FCST TO REACH 90 OR LOW 90S IN MANY
LOCS...ESP FROM PHL S AND E. SFC DEWPTS ARE FCST TO BE SLIGHTLY
LOWER THAN TODAY...BUT APPARENT TEMPS WILL STILL BE UP IN THE LOWER
TO MID 90S.

A WELL-DEFINED UPPER-LEVEL SHORTWV TROF WILL BE APPROACHING FROM THE
WEST ON TUESDAY...AND THE ASSOCD SFC COLD FRONT SHOULD BE PUSHING
INTO NW PA BY AFTN. MOS GUIDANCE PLUS MODEL UVV/QPF SUGGESTS THAT
THE BULK OF THE FRONTAL PRECIP/CNVTN WILL NOT REACH ERN PA UNTIL
AFTER 00Z WED. HWVR...CANNOT RULE OUT SOME PRE-FRONTAL TROF CONVTN
SO HAVE INCLUDED SLGT-CHC TO CHC POPS INCREASING FROM W TO E FOR
TMRW AFTN.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
TUESDAY NIGHT...THE GFS SHOWED A SLIGHTLY SLOWER SOLUTION WITH THE
LATEST RUN, NOW WITH THE COLD FRONT ARRIVING IN SE PA BY LATE
EVENING, THE COASTAL WATERS BY WEDNESDAY MORNING. GIVEN THE RATHER
LATE ARRIVAL OF THE FRONT, INSTABILITY SHOULD BE BE MINIMAL. ALSO,
THE UPPER LEVEL SHORT WAVE TROUGH SHOULD STAY WELL TO THE NORTH OF
THE REGION RESULTING IN LIMITED SYNOPTIC SCALE LIFT.
THUS...DESPITE THE SLIGHT RISK FOR SEVERE STORMS TO OUR WEST,
THINK THE SEVERE THREAT WITHIN OUR REGION WILL BE MINIMAL.

WEDNESDAY AND THURSDAY...THOUGH THERE WON`T BE SIGNIFICANT COLD
AIR ADVECTION BEHIND THE FRONT, THERE WILL BE CONSIDERABLE DRY AIR
ADVECTION, ALBEIT SHORT LIVED. THUS, WHILE HIGHS WILL STILL BE
ABOVE NORMAL, IT WILL FEEL A BIT MORE PLEASANT WITH HEAT INDEX
VALUES NEAR AIR TEMPERATURES.

FRIDAY INTO SUNDAY...AS THE SURFACE HIGH SLIDES OFF SHORE FRIDAY,
THE REGION WILL ONCE AGAIN SEE LOW LEVEL MOIST FLOW AHEAD OF THE
NEXT COLD FRONT. THE COLD FRONT IS SET TO ARRIVE SATURDAY...THOUGH
THERE HAS BEEN POOR RUN TO RUN CONSISTENCY ON THE TIMING OF THE
FRONT. AN ADDED COMPLICATION IS THAT BOTH THE GFS AND ECMWF
CONTINUE TO SHOW THE FRONT STALLING, EITHER OVER OUR REGION OR
JUST SOUTH OF THE REGION. DEPENDING ON HOW FAR NORTH IT STALLS,
THE REGION COULD BE UNDER MOIST ON SHORE/UPSLOPE FLOW THROUGH
EARLY NEXT WEEK. FOR NOW, HAVE STAYED CLOSE TO THE PREVIOUS
FORECAST CONSIDERING THE UNCERTAINTY.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

MAINLY VFR CONDS ARE EXPECTED THROUGH TONIGHT AND WEDNESDAY.
EXCEPTIONS ARE LOCALLY MVFR/IFR CONDS IF A HEAVY SHOWER OR T-STORM
HAPPENS TO MOVE OVER ONE OF THE TAF SITES. SO FAR THE CNVTN HAS BEEN
RATHER WIDELY SCT BUT IT WILL BE MONITORED CLOSELY AND TAF AMENDED
AS NECESSARY. ALSO...SOME PATCHY FOG WILL LIKELY DEVELOP OVERNIGHT
AND COULD PRODUCE MVFR CIGS/VSBYS FOR A FEW HOURS AROUND SUNRISE
TMRW. WINDS WILL BE SW 5 TO 10 KT THIS AFTN...DECREASING TO 5 KT OR
LESS TONIGHT...THEN PICKING UP A LITTLE STRONGER ON TUES WITH A
SMWHT TIGHTER PRES GRADIENT AHEAD OF THE APPROACHING FRONTAL TROF.

OUTLOOK...
TUESDAY NIGHT...THUNDERSTORMS AND AN ABRUPT WIND SHIFT POSSIBLE
WITH A COLD FRONT THAT WILL MOVE THROUGH OVERNIGHT. MVFR CEILINGS
AND VISIBILITIES AS LOW AS IFR WILL BE POSSIBLE WITH ANY
THUNDERSTORMS. OTHERWISE VFR CONDITIONS EXPECTED.

WEDNESDAY THROUGH FRIDAY...VFR CONDITIONS EXPECTED.

FRIDAY NIGHT INTO SATURDAY...AS A COLD FRONT MOVES IN FROM THE
WEST...IFR CONDITIONS AND THUNDERSTORMS POSSIBLE.

&&

.MARINE...
SUB SCA CONDS ARE EXPECTED THROUGH TUESDAY. SW WINDS WILL CONTINUE
AROUND THE SUMMERTIME BERMUDA WITH AT 10 TO 15 KT OR SO. SEAS WILL
BE IN THE 2 TO 4 FT RANGE OVER THE COASTAL WATERS. CONDS COULD BE
LOCALLY ROUGHER IN WIDELY SCT AFTN/EVE THUNDERSTORMS OVER THE
COASTAL WATERS AND DELAWARE BAY.

OUTLOOK...
TUESDAY NIGHT...THOUGH SEAS SHOULD REMAIN BELOW SMALL CRAFT
ADVISORY CRITERIA, GUSTY WINDS WILL BE POSSIBLE IN THE VICINITY OF
ANY STORMS THAT DEVELOP WITH THE COLD FRONT.

WEDNESDAY THROUGH FRIDAY...WINDS AND SEAS ARE EXPECTED TO REMAIN
BELOW SCA CRITERIA.

FRIDAY NIGHT INTO SATURDAY...SEAS SHOULD REMAIN JUST BELOW SCA
CRITERIA. GUSTY WINDS WILL BE POSSIBLE IN THE VICINITY OF
ANY STORMS THAT DEVELOP.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

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






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