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Area Forecast Discussion
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000
FXUS61 KPHI 020315
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1115 PM EDT MON SEP 1 2014

.SYNOPSIS...
SOUTHERLY RETURN FLOW AROUND HIGH PRESSURE WILL RESULT IN WARM
AND MUGGY CONDITIONS THROUGH TUESDAY. A COLD FRONT IS THEN
EXPECTED TO MOVE ACROSS OUR 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/...
A WARM AND MUGGY NIGHT FOR THE ENTIRE REGION. DESPITE A LACK OF
ANY ORGANIZED FORCING, SOME SHOWERS HAVE DEVELOPED AND ARE MOVING
TOWARD OUR WESTERN ZONES. THESE ARE ISOLATED, AND APPEAR TO BE
TIED TO A SUBTLE WAA PUSH IN COMBINATION WITH LINGERING
INSTABILITY. THE AIRMASS IS BUOYANT OWING TO THE MUGGY AND WARM
BOUNDARY LAYER AND THEREFORE IT WILL NOT TAKE MUCH TO POP A FEW
SHOWERS. OUR CONFIDENCE LOWERS WITH AN EASTWARD EXTENT, THEREFORE
DID NOT BRING THE SLIGHT CHC POPS TO FAR EAST ATTM. WE WILL
MONITOR RADAR TRENDS IN THE EVENT AN EXPANSION TO THE LOW POPS IS
NEEDED. OVERALL, ANY SHOWERS ARE ANTICIPATED TO BE RATHER ISOLATED
AND BRIEF.

OTHERWISE, SOME CLOUDS AND PATCHY FOG THROUGH THE OVERNIGHT.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
FOR TUESDAY...OVERALL CONDS WILL BE SIMILAR TO LABOR DAY...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 /03Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, 
KMIV, KACY AND SURROUNDING AREAS.

VFR IN GENERAL. LIGHT SOUTHWESTERLY WINDS, BECOMING CALM AT
SEVERAL TERMINALS. PATCHY FOG SHOULD DEVELOP ESPECIALLY TOWARD
DAYBREAK, HOWEVER THIS COULD BE DISRUPTED AT TIMES WITH SOME
CLOUDS MOVING THROUGH. WITH SUCH A MUGGY AIRMASS IN PLACE,
TEMPORARY IFR POSSIBLE TOWARD DAYBREAK TUESDAY MORNING AT THE
FOG-PRONE TERMINALS SUCH AS KRDG/KMIV/KABE IF BREAKS IN THE CLOUD
COVER PERSISTS LONG ENOUGH. AN ISOLATED SHOWER AROUND MAINLY WEST OF
KPHL.

TUESDAY, S-SW WINDS INCREASE DURING THE DAY AS THE PRESSURE
GRADIENT INCREASES AHEAD OF A COLD FRONT THAT IS APPROACHING FROM
THE WEST. CHANCES FOR SHRA/TSRA DELAYED UNTIL LATE IN THE DAY TUE
WITH ARRIVAL OF FRONT NOT EXPECTED UNTIL TUE NGT. THIS FAR OUT,
INCLUDED A PROB30 GROUP FOR SHRA IN THE 00Z TAFS STARTING AFTER
20Z FOR ONLY THE WESTERN TERMINALS /KRDG AND KABE/.

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. CHANCES FOR
SHOWERS AND TSTMS LATE IN THE AFTN TUE AS A COLD FRONT APPROACHES
FROM THE WEST.

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/KLEIN
NEAR TERM...GORSE
SHORT TERM...AMC
LONG TERM...JOHNSON
AVIATION...AMC/JOHNSON/KLEIN
MARINE...AMC/JOHNSON/KLEIN




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