Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 210930
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
530 AM EDT MON JUL 21 2014

.SYNOPSIS...
HIGH PRESSURE WILL ESTABLISH ITSELF OVER OUR REGION TODAY THROUGH
TUESDAY NIGHT. A COLD FRONT IS ANTICIPATED TO ARRIVE WEDNESDAY NIGHT
AND DRIFT JUST TO THE SOUTHEAST OF OUR FORECAST AREA THURSDAY NIGHT.
WEAK HIGH PRESSURE FOLLOWS FRIDAY THEN MERGES WITH THE BERMUDA HIGH
SATURDAY. A WARM FRONT IS THEN FORECAST TO APPROACH FROM THE SOUTH
ON SUNDAY AS LOW PRESSURE DEVELOPS FROM THE GREAT LAKES TO THE MID
ATLANTIC STATES.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE OVERALL SYNOPTIC SITUATION HAS NOT CHANGED MUCH...HIGH PRESSURE
REMAINS OFFSHORE TO THE NORTHEAST AND EXPANDS BACK ACROSS OUR AREA
TODAY. A WEAK UPPER TROUGH CROSSES THE AREA LATER TODAY AND TONIGHT
IN RESPONSE TO BUILDING H5 HEIGHTS OUT WEST. A FAIR WEATHER DAY IS
EXPECTED WITH PARTLY TO MOSTLY SUNNY SKIES. SOME CU/AC WILL CROSS
THE ARE AT TIMES AND TEMPERATURES WILL BE A FEW DEGREES BELOW NORMAL
FOR LATE JULY. HIGHS WILL MOSTLY BE IN THE LOW/MID 80S ACROSS THE
AREA. A SLGT CHC FOR A SHOWER WAS LEFT IN THE FCST FOR THE WRN
COUNTIES THIS AFTERNOON WITH SOME INSTABILITY AND THE UPPER TROUGH
APPROACHING. DEW POINTS WILL BE A BIT HIGHER THAN OVER THE
WEEKEND...BUT STILL NOT TOO UNCOMFORTABLE. WINDS WILL BE LIGHT
FAVORING THE E OR SE.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
LOW LEVEL MOISTURE WILL CONTINUE TO SLOWLY INCREASE TONIGHT WITH THE
HIGH STILL OFF TO THE EAST. A PERIOD OF LOW CLOUDS AND MAYBE SOME
FOG WILL DEVELOP ACROSS THE DELMARVA AND SRN NJ. NO PCPN IS EXPECTED
TONIGHT. LOWS WILL BE A FEW DEGREES ABOVE NORMAL WITH UPPER 60S TO
LOW 70S EXPECTED ACROSS THE REGION.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
500MB: EXPANSIVE BROAD WARM RIDGE FROM THE ROCKIES TO THE WESTERN
ATLANTIC WILL BE SPLIT BY EAST COAST TROUGHING LATE WEDNESDAY OR
THURSDAY AND THEN POTENTIALLY MORE SUBSTANTIAL TROUGHING DEVELOPS
LATE SUNDAY OVER THE UPPER MIDWEST.

TEMPERATURES: THE MONTH SO FAR HAS AVERAGED ABOUT A DEGREE ABOVE
NORMAL EXCEPT KACY AREA WHICH HAS AVERAGED A DEGREE BELOW NORMAL.
TUESDAYS SLIGHTLY ABOVE NORMAL CALENDAR DAY AVG TEMPERATURES
SHOULD BE ABOUT 6 DEGREES ABOVE NORMAL WEDNESDAY AND POSSIBLY
STILL 5 DEGREES ABOVE NORMAL THURSDAY BEFORE COOLING TO NEAR OR
SLIGHTLY BELOW NORMAL FRI-SUN.

AS YOU MAY BE AWARE...THIS SUMMER IS NOT LIKE THE BOILERS OF 2010
(#2) AND 2013 (#3). STILL DESPITE THE RELATIVELY NUMBER OF NICE
DAYS...THE AVG TEMP FROM JUNE 1-JUL 20 IS TIED FOR THE 14TH
WARMEST ON RECORD HERE AT KPHL.

FORECAST BASIS: UNLESS OTHERWISE NOTED THE LONG TERM PERIOD OF THIS
FORECAST IS GENERALLY BASED ON A 50 50 BLEND OF THE 00Z/21 NAM/GFS
MOS FOR THE PERIOD TUESDAY-WEDNESDAY... THE 00Z/21 GFS MOS WEDNESDAY
NIGHT AND THURSDAY AND THEN THEREAFTER (THURSDAY NIGHT ONWARD) THE
0543Z/21 WPC GRIDDED GUIDANCE WHICH AT TIMES IS BLENDED 50 50 WITH
THE 00Z/21 MEXMOS. ALL THIS IS EVENTUALLY CHECKED AGAINST THE 00Z/21
ECMWF TO SEE IF WE`RE IN THE BALLPARK WITH ECMWF CYCLICALLY PERSISTENT
18Z 2 METER TEMPERATURES. THE PRECIPITATION PROBABILITY GUIDANCE
IS CHECKED AGAINST THE 21Z/20 SREF POPS FOR .01 IN 3 HRS THROUGH
12Z THURSDAY AND THEREAFTER THE 00Z/21 GEFS 6HR POPS FOR 0.05 .

THE DAILIES...

TUESDAY...CONSIDERABLE EARLY MORNING CLOUDINESS THEN HIGHS WARMING
INTO THE UPPER 80S IN MUCH OF OUR REGION TUESDAY AFTERNOON. A FEW
SPOTS MAY HIT 90 INCLUDING KPHL BUT AT THIS TIME SIDED WITH THE
SLIGHTLY COOLER ECMWF. CONDITIONS ARE FORECAST TO REMAIN MARGINALLY
STABLE ON THE COASTAL PLAIN. HOWEVER, THERE MAY BE ENOUGH INSTABILITY
IN EASTERN PENNSYLVANIA AND NORTHERN NEW JERSEY TO RESULT IN
ISOLATED SHOWERS OR A THUNDERSTORM TUESDAY AFTERNOON?

TUESDAY NIGHT...PATCHY LOW CLOUDS AND THICK FOG MAY FORM LATE?
MINIMUM TEMPERATURES ARE ANTICIPATED TO BE MOSTLY IN THE UPPER
60S AND LOWER 70S.

WEDNESDAY...SHOULD BE THE HOTTEST DAY OF THIS LONG TERM FORECAST
PERIOD. TEMPERATURES AT THE 850 HPA LEVEL ARE EXPECTED TO RISE TO
AROUND 18C. WE WILL CONTINUE TO CARRY MAXIMUM TEMPERATURES MOSTLY
IN THE LOWER 90S WITH PEAK HEAT INDEX VALUES MAINLY IN THE UPPER
90S WITH A 100F HEAT INDEX POSSIBLE IN CENTRAL NJ AND THE
DELMARVA. IT WILL BE COOLER THAN THAT IN THE ELEVATED TERRAIN UP
NORTH AND IN AREAS ALONG THE COAST.

WE WILL CONTINUE TO MENTION A CHANCE OF THUNDERSTORMS MOVING INTO
OUR REGION FROM THE NORTHWEST ON WEDNESDAY. MIXED LAYER CAPE
VALUES ARE EXPECTED TO RISE AROUND 2000 J/KG ALONG THE INTERSTATE
95 CORRIDOR DURING THE AFTERNOON. HOWEVER, A BIT OF A CAP MAY
INITIALLY PREVENT THE ACTIVITY FROM BECOMING WIDESPREAD.

HOWEVER...AN APPROACHING COLD FRONT COULD SEND A BAND OF SCT STRONG
TSTMS INTO E PA AND NJ. KI 34 TT 49 SWI -2. 0-6KM BULK SHEAR AND
500MB WINDS LOOK TOO WEAK TO SUPPORT MUCH SVR BUT IF THE TIMING IS
CLOSE ENOUGH TO UTILIZE THE 2000J ML CAPE...THEN ISO SVR COULD BE
POSSIBLE ALONG AND N OF I-78.

WEDNESDAY NIGHT-THURSDAY...THE COLD FRONT WILL PROGRESS SLOWLY
TO THE SOUTHEAST AND IT SHOULD CROSS OUR REGION LATER WEDNESDAY
NIGHT OR THURSDAY. WE CONTINUE TO MENTION A CHANCE OF SHOWERS AND
THUNDERSTORMS FOR WEDNESDAY NIGHT AND THURSDAY. SUSPECT THE
STATISTICAL PROBABILITIES FOR CLUSTERS OF SHOWERS AND TSTMS WILL
SHIFT TO THE PHL AREA SOUTHWARD THROUGH THE DELMARVA FOR THURSDAY
AFTERNOON. HIGH TEMPERATURES ON THURSDAY SHOULD RANGE FROM THE
UPPER 70S IN THE NORTH TO AROUND 90 IN THE SOUTH. IT MAY EVEN
TOUCH 90 IN PHL ALTHOUGH THE ECMWF IS SIGNIFICANTLY COOLER.

FRIDAY-WEEKEND...A MID LEVEL TROUGH OVER THE NORTHEASTERN STATES
ON FRIDAY SHOULD LIFT TO THE NORTHEAST WITH ANOTHER TROUGH
EXPECTED TO DROP OVER THE GREAT LAKES REGION ON SUNDAY. HIGH
PRESSURE AT THE SURFACE IS ANTICIPATED TO BUILD ACROSS OUR REGION
FOR FRIDAY AND SATURDAY WITH LOW PRESSURE AND A WARM FRONT
APPROACHING FROM THE SOUTH ON SUNDAY. DAYTIME HIGHS ARE EXPECTED
TO BE MAINLY IN THE 80S WITH OVERNIGHT LOWS GENERALLY IN THE 60S.
SHOWERS AND ISOLATED TSTMS COULD DEVELOP WITH THE WARM FRONT
SUNDAY....THE ECMWF HAS BEEN QUITE EMPHATIC ABOUT CONSIDERABLE
SHOWER AND TSTM ACTIVITY FOR SUNDAY IN AT LEAST ITS PAST TWO
CYCLES.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

CONDITIONS ARE VFR AT THE TERMINALS AS OF 06Z. SOME OF THE GUIDANCE
SUGGESTS THAT SOME LOW CLOUDS AND/OR FOG MAY DEVELOP BEFORE DAWN AND
BRING MVFR OR PERHAPS IFR CONDITIONS FOR AWHILE. WHILE I HAVE NOT
COMPLETELY DISCOUNTED THAT FROM HAPPENING...I DID NOT  FULLY BUY IT
EITHER. I HAVE KEPT THE MENTION OF LOW CLOUDS AT KILG-KMIV AND
KACY...CLOSEST TO THE HIGHER DEW POINTS. WINDS WILL REMAIN VERY
LIGHT...MOSTLY ERLY OR SERLY.

TODAY WILL FEATURE MOSTLY SUNNY SKIES WITH SOME AFTERNOON CU AT
TIMES. A ISOLATED SHOWER IS POSSIBLE FAR N/W...BUT NOT MENTIONED IN
THE TAFS ATTM. WINDS MOSTLY 5 TO 10 KTS...AGAIN MOSTLY ERLY/SERLY
EARLY THEN SRLY LATE. TONIGHT...MOSTLY VFR WITH LIGHT WINDS. MORE
LOW CLOUDS/FOG POSSIBLE TOWARDS DAWN.

OUTLOOK...
TUESDAY...MAINLY VFR. A SLIGHT CHANCE OF AFTERNOON THUNDERSTORMS
VICINITY KRDG AND KABE NORTHWESTWARD.

TUESDAY NIGHT AND WEDNESDAY...MAINLY VFR. PATCHY LATE NIGHT AND
EARLY MORNING MVFR OR IFR CONDITIONS IN LOW CLOUDS, FOG AND HAZE.
A CHANCE OF AFTERNOON THUNDERSTORMS....ESPECIALLY THE I-78
CORRIDOR NORTHWARD INCLUSIVE OF KRDG AND KABE.

WEDNESDAY NIGHT AND THURSDAY...MVFR AND IFR CONDITIONS AT TIMES IN
SHOWERS AND THUNDERSTORMS...STRATUS AND FOG.

THURSDAY NIGHT...IFR POSSIBLE IN PATCHY STRATUS AND FOG.

FRIDAY...MAINLY VFR.

&&

.MARINE...
SEAS AT 44009 ARE NOW BELOW SCA CRITERIA...SO WE CANCELED THE SCA
FLAG WITH THE 321 AM CWF ISSUANCE. HIGH PRESSURE WILL STAY NORTH OF
THE WATERS TODAY AND TONIGHT. WINDS WILL REMAIN MOSTLY ERLY OR
SERLY...MOSTLY UNDER 10 KTS...THROUGH TONIGHT. SEAS 2-3 FT ON THE
OCEAN AND 1-2 T ACROSS DEL BAY. FAIR WEATHER IS EXPECTED TODAY AND
TONIGHT.

OUTLOOK...
TUESDAY THROUGH FRIDAY...NO MARINE HEADLINES ARE ANTICIPATED.

&&

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

&&

$$
SYNOPSIS...DRAG
NEAR TERM...O`HARA
SHORT TERM...O`HARA
LONG TERM...DRAG  529AM
AVIATION...DRAG/O`HARA
MARINE...DRAG/O`HARA






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