Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 202113
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
513 PM EDT WED AUG 20 2014

.SYNOPSIS...
WEAK LOW PRESSURE WILL MOVE NORTH OF THE AREA TONIGHT AND THURSDAY.
ANOTHER LOW PRESSURE SYSTEM WILL MOVE SOUTH OF THE AREA THURSDAY
NIGHT THROUGH EARLY SATURDAY. HIGH PRESSURE WILL BUILD IN FROM THE
NORTH LATER FRIDAY, THEN REMAIN FOR THE WEEKEND AND INTO EARLY NEXT
WEEK.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
A SHORT WAVE TROUGH AHEAD OF A MAIN UPPER-LEVEL TROUGH DROPPING DOWN
ACROSS THE GREAT LAKES REGION WILL LIFT EAST-NORTHEASTWARD THROUGH
TONIGHT. THE INITIAL LINE OF SHOWERS AND THUNDERSTORMS WITH THIS
FEATURE CONTINUES TO WEAKEN AND FRAGMENT AS IT ENTERS OUR FAR
WESTERN ZONES. THIS SHOULD CONTINUE AS IT ENCOUNTERS A MORE STABLE
AIRMASS WITH AN EASTWARD EXTENT AND ALSO LESS MOISTURE. THERE IS
SOME AIRMASS RECOVERY OCCURRING TO THE WEST OF THE LINE AND AN
ANALYSIS SHOWED DEEPER MOISTURE FARTHER TO THE WEST. WHILE SOME
SHOWERS /PERHAPS A RUMBLE OF THUNDER/ SHOULD MAKE THEIR WAY TO THE
EAST TONIGHT ESPECIALLY ACROSS PORTIONS OF EASTERN PENNSYLVANIA AND
NORTHERN NEW JERSEY, THEY SHOULD BE WEAKER. WE WILL MONITOR RADAR
TRENDS AND ADJUST THE POPS ACCORDINGLY. IN ADDITION, SOME
THUNDERSTORMS ARE DEVELOPING NEAR WASHINGTON DC HOWEVER THIS IN
WITHIN AN AREA OF HIGHER INSTABILITY.

OTHERWISE, ENOUGH MOISTURE AND THE LEFTOVER DEBRIS CLOUDS SHOULD
RESULT IN MORE CLOUDINESS THROUGH THE NIGHT ESPECIALLY EAST AND SOUTH
WHERE THE SKY HAS CLEARED THUS FAR. THE HOURLY GRIDS WERE TWEAKED
BASED ON THE LATEST OBSERVATIONS AND THEN THE LAMP/LAV GUIDANCE WAS
BLENDED IN TO HELP ASSIST WITH TRENDS.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
THURSDAY...ANOTHER SHORT WAVE IN THE WNW FLOW OVER SOUTHERN NEW
YORK STATE SHOULD REDEVELOP HEAVY CONVECTION DURING THE AFTN OVER
E PA...POSSIBLY EXTENDING INTO W NJ AND THE MD E SHORE CLOSER TO THE
CONVERGENCE OF THE SFC LOW AND INVERTED TROUGH EXTENDING NWD FROM
THE VCNTY OF DCA. PWAT VALUES ARE GENERALLY FORECAST AROUND
1.5-1.75 INCHES, SO SOME SHOWERS/STORMS COULD PRODUCE A PERIOD OF
MODERATE TO HEAVY RAINFALL. ISOLATED SMALL HAIL NOT IMPOSSIBLE AS
TT NEAR 50 IN AREA OF MAX INSTABILITY IN NJ (NEAR THE DELAWARE
RIVER).

FORECAST BASIS: POPS WERE BLENDED NCEP MOS POPS WITH THE 09Z SREF AND
THAT GIVES THE BEST CHANCE FOR SOME NEEDED RAIN TO E PA. OTRW A 50
50 BLEND OF 12Z/20 NCEP MOS EXCEPT BLENDED RGEM SKY WITH NAM SKY
AND GFS MOS GUIDE.

NEAR OR SLIGHTLY ABOVE NORMAL TEMPS.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
THE LONG TERM FORECAST STARTS OFF WITH RAIN CHANCES, BEFORE A DRYING
OUT PERIOD SETS IN ACROSS THE AREA.

THE WEAK AREAS OF LOW PRESSURE TO THE NORTH (THU NIGHT AND
FRIDAY) AND THE SOUTH (FRIDAY THRU SATURDAY) WILL FORCE US TO KEEP
LOW CHC POPS OR SLGT CHC POPS FOR THOSE PERIODS. THE SYSTEMS DO
NOT LOOK STRONG ENOUGH TO PRODUCE ANY HEAVY RAINS HOWEVER. DRY
WEATHER IS EXPECTED FOR SUNDAY INTO EARLY NEXT WEEK. HIGH PRESSURE
WILL BUILD IN FROM THE NORTH/NORTHEAST ALLOWING DRY AIR TO
OVERSPREAD THE AREA.

TEMPERATURES THROUGH THE LONG RANGE WILL START NEAR NORMAL
FRIDAY...BEFORE DROPPING TO BELOW NORMAL FOR THE WEEKEND AND NEXT
MONDAY. READINGS WILL REBOUND BACK TO NEAR NORMAL NEXT TUESDAY AND
THEN POSSIBLY GO ABOVE NORMAL WEDNESDAY.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

TONIGHT...VFR CEILINGS AT OR ABOVE 4000 FEET SPREADING FROM WEST TO
EAST. SOME SHOWERS SHOULD BE AROUND MAINLY NORTH AND WEST OF KPHL.
LIGHT SOUTHERLY WINDS. THERE COULD BE SOME LOCALIZED MVFR CEILINGS
WITH FOG TOWARD DAYBREAK.

THURSDAY...GENERALLY VFR CEILINGS. SOME SHOWERS AND THUNDERSTORMS
ARE EXPECTED TO OCCUR ESPECIALLY FARTHER INLAND, WHICH MAY LOWER
CEILINGS AND VISIBILITIES TO BRIEFLY IFR. SOUTHERLY WINDS GENERALLY
5-10 KNOTS.

OUTLOOK...
THU NIGHT THRU SATURDAY...MOSTLY VFR. SHOWERS WITH LOWER
CONDITIONS ARE POSSIBLE.

SAT NIGHT THRU MONDAY...MOSTLY VFR.

&&

.MARINE...
NO MARINE RELATED HEADLINES THROUGH THURSDAY.

EAST-SOUTHEAST WINDS BETWEEN 5-15 KT.

OUTLOOK...
THU NIGHT THRU FRI NIGHT...SUB SCA CONDITIONS W/ SCT SHOWERS.
SAT THRU MON...LOW END SCA SEAS EXPECTED ON THE OCEAN. MOSTLY FAIR WX.

&&

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

&&

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




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