Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 240129
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
929 PM EDT SUN AUG 23 2015

.SYNOPSIS...
A COLD FRONT IS EXPECTED TO ARRIVE IN OUR REGION MONDAY NIGHT, THEN
WEAK LOW PRESSURE IS FORECAST TO DEVELOP ALONG THE FRONT. THE
FORWARD SPEED OF THE FRONT WILL DECREASE AND IT IS EXPECTED TO MOVE
SLOWLY OFF THE COAST TUESDAY AND TUESDAY NIGHT. HIGH PRESSURE IS
ANTICIPATED TO FOLLOW FOR WEDNESDAY INTO FRIDAY, BEFORE SHIFTING
OFFSHORE DURING THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
LOW PRESSURE REMAINS WELL OFFSHORE WHILE HIGH PRESSURE BUILDS ACROSS
THE CANADIAN MARITIMES. OUR REGION GENERALLY REMAINS IN A WEAKNESS
BETWEEN THESE TWO SYSTEMS AND ALSO A THIRD WHICH IS A COLD FRONT
LOCATED IN THE GREAT LAKES AND OHIO VALLEY.

THERE APPEARS TO BE A SURFACE TROUGH EXTENDING NORTHWESTWARD FROM
THE OFFSHORE LOW, AND THIS FEATURE MAY SLIDE WESTWARD SOME THROUGH
THE OVERNIGHT. ANY SHOWERS REMAIN WELL OFFSHORE, AND MUCH OF THE
CUMULUS THAT DEVELOPED DURING THE COURSE OF THE DAY HAS DISSIPATED.
WE THEREFORE MAINTAINED A DRY FORECAST.

OTHERWISE, SOME LINGERING MID TO HIGH LEVEL CLOUDS ARE AROUND. SOME
ONSHORE COMPONENT TO THE LOW-LEVEL WIND THOUGH, ALTHOUGH RATHER
LIGHT, MAY RESULT IN SOME CLOUD REDEVELOPMENT OVERNIGHT MAINLY
ACROSS OUR NORTHEAST AND EAST ZONES WHERE DEW POINTS ARE MOSTLY
HIGHER. THIS COULD RESULT IN SOME STRATUS ESPECIALLY ALONG THE
COAST, HOWEVER THIS DEVELOPMENT IS OF LOW CONFIDENCE. THERE COULD BE
PATCHY FOG TOWARD DAYBREAK, ALTHOUGH THIS WOULD PROBABLY BE LIMITED
TO FIELD/VALLEY AREAS AND MORE OF A SHALLOW GROUND FOG.

THE HOURLY GRIDS WERE ADJUSTED BASED ON THE LATEST OBSERVATIONS,
THEN THE LAMP/LAV GUIDANCE WAS BLENDED IN. NO MAJOR CHANGES WERE
MADE TO THE LOW TEMPERATURES ATTM.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
ON MON, A LARGE AREA OF LOW PRES IN ONTARIO WILL MOVE EWD AND ITS
ATTENDANT CDFNT WILL APPROACH THE AREA DURG THE DAY, REACHING WRN
SECTIONS BY THE END OF THE PD. EXPECT MOST AREA TO REMAIN DRY DURG
THE DAYLIGHT HOURS. HOWEVER, NRN AND WRN SECTIONS WILL SEE SOME
CHC POPS BY EVE AS THE CDFNT APPROACHES. CLOUD COVER WILL BE ON
THE INCREASE AS WELL THROUGHOUT THE DAY IN ADVANCE OF THE FRONT.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
A MID LEVEL LOW IS FORECAST TO BE LOCATED OVER CENTRAL ONTARIO ON
MONDAY NIGHT. THE FEATURE IS EXPECTED TO DRIFT EASTWARD, BECOMING
AN OPEN WAVE OVER WESTERN QUEBEC AROUND WEDNESDAY NIGHT. THE
ASSOCIATED MID LEVEL TROUGH IS ANTICIPATED TO INFLUENCE OUR
WEATHER INTO THURSDAY NIGHT BEFORE LIFTING TO THE NORTHEAST ON
FRIDAY. SOME RIDGING MAY THEN DEVELOP OVERHEAD BEFORE ANOTHER MID
LEVEL TROUGH POSSIBLY APPROACHES FROM THE GREAT LAKES OVER THE
WEEKEND.

A SURFACE COLD FRONT IS FORECAST TO MOVE INTO OUR REGION FROM THE
WEST ON MONDAY NIGHT. WEAK LOW PRESSURE IS EXPECTED TO DEVELOP ON
THE FRONT IS NORTHERN VIRGINIA AND CENTRAL MARYLAND ON MONDAY
EVENING BEFORE DRIFTING NORTHEASTWARD ACROSS OUR REGION FROM LATE
MONDAY NIGHT INTO TUESDAY MORNING. WE WILL CONTINUE TO MENTION A
CHANCE OF SHOWERS AND THUNDERSTORMS WITH AND AROUND THE FRONT.
INSTABILITY IS ANTICIPATED TO BE MARGINAL SO THERE IS A LOW
POTENTIAL FOR SEVERE WEATHER. ALSO, PRECIPITABLE WATER VALUES
SHOULD RISE ONLY INTO THE 1.6 TO 1.7 INCH RANGE. WHILE LOCALIZED
DOWNPOURS ARE POSSIBLE, THE CHANCE FOR FLOODING IS LOW.

THE MID LEVEL FLOW OVER OUR REGION IS FORECAST TO BACK TO THE
SOUTHWEST FOR TUESDAY AND IT, ALONG WITH THE WEAK SURFACE LOW,
SHOULD CAUSE THE FORWARD PROGRESS OF THE COLD FRONT TO SLOW
CONSIDERABLY. THE BOUNDARY IS ANTICIPATED TO DRIFT OFF THE COAST
AND OUT TO SEA ON TUESDAY AND TUESDAY NIGHT. DRY AIR IS EXPECTED
TO BEGIN FILTERING INTO OUR REGION FROM THE WEST AND NORTHWEST ON
TUESDAY AFTERNOON WITH A DECREASING CHANCE OF PRECIPITATION FROM
WEST TO EAST.

HIGH PRESSURE AND DRY AIR ARE FORECAST TO BUILD INTO OUR REGION
FROM THE WEST FOR WEDNESDAY, THURSDAY AND FRIDAY. WE ARE EXPECTING
MOSTLY SUNNY SKIES DURING THE DAY WITH SCATTERED CUMULUS
DEVELOPING AS SOME COOL AIR BUILDS OVERHEAD. WEAK IMPULSES IN THE
MID LEVEL FLOW MAY HELP TO ENHANCE THE AMOUNT OF CUMULUS OVER OUR
NORTHERN COUNTIES ON WEDNESDAY AFTERNOON AND THURSDAY AFTERNOON.
VERY WEAK INSTABILITY IN THE NORTH COULD RESULT IN SCATTERED
SPRINKLES THERE. MEANWHILE, THE NIGHTS SHOULD BE MAINLY CLEAR WITH
PERHAPS SOME LATE NIGHT VALLEY FOG DEVELOPING IN EASTERN
PENNSYLVANIA AND NORTHERN NEW JERSEY.

TEMPERATURES FOR THE PERIOD FROM WEDNESDAY THROUGH FRIDAY SHOULD
BE NEAR OR SLIGHTLY BELOW NORMAL.

THE CENTER OF THE SURFACE HIGH IS FORECAST TO PASS ACROSS OUR
REGION ON FRIDAY BEFORE MOVING OUR TO SEA OVER THE WEEKEND. THE
RETURN SOUTH TO SOUTHWEST FLOW ON THE BACKSIDE OF THE HIGH SHOULD
RESULT IN A GRADUAL INCREASE IN HEAT AND HUMIDITY AT THAT TIME.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

OVERNIGHT...VFR OVERALL. THERE IS THE POTENTIAL FOR LOCAL LOW CLOUDS
AND/OR FOG DEVELOPMENT TOWARD DAYBREAK, MAINLY THE MORE RURAL AND
CLOSER TO THE COAST TERMINALS. THIS IS OF LOW CONFIDENCE AND
THEREFORE NOT INCLUDED AT THIS TIME. WINDS MAINLY LIGHT AND VARIABLE
TO LOCALLY CALM.

MONDAY...POSSIBLE LOCAL MVFR FOG/CEILINGS EARLY, OTHERWISE VFR.
LIGHT AND VARIABLE TO CALM WINDS, BECOMING SOUTHERLY AND INCREASING
UP TO 10 KNOTS IN THE AFTERNOON. A COLD FRONT WILL BE APPROACHING
FROM THE WEST, AND SOME SHOWERS AND THUNDERSTORMS COULD BE
APPROACHING THE KRDG AND KABE AREAS TOWARD 00Z.

OUTLOOK...
MONDAY NIGHT INTO TUESDAY...A CHANCE OF SHOWERS AND THUNDERSTORMS
THAT MAY LOWER CONDITIONS INTO THE MVFR OR IFR CATEGORIES AT
TIMES.

TUESDAY NIGHT...MAINLY VFR WITH PATCHY LOW CLOUDS AND FOG
POSSIBLE.

WEDNESDAY THROUGH FRIDAY...MAINLY VFR.

&&

.MARINE...
NO MARINE FLAGS ARE ANTICIPATED THRU THE NR AND SHORT TERM PDS.
SEAS WILL GENLY BE IN THE 3 TO 4 FT RANGE. WIND WILL GENLY BE NE
THRU ERLY TONIGHT THEN EVENTUALLY SWING AROUND MORE TO THE SE BY
LATER MON AS A CDFNT APPROACHES FROM THE NW.

OUTLOOK...
MONDAY NIGHT THROUGH FRIDAY...NO MARINE HEADLINES ARE
ANTICIPATED.

&&

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

&&

$$
SYNOPSIS...GORSE/IOVINO
NEAR TERM...GORSE
SHORT TERM...NIERENBERG
LONG TERM...IOVINO
AVIATION...GORSE/IOVINO
MARINE...IOVINO/NIERENBERG


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