Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 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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