Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 060129 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 929 PM EDT SUN JUL 5 2015 .SYNOPSIS...
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WEAK HIGH PRESSURE WILL SHIFT OFF THE COAST TONIGHT AND MONDAY. A WARM FRONT IS FORECAST TO LIFT NORTHWARD AND THROUGH OUR REGION MONDAY NIGHT INTO TUESDAY MORNING. ANOTHER FRONTAL BOUNDARY IS EXPECTED TO ARRIVE ON WEDNESDAY, THEN THE FRONT IS ANTICIPATED TO MEANDER IN OR NEAR OUR REGION WEDNESDAY NIGHT INTO FRIDAY AS LOW PRESSURE MOVES ALONG IT. WEAK HIGH PRESSURE MAY TRY TO BUILD DOWN FROM THE NORTHWEST NEXT WEEKEND AS THE FRONT REMAINS NEARBY.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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A WELL DEFINED UPPER-LEVEL LOW MOVING ACROSS WEST VIRGINIA THIS EVENING WILL CONTINUE TO LIFT NORTHEAST THROUGH THE NIGHT, HOWEVER IT MAY WEAKEN SOME. THIS IS ASSISTING IN PULLING MOISTURE NORTHWARD WITH MAINLY HIGH LEVEL CLOUDS ACROSS OUR AREA ATTM. HOWEVER THE MODEL GUIDANCE SHOWS A PW SURGE OCCURRING OVERNIGHT WITH AN INCREASE TO 2.00 INCHES BY MORNING. THIS IS COMBINATION WITH SOME WAA AND ALSO SOME INCREASE IN LIFT WITH THE AFOREMENTIONED UPPER-LEVEL LOW MAY RESULT IN SOME SHOWERS. THIS LOOKS TO BE MOSTLY ACROSS PORTIONS OF THE DELMARVA TO PERHAPS OUR FAR WESTERN ZONES. THE POPS WERE TWEAKED A BIT TO SHOW A LITTLE FASTER INCREASE TO CHC ACROSS THE FAR SOUTHERN AREAS OVERNIGHT. THE COVERAGE/TIMING IS A BIT UNCERTAIN GIVEN THE BEST LIFT LOOKS TO BE TO OUR WEST. THE ONGOING CONVECTION THOUGH IN VIRGINIA WILL NEED TO BE WATCHED AS IT IS GRADUALLY LIFTING NORTHWARD. OTHERWISE, AN INCREASE IN CLOUDS THROUGH THE NIGHT WITH THE CHC OF SOME LOW CLOUDS/FOG. THE BEST CHC OF THE LATTER APPEARS TO BE OUR WESTERN ZONES GIVEN THE LIGHT UPSLOPE COMPONENT TO THE LOW-LEVEL FLOW WITHIN A MOISTENING ENVIRONMENT. 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.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
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AN AREA OF SHOWERS WILL BRING THE BEST CHCS OF RAIN TO THE DELMARVA AND WRN SECTIONS OF THE AREA DURG THE DAY. IT IS PSBL THAT ERN AREAS REMAIN DRY, BUT WILL CARRY VERY LOW POPS IN THESE LOCATIONS LATER IN THE DAY. OVERALL THE AVERAGE QPF APPEARS TO BE ON THE LOWER SIDE, HOWEVER LOCAL DOWNPOURS /HIGHER QPF/ CAN OCCUR GIVEN PW VALUES FORECAST TO BE ABOUT 2.00 INCHES. HIGH TEMPS WILL BE IN THE MID TO UPPER 80S.
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&& .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... THE MID LEVEL RIDGE THAT WAS OVER THE WESTERN STATES IS FORECAST TO DISAPPEAR FOR THE NEW WEEK AS LOW PRESSURE MEANDERS OFF THE CALIFORNIA COAST, MOVES INLAND AND FILLS. THE MID LEVEL FLOW EAST OF THE ROCKIES IS EXPECTED TO BECOME SOMEWHAT ZONAL, RESULTING IN ANOTHER POTENTIALLY ACTIVE WEEK FOR OUR REGION. THE WESTERN RIDGE IS ANTICIPATED TO RETURN NEXT WEEKEND. IT CONTINUES TO APPEAR AS THOUGH A WAVERING FRONTAL BOUNDARY TO OUR SOUTH WILL RETURN NORTHWARD AS A WARM FRONT ON MONDAY NIGHT. THE BOUNDARY IS EXPECTED TO PASS THROUGH OUR REGION FROM MONDAY NIGHT INTO TUESDAY MORNING. AS A RESULT, WE MAY SEE SOME LOW CLOUDS AND PATCHY FOG AND HAZE, ALONG WITH A CHANCE OF SHOWERS OR A THUNDERSTORM. A MID LEVEL SHORT WAVE TROUGH IS FORECAST TO BE LOCATED OVER THE UPPER OHIO RIVER VALLEY AND VICINITY ON MONDAY EVENING. THE FEATURE WILL DRIFT EASTWARD AND IT IS EXPECTED TO PASS OVER OUR REGION ON TUESDAY AFTERNOON. THE INCREASE IN MOISTURE AND THE DEVELOPMENT OF INSTABILITY DUE TO DAYTIME HEATING ALONG WITH THE MID LEVEL TROUGH PASSING OVERHEAD COULD RESULT IN THE DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS ON TUESDAY AFTERNOON. THE GREATEST POTENTIAL APPEARS TO BE IN EASTERN PENNSYLVANIA AND NORTHERN AND CENTRAL NEW JERSEY WHERE MIXED LAYER CAPE VALUES ARE FORECAST TO RISE AROUND OR JUST ABOVE 1000 J/KG. THE TIMING OF ADDITIONAL IMPULSES IN THE NEARLY ZONAL MID LEVEL FLOW DURING THE MID AND LATE WEEK PERIOD BECOMES A BIT OF A CHALLENGE AFTER THE INITIAL MID LEVEL TROUGH PASSES ON TUESDAY AFTERNOON. WHILE IT SEEMS THAT CONVECTION WILL OCCUR IN PARTS OF OUR AREA ON WEDNESDAY, AND PERHAPS ON THURSDAY AND FRIDAY, AS WELL, THE EXACT LOCATION OF THE GREATEST POTENTIAL REMAINS A LOW CONFIDENCE FORECAST. PRESENTLY, IT LOOKS AS THOUGH OUR HIGHEST CHANCE FOR SEVERE THUNDERSTORMS MAY BE ON WEDNESDAY AFTERNOON AND EVENING WITH THE ARRIVAL OF THE FRONT FROM THE NORTHWEST. THE FORECAST WIND PROFILES FOR THAT TIME PERIOD SUGGEST THAT IF CONVECTION DEVELOPS IT COULD BECOME ORGANIZED. CAPE VALUES IN EXCESS OF 1000 J/KG ARE ANTICIPATED. THE LATEST GENERAL TIMING OF THE MAIN SURFACE LOW RIDING ALONG THE FRONTAL BOUNDARY BRINGS IT ACROSS OUR REGION ON THURSDAY NIGHT. AS IS THE CASE WITH THE MID LEVEL FEATURES, THE TIMING OF THE SURFACE WAVE REMAINS IN QUESTION. WE WILL KEEP A CHANCE OF SHOWERS AND THUNDERSTORMS FOR THURSDAY INTO THURSDAY NIGHT, WITH MAINLY A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS FOR FRIDAY. PRECIPITABLE WATER VALUES ARE FORECAST TO RISE NEAR OR ABOVE 2 INCHES DURING THE MID AND LATE WEEK PERIOD. ANY THUNDERSTORMS COULD BRING HEAVY DOWNPOURS ALONG WITH LOCALIZED FLOODING OF ROADWAYS AND AREAS OF POOR DRAINAGE. ALSO, WE WILL KEEP AN EYE ON THE FLASH FLOODING POTENTIAL ESPECIALLY IF CERTAIN AREAS ARE AFFECTED BY HEAVY RAINFALL ON MORE THAN ONE DAY. THE GUIDANCE DIFFERS WITH THE FORECAST FOR NEXT WEEKEND. THE MAIN QUESTION CONCERNS WHETHER THE FRONTAL BOUNDARY WILL BE PUSHED FAR ENOUGH SOUTH TO ALLOW WEAK HIGH PRESSURE TO BUILD INTO OUR REGION FROM THE NORTHWEST AND NORTH. AS A RESULT, WE WILL CONTINUE TO CARRY EITHER A LOW OR SLIGHT CHANCE FOR PRECIPITATION. DAYTIME TEMPERATURES ARE ANTICIPATED TO BE WITHIN A FEW DEGREES OF NORMAL FOR THE PERIOD FROM MONDAY NIGHT THROUGH SUNDAY. NIGHTTIME TEMPERATURES ARE FORECAST TO BE SOLIDLY ABOVE NORMAL. && .AVIATION /02Z MONDAY THROUGH FRIDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TONIGHT...VFR OVERALL WITH AN INCREASE IN CLOUDS. SOME MVFR CEILINGS AND/OR VISIBILITIES SHOULD DEVELOP LATE ESPECIALLY IN THE KABE TO KRDG AREAS. LIGHT SOUTHERLY WIND BECOMING LIGHT AND VARIABLE. SOME SHOWERS ARE POSSIBLE CLOSER TO DAYBREAK NEARING KRDG TO KILG, HOWEVER CONFIDENCE IS ON THE LOWER SIDE. MONDAY...ANY MVFR CONDITIONS SHOULD LIFT EARLY, OTHERWISE MAINLY VFR. SOME SHOWERS AND THUNDER ARE ANTICIPATED TO DEVELOP, MAINLY SOUTH AND WEST OF KPHL. SINCE COVERAGE AND OVERALL TIMING IS A BIT UNCERTAIN, USED A VCSH FOR NOW AT INLAND TERMINALS. LIGHT AND VARIABLE WINDS, BECOMING SOUTH-SOUTHEAST UP TO 10 KNOTS. OUTLOOK... MONDAY NIGHT AND TUESDAY MORNING...CONDITIONS POSSIBLY LOWERING TO MVFR OR IFR IN LOW CLOUDS, HAZE AND FOG ESPECIALLY DURING THE LATE NIGHT AND EARLY MORNING HOURS. A CHANCE OF SHOWERS AND THUNDERSTORMS. TUESDAY AFTERNOON AND TUESDAY EVENING...MAINLY VFR WITH A CHANCE OF SHOWERS AND THUNDERSTORMS. TUESDAY NIGHT AND WEDNESDAY MORNING...CONDITIONS POSSIBLY LOWERING TO MVFR OR IFR IN LOW CLOUDS, HAZE AND FOG ESPECIALLY DURING THE LATE NIGHT AND EARLY MORNING HOURS. WEDNESDAY AFTERNOON THROUGH THURSDAY NIGHT...A CHANCE OF SHOWERS AND THUNDERSTORMS WHICH MAY CAUSE CONDITIONS TO LOWER TO MVFR OR IFR AT TIMES. FRIDAY...MAINLY VFR.
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&& .MARINE... NO MARINE HEADLINES ARE ANTICIPATED THRU THE NEAR AND SHORT TERM PDS. 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...GORSE/NIERENBERG LONG TERM...IOVINO AVIATION...GORSE/IOVINO MARINE...IOVINO/NIERENBERG

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