Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 010134 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 934 PM EDT THU JUL 31 2014 .SYNOPSIS... WEAK HIGH PRESSURE WILL REMAIN ACROSS THE REGION TONIGHT AND INTO EARLY FRIDAY. SEVERAL WEAK DISTURBANCES AND A COASTAL FRONT WILL AFFECT THE AREA THIS WEEKEND. HIGH PRESSURE WILL BUILD ACROSS THE AREA EARLY NEXT WEEK. ANOTHER DISTURBANCE WILL MOVE TOWARD THE AREA TOWARD THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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IT LOOKS LIKE THE LAST OF THE ISOLATED SHOWERS HAS DISSIPATED ACROSS OUR CWA AND THE ONES LEFT TO THE WEST ARE RUNNING ON FUMES. THE NEXT SHOT FOR PCPN IS TOWARD MORNING IF PCPN IN THE CAROLINAS CAN MAKE IT INTO OUR CWA. THE SHORT WAVES LOOK VIGOROUS ENOUGH, SO WHILE WE SLOWED THE ARRIVAL BASED ON COSPA/HRRR AND RUC TRENDS, WE DID NOT COMPLETELY REMOVE POPS. CONVECTIVE PARAMETERS SUGGEST THUNDER NOT LIKELY. WE ADJUSTED TEMPERATURES DOWNWARD SLIGHTLY NORTHWEST AND UPWARD SOUTHEAST BASED ON CLOUD TREND. CLOUDINESS IS LINED PARALLEL TO THE UPPER AIR FLOW, SO IT WILL TAKE A WHILE FOR IT TO BACK NORTHWEST. ANOTHER COOL AND COMFORTABLE NIGHT IS IN STORE FOR MOST OF US, WITH THE EXCEPTION BEING DELAWARE AND SOUTH JERSEY WHERE HUMIDITY WILL BE NUDGING EVER SO SLIGHTLY HIGHER. SOME LOW CLOUDS AND BRIEF LOCALIZED FOG IS POSSIBLE TOWARDS SUNRISE AS WELL. STAYED CLOSE TO THE MAV/MET ON TEMPERATURES TONIGHT AND ADJUSTED THE EVENING TEMPERATURES SLIGHTLY BASED ON THE LATEST METAR OBS AND INCORPORATED THE LATEST LAMP/LAV GUIDANCE. CLOUDS WILL BE ON THE INCREASE AHEAD OF THE NEXT SYSTEM BY SUNRISE.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... ANOTHER SHORTWAVE TO OUR WEST WILL CAUSE A SOUTHEASTERLY FLOW TO DEVELOP OVER THE REGION AND AN OFFSHORE FRONT TO BACK AND MOVE CLOSER TO THE COAST. AS A RESULT, MOISTURE WILL BE ON THE RISE ON FRIDAY, BOTH AT THE SURFACE AND AT MID-LEVELS. IT WILL FEEL MUGGY AGAIN JUST IN TIME FOR AUGUST. ALTHOUGH THE ONSHORE FLOW WILL LESSEN ANY INSTABILITY THAT DEVELOPS, SHOWERS AND ISOLATED THUNDERSTORMS WILL STILL BE POSSIBLE IN THE AFTERNOON FRIDAY WITH THE GREATEST THREAT IN THE WESTERN PARTS OF THE REGION WHERE THE SOUTHEAST FLOW WILL HAVE A LESSER IMPACT ON INSTABILITY. CAPE VALUES ARE EXPECTED TO BE NEAR 1000 J/KG IN THE WESTERN PART OF THE REGION, AND AROUND 500-800 J/KG ELSEWHERE. THIS WILL LIMIT THE THREAT FOR STRONG THUNDERSTORMS BUT WILL STILL ENOUGH TO HAVE THUNDER IN THE GRIDS. WENT A TOUCH COOLER THAN THE MAV/MET FOR TEMPERATURES BASED ON THE LIKELIHOOD OF CLOUDS AND SPOTTY SHOWERS. NOT SOLD ON THE WETNESS OF THE NAM/SREF IN TERMS OF QPF, SO WENT RATHER LIGHT WITH THIS ELEMENT. DUE TO THE SPOTTY NATURE OF ANY SHOWERS IN THE AFTERNOON WENT FAIRLY LOW WITH CHANCE POPS AND SLOWER TIMING ON ANY RAIN WHEN COMPARED TO THE NAM/GFS MORE IN LINE WITH THE RGEM/ECMWF. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... AN UNSETTLED PERIOD EXPECTED THIS WEEKEND INTO EARLY MONDAY...BEFORE AN IMPROVING PICTURE NEXT WEEK. A FRONT/INVERTED TROUGH WILL LINGER ALONG THE EAST COAST THIS WEEKEND WHILE UPPER HEIGHTS BEGIN TO BUILD. THE UPPER HIGH ACROSS THE OCEAN WILL BEGIN TO BUILD BACK ACROSS THE AREA LATE THIS WEEKEND INTO NEXT WEEK. THIS WILL BRING AN ONSHORE FLOW WITH ABUNDANT MOISTURE THIS WEEKEND. SCT SHOWERS AND TSTMS WILL BE IN THE FCST FOR FRI NIGHT AND THRU THE WEEKEND. TEMPERATURES WILL HOLD TO MOSTLY NORMAL OR A BIT BELOW NORMAL WITH ALL THE EXTRA CLOUDINESS. IT WILL BE A RATHER HUMID PERIOD HOWEVER. BY MONDAY...THE BUILDING HIGH WILL CAUSE THE ONSHORE FLOW TO WEAKEN AND THE MEAN FLOW ALOFT WILL SWITCH TO MOVE WRLY/SWLY. THIS WILL ALLOW DRIER AIR TO ARRIVE...BUT ALSO WARMER TEMPERATURES. HIGHS TUE-THU WILL MOSTLY BE IN THE MID/UPPER 80S ACROSS THE SRN AREAS AND LOW/MID 80S NORTH. THESE TEMPERATURES ARE AT OR A BIT ABOVE NORMAL. SCT SHOWERS EARLY MONDAY...THEN A MOSTLY DRY FCST FOR NEXT WEEK. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. 00Z TAFS ARE GENERALLY VFR EXCEPT FOR SOME PATCHY MVFR FOG AT MORE RURAL AIRPORTS EARLY FRIDAY MORNING. FOR TONIGHT, DEBRIS VFR CLOUDINESS OVER THE SOUTHERN MID ATLANTIC IS FORECAST TO OVERSPREAD THE TERMINALS AND SOUTHERN AIRPORTS ESPECIALLY. NOT AS CONFIDENT FAR NORTHWEST. BECAUSE OF THIS WE ARE PREDICTING SOME MVFR VSBY RESTRICTIONS NORTHWEST TERMINALS AND ALSO AT KMIV. IF THESE CLOUDS DO NOT MATERIALIZE, THERE MAY BE MORE WIDESPREAD MVFR TO LOCALLY IFR FOG AROUND SUNRISE ON FRIDAY. ALONG WITH THE DEBRIS CLOUDINESS SOME LEFTOVER SHOWERS MIGHT MAKE IT INTO THE SOUTHERN TERMINALS BEFORE SUNRISE. BEST CHANCES THOUGH ARE IN DELMARVA AIRPORTS. WINDS WILL BE LIGHT FROM THE SOUTH TH SOUTHWEST AT LESS THAN 10 KNOTS. ON FRIDAY WE ARE EXPECTING MORE WIDESPREAD VFR CLOUDINESS (MOST LIKELY AT THE ALTOCU LEVEL). OVERALL COVERAGE OF SHOWERS AND THUNDERSTORMS SHOULD BE MORE THAN TODAY, BUT STILL TOO ISOLATED TO CONFIDENTLY INCLUDE THEM. SOUTH WINDS SHOULD AVERAGE AROUND 10 KTS. GUIDANCE IS NOT SHOWING A CLEAR CUT SEA BREEZE FRONT FOR NOW. OUTLOOK... FRI NIGHT THRU SUN NIGHT...LOWER CIGS EXPECTED AT TIMES WITH ON ONSHORE FLOW. SCT SHOWERS/TSTMS AT TIMES WITH LOWER VSBYS. MON THRU TUE...MOSTLY VFR WITH SCT SHOWERS.
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&& .MARINE...
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SEAS AND WINDS ARE EXPECTED TO REMAIN BELOW SCA CRITERIA ATTM. OUTLOOK... FRI NIGHT THRU TUESDAY ...SUB- SCA CONDITIONS EXPECTED THROUGH THE PERIOD. SCT TSTMS WILL CREATE LOCALLY HIGHER WINDS AND SEAS.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...O`HARA/99 NEAR TERM...GAINES/GIGI/VIVOLA SHORT TERM...GAINES LONG TERM...O`HARA AVIATION...GIGI/O`HARA MARINE...GAINES/O`HARA

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