Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 230735 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 335 AM EDT WED JUL 23 2014 .SYNOPSIS... A COLD FRONT WILL APPROACH OUR AREA FROM THE NORTHWEST TODAY AND CROSS THE REGION TONIGHT INTO THURSDAY MORNING. HIGH PRESSURE WILL BUILD IN BEHIND THE DEPARTING FRONT FOR THE END OF THE WEEK INTO THE FIRST PART OF THE WEEKEND. THEN, A COMPLEX SYSTEM WILL AFFECT THE REGION FOR SUNDAY INTO MONDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... FAIR EARLY THIS MORNING...PATCHY FOG TOWARD 10Z...MAINLY NW NJ. PATCHY CLOUDINESS FORMING...AOA 5000 FT AS A SEPARATE KI AXIS DEVELOPS OVER NJ/EPA TOWARD 12Z. TODAY...LITTLE CHANGE FROM PRIOR FORECASTS. MODEL GUIDANCE STATES WIDESPREAD LOWER 90S (NEAR 18C 850 MB AND 925MB HOTTEST TEMPS ARE JUST WEST AND NORTHWEST OF OUR FCST AREA). POCONOS AND IMMEDIATE ATLC SHORE A BIT COOLER. ECMWF SEEMS TO HOLD BACK SLIGHTLY. THE FCST TEMPS ISSUED AT 330 AM MAY BE A DEGREE TOO WARM. HEAT INDEX UPPER 90S....CLOSE TO 100 BUT NO HEAT ADVY ISSUED ATTM. TSTMS PROBABLY RESTRICTED TO NW NJ AND E CENTRAL AND NE PA AFTER 21Z...POSSIBLY A SECOND CLUSTER CROSSING CHES BAY? TT 48+ SWI -2 KI INCREASING TO 38C VCNTY POCS AND E VA. APPEARS TO BE A SEE TEXT CASE...UNLIKELY SVR THROUGH 00Z DUE TO LACK OF BULK SHEAR...500MB WINDS UNDER 30 KT AND MLCAPE CLOSER TO 1600J. NOTE THAT THERE SHOULD BE CU FIELDS FORMING THIS MORNING OVER NNJ IN A LEADING EDGE AREA OF KI 33C BUT WITH LITTLE OR NO PRIMARY FORCING...AM NOT EXPECTING TO YIELD ANY LATE MORNING TSTMS IN NNJ AS THIS LEADING PATCH OF INSTABILITY SHOVES ENE TO LI BY 18Z. TODAYS FCST BASIS: NAM TEMPS (50 50 BLEND OF 00Z/23 NAM METMOS AND THE NAM 2M TEMPS). OTHERWISE...OTHER ELEMENTS A 50 50 BLEND OF THE 00Z/23 NAM/GFS GUIDANCE IN THIS 330 AM ISSUANCE. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... SLOW SEWD PROGRESS OF THE COLD FRONT INTO THE UNSTABLE AIRMASS SHOULD YIELD BANDS OF TSTMS INTO THE NIGHT BUT NOT NECESSARILY WIDESPREAD. ONE OR 2 TSTMS COULD BE SVR BUT BULK SHEAR FOR SVR IS MARGINAL AT WORST AND ONLY THE TT AND SOME CAPE ALLOW FOR MODEST ISOLATED SVR POTENTIAL. PWAT 1.8 INCHES OFFERS A CHANCE OF NARROW PATHS OF 2 INCH RAINS BENEATH THE BIGGEST STORMS. LIGHTNING STRIKES MIGHT BE THE BIG PROBLEM? FCST BASIS; 50 50 BLEND OF THE 00Z/23 GFS/NAM GUIDANCE IN THIS 330 AM ISSUANCE EXCEPT MOSTLY NAM METMOS TEMPS. && .LONG TERM /THURSDAY THROUGH TUESDAY/... THE CDFNT WILL BE EXITING THE AREA ERLY THU, BUT LINGERING SHWRS AND TSTMS ARE STILL EXPECTED WITH ANY INSTABILITY STILL AROUND. THE BEST CHCS ARE ERLY. THEN, HIGH PRESSURE WILL BUILD IN FROM THE W AND DOMINATE THE WX PATN THRU THE ERLY PART OF THE WEEKEND. DRY WX IS THEN EXPECTED THRU SAT. AS THE HIGH SLOWLY MOVES EWD, THE FLOW WILL BECOME MORE SLY AND SWLY AND EXPECT A RISE IN TEMPS AND HUMIDITY BY THE WEEKEND. THEN, BY SUN, AN AREA OF LOW PRESSURE NR THE GRTLKS WILL BE MOVG EWD. WHILE ITS EXACT TRACK IS STILL A MATTER OF DEBATE BTWN THE MDLS, THEY DO AGREE THAT THERE WILL BE SOME KIND OF DOUBLE BARRELED-LOW STRUCTURE BY SUN NIGHT. THERE COULD BE A WK CFP WITH THE FIRST LOW SUN NIGHT OR MON, THE MAIN CFP WILL BE MON NIGHT OR TUE WITH THE SECOND LOW. AGAIN, THE DETAILS WILL STILL NEED TO BE RESOLVED AT THIS TIME SCALE, BUT THE SUN INTO MON TIME FRAME COULD BE STORMY DEPENDING ON HOW THINGS ULTIMATELY PLAY OUT. HIGH PRES WILL BUILD IN BEHIND THIS DEPARTING CDFNT FOR TUE. TEMPS LOOK TO BE AT OR SLIGHTLY ABOVE NRML THRU THE PD, UNTIL THE CFP ON TUE WHEN TEMPS WILL BE BELOW NRML. EXPECT COMFORTABLE HUMIDITY ERLY IN THE PD, THEN INCREASING HUMIDITY IN ADVANCE OF THE CFP ERLY NEXT WEEK. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. EARLY THIS MORNING BEFORE 12Z...PRIMARILY VFR WITH SCT CLOUDS AOA 4000 FT. PATCHY 2 TO 5 MI FOG POSSIBLE IN THE COUNTRYSIDE TAF LOCATIONS BUT CONFIDENCE IS LESS THAN IT WAS AT THIS TIME YDY. TEMP-DEWPOINT SPREADS AT 3 AM ARE JUST TOO LARGE FOR FOG. LIGHT S-SW WIND. TODAY AFTER 12Z...VFR SCT AOA 5000 FT. BRIEFLY BKN CIGS NEAR 5000 FT VCNTY KABE AND KRDG THIS AFTN AND CHC OF A TSTM THERE AFTER 22Z WITH GUSTY WEST WIND 30-40 KT. OTHERWISE NON TSTM GRADIENT WINDS SUGGEST SW WIND GUST 17 KT THIS AFTN MOST TAF LOCATIONS. TONIGHT...VFR CIGS WITH A BETTER CHC OF BRIEF IFR CONDS IN TSTMS. LIGHT SW WIND SHIFT N TOWARD MORNING WHEN PATCHY IFR ST/FOG MIGHT FORM IN THE FRONTAL ZONE OR WHERE IT RAINS THIS EVENING. STRONG GUSTY WEST WIND IN A TSTM POSSIBLE BETWEEN 00Z AND 04Z FOR KTTN KPNE KPHL AND KILG BUT LESS CONFIDENCE THAN FOR KABE AND KRDG OUTLINED IN THE PREVIOUS PARAGRAPH. OUTLOOK... THU...MVFR AND IFR CONDITIONS AT TIMES IN SHOWERS AND THUNDERSTORMS, ESPECIALLY EARLY. PATCHY FOG THU MORNING. MODERATE CONFIDENCE. THU NIGHT THROUGH SAT...MAINLY VFR UNDER HIGH PRESSURE. HIGH CONFIDENCE. SUN...SUB-VFR POSSIBLE IN SCATTERED SHOWERS AND THUNDERSTORMS. MODERATE CONFIDENCE. && .MARINE... NO HEADLINES THROUGH TONIGHT. MAINLY S-SW WIND G UNDER 20 KT SHIFT TO NORTH TOWARD DAWN THURSDAY. WAVE HEIGHTS ON OUR OCEAN WATERS SHOULD BE 2 TO 4 FEET. WAVES ON DELAWARE BAY ARE EXPECTED TO BE 2 FEET OR LESS. SCATTERED THUNDERSTORMS TONIGHT. OUTLOOK... THU THROUGH SAT...NO MARINE HEADLINE EXPECTED WITH HIGH PRES OVERHEAD. SUN...INCREASING SEAS AHEAD OF NEXT SYS MAY YIELD SCA, ESPECIALLY N BY LATER IN THE DAY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...NIERENBERG NEAR TERM...DRAG SHORT TERM...DRAG LONG TERM...NIERENBERG AVIATION...DRAG/NIERENBERG MARINE...DRAG/NIERENBERG

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