Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 300130 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 930 PM EDT MON SEP 29 2014 .SYNOPSIS... LOW PRESSURE OVER THE EASTERN GREAT LAKES TONIGHT WILL MOVE ACROSS PENNSYLVANIA TUESDAY WHILE A WEAK COLD FRONT SLIDES SOUTH ACROSS THE REGION. THAT LOW PRESSURE SYSTEM WILL DEVELOP OUT TO SEA WEDNESDAY WITH HIGH PRESSURE IN EASTERN CANADA RIDGING DOWN INTO THE MID ATLANTIC STATES THURSDAY. A STRONGER COLD FRONT WILL MOVE EAST ACROSS THE MID ATLANTIC STATES EARLY SATURDAY. WEAK HIGH PRESSURE FOLLOWS NEXT SUNDAY. A WARM FRONT APPROACHES THE REGION EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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930 PM UPDATE...THE BROAD AREA OF LIGHT RAIN CONTINUES TO LIFT NORTHEAST OVER EASTERN NJ. ANOTHER BAND IS CURRENTLY MOVING INTO SOUTHERN DELMARVA. ADJUSTED POPS TO REFLECT CURRENT RADAR TRENDS. HOWEVER, DO NOT EXPECT THE PRECIP TO LAST TOO MUCH PAST 06Z AS THE UPPER LEVEL SHORTWAVE TROUGH SHOULD BEGIN TO SLIDE EAST OF THE REGION AT THAT TIME. GUIDANCE CONTINUES TO BE TOO LOW FOR DEW POINTS. ADJUSTED THE DEW POINTS UP THROUGH THE OVERNIGHT HOURS. ALSO, SINCE THE CLEARING LINE OF HIGH CLOUDS IS JUST WEST OF THE CWA, EXPANDED THE MENTION OF PATCHY FG ESPECIALLY WEST OF THE DELAWARE RIVER VALLEY. HOWEVER, STILL UNCERTAIN HOW LOW VISIBILITIES WILL GO SINCE WINDS REMAIN AROUND 5 MPH AND MOSTLY OUT OF THE SOUTHWEST AT THIS HOUR. PREVIOUS NEAR TERM DISCUSSION...MID AND HIGH LEVEL CLOUDS CONTINUE TO STREAM IN FROM THE SOUTHWEST IN ASSOCIATION WITH A INVERTED TROUGH EXTENDING FROM A LOW PRESSURE WELL TO OUR SOUTH. SOUNDINGS HAVE SHOWN ALL DAY A CONSIDERABLE AMOUNT OF DRY AIR IN THE MID- LEVELS. EVEN THOUGH THE RADAR SHOWS SOME PRECIPITATION MOST OF IT WILL BE VIRGA. HOWEVER THE RAP AND HRRR BRING IN SOME LIGHT PRECIPITATION (UNDER .05 INCHES) THIS EVENING ACROSS DELMARVA AND SOUTH NJ. DID INCLUDE THE THREAT FOR AN ISOLATED LIGHT RAIN SHOWER FOR THESE AREAS. KEPT MANY WEATHER ELEMENTS INCLUDING LOWS NEAR THE MET/MAV. THE MAV HAS BEEN TO DRY WITH SURFACE DEWPOINTS ALL DAY AND DID NOT INCORPORATE THIS SET FOR DEWPOINTS. WE MAY SEE SOME CLEARING AS WELL BY SUNRISE PERHAPS ALLOWING FOR A FEW HOUR WINDOW FOR THE FORMATION OF PATCHY FOG.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... THE INVERTED TROUGH WILL BE WELL EAST OF OUR REGION. HOWEVER AN UPPER LEVEL LOW WILL BE QUICKLY ON ITS HEALS WITH AN ASSOCIATED COLD FRONT. THIS FRONT ALONG WITH MID-LEVEL SUPPORT MAY ALLOW FOR THE GENERATION OF SOME SCATTERED SHOWERS IN THE AFTERNOON FOCUSED NW OF PHL. FOR TEMPERATURES WENT SLIGHTLY WARMER THAN THE MAV/MET GUIDANCE SETS. ECMWF 925 MB TEMPERATURES WOULD YIELD TO SURFACE HIGHS IN THE LOW 80`S FOR PHL. HOWEVER WITH THE POTENTIAL FOR A FAIR AMOUNT OF CLOUDS KEPT HIGHS IN THE 70`S ACROSS THE REGION. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... VERY FEW CHANGES IN THE EXTENDED PERIOD FORECAST FROM 12 HOURS AGO. SEVERAL CHANCES FOR RAIN THROUGH THIS TIME PERIOD BUT AMOUNTS LOOK LIKE THEY WILL BE ON THE RELATIVELY LIGHT SIDE. TEMPERATURES FOR THE TIME PERIOD WILL BE SLIGHTLY ABOVE NORMAL EARLY IN THE PERIOD, THEN TRENDING TO NEAR NORMAL LATE IN THE PERIOD. RAIN CHANCES TUESDAY NIGHT ARE ASSOCIATED WITH DEPARTING UPPER LEVEL TROUGH AND ASSOCIATED BACKDOOR COLD FRONT. HIGH PRESSURE BUILDS INTO THE REGION FOR LATE WEDNESDAY INTO FRIDAY. COLD FRONTAL BOUNDARY APPROACHING WITH NEXT UPPER LEVEL SYSTEM MOVES THROUGH LATE FRIDAY/EARLY SATURDAY BRINGING ANOTHER CHANCE OF RAIN. HIGHEST POPS THROUGH THE LONG TERM PERIOD ARE ASSOCIATED WITH THIS SYSTEM. HIGH PRESSURE BUILDS IN ONCE AGAIN FOR THE REMAINDER OF THE WEEKEND BEFORE A WARM FRONTAL BOUNDARY APPROACHES FROM THE SOUTHWEST LATE ON MONDAY, ONCE AGAIN BRINGING A CHANCE OF PRECIPITATION. USE WPC GUIDANCE PREDOMINATELY FOR DAYS 4 THOUGH 7. FOR TUE NIGHT INTO THU, USED A 50/50 BLEND OF PREVIOUS FORECAST AND ADJUSTED GFS MAV MOS && .AVIATION /01Z TUESDAY THROUGH SATURDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. FOR THE 00Z TAFS...A BROAD AREA OF BKN100 CONTINUES TO STREAM OVER THE REGION. HOWEVER, THE CLEARING LINE IS NOT TOO FAR WEST OF KRDG AND KABE. CLOUDS SHOULD BEGIN TO MOVE OUT FROM WEST TO EAST AFTER 06Z. THERE REMAINS A SMALL THREAT OF BR DEVELOPMENT FOR MUCH OF THE REGION. AT THIS TIME, THE HIGHEST THREAT APPEARS TO BE KRDG AND KMIV. HOWEVER, WITH WINDS STILL WITH A SLIGHT DOWNSLOPE COMPONENT, AND CLOUDS HANGING ON THROUGH AT LEAST 06Z, DO NOT EXPECT VISIBILITIES TO GET BELOW MVFR AT THIS TIME. ANY BR SHOULD DISSIPATE BY 15Z TUESDAY LEAVING FEW TO SCT050, SO ANOTHER VFR DAY TUESDAY. WINDS WILL BE SHIFTING FROM SOUTHERLY TO EASTERLY TO NORTHEASTERLY THROUGH THE DAY, BUT SHOULD REMAIN BELOW 10KT. THE NEXT FRONT WILL APPROACH FROM THE NORTHWEST TUESDAY NIGHT. LOW CHANCE OF SHOWERS AT RDG AND ABE LATE IN THE TAF PERIOD. OUTLOOK... WEDNESDAY...MAINLY VFR CIGS WITH POSSIBLE MVFR CONDS IN SHOWERS KABE/KRDG/KTTN DURING THE MORNING. E/NE WINDS GUST 15 KNOTS. THURSDAY...POSSIBLE MVFR FOG EARLY OTHERWISE VFR SCT-BKN CLOUDS AOA 4000 FT. N-NW WIND GUST 15 KT. FRIDAY...VFR CIGS EXCEPT POSSIBLE MVFR CONDS IN ST/FOG EARLY FRIDAY MORNING AND THEN AGAIN FRIDAY NIGHT IN SHOWERS NEAR A COLD FRONT. E-SE WIND BECOMING S OR SW LATE AT NIGHT. SATURDAY...VFR CONDITIONS EXPECTED.
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&& .MARINE... SEAS THIS EVENING ARE AROUND TWO FEET ACROSS THE REGION. WINDS WILL BE LIGHT THROUGH TONIGHT AS WELL. TOMORROW WE WILL GRADUALLY SEE SEAS BUILD AND WINDS INCREASE OUT OF NORTHEAST. SEAS MAY REACH FOUR FEET TUESDAY AFTERNOON WITH SOME WIND GUSTS AROUND 20 KNOTS AS WELL. CONDITIONS BELOW SCA CRITERIA FOR THIS PERIOD. OUTLOOK... TUESDAY NIGHT THROUGH WEDNESDAY NIGHT: NE FLOW TUESDAY NIGHT THROUGH WEDNESDAY NIGHT SHOULD INCREASE TO SCA CRITERIA ALONG THE NNJ COAST TUESDAY NIGHT AND THEN POSSIBLY SOUTHWARD TO THE ENTIRE ATLC COAST LATER WEDNESDAY OR WEDNESDAY NIGHT. DELAWARE BAY MAY NOT SEE WIND GUSTS ABOVE 22 KT WITH ANY SCA HEADLINE THERE NOT LIKELY. HAVE HELD OFF ON ISSUING ANY FORMAL HEADLINES ON THIS FORECAST UPDATE AS CONDITIONS WILL JUST MEET LOWER END SCA CRITERIA AND CONFIDENCE IS NOT YET HIGH. THURSDAY...SMALL CHANCE OF SCA SEAS ON THE ATLANTIC WATERS FROM NE SWELLS GENERATED BY AN OFFSHORE LOW. FRIDAY...WIND BECOMING SOUTH BY NIGHT. SMALL CHANCE OF AN SCA AT NIGHT. SATURDAY...SCA CONDITIONS POSSIBLE EARLY WITH COLD FRONT PASSAGE, THEN IMPROVING CONDITIONS EXPECTED. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...SZATKOWSKI NEAR TERM...GAINES/HEAVENER/JOHNSON SHORT TERM...GAINES/HEAVENER LONG TERM...SZATKOWSKI AVIATION...GAINES/SZATKOWSKI/HEAVENER/JOHNSON MARINE...GAINES/SZATKOWSKI/HEAVENER

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