Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 201829 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 229 PM EDT WED AUG 20 2014 .SYNOPSIS... LOW PRESSURE IN GREAT LAKES REGION WILL WEAKEN AS IT MOVES TO NEAR LAKE ONTARIO THURSDAY. A SECOND AREA OF LOW PRESSURE WILL DEVELOP NEAR THE CHESAPEAKE BAY THURSDAY NIGHT. HIGH PRESSURE IN EASTERN CANADA WILL BUILD DOWN ALONG THE EAST COAST LATER THIS WEEKEND INTO NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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A WEAK SHORT MOVING ESEWD THRU NORTHERN PA SHOULD SHOVE THE BAND OF SHOWERS AND ISOLATED TSTMS IN CENTRAL PA EWD INTO PARTS OF OUR AREA THIS EVENING AND TONIGHT WITH A TENDENCY FOR THE BAND TO PROBABLY DIMINISH DURING THE NIGHT. STILL A PWAT OF 1.5" PLUS PERMITS SOME OF THE SHOWERS THIS EVENING TO BE POTENTIALLY BRIEFLY HEAVY IN E PA. FORECAST BASIS: POPS WERE BLENDED NCEP MOS POPS WITH THE 09Z SREF AND THAT GIVES THE BEST CHANCE FOR SOME NEEDED RAIN TO E PA. OTRW A 50 50 BLEND OF 12Z/20 NCEP MOS EXCEPT BLENDED RGEM SKY WITH NAM SKY AND GFS MOS GUIDE. NEAR OR SLIGHTLY ABOVE NORMAL TEMPS.
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&& .SHORT TERM /THURSDAY/...
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THURSDAY...ANOTHER SHORT WAVE IN THE WNW FLOW OVER SOUTHERN NEW YORK STATE SHOULD REDEVELOP HEAVY CONVECTION DURING THE AFTN OVER E PA...POSSIBLY EXTENDING INTO W NJ AND THE MD E SHORE CLOSER TO THE CONVERGENCE OF THE SFC LOW AND INVERTED TROUGH EXTENDING NWD FROM THE VCNTY OF DCA. PWAT VALUES ARE GENERALLY FORECAST AROUND 1.5-1.75 INCHES, SO SOME SHOWERS/STORMS COULD PRODUCE A PERIOD OF MODERATE TO HEAVY RAINFALL. ISOLATED SMALL HAIL NOT IMPOSSIBLE AS TT NEAR 50 IN AREA OF MAX INSTABILITY IN NJ (NEAR THE DELAWARE RIVER). FORECAST BASIS: POPS WERE BLENDED NCEP MOS POPS WITH THE 09Z SREF AND THAT GIVES THE BEST CHANCE FOR SOME NEEDED RAIN TO E PA. OTRW A 50 50 BLEND OF 12Z/20 NCEP MOS EXCEPT BLENDED RGEM SKY WITH NAM SKY AND GFS MOS GUIDE. NEAR OR SLIGHTLY ABOVE NORMAL TEMPS.
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&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... THE LONG TERM FORECAST STARTS OFF WITH RAIN CHANCES, BEFORE A DRYING OUT PERIOD SETS IN ACROSS THE AREA. THURSDAY NIGHT...A SECOND AREA OF SURFACE LOW PRESSURE IS FORECAST TO DEVELOP NEAR THE CHESAPEAKE BAY ALONG THE STATIONARY BOUNDARY TO OUR SOUTH. IT IS POSSIBLE THAT THIS MAY HELP KEEP A FOCUS FOR PRECIPITATION THURSDAY NIGHT, BEFORE IT SAGS TO OUR SOUTH. FOR FRIDAY INTO THE WEEKEND, THE MID/UPPER LOW WILL REMAIN TO OUR NORTHEAST, KEEPING A NORTHWEST FLOW ALOFT ACROSS OUR AREA. MEANWHILE, HIGH PRESSURE WILL BEGIN BUILDING DOWN ACROSS THE EAST COAST FROM EASTERN CANADA. BEFORE THE HIGH TAKES FULL CONTROL OF THE WEATHER, THERE WILL REMAIN A CHANCE OF SCATTERED SHOWERS FRIDAY AND SATURDAY AS THERE MAY BE A FEW SHORT WAVE/VORT MAXES THAT AFFECT THE AREA IN THE NORTHWEST FLOW ALOFT. BY SUNDAY INTO EARLY NEXT WEEK, THE SURFACE HIGH BUILDS FURTHER INTO THE MID-ATLANTIC REGION, WHICH SHOULD BRING DRY WEATHER TO THE AREA. HIGHS ARE EXPECTED TO START OUT CLOSE TO OR SLIGHTLY ABOVE NORMAL THURSDAY INTO FRIDAY, BUT AS THE HIGH BUILDS DOWN OUT OF EASTERN CANADA AND THE NORTHWEST FLOW ALOFT REMAINS ACROSS THE AREA OVER THE WEEKEND, 925/850 MB TEMPS AND THICKNESSES LOWER. THIS WILL ALLOW FOR SLIGHTLY BELOW NORMAL TEMPERATURES OVER THE WEEKEND. AS WE MOVE INTO EARLY NEXT WEEK, WE SHOULD START TO GET MORE OF A RETURN SURFACE FLOW AND RIDGING ALOFT BEGINS TO TAKE PLACE ONCE AGAIN, ALLOWING FOR REBOUNDING TEMPERATURES. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. REST OF TODAY...VFR SCT-BKN AOA 4000 FT. LIGHT SE TO S WIND. TONIGHT...VFR CIGS AOA 4000 FT SPREAD EWD DURING THE NIGHT WITH A PERIOD OF SHOWERS POSSIBLE. LIGHT SOUTH WIND. THURSDAY...GENERALLY VFR CIGS. LIGHT SOUTH WIND. SCATTERED SHOWERS AND THUNDERSTORMS WHICH MAY LOWER CIGS/VSBYS TO BRIEFLY IFR CONDITIONS. OUTLOOK... THURSDAY NIGHT...GENERALLY VFR. CHANCE OF SHOWERS AND THUNDERSTORMS WHICH MAY LOWER CIGS/VSBYS. FRIDAY-SUNDAY...PERIODS OF LOW END VFR OR MVFR CIGS POSSIBLE WITH A CHANCE OF SHOWERS, ESPECIALLY FRIDAY INTO SATURDAY. && .MARINE... NO MARINE RELATED HEADLINES THROUGH THURSDAY. EAST-SOUTHEAST WINDS BETWEEN 5-15 KT. OUTLOOK... THURSDAY-FRIDAY NIGHT...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED. SATURDAY-SUNDAY...SEAS MAY BEGIN TO APPROACH SMALL CRAFT ADVISORY LEVELS AS A LONG FETCH DEVELOPS AROUND HIGH PRESSURE BUILDING IN FROM THE NORTHEAST OUT OF EASTERN CANADA. && .CLIMATE... WE ARE AWARE HOW DRY ITS BEEN RECENTLY IN FAR NORTHERN NEW JERSEY...I80 NORTH AND IN FACT 70 TO 90 PCT OF NORMAL THERE THE PAST YEAR AND 5 O 25 PCT OF NORMAL THERE THE PAST MONTH. WHATEVER RAINFALL OCCURS THERE NEEDS TO DEVELOP BETWEEN TONIGHT AND FRI EVENING...OTRW WE PROBABLY NEED TO WAIT TIL THE END OF NEXT WEEK. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...DRAG/ROBERTSON NEAR TERM...DRAG 229 SHORT TERM...DRAG 229 LONG TERM...ROBERTSON AVIATION...DRAG/ROBERTSON MARINE...DRAG/ROBERTSON CLIMATE...

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