Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KPHI 281957 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 357 PM EDT MON JUL 28 2014 .SYNOPSIS... LOW PRESSURE MOVING INTO NEW ENGLAND THIS EVENING IS SHOVING A COLD FRONT OFF THE MID ATLANTIC COAST. WEAK HIGH PRESSURE WILL FOLLOW LATER TUESDAY THROUGH WEDNESDAY. IT THEN MERGES INTO THE WESTERN ATLANTIC HIGH PRESSURE SYSTEM LATE THIS WEEK. MEANWHILE...THE FRONT WILL BE LURKING JUST OFF THE COAST AS A STATIONARY FRONT. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... THE COLD FRONT IS APPROACHING OUR NORTHWESTERN ZONES LATE THIS AFTERNOON AND WILL PROGRESS ACROSS THE CWA THIS EVENING AND SHOULD PASS COMPLETELY THROUGH BY MIDNIGHT. A LINE OF SHOWERS AND VERY ISOLATED THUNDERSHOWERS HAVE FORMED ALONG THE FRONT THIS AFTERNOON. ALL OF THE GUIDANCE INDICATES THE SHOWERS/THUNDER DISSIPATING AND/OR WEAKENING AS THEY REACH OUR AREA THIS EVENING AS THE MID-LEVEL TROUGH LIFTS TO OUR NORTHEAST. THERE WILL BE ANOTHER SHORT WAVE/VORTICITY IMPULSES MOVE INTO THE AREA ALONG WITH THE COLD FRONT, SO THERE IS THE POSSIBILITY THE SHOWERS COULD MAINTAIN THEMSELVES ACROSS A PORTION OF THE AREA. THEREFORE WE WILL KEEP ISOLATED SHOWERS INTO THE EVENING FROM THE DELAWARE VALLEY NORTHWARD, BUT WE END EVERYTHING BY MIDNIGHT. AFTER THE SHOWERS END, CLOUDS SHOULD SCATTER OUT OVERNIGHT, BUT HOW MUCH THEY SCATTER WILL DETERMINE HOW COOL IT GETS TONIGHT. FOR NOW WE USED A BLEND OF MAV/MET MOS AND MOSGUIDE WHICH DROPS EVERYONE SEVERAL DEGREES COOLER THAN LAST NIGHT AND ENDS UP BEING SEVERAL DEGREES BELOW NORMAL. WINDS WILL REMAIN GUSTY INTO THIS EVENING, BUT THE GUSTS SHOULD DROP OFF AFTER SUNSET THROUGH THE OVERNIGHT HOURS. WESTERLY WINDS AHEAD OF THE COLD FRONT WILL SWITCH TO MORE NORTHWESTERLY BEHIND IT. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... A NICE TUESDAY AHEAD AS COOLER, DRIER AIR CONTINUES TO MOVE IN ACROSS THE AREA AS WEAK HIGH PRESSURE BEGINS TO BUILD IN FROM THE WEST. WITH PW VALUES BELOW ONE INCH AND NO SIGNIFICANT SHORT WAVE/VORTICITY IMPULSES, TUESDAY IS EXPECTED TO BE DRY ACROSS THE AREA. TEMPERATURES WILL BE COOLER THAN THE LAST COUPLE OF DAYS AS 925/850 MB TEMPS AND THICKNESSES DECREASE INTO TUESDAY. USED A BLEND OF MAV/MET MOS, MOSGUIDE, AND MIXED 925 MB TEMPS FOR HIGHS ON TUESDAY WHICH ENDS UP BEING SEVERAL DEGREES BELOW NORMAL. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... 500 MB: A LARGE TROUGH IN THE EAST WILL SLOWLY WEAKEN LATE THIS WEEK INTO EARLY NEXT WEEK. TEMPERATURES: ABOUT 5 DEGREES BELOW NORMAL WEDNESDAY WARMING TO NEAR NORMAL THIS COMING WEEKEND AND EARLY NEXT WEEK. FORECAST BASIS: UNLESS OTHERWISE NOTED THE LONG TERM PERIOD OF THIS FORECAST IS GENERALLY BASED ON A 50 50 BLEND OF THE 12Z/28 NAM/GFS MOS FOR THE PERIOD TUESDAY NIGHT - WEDNESDAY NIGHT... THE 12Z/28 GFS MOS THURSDAY AND THURSDAY NIGHT AND THEN THEREAFTER (FRIDAY ONWARD) THE 1522Z/28 WPC GRIDDED GUIDANCE FOR ALL ELEMENTS EXCEPT HAVE APPLIED THE WARMER 12Z/28 MEXMOS TEMPS. ALL THIS WAS CHECKED AGAINST THE 12Z/28 ECMWF TO ENSURE WE`RE IN THE BALLPARK (BARRING MIDDAY OVC SKIES AND RAIN) WITH ECMWF CYCLICALLY PERSISTENT 18Z 2METER TEMPERATURES. THE PRECIPITATION PROBABILITY GUIDANCE WAS CHECKED AGAINST THE 09Z/28 SREF POPS FOR .01 IN 3 HRS THROUGH 00Z FRIDAY AND THEREAFTER THE 12Z/28 GEFS 6HR POPS FOR 0.05 . THE DAILIES... IT SORT OF LOOKS LIKE WE`RE PRIMARILY IN A WEAK SURFACE RIDGE REGION THIS 6 DAY PERIOD AND NOT FAVORABLE FOR MUCH RAIN. BASICALLY FOR NOW ITS A GENERALLY FAIR WEATHER FORECAST THIS 6 DAY PERIOD. THERE IS A CHANCE FOR LATE DAY OR EVENING CONVECTION NE PA AND NW NJ LATER IN THE WEEK BUT FOR NOW IS CHANCEY AND LOW CONFIDENCE. AS FOR THE LURKING QUASI STATIONARY ALONG THE COAST... IT MAY DRIFT CLOSER TO THE SHORE BY THE WEEKEND AS A WARM FRONT WITH ITS CONVECTION POSSIBLY SPREADING ASHORE BUT CONFIDENCE FOR THIS SCENARIO IS ALSO BELOW AVERAGE. IT DOES APPEAR THIS QUASI STATIONARY BOUNDARY WILL EVENTUALLY DISSIPATE AND AS IT DOES...HIGHER HUMIDITY SHOULD SLOWLY RETURN TO THE AREA LATE THIS WEEKEND INTO EARLY NEXT WEEK. TEMPERATURES AND POPS AS DESCRIBED ABOVE IN THE FORECAST BASIS. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. MOSTLY VFR CONDITIONS EXPECTED ACROSS THE TAF SITES THROUGH TONIGHT AND INTO TUESDAY. A LINE OF SHOWERS/ISOLATED THUNDERSHOWERS HAVE DEVELOPED ALONG A COLD FRONT THAT WILL MOVE ACROSS THE AREA THIS EVENING THROUGH MIDNIGHT. MODEL GUIDANCE INDICATES THE SHOWERS/THUNDER WILL DISSIPATE/WEAKEN AS IT MOVES INTO OUR AREA THIS EVENING, HOWEVER, WE HAVE INCLUDED A TEMPO SHOWER GROUP FOR THE DELAWARE VALLEY TAFS THIS EVENING, AND ENDED UP ADDING A TEMPO THUNDERSTORM GROUP FOR ABE/RDG THIS EVENING. IT`S POSSIBLE THAT VSBYS MAY BRIEFLY DROP TO 5SM OR LESS, MAINLY FOR ABE/RDG, SO ADDED IT IN FOR THESE TWO SITES. THE REST WERE LESS CONFIDENT, SO LEFT THEM OUT FOR NOW. WESTERLY WINDS GUSTING 20-25 KNOTS WILL CONTINUE THROUGH SUNDOWN, THEN THE GUSTS SHOULD DROP OFF, AND WINDS WILL BECOME NORTHWESTERLY BEHIND THE COLD FRONT OVERNIGHT INTO TUESDAY. WINDS MAY BEGIN SWITCHING TO WEST OR SOUTHWEST AGAIN BY LATE TUESDAY INTO TUESDAY EVENING, AND A SEABREEZE MAY FORM ALONG THE COAST BY THE AFTERNOON. OUTLOOK... TUESDAY NIGHT-WEDNESDAY NIGHT...MAINLY VFR. THURSDAY-SATURDAY...MAINLY VFR. ISOLATED SHOWERS/THUNDERSTORMS POSSIBLE EACH DAY BUT LOW CONFIDENCE ON OCCURRENCE. PATCHY IFR FOG OR STRATUS IS POSSIBLE FRI NIGHT. && .MARINE... THE SMALL CRAFT ADVISORY FOR THE DELAWARE BAY AND THE SOUTHERN HALF OF THE ATLANTIC COASTAL WATERS WAS EXTENDED THROUGH MIDNIGHT TONIGHT AS WINDS ARE GUSTING AROUND 25-30 KNOTS NOW, AND SHOULD CONTINUE INTO THE EVENING AHEAD OF THE FRONTAL BOUNDARY. AS THE FRONTAL BOUNDARY MOVES THROUGH, THE GUSTS WILL SWITCH FROM WEST TO NORTHWEST AND DROP OFF SLIGHT, AND SEAS SHOULD LOWER AS WELL. THE SEAS MAY REMAIN LONGER ON THE NORTHERN WATERS A FEW MORE HOURS, SO WE LEAVE THE NORTHERN HALF ENDING AT 6 AM TUESDAY. OUTLOOK... TUESDAY NIGHT-SATURDAY...NO HEADLINES ANTICIPATED. LOOKS LIKE GOOD WEATHER FOR BEING ON THE WATERS IN THIS TIME FRAME. WE ARE MONITORING THE GFS OPERATIONAL RUN DEPICTION (FOR SEVERAL FORECAST CYCLES) OF A TROPICAL SYSTEM IN THE ATLANTIC BASIN FOR EARLY NEXT WEEK BUT THE ECMWF OPERATIONAL VERSION STILL DOESNT HAVE IT. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ430-431- 452>455. SMALL CRAFT ADVISORY UNTIL 6 AM EDT TUESDAY FOR ANZ450-451. && $$ SYNOPSIS...DRAG 356 NEAR TERM...ROBERTSON SHORT TERM...ROBERTSON LONG TERM...DRAG/ROBERTSON 356 AVIATION...DRAG/ROBERTSON 356 MARINE...DRAG/ROBERTSON 356

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.