Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 231057 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 657 AM EDT SAT AUG 23 2014 .SYNOPSIS... HIGH PRESSURE WILL SLOWLY BUILD SOUTH OUT OF CANADA TOWARDS OUR REGION THROUGH THE WEEKEND. THE HIGH WILL BE ENTRENCHED OVER OUR REGION THROUGH AT LEAST MID WEEK BEFORE IT WEAKENS. A COLD FRONT COULD PUSH THROUGH THE REGION LATE IN THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THERE HAS BEEN A PERSISTENT AREA OF SHOWERS ASSOCIATED WITH A WEAK VORTICITY IMPULSE THAT HAVE SLOWLY DRIFTING EASTWARD THROUGH THE NIGHT. WITHOUT MUCH FLOW ALOFT, THEY ARE SLOW TO MOVE. HOWEVER, AS THE WEAK IMPULSE CONTINUES TO SLIDE EASTWARD THOUGH THE MORNING HOURS. THERE WILL REMAIN A CHANCE FOR SCATTERED SHOWERS THROUGH THE DAY AS A STRONGER SHORT WAVE/VORTICITY IMPULSE MOVES ACROSS THE AREA. VERTICAL MOISTURE IS EXPECTED TO DRY LATER IN THE DAY AS THE IMPULSE APPROACHES AS HIGH PRESSURE CONTINUES TO PUSH FARTHER SOUTH INTO THE AREA. HOWEVER, THERE SHOULD BE ENOUGH TO INTERACT WITH THE SHORT WAVE TO PRODUCE SOME SHOWER ACTIVITY. WITH PW VALUES NEAR 1.5 INCHES, THERE REMAINS THE POTENTIAL FOR SOME HEAVY RAIN WITH ANY SHOWER DEVELOPMENT. THERE IS REALLY NO INSTABILITY EXPECTED TODAY, SO WE DO NOT HAVE THUNDERSTORMS IN THE FORECAST, ALTHOUGH IT WOULD NOT BE SURPRISING TO SEE AN COUPLE OF ISOLATED LIGHTNING STRIKES. FOR HIGHS, USED A BLEND OF MAV/MET MOS, MOSGUIDE, AND MIXED 925 MB TEMPS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... THE SHORT WAVE/VORT MAX WILL BE MOVING THROUGH OUR SOUTHERN AREAS THIS EVENING, WHILE HIGH PRESSURE CONTINUES TO BUILD IN FROM THE NORTH. MEANWHILE, PW VALUES WILL BE DROPPING OFF QUITE SHARPLY AS DRIER AIR MOVES IN. THERE MAY BE A FEW ISOLATED SHOWERS EARLY IN THE EVENING, BUT WHATEVER IS OUT THERE SHOULD DISSIPATE AND/OR MOVE SOUTHWARD THROUGH THE EVENING, AND THE REMAINDER OF THE NIGHT SHOULD BE RAIN FREE. FOR OVERNIGHT LOWS USED A BLEND OF MAV/MET MOS AND MOSGUIDE. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... NOT MANY CHANGES THROUGH MID WEEK FROM THE PREVIOUS FORECAST. STILL EXPECTING AN EXTENDED PERIOD OF DRY WEATHER AS THE SURFACE HIGH BUILDS OVER OUR REGION, AND IN THE UPPER LEVELS, A SHORT WAVE RIDGE PROPAGATES SOUTHEAST OVER OUR REGION MONDAY INTO TUESDAY. WITH THE COOLER AIR SETTLING IN ON SUNDAY, SHOULD START WITH BELOW NORMAL TEMPERATURES, BUT HAVE A STEADY WARMING TREND THROUGH MID WEEK, ESPECIALLY AS LOW LEVEL SOUTHWESTERLY FLOW DEVELOPS WEDNESDAY. THURSDAY THROUGH SATURDAY REMAINS THE PERIOD OF MOST INTEREST OVER THE NEXT WEEK, BUT ALSO WITH THE GREATEST UNCERTAINTY. THERE ARE THREE FEATURES THAT WILL BE WATCHED OVER THE NEXT FEW DAYS THAT COULD HAVE BIG IMPACTS WITH OUR WEATHER IN THE LATE WEEK PERIODS. FIRST...THE TOPICAL SYSTEM WHICH COULD DEVELOP OVER THE NEXT FEW DAYS. WHILE NEARLY ALL OF THE LONG RANGE MODELS HAVE THIS SYSTEM STAYING WELL OFF SHORE, AND THUS NOT DIRECTLY IMPACTING US, IT COULD HELP TO WEAKEN THE SURFACE HIGH OVER THE MID ATLANTIC EARLIER THAN PREVIOUSLY FORECAST, RESULTING IN AN INDIRECT IMPACT. SECOND, THE SURFACE COLD FRONT, WHICH LONG RANGE MODELS EITHER KEEP PUSHING BACK THE ARRIVAL IN OUR REGION, OR KEEP IT NORTH OF US ALL TOGETHER. AT THIS POINT, IT STILL SEEMS LIKELY THAT THE FRONT WILL PUSH THROUGH OUR REGION, BUT PROBABLY NOT UNTIL FRIDAY AS THE THIRD FEATURE, A BROAD UPPER LEVEL TROUGH, SLIDES EAST OVER THE GREAT LAKES REGION. ALL THAT SAID, OUR NEXT GOOD CHANCE FOR RAIN WILL COME WHEN THE FRONT ARRIVES, ALONG WITH TEMPERATURES WELL BELOW NORMAL. HOWEVER, GIVEN THE UNCERTAINTY IN THE TIMING AND TRACK OF THE FRONT, HAVE KEPT POPS THROUGH THE LATE WEEK PERIOD IN THE 20S AND 30S. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. MANY TAF SITES REMAIN VFR AT THE START OF THE PERIOD, HOWEVER, WE STILL EXPECT ALL CIGS TO DROP TO MVFR FOR A FEW HOURS THIS MORNING AS THERE REMAINS QUITE A BIT OF LOW LEVEL MOISTURE AROUND THE AREA. ONCE THESE LOWER CIGS DEVELOP, WE EXPECT THEM TO REMAIN THROUGH THE MID-LATE MORNING HOURS, BEFORE AN IMPROVEMENT TO VFR FOR THE AFTERNOON. AN AREA OF SHOWERS IS MOVING THROUGH EASTERN PENNSYLVANIA, AND ADDITIONAL SHOWERS ARE POSSIBLE LATER IN THE DAY, SO HAVE INCLUDED THEM IN THE LATEST TAF. IF ANY SHOWERS DO OCCUR, THEY COULD BRIEFLY REDUCE CIGS/VSBYS. VFR CONDITIONS ARE EXPECTED FOR THE OVERNIGHT HOURS AS DRIER AIR FILTERS IN AS HIGH PRESSURE BUILDS IN FROM THE NORTH. WINDS WILL BE MOSTLY OUT OF THE EAST TO NORTHEAST 5-10 KNOTS OR LESS THROUGH THE PERIOD. OUTLOOK... SUNDAY THROUGH WEDNESDAY...VFR CONDITIONS EXPECTED. && .MARINE... SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR THE OCEAN, AND HAS BEEN EXPANDED TO INCLUDE THE ENTIRE NEW JERSEY ATLANTIC COAST. SEAS ARE EXPECTED TO BUILD LATER TODAY AND CONTINUE INTO TONIGHT AS THE EAST TO NORTHEASTERLY FLOW INCREASES. WINDS MAY GUST AROUND 20-25 KNOTS AS WELL LATER TODAY INTO TONIGHT. OUTLOOK... SUNDAY...SEAS AND WINDS ARE EXPECTED TO SUBSIDE BELOW SMALL CRAFT ADVISORY EARLY IN THE DAY. MONDAY THROUGH WEDNESDAY...WINDS AND SEAS WILL LIKELY STAY BELOW SMALL CRAFT ADVISORY CONDITIONS. && .RIP CURRENTS... A MODERATE RISK OF RIP CURRENTS REMAINS TODAY INTO TONIGHT AS SEAS ARE EXPECTED TO BUILD IN THE PERSISTENT EASTERLY FLOW. THE MODERATE RISK MAY CONTINUE INTO SUNDAY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 8 AM EDT SUNDAY FOR ANZ450>455. && $$ SYNOPSIS...JOHNSON NEAR TERM...ROBERTSON SHORT TERM...ROBERTSON LONG TERM...JOHNSON AVIATION...JOHNSON/ROBERTSON MARINE...JOHNSON/ROBERTSON RIP CURRENTS...ROBERTSON

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