Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 192157 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 557 PM EDT SAT JUL 19 2014 .SYNOPSIS... HIGH PRESSURE CENTERED NEAR NOVA SCOTIA WILL DRIFT NORTHEASTWARD THROUGH TONIGHT. MEANWHILE, WEAK LOW PRESSURE OFF THE NORTH CAROLINA COAST WILL MOVE TO THE NORTHEAST AND OUT TO SEA ON SUNDAY. ANOTHER AREA OF HIGH PRESSURE IS EXPECTED TO ESTABLISH ITSELF OVER OUR REGION FOR MONDAY THROUGH WEDNESDAY. A COLD FRONT IS THEN ANTICIPATED TO ARRIVE THURSDAY WITH HIGH PRESSURE FOLLOWING FOR FRIDAY AND SATURDAY. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... OUR AREA IS MAINLY BETWEEN A WEAKENING UPPER-LEVEL TROUGH TO THE WEST AND A SURFACE LOW TO OUR SOUTHEAST. THE MODEL GUIDANCE INDICATES A DOUBLE UPPER-LEVEL JET STRUCTURE WITH OUR REGION WITHIN THE RIGHT ENTRANCE REGION OF THE FARTHER NORTHWEST JET SEGMENT. THE OTHER JET ENTRANCE REGION IS GENERALLY OFFSHORE AND IS PROBABLY ASSISTING IN SHOWER DEVELOPMENT THERE ALONG WITH THE WEAK SURFACE LOW. OVERALL, THE FORCING IS WEAK AND THEREFORE ANY SPRINKLES OR LIGHT SHOWERS SHOULD BE LIMITED IF THEY OCCUR AWAY FROM THE COAST. THERE ARE SHOWERS TO OUR WEST AND SOUTHWEST AND SOME OF THEM COULD MAKE A RUN AT OUR WESTERN ZONES BEFORE WEAKENING. WE WILL CONTINUE TO MENTION SOME SPRINKLES OR SLIGHT CHC TO LOW CHC POPS ESPECIALLY CLOSER TO THE COAST FOR AWHILE. OTHERWISE, THE UPPER-LEVEL JETS ARE PROVIDING A DECENT AMOUNT OF CLOUD COVER ALTHOUGH THERE IS A GAP BETWEEN THE TWO AFOREMENTIONED SYSTEMS. THIS WILL RESULT IN LESS CLOUDS FOR A TIME AWAY FROM THE COAST BUT OVERALL THE CLOUDS SHOULD WIN OUT THROUGH THE OVERNIGHT. THERE IS AN ONSHORE FLOW AND WITH THE ONSET OF BOUNDARY LAYER COOLING, SOME LOW CLOUDS COULD DEVELOP ESPECIALLY CLOSER TO THE COAST. DEPENDING ON THE THICKNESS OF THE CLOUD COVER, PATCHY FOG COULD DEVELOP LATE. THE HOURLY GRIDS WERE ADJUSTED WITH THE LATEST OBSERVATIONS, THEN THE LAMP/LAV GUIDANCE WAS BLENDED IN TO ASSIST. NO MAJOR CHANGES WERE MADE ATTM OTHER THAN SOME ADJUSTMENTS TO THE POPS. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... THERE WAS GOOD AGREEMENT FOR MOST WEATHER ELEMENTS IN THIS FORECAST PERIOD. USING THE 925 MB TEMPERATURES AS REFERENCE WOULD YIELD A HIGH OF 83 AT PHL TOMORROW WHILE THE MODELED TWO METER TEMPERATURES WERE AROUND 80. COMPONENTS OF THE MAV AND MET WERE USED TO GET IN THIS RANGE. THE OVERALL FLOW WILL CONTINUE TO BE FROM THE EAST TO SOUTHEAST AS WELL. IN TERMS OF POPS AND CLOUD COVER, SOME WEAK SHORTWAVES MAY PASS THROUGH THE REGION BUT APPEAR TO HAVE LIMITED MOISTURE ASSOCIATED WITH THEM. AS A RESULT, MOSTLY CLOUDY SKIES ARE STILL EXPECTED BUT HAVE KEPT THE FORECAST DRY. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... A MID LEVEL TROUGH IS FORECAST TO BE LOCATED OVER THE NORTHEASTERN STATES ON SUNDAY EVENING. THE TROUGH IS EXPECTED TO CONTINUE LIFTING NORTHEASTWARD WITH RIDGING BUILDING OVERHEAD FROM THE WEST AND SOUTH FOR MONDAY AND TUESDAY. WE ARE ANTICIPATING A FAIR AMOUNT OF MID LEVEL CLOUDINESS ALONG WITH SOME STRATOCUMULUS FOR SUNDAY NIGHT INTO MONDAY MORNING, THEN A GENERAL DECREASE IN CLOUD COVER. CONDITIONS ARE EXPECTED TO REMAIN MARGINALLY STABLE FOR MONDAY AND TUESDAY WITH JUST A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS ON TUESDAY AFTERNOON, MAINLY ON THE NORTHWESTERN EDGE OF OUR FORECAST AREA FROM BERKS COUNTY INTO THE LEHIGH VALLEY AND THE POCONOS. HIGH TEMPERATURES SHOULD BE MAINLY IN THE MIDDLE 80S ON MONDAY AND IN THE UPPER 80S ON TUESDAY WITH AN INCREASE IN HUMIDITY AS THE SURFACE FLOW VEERS FROM THE NORTHEAST AND EAST TO THE SOUTH. IT CONTINUES TO APPEARS AS THOUGH WEDNESDAY WILL BE THE HOTTEST DAY OF THE NEW WEEK. A PIECE OF THE HOT AIR FROM THE GREAT PLAINS IS FORECAST TO DRIFT EASTWARD AND IT SHOULD AFFECT OUR REGION AT THAT TIME. TEMPERATURES AT THE 850 HPA LEVEL ARE FORECAST TO RISE AROUND 18C OR 19C. THE INCREASE IN HUMIDITY SHOULD PREVENT TEMPERATURES FROM RISING TO THEIR DRY ADIABATIC POTENTIAL. WE WILL CONTINUE TO PREDICT MAXIMUM TEMPERATURES MOSTLY IN THE LOWER 90S. IT NO LONGER LOOKS AS THOUGH WE WILL REACH HEAT INDEX VALUES OF 100 FROM THE URBAN CORRIDOR SOUTHEASTWARD. PEAK HEAT INDEX VALUES ARE NOW FORECAST TO BE MOSTLY IN THE MIDDLE 90S, SO THE MENTION WILL BE REMOVED FROM THE HAZARDOUS WEATHER OUTLOOK PRODUCT. WE WILL MENTION A CHANCE OF THUNDERSTORMS MOVING INTO OUR REGION FROM THE NORTHWEST ON WEDNESDAY. HOWEVER, A BIT OF A CAP MAY PREVENT THE ACTIVITY FROM BECOMING WIDESPREAD AT THAT TIME. THE GUIDANCE IS COMING TOGETHER WITH A COLD FRONTAL PASSAGE ON THURSDAY. WE WILL MENTION A CHANCE OF SHOWERS AND THUNDERSTORMS FOR WEDNESDAY NIGHT INTO THURSDAY AHEAD OF AND WITH THE BOUNDARY. ALSO, WE ARE SEEING A TREND TOWARD CONSENSUS ON DRY AIR BUILDING INTO OUR REGION FROM THE NORTHWEST FOR FRIDAY AND SATURDAY. DAYTIME HIGHS ARE ANTICIPATED TO RETURN TO THE MIDDLE 80S AT MOST LOCATIONS. && .AVIATION /22Z SATURDAY THROUGH THURSDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TONIGHT...A CEILING MOSTLY AT OR ABOVE 10000 FEET, HOWEVER AN ONSHORE FLOW COULD ALLOW FOR SOME MVFR CEILINGS TO DEVELOP MAINLY SOUTH AND EAST OF KPHL. LOCALIZED MVFR FOG CANNOT BE RULED OUT LATE ESPECIALLY IF CLOUDS THIN LONG ENOUGH, HOWEVER THE CHC AND CONFIDENCE IS LOW AND THEREFORE NOT INCLUDED AT THIS TIME. ANY ISOLATED LIGHT SHOWER OR BRIEF SPRINKLES ARE EXPECTED TO HAVE NO IMPACT. EASTERLY WINDS BECOMING NORTHEAST LESS THAN 10 KNOTS. SUNDAY...LOCALIZED MVFR CEILINGS POSSIBLE TO START, OTHERWISE A VFR CEILING. NORTHEAST WINDS BECOMING SOUTHEASTERLY IN THE AFTERNOON NEAR 10 KNOTS. OUTLOOK... SUNDAY NIGHT THROUGH TUESDAY...MAINLY VFR. TUESDAY NIGHT AND WEDNESDAY...MAINLY VFR. POSSIBLE LATE NIGHT AND EARLY MORNING MVFR OR IFR CONDITIONS IN LOW CLOUDS, FOG AND HAZE. A CHANCE OF AFTERNOON THUNDERSTORMS. WEDNESDAY NIGHT AND THURSDAY...MVFR AND IFR CONDITIONS AT TIMES IN SHOWERS AND THUNDERSTORMS. && .MARINE... SEAS AND WINDS ARE EXPECTED TO REMAIN BELOW SCA CRITERIA. SEAS AROUND FOUR FEET ARE LIKELY TOMORROW ON THE OCEAN WITH AN EASTERLY FLOW. WIND GUSTS AROUND 20 KNOTS ARE POSSIBLE ON THE OCEAN SUNDAY AFTERNOON. OUTLOOK... SUNDAY NIGHT THROUGH THURSDAY...NO MARINE HEADLINES ARE ANTICIPATED. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GORSE/IOVINO NEAR TERM...GORSE SHORT TERM...GAINES LONG TERM...IOVINO AVIATION...GORSE/IOVINO MARINE...GAINES/IOVINO

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