Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 261603 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1203 PM EDT WED AUG 26 2015 .SYNOPSIS... HIGH PRESSURE ACROSS THE UPPER GREAT LAKES REGION WILL SETTLE ACROSS THE DELAWARE VALLEY BY FRIDAY AND THEN MOVE OFFSHORE THIS WEEKEND. A LOW PRESSURE SYSTEM AND FRONT WILL AFFECT THE WEATHER SUNDAY AND INTO EARLY MONDAY. MORE HIGH PRESSURE BUILDS ACROSS THE AREA NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... NO BIG CHANGES WILL BE MADE WITH THE 1230 PM UPDATE. MORNING 12Z SOUNDINGS ARE SUPPORTING TODAY`S PREDICTED MAX TEMPS. RECENT HRRRS STILL BRING ECHOES INTO THE POCONOS LATER THIS AFTERNOON. IT IS A DECENTLY STRONG SHORT WAVE AND WITH CONVECTIVE TEMPS BEING REACHED, WE KEPT IN THE CHANCE FOR SPRINKLES. A COLD FRONT WAS POSITIONED OVER NEW ENGLAND, EXTENDING SOUTHWARD OFF THE NJ AND DE COAST. THE FRONT WILL CONTINUE TO PROGRESS FARTHER OFFSHORE TODAY WHILE EXPANSIVE HIGH PRESSURE CENTERED OVER THE MIDWEST BUILDS EASTWARD INTO THE MID ATLANTIC. LATEST WATER VAPOR SATELLITE IMAGERY SHOWS A WELL- DEFINED SPIN IN THE ATMOSPHERE THAT WAS ASSOCIATED WITH AN UPPER LOW LOCATED JUST SOUTHEAST OF JAMES BAY. FOR OUR AREA, CYCLONIC FLOW AROUND THE TROUGH WILL SUSTAIN A CAA PATTERN IN THE LOW-LEVELS OF THE ATMOSPHERE. A MODIFIED CANADIAN AIRMASS WILL BE OVERHEAD, PROTECTING OUR AREA FROM THE HEAT AND HUMIDITY. MAX TEMPS IN THE 70S IN THE HIGHLANDS OF NORTHEAST PA/NORTHWEST NJ AND LOW TO MID 80S ELSEWHERE WILL BE AT, IF NOT A COUPLE DEGREES BELOW CLIMO. WEST WINDS THIS AFTERNOON BACKING IN FRONT OF THE SHORT WAVE. HAD TO DO SOME TWEAKING WITH THE DEWPOINT GRIDS FOR THIS AFTN TO ACCOUNT FOR DRIER AIR MIXING DOWN TO THE SURFACE. FORECAST DEWPOINTS OF 9-11C AT THE TOP OF THE BOUNDARY LAYER SHOULD TRANSLATE TO UPPER 40S/LOW 50S DEWPOINTS AT THE SURFACE. DAYTIME CU IS DEVELOPING. A BRIEF SPRINKLE IS POSSIBLE IN THE POCONOS LATE THIS AFTERNOON WITH WEAK DPVA ARRIVING AHEAD OF A MID-LEVEL SHORTWAVE TROUGH. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... HIGH PRESSURE CENTERED OVER THE GREAT LAKES REGION WILL CONTINUE TO BUILD INTO OUR AREA TONIGHT. MIN TEMP FORECAST IS A BIT TRICKY AS THE PRESSURE GRADIENT MODESTLY TIGHTENS AND COULD BE STRONG ENOUGH TO PREVENT ALL AREAS FROM DECOUPLING. HOWEVER, THE TYPICAL SHELTERED/RURAL LOCALES (E.G., NE PA/NW NJ, PINE BARRENS) WOULD BE MOST SUSCEPTIBLE TO DECOUPLING AND THUS SEE TEMPS BOTTOMING OUT IN THE LOW TO MID 50S (PERHAPS 40S IN THE POCONOS) TONIGHT. URBAN AND COASTAL LOCALES AND AREAS WHERE A LIGHT NW WINDS PERSISTS OVERNIGHT, TEMPS WILL REMAIN IN THE LOW TO MID 60S. && .LONG TERM /THURSDAY THROUGH TUESDAY/... THURSDAY THRU FRIDAY NIGHT...DRY WEATHER EXPECTED THIS PERIOD WITH HIGH PRESSURE CRESTING ACROSS THE AREA FRIDAY. TEMPERATURES NEAR NORMAL WITH HIGHS MOSTLY LOW/MID 80S SOUTH AND UPPER 70S TO LOW 80S NORTH. COOL TEMPERATURES THU NIGHT WITH MOSTLY 50S AWAY FROM THE URBAN AREAS/DELMARVA. MILDER LOW TEMPS FRI NIGHT WITH LOW/MID 60S AND SOME 50S NORTH. SAT THRU SUN NIGHT...MUCH OF THIS PERIOD WILL BE DRY ALSO...BUT THERE IS A WEAK FRONT AND LOW SHOWN BY THE OP MODELS CROSSING THE AREA. WE HAVE DECIDED TO KEEP THE SLIGHT CHC POPS FOR SUN FOR NOW. THE 00Z GFS ALSO SHOWS SOME SHOWERS POSSIBLE SAT/SAT NIGHT...BUT THE 00Z EC IS DRY. MOST OF OUR SURROUNDING OFFICE SEEM TO HAVE THIS PERIOD DRY ALSO...SO WITH THE UNCERTAINTY...WE WILL JUST KEEP IT SUB-14PCT POPS AT THIS TIME. TEMPERATURES WILL CLIMB ABOVE NORMAL THIS WEEKEND AND HUMIDITY LEVELS WILL START TO RISE ALSO. HIGHS IN THE MID/UPPER 80S EXPECTED IN MOST AREAS WITH COOLER TEMPS ACROSS THE SRN POCONOS AND AT THE SHORE. MON THRU WED...MORE HIGH PRESSURE BUILDS AT THE SFC AND ALOFT. THE BEGINNING OF A LATE SUMMER HEAT WAVE POSSIBLE THIS PERIOD WITH HIGHS NEAR 90 MON AND LOW 90S TUE. MAXS OF NEAR 90 PSBL WED TOO. HUMIDITY LEVELS MODERATE WITH DPS IN THE MID 60S ACROSS THE DEL VALLEY AND CLOSER TO 70 OVER THE DELMARVA. THE RIDGE ALOFT WILL DISCOURAGE SHOWER FORMATION...ANOTHER DRY FEW DAYS. && .AVIATION /16Z WEDNESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR TODAY AND TONIGHT. SOME HIGH BASED CU TODAY. LIGHT NW WINDS UNDER 10 KT THIS MORNING WILL BECOME WLY AROUND 10 KT THIS AFTERNOON AND THEN NWLY AROUND 5 KT TONIGHT. BACKGROUND FLOW SHOULD PREVENT SEA- BREEZE FRONT FROM MOVING VERY FAR INLAND. KEPT THE SEA BREEZE OUT OF ACY BUT IT WILL BE CLOSE. OUTLOOK... THU THRU SAT NIGHT...MOSTLY VFR. PATCHY FOG PSBL DURING THE PREDAWN HOURS. SUN...MOSTLY VFR. SHOWERS POSSIBLE WITH LOWER CONDITIONS. && .MARINE... WINDS AND SEAS EXPECTED TO BE BELOW SCA CRITERIA TODAY. NW WINDS AROUND 15 KT EARLY THIS MORNING WILL BECOME LIGHT/VARIABLE AROUND MIDDAY. SOUTHERLY WINDS OF 10-15 KT IN ASSOCIATION WITH A SEA BREEZE DEVELOP DURING THE AFTERNOON IN OUR ATLANTIC COASTAL ZONES. WINDS EVENTUALLY BECOME OFFSHORE AGAIN LATE IN THE DAY AND TONIGHT. OUTLOOK... SUB-SCA CONDITIONS THRU THE PERIOD. SEAS WILL BUILD TO AROUND 4 FT ON THE OCEAN SAT NIGHT INTO SUNDAY. WIDELY SCT SHOWERS/TSTMS POSSIBLE SUN. && .RIP CURRENTS... WINDS ARE CURRENTLY OFFSHORE (NORTHWESTERLY) THIS MORNING BUT ARE EXPECTED TO BECOME MORE ALONGSHORE (SOUTHERLY) THIS AFTERNOON. HI- RES MODEL GUIDANCE SHOWS THE STRONGEST SOUTHERLIES DEVELOPING OVER THE NJ COAST LATE IN THE DAY. LONG PERIOD SWELLS WILL BE AROUND 11 SECONDS TODAY. WENT WITH A CONSERVATIVE/WORST-CASE SCENARIO FOR THE RIP CURRENT FORECAST, WHICH GIVES A MODERATE RISK FOR THE FORMATION OF DANGEROUS RIP CURRENT ALONG THE NJ BEACHES, THOUGH THE RISK MAY NOT REACH MODERATE THRESHOLD UNTIL LATE IN THE DAY, WHEN MOST LIFEGUARDS ARE ENDING THEIR SHIFT. THE RISK IS LOW FOR DELAWARE BEACHES. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...O`HARA NEAR TERM...GIGI/KLEIN SHORT TERM...KLEIN LONG TERM...O`HARA AVIATION...KLEIN/O`HARA MARINE...KLEIN/O`HARA RIP CURRENTS...

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