Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 151153 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 653 AM EST MON DEC 15 2014 .SYNOPSIS... HIGH PRESSURE EXTENDING OVER MUCH OF THE EASTERN UNITED STATES WILL GRADUALLY MOVE EAST AND OFFSHORE LATER TONIGHT. A WARM FRONT IS EXPECTED TO LIFT NORTH THROUGH THE AREA TUESDAY, FOLLOWED BY A COLD FRONT TUESDAY NIGHT INTO WEDNESDAY. HIGH PRESSURE TO OUR WEST WILL THEN SLOWLY BUILD EASTWARD INTO OUR REGION THROUGH THE END OF THE WORK WEEK. BY SATURDAY, A LOW PRESSURE SYSTEM IS FORECAST TO APPROACH THE AREA FROM THE SOUTHWEST, EVENTUALLY EMERGING OFF THE EAST COAST SUNDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE AREA OF CLEAR SKIES ACROSS NORTHEASTERN NEW JERSEY IS STEADILY COLLAPSING THOUGH TEMPERATURES UNDER THIS AREA WERE ABLE TO BOTTOM OUT IN THE UPPER-20S. HAVE ADJUSTED THE EARLY MORNING TEMPERATURES ACCORDINGLY AND HAVE INCREASED THE SKY COVERAGE MOST PLACES...DOESN`T LOOK LIKE THIS LOW STRATUS DECK IS GOING ANYWHERE ANYTIME SOON. OTHERWISE, TRANQUIL DAY IS IN STORE FOR THE REGION AS MID-LEVEL AND SURFACE RIDGING CONTINUE TO BUILD IN FROM THE WEST. WE WILL MAINTAIN THE NORTHERLY FLOW WHICH COULD MEAN WE KEEP THE AMPLE LOW-LEVEL MOISTURE IN PLACE UNDER THE DEEPENING INVERSION. IT IS QUITE POSSIBLE, WITH THE RIDGING NEARLY OVERHEAD THIS AFTERNOON, THAT THE INVERSION WILL LOWER THROUGHOUT THE DAY AND THE CEILINGS WILL LOWER WITH TIME. THE LOWERING INVERSION WILL ALSO HAVE AN EFFECT ON THE HIGHS FOR TODAY. AS WE LOWER THE BASE OF THE INVERSION WE WILL NOT BE ABLE TO MIX AS HIGH AS YESTERDAY AND THEREFORE WILL END UP COOLER THAN YESTERDAY. FOR HIGHS TODAY WE USED A HEAVIER WEIGHTING OFF THE MAVMOS THOUGH DID ADD IN A MINIMAL AMOUNT OF THE METMOS. IT SHOULD BE NOTED THAT THE MET HAD HIGHS ACROSS THE REGION THAT WERE COOLER THAN THE EARLY MORNING HOURLY OBSERVATIONS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... HIGH PRESSURE OVERHEAD SO NO MEASURABLE PRECIPITATION IS EXPECTED. IT IS POSSIBLE THAT AS WE BEGIN TO DEVELOP AN SOUTH-SOUTHEASTERLY FLOW FLOW VERY LATE TONIGHT THERE COULD BE SOME PATCHY DRIZZLE AHEAD OF THE APPROACHING COLD FRONT...MOSTLY CONFINED TO OUR WESTERN ZONES WITH GENTLE UPSLOPE FLOW. OTHERWISE WE WILL REMAIN CLOUDY WITH TEMPERATURES SLIGHTLY BELOW AVERAGE. && .LONG TERM /TUESDAY THROUGH SUNDAY/... THE START OF THE LONG TERM WILL FEATURE SURFACE HIGH PRESSURE AND A MID-LEVEL RIDGE PASSING JUST OFFSHORE, WITH A LOW PRESSURE SYSTEM TRACKING ACROSS THE GREAT LAKES AND ITS ASSOCIATED FRONTAL BOUNDARIES MOVING OVER OUR REGION TUESDAY INTO WEDNESDAY. THEN, A RELATIVE LULL IS EXPECTED FOR THE AREA THROUGH THE REST OF THE WORK WEEK AS HIGH PRESSURE TO THE WEST SLOWLY BUILDS EASTWARD. THE NEXT MORE SIGNIFICANT SYSTEM LOOKS TO APPROACH AND PASS OFF THE EAST COAST NEXT WEEKEND, POTENTIALLY BRINGING MIXED PRECIP TO OUR AREA. FOR TUESDAY, A WARM FRONT IS FORECAST TO APPROACH OUR REGION FROM THE SOUTHWEST AND SLOWLY LIFT NORTHWARD THROUGH THE DAY. THE EARLY PART OF THE DAY SHOULD BE MAINLY DRY FOR THE MORNING COMMUTE AS THE MODELS HAVE BEEN TRENDING SLOWER WITH THE APPROACH OF THE FRONT AND THE ASSOCIATED LIFT AND ONSET OF PRECIP. BY MID-MORNING, WE DO INTRODUCE CHANCE POPS ACROSS OUR WESTERN AND SOUTHERN ZONES FOR RAIN SHWRS, AND WE STEP-UP POPS INTO THE LIKELY CATEGORY FOR TUESDAY AFTERNOON AND EVENING FOR THE FORECAST AREA. WITH THE LATER ONSET OF PRECIP INTO THE REGION, THERE NO LONGER LOOKS TO BE ANY P-TYPE ISSUES AT THE START OF THIS EVENT AS TEMPERATURES WILL HAVE WARMED, WITH RAIN EXPECTED AT THE ONSET. INTO TUESDAY NIGHT, WE TRIM BACK POPS TO CHANCE AND THEN SLIGHT CHANCE INTO THE OVERNIGHT HOURS, AS MOST OF THE LIFT AND MOISTURE WITH THE APPROACHING COLD FRONT LOOKS TO PASS BY TO OUR NORTH. QPF AMOUNTS INTO TUESDAY NIGHT WILL BE PRETTY LIGHT, AND WHILE TEMPERATURES FOR THE MOST PART ARE EXPECTED TO REMAIN ABOVE FREEZING THROUGH THE NIGHT, THERE COULD BE SOME MIXING OF SNOW WITH RAIN BEFORE THE PRECIP TAPERS OFF, MAINLY FOR PORTIONS OF NORTHWEST NJ AND INTO THE POCONOS. WHILE SOME IMPROVEMENT IS EXPECTED FOR OUR REGION INTO WEDNESDAY AS A BROAD AREA OF SURFACE HIGH PRESSURE STRETCHING ACROSS THE PLAINS AND MIDWEST SLOWLY STARTS TO BUILD EASTWARD, LINGERING SURFACE AND UPPER LOW PRESSURE LOOK TO HANG AROUND TO OUR NORTHEAST. WHILE WE ARE ANTICIPATING A MAINLY DRY WEDNESDAY WITH MIXED CLOUDS AND SUN, SOME ISOLATED TO SCATTERED RAIN/SNOW SHWRS CANNOT BE RULED OUT FOR THE HIGHER TERRAIN OF OUR NORTHWEST ZONES, ESPECIALLY IN THE ANTICIPATED WEST-NORTHWEST FLOW. THROUGH THE END OF THE WORK WEEK THEN, FAIRLY QUIET WEATHER IS EXPECTED AS THE PREVIOUSLY MENTIONED BROAD HIGH PRESSURE GRADUALLY PROGRESSES EASTWARD. MIXED SUN AND CLOUDS ARE EXPECTED FOR THE MOST PART THROUGH THURSDAY AND FRIDAY WITH NEAR TO BELOW AVERAGE TEMPERATURES; ALTHOUGH, SOME FLURRIES CANNOT BE RULED OUT IN THE CONTINUED NORTHWEST FLOW FOR THE POCONOS, ESPECIALLY ON THURSDAY. THE NEXT SYSTEM ON THE HORIZON TO WATCH AT THE VERY END OF THE LONG TERM PERIOD WILL BE A DEVELOPING LOW PRESSURE SYSTEM AROUND THE GULF COAST STATES LATE FRIDAY INTO SATURDAY. THERE CONTINUES TO BE MUCH UNCERTAINTY AT THIS TIME WITH THIS SYSTEM BETWEEN THE GFS, ECMWF, AND OTHERS REGARDING THE STRENGTH OF AN INCOMING SHORTWAVE AND ITS INTERACTION WITH THE DEVELOPING SURFACE LOW ACROSS THE DEEP SOUTH. IN ADDITION, THE TRACK AND INTENSITY OF THIS LOW PRESSURE INTO SATURDAY AND SUNDAY CONTINUES TO BE HIGHLY UNCERTAIN, AND THE LATEST MODEL GUIDANCE STILL RAISES MORE DIFFERENCES RATHER THAN SIMILARITIES. THE ECMWF OVERALL DEVELOPS A MORE INTENSE LOW PRESSURE THAT REMAINS FARTHER SOUTH, TRACKING FROM THE GULF COAST REGION TO THE CAROLINAS THROUGH THE COURSE OF SATURDAY. THIS STRONG LOW PRESSURE IS THEN PROGGED TO EMERGE JUST OFF THE EAST COAST AROUND THE VIRGINIA TIDEWATER AREA SATURDAY NIGHT AND THEN TRACK EAST-NORTHEAST OUT TO SEA THROUGH SUNDAY. THE GFS AT THIS TIME DEVELOPS A MUCH WEAKER SYSTEM THAT TAKES MORE OF AN INLAND TRACK, WITH A WEAKER LOW EMERGING OFF THE SOUTHERN MID ATLANTIC COAST AND TRACKING MORE DIRECTLY EASTWARD OUT TO SEA. FACTORING IN THE CMC MODEL AND VARIOUS ENSEMBLE DATA, WE HAVE TAKEN A MIDDLE OF THE ROAD APPROACH WITH REGARDS TO THE TRACK AND INTENSITY OF THE DEVELOPING LOW PRESSURE AND HOW THESE FACTORS WILL ULTIMATELY AFFECT PRECIP TIMING AND PRECIP TYPE FOR OUR REGION SATURDAY AND SUNDAY. WE MOSTLY TOOK A BLEND OF WPC GUIDANCE WITH CONTINUITY FOR TEMPS/WINDS/POPS AND WILL LOOK TO FUTURE MODEL RUNS FOR MORE SIMILARITIES AND AGREEMENT WITH THE DEVELOPMENT OF THIS SYSTEM. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TODAY...MVFR. WE COULD BE SOCKED IN ALL DAY WITH A 1500 TO 2500 FOOT DECK PLAGUING THE REGION. LIGHT NORTHWESTERLY WINDS WILL KEEP COOL, MOIST AIR FLOWING IN FROM THE GREAT LAKES REGION. TONIGHT...HIGH PRESSURE WILL SLIDE OVERHEAD TONIGHT ALLOWING WINDS TO DROP OFF, GOING CLAM IN A LOT OF PLACES. MORE MOISTURE SHOULD ADVECT IN FROM THE EAST AS A WEAK ONSHORE FLOW DEVELOPS. MVFR OR POSSIBLY LOWER WILL BE AROUND. OUTLOOK... TUESDAY...MVFR CONDITIONS TO START THE DAY, BUT IFR CONDITIONS MAY SET IN AS RAIN SHWRS DEVELOP ACROSS THE REGION. WEDNESDAY...POSSIBLE MVFR CONDITIONS TO START, WITH IMPROVEMENT BACK TO VFR EXPECTED BY MIDDAY TO AFTN. THURSDAY AND FRIDAY...VFR CONDITIONS WITH NORTHWEST WINDS. && .MARINE... TODAY - TONIGHT...SUB-SCA CONDITIONS EXPECTED WITH LIGHT NORTHERLY WINDS, AROUND 10 KNOTS. SEAS WILL REMAIN AROUND 2 FEET. OUTLOOK... TUESDAY...SUB-ADVISORY CONDITIONS ARE EXPECTED. WEDNESDAY AND THURSDAY...WHILE SEAS ARE EXPECTED TO REMAIN BELOW SCA LEVELS, NORTHWEST WIND GUSTS COULD REACH THE SCA THRESHOLD OF 25 KNOTS AT TIMES. FRIDAY...MOSTLY SUB-ADVISORY CONDITIONS ARE EXPECTED. SOME NORTHWEST WIND GUSTS COULD STILL BE IN THE 20 PLUS KNOT RANGE, THOUGH. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...KLINE NEAR TERM...HEAVENER SHORT TERM...HEAVENER LONG TERM...KLINE AVIATION...HEAVENER/KLINE MARINE...HEAVENER/KLINE

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