Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 261826 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 126 PM EST WED NOV 26 2014 .SYNOPSIS... A LOW PRESSURE SYSTEM WILL MOVE UP THE MIDDLE ATLANTIC COAST THIS AFTERNOON AND THEN QUICKLY MOVE NORTHEASTWARD TONIGHT. HIGH PRESSURE WILL THEN BUILD TOWARD THE REGION THURSDAY, BUILD ACROSS TO THE SOUTH OF THE REGION FRIDAY AND THEN SLIDE TO THE SOUTH AND EAST ON SATURDAY. A COLD FRONT WILL SLOWLY MOVE TOWARDS THE REGION AND CROSS THE AREA MONDAY INTO MONDAY NIGHT. HIGH PRESSURE WILL THEN RETURN FOR MIDWEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1140 AM UPDATE...ADDED NEW CASTLE AND CECIL COUNTIES IN A WINTER WX ADVISORY. WE RECEIVED SEVERAL REPORTS OF RAIN CHANGING TO SNOW ALREADY. THERE IS A POTENTIAL FOR UP TO 3 INCHES OF SNOW IN THE NORTHERN PART OF THESE COUNTIES, WHERE THE LATEST MESONET OBSERVATIONS SHOW TEMPS NEAR FREEZING. ALSO ADDED THUNDER FOR SOUTHEASTERN PA, THE DELMARVA AND SOUTHWEST NJ WITH WEAK ELEVATED INSTABILITY ORIGINATING FROM THE 600 MB WARM NOSE. THERE HAVE BEEN SEVERAL LIGHTNING STRIKES REPORTED WITHIN THE LAST FEW MINUTES. OTHERWISE, WINTER HEADLINES AND FORECAST SNOWFALL ACCUMULATIONS LOOK TO BE IN PRETTY GOOD SHAPE AFTER LOOKING AT THE LATEST OBSERVATIONS AND HI-RES MODEL GUIDANCE. DID ADJUST SNOWFALL ACCUMULATIONS UPWARD ACROSS THE RIDGES ABOVE 500 FT FROM WESTERN CHESTER UP TO NORTHWEST NJ AS SNOWFALL RATIOS INCREASE AT HIGHER ELEVATIONS. PREVIOUS DISCUSSION...15Z SURFACE ANALYSIS SHOWS LOW PRESSURE DEVELOPING OVER THE OUTERBANKS OF NC. THIS COASTAL LOW WILL STEADILY DEEPEN AS IT TRACKS NORTHEASTWARD ALONG A STRONG BAROCLINIC ZONE THAT IS POSITIONED JUST OFF THE MID-ATLANTIC COAST THIS AFTERNOON. WIDESPREAD PRECIP WILL CONTINUE TO STREAM UP THE EASTERN SEABOARD ON THE COLD SIDE OF THE FRONT AND IN THE RIGHT ENTRANCE REGION OF AN UPPER-LEVEL JET STREAK. THE MAIN CONCERN FOR TODAY IS PINPOINTING THE ADVERSE IMPACTS TO TRAVEL FROM THIS STORM SYSTEM ON TYPICALLY ONE OF THE BUSIEST TRAVEL DAY OF THE YEAR. THE IMPACTS WILL BE TIED TO PTYPES AND SNOWFALL ACCUMULATIONS, WHICH IS EXPECTED TO VARY SIGNIFICANTLY FROM NW TO SE NEAR THE I-95 TRAVEL ARTERY TODAY. AS OF 10 AM, THE RAIN-SNOW LINE HAS PROGRESSED SOUTHEASTWARD TOWARD WESTERN PORTIONS OF CHESTER, MONTGOMERY AND BUCKS COUNTIES IN PA AS WELL AS HUNTERDON AND MORRIS COUNTIES IN NJ. WE JUST RECEIVED A SNOWFALL REPORT AT MOUNT POCONO OF 2.6 INCHES. THESE LOCATIONS ARE COVERED UNDER A WINTER STORM WARNING AND NO CHANGES WERE MADE TO THE STORM TOTAL SNOWFALL FORECASTS. SIDED CLOSER WITH THE COOLER THERMAL PROFILES FROM THE 12Z NAM FOR TIMING THE CHANGEOVER FROM RAIN TO SNOW. EXPECT THE RAIN-SNOW LINE TO GRADUALLY SHIFT FARTHER SOUTH AND EAST THRU THE WESTERN SUBURBS OF PHILLY AND WEST-CENTRAL NJ THROUGH MIDDAY. EXPECT THE BULK OF THE ACCUMULATING SNOW FOR THESE TIER OF ZONES TO OCCUR DURING THE AFTERNOON, WHERE A WINTER WEATHER ADVISORY IS IN EFFECT. THE FORECAST GETS EVEN MORE TRICKY FARTHER EAST TOWARD I-95 AS A 700-600 MB WARM LAYER MAY YIELD MORE OF A WINTRY MIX (RAIN/SNOW/ SLEET) IN PHILLY AND ESPECIALLY ITS SOUTHERN/EASTERN SUBURBS AS WELL AS THE I-195 CENTRAL NJ CORRIDOR DURING THE AFTERNOON. THIS MIXING AS WELL AS ABOVE-FREEZING SURFACE TEMPS SHOULD CUT DOWN ON SNOW TOTALS DRASTICALLY. THE ONLY EDITS TO THE SNOWFALL GRIDS, WHICH WERE OVERALL MINOR, WERE TO TIGHTEN THE GRADIENT OF SNOWFALL ACCUMULATIONS EVEN FURTHER ACROSS THE I-95 CORRIDOR. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... PRECIPITATION SHOULD BEGIN TO LIFT OUT OF THE REGION FROM SOUTH TO NORTH SHORTLY AFTER SUNSET. HOWEVER, LOW CLOUDS MAY PERSIST FOR MUCH OF THE NIGHT, TEMPERING HOW COLD IT WILL GET OVERNIGHT EVEN IN LOCATIONS WITH A FRESH SNOW PACK. && .LONG TERM /THURSDAY THROUGH TUESDAY/... THURSDAY...THANKSGIVING DAY...OVERALL THE DAY DOESN`T LOOK TOO SHABBY. THERE WILL BE A CHANCE FOR SOME LIGHT SNOW/RAIN SHOWERS THROUGH THE DAYTIME BUT LARGELY IT LOOKS LIKE MOST AREAS WILL REMAIN DRY. IN THE HIGHER ELEVATIONS, THERE IS A CHANCE FOR SOME LIGHT SNOW ACCUMULATION. ANY LIGHT SHOWERS SHOULD TAPER OFF THROUGH THE AFTERNOON AND BE DONE BY EVENING AS DRIER AIR STARTS TO MOVE INTO THE REGION. COLDER AIR MOVES INTO THE REGION BEHIND THE DEPARTING LOW AND WE WILL ONLY SEE TEMPS RISE INTO THE UPPER 30S TO LOWER 40S THROUGH MOST OF THE REGION DURING THE DAY. TEMPERATURES OVERNIGHT WILL BE QUITE CHILLY AND DROP DOWN INTO THE 20S, WITH SOME TEENS ACROSS THE HIGHER TERRAIN. FRIDAY...COLD AIR WILL BE IN PLACE FOR FRIDAY AS HIGH PRESSURE STARTS TO BUILD INTO OUR AREA. HIGHS WILL BE CLOSE TO THOSE OF THURSDAY BUT MAY BE A DEGREE OR TWO COLDER OVERALL. THERE SHOULD BE PLENTY OF SUNSHINE AROUND AS WELL. SO WHILE IT MAY NOT FEEL WARM OUTSIDE, THE SUNSHINE WILL CERTAINLY MAKE IT LOOK WARMER THAN IT IS. FRIDAY NIGHT TEMPERATURES WILL REMAIN COLD AND DROP DOWN INTO 20S WITH TEENS ACROSS THE HIGHER TERRAIN. SATURDAY...THE AIRMASS WILL MODIFY A BIT AS THE HIGH BUILDS SLIGHTLY NORTHWARD BEFORE STARTING TO SLIDE TO OUR SOUTH AND EAST DURING THE AFTERNOON AND EVENING. TEMPERATURES WILL RESPOND TO THE MODIFICATION AND SHOULD BE ABLE TO RISE INTO THE 40S THROUGH MUCH OF THE AREA. LOWER 50S WILL BE POSSIBLE ACROSS SOUTHERN DELAWARE. AREAS ACROSS THE SOUTHERN POCONOS WILL REMAIN COLDER AND MAY STRUGGLE TO GET OUT OF THE 30S. THE HIGH SHIFTS TO THE SOUTH AND EAST BY SATURDAY NIGH AND WE SHOULD BE ABLE TO REMAIN A BIT WARMER THROUGH THE OVERNIGHT HOURS AS WE HAVE A SOUTHERLY FLOW AND INCREASING CLOUD COVER. LOWS WILL BE IN THE 30S, WARMER ALONG THE COAST. SUNDAY...SKIES WILL CLOUD UP IN ADVANCE OF THE APPROACHING COLD FRONT AS WARMER AND MOISTER AIR OVERSPREADS OUR AREA. HIGHS WILL REACH INTO THE 50S, POSSIBLY INTO THE LOWER 60S ACROSS THE SOUTH. MONDAY...MODEL GUIDANCE SHOWS A SLOWER PROGRESSION OF THE COLD FRONT AND IT DOESN`T LOOK LIKE IT WILL QUITE GET TO THE REGION UNTIL MONDAY AND THEN CONTINUES TO MOVE SLOWLY THROUGH THE AREA, FINALLY PUSHING OFFSHORE MONDAY EVENING. THE MODELS ALSO INDICATE THAT THE MOISTURE PETERS OUT AS IT PUSHES THROUGH OUR AREA. FOR NOW WE KEEP THE CHANCE OF PRECIPITATION IN THE FORECAST WITH THE FRONTAL PASSAGE. WITH THE FRONT TAKING ITS TIME, HIGHS WILL BE IN 40S TO 50S ACROSS THE AREA BEFORE COLDER AIR ONCE AGAIN MOVES IN. TUESDAY...HIGH PRESSURE WILL SLIDE ACROSS TO THE NORTH OF THE AREA ON TUESDAY AND WE SHOULD BE DRY. TEMPERATURES WILL BE, ON AVERAGE, AT LEAST 5 DEGREES COLDER THAN ON MONDAY. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THIS AFTERNOON - THIS EVENING...IFR TO LIFR CONDITIONS ARE EXPECTED THIS AFTERNOON WITH MULTIPLE PRECIPITATION TYPES. RDG AND ABE WILL BE THE ONLY SITES TO REMAIN SNOW THROUGHOUT THE AFTERNOON WHILE ILG/PHL/TTN/PNE WILL BOUNCE AROUND QUITE A BIT BETWEEN RAIN/SNOW...ACY/MIV SHOULD REMAIN MOSTLY RAIN. EXPECTING A HEAVIER BAND OF PRECIPITATION TO MOVE IN FROM THE SOUTHWEST THIS AFTERNOON WHICH COULD ALLOW FOR MODERATE TO HEAVY SNOW UP THE I-95 CORRIDOR, THOUGH IT SHOULD BE RATHER SHORT LIVED. GUSTY NORTHERLY WINDS, UPWARDS OF 30 KNOTS, ARE EXPECTED. TONIGHT...IFR TRENDING TO MVFR AND POSSIBLY VFR LATE. LATER THIS EVENING WE SHOULD SEE THE PRECIPITATION BEGIN TO SLOW DOWN AS THE SURFACE LOW MOVES TO OUR NORTHEAST. THERE IS A CHANCE THAT WE COULD SEE ANOTHER CHANGE OVER TO A LIGHT RAIN/DRIZZLE AS WELL WHICH SHOULD HELP TO IMPROVE CONDITIONS A BIT...WINDS BACK TOWARDS THE NORTHWEST LATE. TOMORROW...VFR CONDITIONS EXPECTED. WINDS TURN MORE WESTERLY WITH MOSTLY DRY CONDITIONS EXPECTED. COULD BE SOME ISOLATED SHOWERS AT ILG/MIV/ACY DURING THE AFTERNOON HOURS. OUTLOOK... THURSDAY NIGHT...MAINLY VFR CONDITIONS EXPECTED. FRIDAY THROUGH SUNDAY...VFR CONDITIONS EXPECTED.
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&& .MARINE... WINDS AND SEAS WILL BE INCREASING WITHIN THE NEXT FEW HOURS, WITH WINDS REACHING GALE CONDITIONS EVERYWHERE BUT THE UPPER DELAWARE BAY BETWEEN 11 AM AND 2 PM. WINDS SHOULD DIMINISH BY MIDNIGHT, BUT SEAS WILL LIKELY REMAIN ABOVE 5 FT ON THE COASTAL WATERS OVERNIGHT. THUS, ONCE WINDS DROP BELOW GALE CONDITIONS, AN SCA WILL LIKELY BE NEEDED. OUTLOOK... THURSDAY THROUGH SATURDAY...SUB-ADVISORY CONDITIONS EXPECTED. SEAS WILL GRADUALLY DIMINISH THROUGH THURSDAY AND REMAIN BELOW 5 FEET THROUGH SATURDAY. WINDS MAY BRIEFLY NEAR 25 KNOTS ON FRIDAY AS THE GRADIENT TIGHTENS A BIT BETWEEN THE DEPARTING LOW TO OUR EAST AND THE BUILDING HIGH TO OUR WEST. SUNDAY...SEAS AND WINDS WILL NEAR SMALL CRAFT ADVISORY LEVELS AS A COLD FRONT APPROACHES THE REGION. && .HYDROLOGY... HEAVY RAIN, WITH RAIN AMOUNTS ABOVE AN INCH WILL BE POSSIBLE FOR MOST OF DELMARVA AND SOUTHEASTERN NEW JERSEY. DEPENDING ON RAIN RATES, THIS COULD LEAD TO PONDING OF WATER IN POOR DRAINAGE AREAS. IN ADDITION FOR COASTAL LOCATIONS, TODAY`S HIGH TIDE IS EXPECTED TO BE HIGHER THAN NORMAL WHICH COULD EXACERBATE ANY POOR DRAINAGE FLOODING ALREADY OCCURRING ESPECIALLY ON THE BARRIER ISLANDS. && .CLIMATE... HERE ARE THE DAILY SNOWFALL RECORDS FOR OUR 4 SNOW CLIMATE SITES FOR NOVEMBER 26. ACY - TRACE IN 1977, 1957, 1955 PHL - 6.0 INCHES IN 1898 ILG - 0.1 INCHES IN 1950 ABE - 1.7 INCHES IN 1925. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...WINTER STORM WARNING UNTIL 10 PM EST THIS EVENING FOR PAZ054- 055-060>062-101-103-105. WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR PAZ070-071-102-104-106. NJ...WINTER STORM WARNING UNTIL 10 PM EST THIS EVENING FOR NJZ001- 007>010. WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR NJZ012-015. DE...WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR DEZ001. MD...WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR MDZ008. MARINE...GALE WARNING UNTIL 10 PM EST THIS EVENING FOR ANZ431-450>455. SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR ANZ430. && $$ SYNOPSIS...MEOLA NEAR TERM...KLEIN SHORT TERM...JOHNSON LONG TERM...MEOLA AVIATION...HEAVENER/MEOLA MARINE...JOHNSON/KLEIN/MEOLA HYDROLOGY... CLIMATE...

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