Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 231442 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 942 AM EST FRI JAN 23 2015 .SYNOPSIS... HIGH PRESSURE MOVES OVERHEAD TODAY WHILE A QUICK MOVING LOW PRESSURE SYSTEM TRACKS ALONG THE EAST COAST LATER TONIGHT. THE LOW WILL MOVE OFF TOWARDS NEW ENGLAND SATURDAY MORNING WITH A BRIEF SHOT OF HIGH PRESSURE TO FOLLOW. ANOTHER CLIPPER SYSTEM IS EXPECTED TO MOVE ACROSS THE REGION EARLY MONDAY MORNING. LARGE ARCTIC HIGH PRESSURE FILLS IN ON TUESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... HIGH PRESSURE, CENTERED OVER THE CHESAPEAKE BAY REGION AT MID MORNING, WILL SLIDE EASTWARD AND OFF THE COAST TODAY. A LIGHT AND VARIABLE WIND THIS MORNING SHOULD SETTLE INTO THE SOUTHWEST AND SOUTH DURING THE AFTERNOON AT SPEEDS LESS THAN 10 MPH. A LARGE FIELD OF STRATOCUMULUS COVERED MUCH OF WESTERN, CENTRAL AND NORTHEASTERN PENNSYLVANIA THIS MORNING. THE MOISTURE IS TRAPPED UNDER A WEAK TEMPERATURE INVERSION AND THE CLOUDS WILL BE SLOW TO ERODE. THE MASS OF CLOUDS IS FORECAST TO CONTINUE LIFTING SLOWLY NORTHEASTWARD. THE ONLY PARTS OF OUR FORECAST AREA THAT SHOULD BE AFFECTED BY THE CLOUDS ARE THE POCONOS, AND PERHAPS SECTIONS OF BERKS COUNTY, THE LEHIGH VALLEY AND FAR NORTHERN NEW JERSEY. MEANWHILE, HIGH CLOUDS AHEAD OF THE APPROACHING STORM HAD ALREADY OVERSPREAD THE SOUTHERN HALF OF OUR FORECAST AREA AT MID MORNING. THE HIGH CLOUDS WILL CONTINUE TO EXPAND NORTHWARD. MID LEVEL CLOUDS WERE AS FAR NORTH AS CENTRAL VIRGINIA AT 930 AM. THE MID CLOUDS ARE EXPECTED TO REACH NORTHEASTERN MARYLAND AND DELAWARE LATE THIS AFTERNOON. THE LEADING EDGE OF THE PRECIPITATION IS ANTICIPATED TO REACH KENT ISLAND AND DENTON IN MARYLAND, AND GEORGETOWN IN DELAWARE TOWARD 600 PM. IT CONTINUES TO APPEAR AS THOUGH TODAY`S HIGHS WILL BE MAINLY IN THE UPPER 30S AND LOWER 40S. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... WINTER WEATHER ADVISORIES ISSUED FOR MUCH OF THE AREA IN SIX SEGMENTS TO PERMIT MORE SPECIFIC TIMING AND SNOW/ICE AMOUNTS. CONFIDENCE COMMENTS: THE SOUTHERNMOST ADVISORY SEGMENTS FROM VCNTY EASTON MD TO CAPE MAY NJ SOUTHWARD ARE LEAST LIKELY TO VERIFY BUT A BIT OF ICE COULD OCCUR THERE THIS EVENING. SNOW AMOUNTS MAY BE AN INCH OR SO ON THE HIGH SIDE ELSEWHERE AND ICE COULD OCCUR FURTHER NORTHWEST THAN CURRENTLY ADVISED (IE NORTH OF I78. CONFIDENCE ON A DIFFICULT OVERNIGHT COMMUTE IS MUCH ABOVE AVERAGE FROM NEAR I-95 NORTHWESTWARD. IT WAS A CLOSE CALL ON COMBINED WARNING AMOUNTS FOR JUST NORTHWEST OF THE INTERSTATE 95 CORRIDOR AND 40 MILES TO THE NORTHWEST INCLUDING CHESTER... MONTGOMERY...BUCKS COUNTIES IN PA HUNTERDON AND SOMERSET IN NJ. WE OPTED FOR THE MORE CONSERVATIVE ADVISORY APPROACH. NEVERTHELESS...PLEASE MONITOR FUTURE AFTERNOON FORECASTS FOR A POSSIBLE UPGRADE. WE THINK 3 TO 6 INCHES OF SNOW JUST NW OF I95 AND UP TO .15 INCH ICE EXCEPT ALL OR MAINLY SNOW FROM NORTHWEST BERKS COUNTY THROUGH THE LEHIGH VALLEY JUST NORTH OF KABE INTO WARREN AND SUSSEX COUNTIES NORTHWARD. YOU WILL BE SHOVELING THERE TOMORROW MORNING AND TRAVEL WILL BE SLOW. ITS POSSIBLE THERE WILL BE ICE ACCUMS APPROACHING 1/4 INCH WITHIN 15 MILES OF I95 SATURDAY MORNING. ICY SLIPPERY TRAVEL SHOULD OCCUR FOR A FEW HOURS LATE THIS EVENING INTO PART OF THE NIGHT FOR PORTIONS OF SNJ NORTHERN DELAWARE AND MARYLAND`S LOWER EASTERN SHORE THOUGH THIS IS STATED WITH LESS CONFIDENCE. WE RAN THIS FORECAST PRIMARILY OFF THE NAM WITH TOP DOWN AND PARTIAL THICKNESS WEATHER EVALUATION...CHANGING ALL SLEET TO FREEZING RAIN AS THE BOUNDARY LAYER DOES NOT LOOK COLD ENOUGH TO CHANGE ANY MELTED SNOW BACK TO ICE PELLETS...SAVE FOR MAYBE AN HOUR DURING THE TRANSITION. SNOW COULD BE HEAVY FOR AN HOUR OR SO IN THE WINDOW OF ROUGHLY 4Z AND 10Z. THIS CAUSED BY ABOUT TWO WAVES OF NOTABLE FGEN IN THE 900-600MB LAYER. NO 850MB LOW TO ENSURE ALL SNOW NW NJ AND NE PA BUT THE SOUTHERLY FLOW 850MB CONVERGENCE AND MODEST CAD IN THE 06Z TIME FRAME LOOKS SUFFICIENT FOR A BURST OF MODERATE SNOW. A FRONT END SNOW THUMP FOR MUCH OF THE AREA THEN TRANSITIONING TO A COLD RAIN FROM SSE TO NNW. RAIN WILL BE HEAVY EARLY SATURDAY MORNING OVER THE REGION NEAR AND EAST OF I95. MOST OF THE EFFECTIVE WINTRY PORTION OF THE STORM COULD BE DONE BY 12Z. SO...THE TEMP FCST TONIGHT WAS MOSTLY THE NAM MOS BLENDED WITH ITS 2M TEMP FCST. THE GFS MOS LOOKED TOO WARM AND THE ECMWF SUPPORT THE COLDER SCENARIO. && .LONG TERM /SATURDAY THROUGH THURSDAY/... MEDIUM RANGE GUIDANCE IS IN DECENT AGREEMENT WITH PACIFIC RIDGING ALLOWING FOR MEAN EAST COAST TROUGHING THROUGH A MAJORITY OF THE LONG TERM PERIOD. AT LEAST TWO DISTINCT WAVES MOVE THROUGH THIS MEAN TROUGH THIS WEEKEND INTO EARLY NEXT WEEK, EACH CARVING INTO THE BASE OF THE TROUGH. A WEAKENING IN THE PACIFIC RIDGING TOWARDS THE END OF THE PERIOD SHOULD ALLOW FOR SLIGHTLY MORE ZONAL FLOW TO COMMENCE. SATURDAY...RAPIDLY DEEPENING SYSTEM ACROSS OUR WATERS WILL BE QUICKLY MOVING BY TO THE NORTHEAST. 0C 850MB ISOTHERM CONTINUES TO RUN INLAND THOUGH IT SHOULD STOP SOMEWHERE JUST SOUTH AND EAST OF AN RDG-UKT-SMQ LINE LATE IN THE MORNING BEFORE SHIFTING BACK TOWARDS THE EAST BY EARLY AFTERNOON. THERE DOES NOT LOOK TO BE A LOT OF COLD AIR IN PLACE AND WITH THE LACK OF BLOCKING DOWNSTREAM THIS SYSTEM MUST CONTINUE TO MAKE ITS OWN COLD AIR. STILL THINK THE BEST CHANCES FOR AN ALL SNOW EVENT ARE ACROSS THE LEHIGH VALLEY AND POCONOS/NNJ THOUGH SOME RIMING OF THE SNOW WILL MORE THAN LIKELY TAKE PLACE IN THE SOUTHERN EXTENT OF THESE AREAS...LOWER SLR EXPECTED. HAVE A DECENT CHANCE AT SEEING AN ADDITIONAL 1-2" ACROSS NNJ SATURDAY AFTERNOON. BY LATER IN THE AFTERNOON THE SYSTEM WILL BE TO OUR NORTHEAST AND WE SHOULD BE DRY EVERYWHERE. IT IS POSSIBLE THAT LATE IN THE AFTERNOON WE LOSE THE ICE CRYSTALS TO PRODUCE THE SNOW AND THEREFORE WOULD END UP BEING A FREEZING DRIZZLE...IF THE COLUMN CAN STAY SATURATED LONG ENOUGH. SUNDAY - MONDAY...BRIEF SHOT OF HIGH PRESSURE FOR MOST OF SUNDAY, AHEAD OF ANOTHER WEAK CLIPPER SYSTEM. LIGHT SNOW SHOULD BEGIN TO OVERSPREAD THE REGION LATE SUNDAY NIGHT/EARLY MONDAY MORNING, FROM THE WEST. THERE COULD BE SOME MIXING ACROSS OUR EXTREME SOUTHERN ZONES WITH THE CURRENT TRACK OF THIS SYSTEM, WHICH IS A BIT FARTHER NORTH THAN PREVIOUS RUNS...USED A PARTIAL THICKNESS OFF THE GFS FOR PTYPE. TOO SOON TO TALK ABOUT ACCUMULATIONS, LET GET THROUGH TONIGHT`S EVENT FIRST, BUT MINOR ACCUMULATIONS ARE POSSIBLE. TUESDAY - THURSDAY...ARCTIC HIGH PRESSURE BUILDS TOWARD THE AREA. DRY WEATHER WITH BELOW NORMAL TEMPS EXPECTED. HIGHS WED WILL BE MOSTLY BELOW FREEZING ACROSS THE FORECAST AREA AND A FEW DEGREES HIGHER THU. LOWS TUE NIGHT AND WED NIGHT WILL BE IN THE SINGLE DIGITS (AND CLOSER TO ZERO) OVER THE SRN POCONOS AND IN THE TEENS ELSEWHERE. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. LATE THIS MORNING...VFR CLEAR OR CIRRUS WITH CIGS 2500-3500 N OF KRDG AND KABE. LIGHT WIND. THIS AFTERNOON...WIND TURN LIGHT SOUTHWEST...MAX GUST 15 KT. CIGS 2500-3500 FT SLIDING NEWD LATE AS PER TAFS. CONFIDENCE ON TIMING THE ARRIVAL IS LESS THAN IDEAL BUT IT APPEARS TO ME THE NAM HAS BEEN VERY GOOD THE LAST SEVERAL DAYS ON ITS TSECTIONS. TONIGHT...IFR OR LIFR CONDITIONS IN SNOW SPREADING NORTHWARD PER THE TAFS. SNOW MAY BRIEFLY CHANGE TO SLEET BEFORE TO FREEZING RAIN AND THEN RAIN KPHL/KILG/KMIV AND KACY LATER TONIGHT. 1 TO 3 INCHES OF SNOW AT THESE AIRPORTS BY 07Z BEFORE THE CHANGE TO FREEZING RAIN. PLEASE SEE TAFS FOR THE FORECAST TIMING DETAILS. VCNTY KPNE AND KTTN...SNOW TO FREEZING RAIN OVERNIGHT 2 TO 4 INCHES BY 10Z SATURDAY. VCNTY KABE AND KRDG..MOSTLY SNOW WITH 2-4 INCHES AT TEMPS 30-32F BY 12Z SATURDAY. SLEET OR FREEZING RAIN POSSIBLE AFTER 10Z. A 1 TO 2 HOUR PERIOD OF 1/2SM MODERATE SNOW APPEARS PROBABLE AT MANY AIRPORTS. PLOWING ANTICIPATED AT MOST AIRPORTS FOR A TIME LATER TONIGHT. DEICING PROBABLY NEEDED FOR THE WETTER SNOW AND OR FREEZING RAIN. FORTUNATELY MOST OF THE SNOW AND ICE IS AFTER HEAVIER ARRIVAL- DEPARTURES BUT THIS FAST MOVING NOR`EASTER WILL PROBABLY IMPACT LATE NIGHT AIR TRAFFIC HERE. WIND LIGHT DURING THE EVENING TURNING NE WITH GUSTS 12-22KT BY 12Z SATURDAY. CONFIDENCE: ABOVE AVERAGE ON THE SCENARIO OUTLINED...TIMING COULD BE IN ERROR BY 2 HOURS. CONDITIONS FROM VFR 10 MILES TO IFR VSBY NEAR 1 MILE... PROBABLY WITHIN 30 TO 60 MINUTES OF SNOW ONSET LATE THIS EVENING. BASICALLY SHOULD BE A WALL OF SNOW MOVING NORTHWARD. SMALL CHC MIXED WITH RAIN FOR A FEW MINUTES AT THE START. OUTLOOK... SATURDAY...WIDESPREAD LIFR/IFR WITH SNOW AND RAIN AFFECTING MUCH OF THE AREA. SAT NIGHT/SUN...IMPROVING CONDITIONS SAT NIGHT. VFR SUNDAY. SUN NIGHT...CONDITIONS DIMINISHING WITH IFR POSSIBLE AND SNOW BY DAWN MON. MON...MVFR/IFR WITH LOWER CIGS/VSBYS IN SNOW. MON NIGHT - TUE...MOSTLY VFR. && .MARINE... LIGHT WIND TODAY. SCA CONDITIONS DEVELOP AFTER 08Z...ESPECIALLY DELAWARE WATERS AS A NOREASTER RACES NEWD TO PASS EAST OF THE DELMARVA NEAR SUNRISE SATURDAY. .OUTLOOK... SATURDAY - SUNDAY...SCA CONDITIONS EXPECTED AS LOW PRESSURE SYSTEM PASSING BY. ELEVATED SEAS MAY LINGER A BIT INTO SUNDAY AFTERNOON. MONDAY - TUESDAY...POSSIBLE SCA/LOW END GALES AS ANOTHER LOW PRESSURE DEEPENS OFF THE COAST. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST SATURDAY FOR PAZ060>062-101-103-105. WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 1 PM EST SATURDAY FOR PAZ054-055. WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 10 AM EST SATURDAY FOR PAZ070-071-102-104-106. NJ...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST SATURDAY FOR NJZ007>010. WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 4 AM EST SATURDAY FOR NJZ016-021>023. WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 1 PM EST SATURDAY FOR NJZ001. WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 7 AM EST SATURDAY FOR NJZ013-017>020-027. WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 10 AM EST SATURDAY FOR NJZ012-015. DE...WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 4 AM EST SATURDAY FOR DEZ001. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 3 AM EST SATURDAY FOR DEZ002. MD...WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 4 AM EST SATURDAY FOR MDZ012. WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 10 AM EST SATURDAY FOR MDZ008. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 3 AM EST SATURDAY FOR MDZ015-019-020. MARINE...SMALL CRAFT ADVISORY FROM 4 AM SATURDAY TO 10 AM EST SUNDAY FOR ANZ450>455. SMALL CRAFT ADVISORY FROM 7 AM TO 6 PM EST SATURDAY FOR ANZ431. && $$ SYNOPSIS...HEAVENER NEAR TERM...IOVINO SHORT TERM...DRAG LONG TERM...HEAVENER AVIATION...DRAG/HEAVENER MARINE...DRAG/HEAVENER

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