Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 300300 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1000 PM EST THU JAN 29 2015 .SYNOPSIS... A FRONTAL SYSTEM WILL MOVE ACROSS THE AREA LATE TONIGHT AS LOW PRESSURE MOVES INTO NEW ENGLAND THEN SLOWLY DRIFTS INTO THE CANADIAN MARITIMES THROUGH THE WEEKEND. HIGH PRESSURE BUILDS TO OUR SOUTH THROUGH THE WEEKEND, FOLLOWED BY ANOTHER FRONTAL BOUNDARY ON SUNDAY. AN AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ALONG THIS BOUNDARY AND PASS JUST TO OUR SOUTH ON MONDAY BUT STILL AFFECT THE AREA. HIGH PRESSURE BUILDS IN ONCE AGAIN FOR MONDAY NIGHT INTO TUESDAY. ANOTHER FRONTAL BOUNDARY IS EXPECTED WEDNESDAY INTO WEDNESDAY NIGHT. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... A MID LEVEL TROUGH WAS PASSING OVERHEAD THIS EVENING. THE AXIS OF THE TROUGH SHOULD BE TO OUR NORTHEAST BY MIDNIGHT, ALONG WITH MUCH OF THE FIRST BATCH OF LIGHT PRECIPITATION. WHILE SOME DRYING IS EXPECTED FOR OUR CENTRAL AND SOUTHERN COUNTIES, LIGHT SNOW IS ANTICIPATED TO LINGER IN OUR NORTHERN COUNTIES BEYOND MIDNIGHT. A SECOND MID LEVEL TROUGH IS FORECAST TO APPROACH FROM THE WEST TOWARD DAYBREAK. AS IT NEARS OUR REGION, ANOTHER AREA OF LIGHT PRECIPITATION IS FORECAST TO DEVELOP OVERHEAD. WE ARE EXPECTING A SECOND SHOT OF LIGHT SNOW AT THAT TIME, WITH SLIGHTLY GREATER ACCUMULATIONS THAN THIS EVENING`S SNOWFALL. WE HAVE MADE SOME MINOR ADJUSTMENTS TO THE SNOWFALL TOTAL MAP FOR THE OVERNIGHT INTO FRIDAY MORNING. HOWEVER, THE GENERAL IDEA OF 1 TO 2 INCHES ACROSS THE NORTHERN HALF OF OUR FORECAST AREA, AND LESS THAN AN INCH ACROSS THE SOUTH CONTINUES TO APPEAR REASONABLE BASED ON THE LATEST GUIDANCE. MINIMUM TEMPERATURES SHOULD BE MAINLY IN THE UPPER 20S AND LOWER 30S WITH A SOUTHWEST WIND AROUND 5 TO 10 MPH. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... ANY COLD FRONTAL RELATED PCPN SHOULD MOVE OFFSHORE EARLY FRIDAY MORNING. BUT THAT MIGHT NOT BE THE END OF PCPN CHANCES AS ANOTHER SHORT WAVE AT THE BASE OF THE TROF WILL BE MOVING THROUGH. IN FACT SOME OF OUR WINDEX/SNOW SQUALL TOOLS ARE GIVING THE SOUTHERN HALF OF OUR CWA THE CHANCE FRIDAY AFTERNOON. SOME OF THE OLDER WINDEX PROCEDURES ARE SLIGHTLY MORE SUBDUED BECAUSE OF THE LACK OF EVEN STEEPER LAPSE RATES AND NO REAL FOCUSING BOUNDARY OR CAPES ABOVE 70J. THE FORECAST SOUNDINGS HAVE THE CAP HIGH ENOUGH TO SUPPORT SNOW SHOWERS EVERYWHERE. FOR NOW WE HAVE PUT IN A LOW CHANCE FOR SNOW SHOWERS AND SEE HOW THE GUIDANCE PROGRESSES. SNOW SHOWERS OR NOT, THE NORTHWEST GRADIENT WILL BE TIGHTENING AS THE AFTERNOON PROGRESSES. WE ARE APPROACHING WIND ADVY CRITERIA LATE IN THE DAY AS MIXING BECOMES DEEPER. BECAUSE WE ARE NOT DEEP INTO THE CRITERIA AND PMDHMD RECOMMENDED THAT THE NAM/WRF IS TOO TUCKED INTO THE COAST WITH THE SFC LOW, WE HELD OFF WITH ISSUING IT FOR NOW. THE KATABATIC NORTHWEST FLOW WILL BE ABLE TO MAINTAIN TEMPS FOR A WHILE AND GIVEN A RELATIVELY HIGH START, WE WERE AT THE HIGH END FOR MAX TEMPS. NOT THAT IT WILL FEEL WARM. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... AS THE LOW PULLS AWAY FROM THE AREA AND INTO THE NEW ENGLAND COASTAL WATERS FRIDAY NIGHT, PRECIPITATION IS EXPECTED TO END ACROSS MOST OF THE AREA. THE EXCEPTION TO THIS WOULD BE ACROSS THE POCONOS AREAS WHERE SOME LINGERING LAKE EFFECT SHOWERS MAY CONTINUE INTO THE NIGHT. OTHERWISE, BITTERLY COLD AIR WILL FILTER DOWN ACROSS THE AREA ALONG WITH STRONG WINDS AS THE PRESSURE GRADIENT TIGHTENS BETWEEN THE DEPARTING LOW AND HIGH PRESSURE BUILDING TO OUR WEST. WINDS COULD GUST 35-40 MPH DURING FRIDAY NIGHT AS WELL. THE COMBINATION OF THE LOW TEMPERATURES AND STRONG WINDS WILL CREATE DANGEROUSLY LOW WIND CHILLS ACROSS MUCH OF THE AREA. SUB-ZERO WIND CHILLS WILL OCCUR ALMOST EVERYWHERE, WITH THE POCONOS -15 TO -20. WE HAVE ISSUED A WIND CHILL ADVISORY FOR CARBON AND MONROE SINCE THEY ARE EXPECTED TO REACH WELL INTO THE ADVISORY RANGE. ELSEWHERE, WIND CHILLS AS OF NOW ARE EXPECTED TO FALL JUST SHORT. SATURDAY WILL CONTINUE TO BE WINDY AND COLD, BUT WIND CHILLS WILL BE ABLE TO REBOUND SOME AS TEMPERATURES WARM DURING THE DAY. DRY WEATHER IS CONTINUED TO BE EXPECTED THROUGH THE DAY SATURDAY. WINDS WILL CONTINUE TO BE GUSTY WITH GUSTS IN THE 25-30 MPH RANGE. WINDS SHOULD DIMINISH LATE IN THE DAY INTO THE NIGHT AS THE PRESSURE GRADIENT WEAKENS. ON SUNDAY, A COLD FRONT IS FORECAST TO SAG DOWN ACROSS THE AREA FROM THE NORTH. IT LOOKS LIKE THE ACTUAL FRONT SHOULD BE DRY AS IT DIPS ACROSS THE AREA. HOWEVER, AN AREA OF LOW PRESSURE IS FORECAST TO DEVELOP ALONG THIS FRONT ACROSS THE MID-MISSISSIPPI VALLEY DURING THE DAY, AND MAKE ITS WAY ACROSS THE CENTRAL APPALACHIANS AND OFF THE MID-ATLANTIC COAST SUNDAY NIGHT INTO MONDAY MORNING. AS THIS HAPPENS, A SHORT WAVE ALOFT APPROACHING FROM THE WEST WILL HELP STRENGTHEN THE LOW AS IT PASSES JUST TO OUR SOUTH OVERNIGHT AND LIFT TO OUR NORTHEAST MONDAY MORNING. MEDIUM RANGE GUIDANCE IS IN GOOD AGREEMENT THAT SNOW WILL OVERSPREAD THE AREA ON THE NORTHERN SIDE OF THE SYSTEM OVERNIGHT SUNDAY INTO MONDAY MORNING. WITH THE LOW BEING TO OUR SOUTH, AND COLD HIGH PRESSURE TO OUR NORTH, IT LOOKS LIKE THE PRECIPITATION SHOULD BE ALL SNOW. AN ACCUMULATING SNOWFALL IS BECOMING MORE LIKELY, FOR MOST, IF NOT ALL OF OUR AREA SUNDAY NIGHT INTO MONDAY, WITH THE SOUTHERN HALF LOOKING TO RECEIVE THE MOST. WE MAY RUN INTO AN INSTANCE WHERE EXTREME SOUTHERN AREAS MAY HAVE MORE QPF BUT LOWER RATIOS, AND NORTHERN AREAS HAVING LESS QPF AND HIGHER RATIOS, AND IN BETWEEN HAVING A LITTLE OF BOTH. AS USUAL, WE`LL REFINE SNOW AMOUNTS IN SUBSEQUENT FORECASTS. ALL SNOW IS EXPECTED TO HAVE ENDED BY MONDAY EVENING AS THE LOW PULLS AWAY FROM THE AREA. VERY COLD AIR, NEAR RECORD LOW TEMPERATURES FOR SOME AREAS, ONCE AGAIN FILTERS DOWN INTO THE AREA OVERNIGHT ACROSS THE AREA AS COLD CANADIAN HIGH PRESSURE BUILDS DOWN INTO THE REGION AGAIN. WINDS SHOULD WEAKEN SOME OVERNIGHT AS THE PRESSURE GRADIENT SLACKENS WHEN THE HIGH STARTS TO BUILD INTO THE AREA. HOWEVER, THERE SHOULD BE ENOUGH WIND AND IT WILL BE COLD ENOUGH FOR WIND CHILLS TO FALL WELL BELOW ZERO MONDAY NIGHT INTO TUESDAY. HIGH PRESSURE ACROSS THE AREA TUESDAY WILL PUSH OFFSHORE TUESDAY NIGHT, AND DRY AND COLD CONDITIONS ARE EXPECTED THROUGH THIS PERIOD. ANOTHER FRONTAL BOUNDARY IS EXPECTED TO APPROACH THE AREA WEDNESDAY INTO WEDNESDAY NIGHT. THIS COULD BRING ANOTHER ROUND OF PRECIPITATION TO THE AREA, WHICH WOULD END UP BEING MOSTLY SNOW WITH THE CURRENTLY EXPECTED TEMPERATURES. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. CONDITIONS WILL CONTINUE TO VARY BETWEEN MVFR AND VFR OVERNIGHT AT KRDG, KABE AND KTTN WITH PERIODS OF SNOW. THERE WILL BE PERIODS OF IFR, AS WELL. MEANWHILE, VFR CONDITIONS SHOULD PREVAIL AT KPNE, KPHL, KILG, KMIV AND KACY. HOWEVER, ANOTHER SHOT OF LIGHT SNOW BETWEEN ABOUT 0800Z AND 1200Z COULD BRING A PERIOD OF MVFR CONDITIONS. CEILINGS ARE FORECAST TO LIFT TO 4000 FEET OR GREATER AT ALL EIGHT OF OUR TAF SITES AROUND 1200Z TO 1300Z ON FRIDAY AS THE POTENTIAL FOR SNOW COMES TO AN END. THE VFR CEILINGS SHOULD PERSIST THROUGH MOST OF THE DAY WITH SOME CLEARING POSSIBLE TOWARD EVENING. A GENERAL SOUTHWEST WIND AROUND 5 TO 10 KNOTS OVERNIGHT SHOULD BECOME WEST AROUND 10 KNOTS NEAR DAYBREAK. A STRONG COLD FRONT SHOULD ARRIVE ON FRIDAY MORNING WITH A GUSTY NORTHWEST WIND IN ITS WAKE. SUSTAINED SPEEDS ARE FORECAST TO BE AROUND 15 TO 20 KNOTS WITH GUSTS INTO THE 30S. OUTLOOK... FRIDAY NIGHT-SATURDAY NIGHT...IMPROVING TO VFR DURING THE EVENING AND CONTINUING INTO SATURDAY. GUSTY NORTHWEST WINDS 25-30 KNOTS POSSIBLE FRIDAY NIGHT INTO SATURDAY, DIMINISHING SATURDAY NIGHT. SUNDAY...VFR EARLY, MVFR POSSIBLE DEVELOPING BY LATE AFTERNOON WITH SNOW SHOWERS POSSIBLE. GUSTY WEST WINDS 15-20 KNOTS. SUNDAY NIGHT...DIMINISHING CONDITIONS TO IFR WITH SNOW LIKELY, ESPECIALLY SOUTHERN AREAS. GUSTY NORTHEAST WINDS 20-25 KNOTS. MONDAY...IFR WITH SNOW LIKELY EARLY, IMPROVING TO MVFR THEN VFR BY LATE AFTERNOON. GUSTY NORTH WINDS EARLY, BECOMING NORTHWEST BY AFTERNOON AROUND 20-25 KNOTS. MONDAY NIGHT-TUESDAY...GENERALLY VFR. && .MARINE... WE MADE A SLIGHT ADJUSTMENT TO THE START OF THE GALE WARNING ON FRIDAY MORNING. THE MODELS ARE TRENDING WEAKER WITH THE GRADIENT AND CONSEQUENTLY THE SEAS FOR MOST OF TONIGHT. WITH JUST BORDERLINE SCA CONDITIONS NOW EXPECTED TONIGHT, WE OPTED TO SINGLE HEADLINE THIS PACKAGE AND WILL MAKE MENTION IN THE MWW. GALE CONDITIONS BECOMING LIKELIER AS FRIDAY PROGRESSES. OUTLOOK... FRIDAY NIGHT-SATURDAY...GALE CONDITIONS CONTINUING THROUGH SATURDAY AFTERNOON. FREEZING SPRAY ADVISORY FRIDAY NIGHT INTO SATURDAY. SATURDAY NIGHT...CONDITIONS DROP TO SMALL CRAFT ADVISORY LEVELS BY EVENING AND MAY DROP BELOW ADVISORY CONDITIONS OVERNIGHT. LIGHT FREEZING SPRAY POSSIBLE. SUNDAY-SUNDAY NIGHT...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED. MONDAY-MONDAY NIGHT...SMALL CRAFT ADVISORY CONDITIONS LIKELY...GALE CONDITIONS POSSIBLE DURING THE DAY MONDAY. FREEZING SPRAY LIKELY MONDAY NIGHT. TUESDAY...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...WIND CHILL ADVISORY FROM MIDNIGHT FRIDAY NIGHT TO 11 AM EST SATURDAY FOR PAZ054-055. NJ...NONE. DE...NONE. MD...NONE. MARINE...FREEZING SPRAY ADVISORY FROM MIDNIGHT FRIDAY NIGHT TO 6 PM EST SATURDAY FOR ANZ430-431-450>455. GALE WARNING FROM 9 AM FRIDAY TO 6 PM EST SATURDAY FOR ANZ430- 431-450>455. && $$ SYNOPSIS...ROBERTSON NEAR TERM...IOVINO SHORT TERM...GIGI/IOVINO LONG TERM...ROBERTSON AVIATION...IOVINO/ROBERTSON MARINE...GIGI/ROBERTSON

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