Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 021712 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1212 PM EST MON MAR 2 2015 .SYNOPSIS... HIGH PRESSURE WILL BUILD OVER OUR AREA TONIGHT, THEN SHIFT OFF THE MID ATLANTIC COAST ON TUESDAY. A WARM FRONT IS EXPECTED TO LIFT THROUGH OUR AREA ON TUESDAY EVENING. A COLD FRONT IS ANTICIPATED TO ARRIVE WEDNESDAY AFTERNOON, THEN THE FRONT SHOULD SETTLE SLOWLY TO THE SOUTHEAST WEDNESDAY NIGHT AND THURSDAY AS LOW PRESSURE RIDES ALONG IT. ANOTHER ARCTIC HIGH IS FORECAST TO BUILD ACROSS OUR REGION FOR FRIDAY INTO SATURDAY. A WARM FRONT MAY BEGIN TO APPROACH FROM THE SOUTHWEST ON SUNDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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HIGH PRESSURE MOVING INTO THE OHIO VALLEY AT MIDDAY WILL CONTINUE TO SLIDE EASTWARD THROUGH THE AFTERNOON. THE COMBINATION OF INCREASING SUBSIDENCE AND DRIER AIR ADVECTING IN CONTINUES TO ERODE THE CLOUDS. THIS IS BEING ENHANCED SOME BY A DOWNSLOPING FLOW. PRIOR TO THIS OCCURRING THOUGH, ENOUGH INSTABILITY AND LIFT AIDED IN THE DEVELOPMENT OF SEVERAL BANDS OF SNOW SHOWERS ACROSS THE NORTH. SOME OF THIS WAS BRIEFLY HEAVY ACROSS THE POCONOS. THIS ACTIVITY CONTINUES TO DIMINISH AS IS SHIFTS OFF THE NORTHEASTERN NEW JERSEY COAST. THE VISIBLE SATELLITE IMAGERY SHOWS THE SNOW/ICE COVER VERY WELL, BUT ALSO SHOWS LESS AND LESS CLOUDS. THEREFORE, LOTS OF SUNSHINE LOOKS TO OCCUR THROUGH THE AFTERNOON. THERE WILL CONTINUE TO BE PLENTY OF MIXING AS THE BOUNDARY LAYER HAS WARMED AND CAA OCCURS ALOFT. THIS WILL PROMOTE WIND GUSTS UP TO 35 MPH ACROSS THE AREA, ALTHOUGH THIS SHOULD START TO DIMINISH LATE IN THE AFTERNOON. THE DOWNSLOPING FLOW AND INCREASING SUNSHINE HAS HELPED BOOST THE TEMPERATURES ESPECIALLY FROM THE INTERSTATE 95 CORRIDOR ON SOUTH AND EASTWARD, AND THEREFORE THE HIGH TEMPERATURES WERE INCREASED SOME. THE HOURLY GRIDS WERE ADJUSTED BASED ON THE LATEST OBSERVATIONS AND THEN BLENDED IN THE LAMP/LAV GUIDANCE.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... HIGH PRESSURE BEGINS TO MOVE INTO THE AREA THIS EVENING, BEFORE CENTERING ITSELF ACROSS THE AREA OVERNIGHT. SKIES WILL CLEAR OUT THIS EVENING, ALTHOUGH SOME HIGH LEVEL CLOUD COVER MAY RETURN OVERNIGHT. WIND GUSTS WILL HAVE DROPPED OFF BY THE EVENING, ALTHOUGH A STEADY BREEZE WILL REMAIN THROUGH THE EVENING, BEFORE BECOMING LIGHT AND VARIABLE OVERNIGHT. WITH MOSTLY CLEAR SKIES AND LIGHT WINDS, TEMPERATURES SHOULD BE ABLE TO DROP WELL BELOW NORMAL OVERNIGHT. && .LONG TERM /TUESDAY THROUGH SUNDAY/... THERE IS NOT MUCH CHANGE REGARDING THE FORECAST FOR TUESDAY INTO WEDNESDAY. PRECIPITATION IS EXPECTED TO OVERSPREAD OUR REGION QUICKLY FROM THE WEST ON TUESDAY AFTERNOON. THE FORECAST TEMPERATURE PROFILES SUGGEST THAT THE PRECIPITATION WILL BEGIN AS SNOW IN MOST LOCATIONS WITH PERHAPS SLEET AT THE START IN OUR FAR SOUTHERN COUNTIES. STRONG WARM ADVECTION IS ANTICIPATED ALOFT FROM TUESDAY AFTERNOON INTO TUESDAY EVENING. WARMING AT THE SURFACE WILL LAG A BIT. THERE SHOULD BE A GRADUAL TRANSITION FROM A WINTRY MIX TO RAIN FROM SOUTH TO NORTH. HOWEVER, TRAPPED COLD AIR IN OUR FAR NORTHERN COUNTIES COULD RESULT IN SEVERAL HOURS OF FREEZING RAIN THERE ON TUESDAY NIGHT INTO EARLY WEDNESDAY MORNING. OUR LATEST PROJECTIONS FOR TUESDAY INTO TUESDAY NIGHT BRING 1 TO 3 INCHES OF SNOW ACROSS OUR NORTHERN COUNTIES AND LESS THAN AN INCH TO OUR CENTRAL AND SOUTHERN COUNTIES WHERE ACCUMULATION MAY BE CUT DOWN BY THE PRESENCE OF SLEET. FREEZING RAIN SHOULD CAUSE A PROBLEM ONLY ACROSS OUR NORTHERN COUNTIES WHERE UP TO A TENTH OF AN INCH OF ICE MAY ACCUMULATE ON TOP OF THE NEW SNOWFALL. IT CONTINUES TO APPEAR AS THOUGH THE PRECIPITATION WILL CHANGE TO ALL RAIN FOR WEDNESDAY. A BIT OF DRYING MAY BEGIN TO WORK ITS WAY DOWN FROM THE NORTHWEST ON WEDNESDAY AFTERNOON. IT SEEMS POSSIBLE THAT SOME LOCATIONS, ESPECIALLY IN THE CENTRAL AND SOUTHERN PARTS OF OUR FORECAST AREA MAY PICK UP A HALF INCH TO AN INCH OF RAINFALL DURING THE PERIOD. THE RAIN IN COMBINATION WITH SNOWMELT AND THE FROZEN GROUND, ALONG WITH ICE MOVEMENT IN AREA WATERWAYS MAY RESULT IN A BIT OF MINOR FLOODING. THE MODELS ARE COMING TOGETHER ON THE IDEA OF A WAVE OF LOW PRESSURE RIDING ALONG THE SLOW MOVING COLD FRONT. IT SHOULD BRING US ANOTHER ROUND OF PRECIPITATION FOR WEDNESDAY NIGHT INTO THURSDAY. AS COLD AIR FILTERS DOWN INTO OUR REGION FROM THE NORTH AND NORTHWEST, THE PRECIPITATION TYPE WILL LIKELY TRANSITION TO SNOW. THERE IS ENOUGH SPREAD IN THE GUIDANCE SOLUTIONS TO MAKE THE DETAILS A BIT UNCERTAIN AT THIS POINT. HOWEVER, IT IS LOOKING INCREASINGLY POSSIBLE THAT WE WILL SEE ACCUMULATING SNOW IN MUCH OF OUR FORECAST AREA AT THAT TIME. HIGH PRESSURE FROM THE WEST IS ANTICIPATED TO BRING DRY WEATHER AND BELOW NORMAL TEMPERATURES FOR THURSDAY NIGHT INTO SATURDAY NIGHT. THE 0000 UTC GFS AND THE 0000 UTC ECMWF ARE BOTH SUGGESTING THE POTENTIAL FOR PRECIPITATION TO BE NEARING OUR REGION FROM THE SOUTHWEST ON SUNDAY DUE TO A WEAK AREA OF LOW PRESSURE ALONG WITH A WARM FRONT. && .AVIATION /17Z MONDAY THROUGH FRIDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THIS AFTERNOON...VFR. NORTHWEST WINDS AROUND 15 KNOTS WITH GUSTS UP TO 30 KNOTS. TONIGHT...VFR. NORTHWEST WINDS QUICKLY DIMINISHING TO 10 KNOTS OR LESS IN THE EVENING, THEN LOCALLY BECOMING LIGHT AND VARIABLE OVERNIGHT. TUESDAY...VFR FOR MUCH OF THE DAY WITH INCREASING CLOUDS. THE CONDITIONS SHOULD LOWER TO MVFR/IFR LATE IN THE AFTERNOON FROM WEST TO EAST AS SNOW AND SLEET OVERSPREADS THE REGION. LIGHT AND VARIABLE WINDS, BECOMING NORTHEAST THEN SOUTHEAST AT 5-8 KNOTS. A SOUTHERLY LOW-LEVEL JET /2000 FEET/ NEAR 40 KNOTS SHOULD ARRIVE LATE IN THE AFTERNOON, THEREFORE INCLUDED LOW-LEVEL WIND SHEAR IN THE 30-HOUR KPHL TAF. OUTLOOK... TUESDAY NIGHT...MVFR AND IFR CONDITIONS WITH A WINTRY MIX OF PRECIPITATION CHANGING TO RAIN FROM SOUTH TO NORTH. THE RAIN MAY BE MODERATE TO HEAVY AT TIMES. LOW LEVEL WIND SHEAR IS POSSIBLE DUE TO A SOUTHWESTERLY LOW LEVEL JET THAT IS FORECAST TO DEVELOP OVERHEAD. WEDNESDAY...MVFR AND IFR CONDITIONS IN RAIN. THE RAIN MAY BE MODERATE TO HEAVY AT TIMES, ESPECIALLY SOUTH OF KPHL. WEDNESDAY NIGHT...MVFR AND IFR CONDITIONS IN RAIN, MIXING WITH THEN CHANGING TO SNOW FROM NORTH TO SOUTH. THURSDAY...MVFR AND IFR CONDITIONS IN MORNING SNOW. CONDITIONS IMPROVING GRADUALLY TO VFR WITH A LESSING CHANCE OF SNOW IN THE AFTERNOON. THURSDAY NIGHT AND FRIDAY...MAINLY VFR.
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&& .MARINE... SMALL CRAFT ADVISORY REMAINS IN EFFECT ON THE WATERS INTO TONIGHT AS WINDS WILL INCREASE. AN OCCASIONAL GUSTY AROUND 34/35 KNOTS IS POSSIBLE AROUND MIDDAY, BUT WE ARE NOT CONFIDENT ON GALE FORCE GUSTS BEING FREQUENT ENOUGH TO NEED A WARNING AT THIS TIME. AS HIGH PRESSURE BUILDS INTO THE AREA OVERNIGHT, WINDS WILL DIMINISH BELOW ADVISORY LEVELS. OUTLOOK.. TUESDAY...NO MARINE HEADLINES ARE ANTICIPATED. TUESDAY NIGHT AND WEDNESDAY...A SMALL CRAFT ADVISORY MAY BE NECESSARY DUE TO A GUSTY SOUTH TO SOUTHWEST WIND. WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...A SMALL CRAFT ADVISORY MAY BE NEEDED TO DUE TO GUSTY NORTHWEST WIND. FRIDAY...NO MARINE HEADLINES ARE ANTICIPATED. && .HYDROLOGY... THE NEXT ROUND OF PRECIPITATION IS FORECAST TO MOVE INTO OUR AREA ON TUESDAY AFTERNOON AND IT WILL CONTINUE INTO WEDNESDAY AND THURSDAY. THIS MIDWEEK EVENT APPEARS TO START AS A WINTRY MIX BEFORE CHANGING OVER TO RAIN AS TEMPERATURES RISE WELL ABOVE FREEZING ON WEDNESDAY. THE QPF AMOUNTS FOR TUESDAY INTO WEDNESDAY FAVOR THE 0.25 TO 0.75 INCH RANGE. THE COMBINATION OF THE BRIEF WARM-UP ON WEDNESDAY, LOCALLY MODERATE TO HEAVY RAINFALL, MELTING SNOW, A FROZEN GROUND, AND ABOVE NORMAL ICE IN CREEKS, STREAMS, AND RIVERS COULD LEAD TO INCREASED RUNOFF AND POSSIBLE FLOODING. WHERE THE DEPTH OF THE SNOWPACK IS GREATEST (IN NE PA AND N NJ), RAPID SNOWMELT IS NOT EXPECTED SINCE TEMPS WILL NOT RISE AS SHARPLY AS IN AREAS TO THE SOUTH. INCREASED FLOW 0N AREA CREEKS, STREAMS, AND RIVERS COULD ALSO START TO MOVE ICE, AND IN A WORST CASE SCENARIO, CREATE RESTRICTIONS OR JAMS. CONTINUE TO MONITOR THE FORECAST. KEEP IN MIND THAT SNOWMELT AND WARMTH BY THEMSELVES TYPICALLY DO NOT CAUSE FLOODING. THE AMOUNT OF RAIN THAT WE RECEIVE WILL BE THE DETERMINING FACTOR. THE RAIN IS FORECAST TO CHANGE BACK TO SNOW ON WEDNESDAY NIGHT. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EST TUESDAY FOR ANZ430-431- 450>455. && $$ SYNOPSIS...GORSE/IOVINO NEAR TERM...GORSE SHORT TERM...ROBERTSON LONG TERM...IOVINO AVIATION...GORSE/IOVINO MARINE...IOVINO/ROBERTSON HYDROLOGY...

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