Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 280136 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 936 PM EDT FRI MAR 27 2015 .SYNOPSIS...
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LOW PRESSURE AND A ASSOCIATED COLD FRONT WILL CONTINUE MOVING OFFSHORE OVERNIGHT. HIGH PRESSURE WILL BUILD EASTWARD FROM THE OHIO VALLEY INTO THE MID-ATLANTIC STATES THIS WEEKEND. A COUPLE OF COLD FRONTS AND ASSOCIATED LOW PRESSURE SYSTEMS WILL MOVE THROUGH EARLY NEXT WEEK. HIGH PRESSURE WILL THEN BUILD BACK INTO THE REGION WEDNESDAY INTO THURSDAY BEFORE ANOTHER COLD FRONT MOVES THROUGH THE REGION BY FRIDAY.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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CONSIDERABLE CLOUDS OVERNIGHT WITH POSSIBLY SOME FLURRIES DRIFTING SOUTHEAST OF THE PA APPALACHIANS AFTER MIDNIGHT. NOTICED THE 18Z RUNS OF THE GFS/NAM AND 12Z EC, SORT OF HAD A SPIKE IN DEEPER RH NEAR 12Z SATURDAY. THE NAM/RAP/HRRR SPOT SOME FLURRIES SEWD TO KRDG OVERNIGHT. NOT SURE HOW EXTENSIVE THIS MIGHT BECOME. PRESSURE GRADIENT IS WEAK OVER OUR AREA AS OF 01Z/28, BETWEEN THE DEVELOPING OFFSHORE LOW EAST OF VIRGINIA AND WHAT I THINK IS A PRETTY COLD AIR MASS BENEATH THE SEWD MOVING AND SHARPENING TROF ALOFT OVER THE GREAT LAKES/S ONTARIO AND WESTERN NYS, POISED TO MAKE ITS MOVE DOWN OVER OUR AREA SATURDAY WHEN THE PRESSURE GRADIENT INCREASES. FOR NOW, WE INCREASE THE GUSTS A BIT TOWARD MORNING, ESPECIALLY THE POCONOS IN DEVELOPING STRONGER CAA.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
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HIGH PRESSURE WILL CONTINUE TO BUILD IN FROM THE WEST ON SATURDAY... BUT THE COLD UPPER-LEVEL TROF WILL ALSO BE MOVG ACROSS THE AREA. DEEP-LAYER MOISTURE WILL GENERALLY BE DECREASING AND THERE DOES NOT SEEM TO BE ANY ORGANIZED UVV. HWVR...WITH COLD AIR ALOFT ANY BREAKS IN THE CLOUDS AND SFC HEATING MAY RESULT IN SOME INSTABILITY AND POSSIBLY SOME SCATTERED SNOW/RAIN SHOWERS. COLD 850 MB TEMPS WOULD CERTAINLY SUPPORT SNOW...HWVR WARMER/DRIER AIR BELOW COULD CAUSE MELTING OR EVAPORATION BEFORE SNOW REACHES THE GROUND...ESPECIALLY FROM PHL SWD AND EWD. SOME OF THE GREATEST INSTABILITY APPEARS TO BE MOVING FROM CENTRAL PA MIDDAY TO THE DELMARVA SATURDAY EVENING. ITS MATCHED WITH A SFC TROUGH. 700MB TEMPS ARE MODELED TO NEAR -24C ALONG THE MASON DIXON LINE NORTH OF KBWI AT 00Z/29. GUSTY NW WINDS WILL INCREASE TO 25-30 MPH DURING THE AFTN ADDING TO AN OTHERWISE NIPPY DAY WITH DAYTIME TEMPS AT LEAST 10 DEGREES BELOW NORMAL! OUR CURRENTLY FCST TEMPS MAY BE A DEG OR TWO ON THE WARM SIDE, ESPECIALLY IF ITS MO CLOUDY
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&& .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... THE MAJORITY OF THIS FORECAST PERIOD WILL BE DOMINATED BY QUICK MOVING COLD FRONTS IN A NORTHWEST FLOW PATTERN WITH CHANCES FOR LIGHT PRECIPITATION. BY LATE IN THE WEEK, THE POTENTIAL FOR A WARMER PATTERN WITH MORE SOUTHERLY FLOW EXISTS. SATURDAY NIGHT THROUGH SUNDAY: FAIRLY QUIET OVERALL WITH HIGH PRESSURE MOVING SOUTH OF THE REGION. SETUP IS VERY FAVORABLE FOR RADIATIONAL COOLING IN THE PINE BARRENS AND ACROSS PARTS OF EASTERN PA WITH CLEAR SKIES AND LIGHT WINDS. CHILLY WITH LOWS IN THE 20`S ACROSS MOST OF THE REGION. TEMPERATURES SHOULD REBOUND INTO THE 40`S SUNDAY AFTERNOON, WITH MODELED TWO METER TEMPERATURES TO COOL. SUNDAY NIGHT AND MONDAY: A COLD FRONT WILL MOVE THROUGH THE REGION MONDAY MORNING. THE PARENT LOW PRESSURE SYSTEM WILL BE LOCATED OVER SOUTHEAST CANADA WITH LIMITED MOISTURE TRANSPORT NORTH. BOTH OF THESE FACTORS KEEP PRECIPITATION LIGHT AND IN THE CHANCE RANGE ATTM. LOW TEMPERATURES NEAR FREEZING NORTHWEST WARRANT MIXED P-TYPE CHANCES ATTM WITH NO WINTRY ACCUMULATION. WITH MORE CLOUDS, LOW TEMPERATURES WILL STAY IN THE 30`S WITH LIGHT SOUTHERLY FLOW. EVEN WITH A WIND DIRECTION CHANGE TO WEST/NORTHWEST ON MONDAY, 925 MB TEMPERATURES DON`T FALL MUCH AND THE POTENTIAL FOR SOME PEAKS OF SUN EXISTS IN THE AFTERNOON. SO WILL GO WITH THE WARMER ECM AND MEX GUIDANCE. WIND GUSTS AROUND 20-25 MPH ARE POSSIBLE MONDAY AFTERNOON WITH SOME MIXING POTENTIAL. MONDAY NIGHT AND TUESDAY: A RETURN TO LIGHT SOUTHERLY FLOW AHEAD OF THE NEXT SYSTEM. MODEL DIVERGENCE IN THE TRACK OF THESE NORTHWEST FLOW SYSTEMS DIVING SOUTHEAST OF CANADA STARTS TO VARY IN THIS PERIOD. FAIRLY TIGHT SPREAD IN ALL GUIDANCE ON THE TEMPERATURES WITH MOST LOCATIONS GETTING INTO THE 50`S AFTER A CHILLY START IN THE 30`S. TUESDAY NIGHT AND WEDNESDAY: THE 12Z GFS AND 00Z ECMWF/UKMET ARE SIMILAR WITH THE TRACK OF A LOW PRESSURE SYSTEM TRACKING IT ACROSS SOUTHERN NEW ENGLAND CLOSE TO THE WPC PROGS. THE CMC LOOKS TO FAR SOUTH WITH THE TRACK. THIS BRINGS A CHANCE OF RAIN SHOWERS AND LIGHT QPF, HIGHEST CHANCES ACROSS THE NORTH. TEMPERATURES MAY RISE LATE TUESDAY NIGHT SOUTH OF THE LOW TRACK. STAYED CLOSE TO ENSEMBLE GUIDANCE IN THIS PERIOD FOR MOST WEATHER ELEMENTS. WEDNESDAY NIGHT THROUGH FRIDAY: THE POTENTIAL EXISTS FOR A STRONGER RIDGE TO DEVELOP OFF THE EAST COAST NEAR BERMUDA. THIS WOULD HAVE THE EFFECT OF INCREASING SOUTHERLY FLOW, PUMPING A MILDER AIRMASS INTO THE REGION. MODELED 925 MB TEMPERATURES RESPOND NICELY TO THIS PATTERN CHANGE IN THIS TIME PERIOD. WILL TAKE THE FORECAST ON THE WARMER SIDE OF THE GUIDANCE RANGE IN THIS TIMEFRAME. A STRONGER COLD FRONT COULD LEAD TO ANOTHER SHOWER CHANCE BY THURSDAY AFTERNOON WITH THE 12Z GFS THE MOST AGGRESSIVE. IN TERMS OF ANY THUNDERSTORMS, SHEAR WILL LIKELY BE ABUNDANT AHEAD OF THE FRONT WITH INSTABILITY LACKING BUT POSSIBLY ENOUGH FOR A FEW RUMBLES OF THUNDER. STILL A CONSIDERABLE TIME TO EXAMINE ANY THUNDER THREAT WITH THIS COLD FRONT. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY, AND SURROUNDING AREAS. REST OF TONIGHT...VFR CIGS AOA 4000 FT. N-NW WIND GUSTS AOB 15 KT MAY INCREASE SLIGHTLY AFTER 09Z. CONFIDENCE: ABOVE AVERAGE. SATURDAY: VFR CIGS AOA 4000 FT. NW WIND GUSTS INCREASE TO 25-30 KT BY OR DURING THE AFTN. SCATTERED SHOWERS OF SNOW OR RAIN/SNOW ARE POSSIBLE ON SATURDAY WHICH COULD TEMPORARILY LOWER CIGS/VSBYS TO MVFR...BUT NOT FOR LONG. CONFIDENCE ON THE OVERALL SCENARIO IS ABOVE AVERAGE THOUGH CONFIDENCE ON ON MVFR CIGS/VSBYS IN SHOWERS IS BELOW AVERAGE. OUTLOOK... SATURDAY NIGHT AND SUNDAY: VFR. NW WIND GUSTS 20-25 KT SATURDAY NIGHT AND EARLY SUNDAY THEN DIMINISHING SUNDAY AFTERNOON. SUNDAY NIGHT AND MONDAY: SOME LOWER MVFR CIGS AND VSBYS IN SCATTERED RAIN SHOWERS. SOUTHERLY/SOUTHWESTERLY WINDS UNDER 10 KNOTS SHIFTING TO WEST/NORTHWEST ON MONDAY AND GUSTING TO AROUND 20-25 KNOTS. MONDAY NIGHT AND TUESDAY: VFR, WINDS UNDER 15 KNOTS SHIFTING FROM NORTHWEST TO SOUTHWEST. TUESDAY NIGHT AND WEDNESDAY: POTENTIAL MVFR RESTRICTIONS WITH SCATTERED SHOWERS WITH THE HIGHEST CHANCES AT ABE AND TTN. WIND SHIFT FROM SOUTH/SOUTHWEST TO NORTHWEST ON WEDNESDAY.
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&& .MARINE...
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NW WIND GUSTS TONIGHT WHICH ARE UNDER 15 KT AT 9 PM EDT WILL INCREASE TOWARD DAWN. HAVE SLIGHTLY DELAYED THE START OF THE SCA ON DELAWARE BAY AND IT MAY NOT REALLY START THERE TIL ABOUT 6 AM. MEANWHILE SEAS OFF THE COASTS ARE GENERALLY AOB4FT EXCEPT NEAR 5 FT AT 44009. SATURDAY...A WIDESPREAD SCA DEVELOPS, ESPECIALLY DURING THE AFTERNOON WITH NW WIND GUSTS INCREASING TO NEAR 30 KT BY DAYS END. OUTLOOK... SATURDAY NIGHT: SCA CONDITIONS CONTINUE WITH NORTHWESTERLY FLOW. SEAS AROUND FIVE FEET WITH GUSTS AROUND AND JUST OVER 25 KNOTS. SUNDAY AND SUNDAY NIGHT: SUB SCA WINDS AND SEAS SUNDAY WHICH INCREASE SUNDAY NIGHT TO SCA CRITERIA BY MONDAY MORNING WITH SOUTHWESTERLY FLOW. MONDAY AND MONDAY NIGHT: SCA SEAS AND WIND GUSTS SHIFTING FROM WEST TO NORTHWEST AND DECREASING BELOW SCA CRITERIA BY MONDAY NIGHT. TUESDAY THROUGH WEDNESDAY: SUB SCA WIND GUSTS AND SEAS.
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&& .CLIMATE...
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MARCH MONTHLY AVG TEMPS DEPARTURES SHOULD BE CLOSE TO THE VALUES SEEN ON THE CF6`S THROUGH THE 26TH. FOR PHL THATS ABOUT 4 DEGREES BELOW NORMAL. NOT A TOP 20 COLDEST MONTH OF MARCH.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ450>455. SMALL CRAFT ADVISORY FROM 2 AM SATURDAY TO 6 AM EDT SUNDAY FOR ANZ430-431.
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&& $$ SYNOPSIS...GAINES NEAR TERM...DRAG 935 SHORT TERM...AMC/DRAG 935 LONG TERM...GAINES AVIATION...DRAG/GAINES 935 MARINE...DRAG/GAINES 935 CLIMATE...935

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