Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 160932 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 432 AM EST TUE DEC 16 2014 .SYNOPSIS... LOW PRESSURE IN THE GREAT LAKES WILL PUSH A WARM FRONT NORTH INTO THE MID ATLANTIC STATES TODAY, WITH SECONDARY LOW PRESSURE DEVELOPING NEAR LONG ISLAND TUESDAY NIGHT. THE COLD FRONT PASSES OFFSHORE WEDNESDAY MORNING AS THE LOWS COMBINE AND HEAD FOR THE CANADIAN MARITIMES THURSDAY. HIGH PRESSURE IN THE GREAT LAKES ASSERTS CONTROL HERE ON FRIDAY. LOW PRESSURE IN GEORGIA SATURDAY MORNING IS FORECAST TO INTENSIFY AS IT MOVES NORTHEASTWARD OFF THE MID ATLANTIC COAST SUNDAY INTO MONDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... AS THE VERTICALLY STACKED LOW LIFTS INTO THE GREAT LAKES REGION, SHOULD SEE A WARM FRONT LIFT THROUGH THE REGION, AND CONSEQUENTLY, INCREASING MOISTURE AS WELL AS RAIN CHANCES. SINCE THE REGION IS IN THE WARM SECTOR ALL DAY, PRECIP IS EXPECTED TO BE ALL RAIN. IN ADDITION, NAM MODEL SOUNDINGS ACROSS SOUTHERN DELMARVA DEPICT MEAGER ELEVATED INSTABILITY. THEREFORE, A RUMBLE OF THUNDER IS NOT OUT OF THE QUESTION, BUT SEEMS QUITE UNLIKELY, SO HAVE ONLY MENTIONED RAIN SHOWERS FOR NOW. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... INITIAL COLD FRONT AND DRY SLOT WILL BE ON OUR DOORSTEP BY 00Z. SHOULD SEE PRECIP CLEAR OUT QUICKLY ONCE THE DRY SLOT MOVES OVER. THE ONE EXCEPTION IS IN THE POCONOS, WHICH WILL BE CLOSER TO A SECOND SHORT WAVE TROUGH PASSAGE LATE TONIGHT, AND WILL ALSO HAVE ENHANCEMENT WITH OROGRAPHIC LIFT. THEREFORE, THAT REGION COULD SEE LIGHT PRECIP CONTINUE THROUGH THE OVERNIGHT HOURS. DESPITE AN INITIAL COLD FRONTAL PASSAGE, TEMPERATURES, EVEN IN THE POCONOS SHOULD BE HIGH ENOUGH TO SUPPORT RAIN. MINS WERE A BLEND OF MAV AND MET. HOWEVER, IF THE CLOUDS CLEAR OUT QUICKER THAN EXPECTED COULD SEE RADIATIONAL COOLING CONTRIBUTE TO LOWER THAN FORECAST MINS. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... RATHER BENIGN PATTERN SETTING UP FROM THURSDAY THROUGH SATURDAY WITH ZONAL-ISH FLOW ALOFT TURNING INTO WEAK RIDGING OVER THE WEEKEND. DEEPER MID-WEST TROUGH LOOKS TO FORM BY EARLY NEXT WEEK WHICH MAY BRING A SOMEWHAT UNSETTLED PATTERN TO THE REGION. A SYSTEM DOES DEVELOP ALONG THE TEXAS COAST AND MOVES INTO THE ATLANTIC BY SUNDAY. FROM THIS POINT ONWARD LOTS OF UNCERTAINTY REMAINS WITH THE TRACK AND INTENSITY OF THE SYSTEM. WEDNESDAY...SECONDARY SHORTWAVE ALOFT COULD TOUCH OFF A FEW STRAY SHOWERS ACROSS THE NORTHERN FRINGE OF THE CWA DURING THE AFTERNOON HOURS. SOME WEAK MID-LEVEL LAPSE RATES, AS THE SHORTWAVE IS RATHER ELONGATED ZONALLY, WOULD ADD TO THE CHANCES OF SHOWERS, MOSTLY LIQUID AT THIS POINT WITH A WARM THERMAL PROFILES. A CHANGEOVER TO SNOW SHOWERS LOOKS LIKELY BUT THE AMOUNT OF MOISTURE BECOMES AN ISSUE LATER IN THE EVENING/OVERNIGHT. GUSTY NORTHWEST WINDS EXPECTED. THERE DOESN`T APPEAR TO BE MUCH ICE LEFT IN THE CLOUDS AT THIS POINT, AND OUTSIDE ANY SEEDER-FEEDER HELP, WE COULD SEE SPOTTY FREEZING DRIZZLE OVERNIGHT. THURSDAY - FRIDAY...DRYING TREND CONTINUES WITH ZONAL-ISH FLOW ALOFT FORMING BY FRIDAY AND NOT MUCH MOISTURE TO WORK WITH. INSTABILITY ALOFT CONTINUES TO LOOK ROBUST ON THURSDAY AS THE CENTER OF MID-LEVEL LOW PASSES OVERHEAD SO THERE COULD BE SOME INSTABILITY SNOW SHOWERS ACROSS THE NORTH. FRIDAY LOOKS DRY. GUSTY NORTHWEST WINDS BOTH DAYS THOUGH A DECREASE IS EXPECTED LATER ON FRIDAY. SATURDAY - SUNDAY...ONE LAST DAY, OR AT LEAST HALF DAY, OF TRANQUILITY ON SATURDAY BEFORE EAST COAST STORM NEARS FROM THE SOUTH-SOUTHWEST. DEPENDING ON THE QUICKNESS AND POSITION OF THE NORTHERN STREAM ENERGY, HELPING TO DEVELOP GULF COAST SURFACE INFLECTION, DICTATES HOW FAST PRECIPITATION OVERSPREADS FROM THE SOUTH LATER ON SATURDAY. GUIDANCE ACROSS THE BOARD IS STILL SHOWING MULTIPLE OUTCOMES AND DEPTHS WITH THIS SYSTEM. THE PAST FEW DAYS OF RUNS THE OP-EC HAS BEEN HOLDING STEADY WITH A CLOSER TO THE COAST SYSTEM BUT NOW WE ARE STARTING TO SEE MORE OF AN OFFSHORE AND WEAKENING TREND WITH A MUCH SLOWER NORTHERLY PROGRESSION. THE EC/GEFS ENSEMBLES TOO HAVE BEGUN TO WAVER A BIT WITH MOST OF THE NOISE ON THE NORTHEAST SIDE OF THE MODELED LOWS CENTER WHICH MEANS A FARTHER EASTWARD JOG IS POSSIBLE. IT IS STILL TOO EARLY TO GO INTO TOO MUCH DEPTH WITH THIS SYSTEM GIVEN THE AMOUNT OF SPREAD THAT WE ARE STILL SEEING. ONE THING THAT SHOWS AVERAGE CONFIDENCE ARE THE CHANCES FOR AN EAST STORM TO IMPACT OUR REGION SOMETIME LATER THIS WEEKEND. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. WIDESPREAD MVFR CONDITIONS, BOTH FOR VISIBILITIES AND CEILINGS, ARE LIKELY AT ALL TAF SITES FOR MOST OF THE DAY TODAY. COULD ALSO SEE LOCALIZED IFR CONDITIONS, ESPECIALLY DURING THE PEAK TIME OF THE -SHRA (GENERALLY BETWEEN 20 AND 00Z). AFTER 00Z, SHOULD SEE DRIER AIR MOVE INTO THE REGION FROM SW TO NE. AS IT DOES SO, SHOULD SEE LOW CLOUDS ERODE, BUT BR MAY REMAIN LIMITING VISIBILITIES TO LESS THAN 6SM. WINDS WILL SHIFT FROM MOSTLY SOUTHERLY THROUGH THE DAY TO MORE WESTERLY BY THIS EVENING, BUT SHOULD GENERALLY BE NEAR OR BELOW 10KT. WEDNESDAY...MOSTLY VFR. WEST WINDS 10-15KT WITH GUSTS 20-25KT. COULD BE SOME LINGERING MVFR ACROSS THE NORTHERN TERMINALS. THURSDAY...VFR. NORTHWEST WINDS 10-15KT WITH GUSTS 20-25KT. FRIDAY - SATURDAY...VFR. && .MARINE... WINDS AND SEAS SHOULD REMAIN BELOW SCA CRITERIA. HOWEVER, WINDS ARE EXPECTED TO INCREASE BEGINNING MID DAY TODAY, AND BY EARLY WEDNESDAY MORNING, COULD HAVE GUSTS NEAR 20KTS. WIND DIRECTION WILL SHIFT FROM MOSTLY SOUTHERLY THROUGH THE DAY TODAY TO WESTERLY BY LATE THIS EVENING. OUTLOOK... WEDNESDAY AND THURSDAY...WHILE SEAS ARE EXPECTED TO REMAIN GENERALLY BELOW SCA LEVELS, NORTHWEST WIND GUSTS SHOULD REACH THE SCA THRESHOLD OF 25 KNOTS AT TIMES LATE WEDNESDAY AFTERNOON THROUGH THURSDAY...POSSIBLY 30 KT. SCA EXPECTED. CONFIDENCE: ABOVE AVERAGE. FRIDAY...MOSTLY SUB-ADVISORY CONDITIONS ARE EXPECTED. SOME NORTHWEST WIND GUSTS COULD STILL BE IN THE 20 PLUS KNOT RANGE, THOUGH. CONFIDENCE: ABOVE AVERAGE. SATURDAY...SCA LIKELY AT NIGHT...POSSIBLY A GALE BUT FOR NOW SCA IS FAVORED FOR A START. CONFIDENCE: AVERAGE. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...DRAG NEAR TERM...JOHNSON SHORT TERM...JOHNSON LONG TERM...HEAVENER AVIATION...HEAVENER/JOHNSON MARINE...DRAG/HEAVENER/JOHNSON

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