Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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433 FXUS61 KPHI 041152 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 652 AM EST THU FEB 4 2016 .SYNOPSIS... A COLD FRONT WILL PUSH EAST OF THE MID-ATLANTIC EARLY TODAY BUT REMAIN NEARBY OFFSHORE INTO TONIGHT. AN AREA OF LOW PRESSURE IS THEN FORECAST TO DEVELOP ALONG THE OFFSHORE FRONT LATE TONIGHT AND MOVE OUT TO SEA FRIDAY. HIGH PRESSURE WILL GRADUALLY BUILD INTO OUR AREA FROM THE SOUTHWEST LATE FRIDAY AND SATURDAY. A WEAK COLD FRONT FROM THE NORTHWEST MAY CROSS THE AREA EARLY SUNDAY, FOLLOWED BY A LOW PRESSURE SYSTEM POSSIBLY AFFECTING THE REGION EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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THE DENSE FOG ADVISORY WAS CANCELLED SINCE THE VISIBILITIES HAVE IMPROVED ACROSS THE AREA WITH THE PASSAGE OF THE COLD FRONT. PREVIOUS DISCUSSION... A COLD FRONT OVER E PA AT 3 AM WILL MOVE EASTWARD THRU THE I-95 CORRIDOR THRU DAYBREAK AND THEN OFF THE NJ/DE COAST BY MID MORNING. DENSE FOG HAS PERSISTED THRU MUCH OF THE OVERNIGHT ALONG AND WEST OF THE FALL LINE WHERE THERE IS STILL RESIDUAL (ALBEIT MINIMAL) SNOW COVER. THE DENSE FOG ADVISORY FOR E PA, C/NW NJ, AND E MD REMAINS IN EFFECT THRU 7 AM BUT WE MAY BE ABLE TO CANCEL IT EARLY AS THE PUSH OF DRY AIR BEHIND THE FRONT ERODES THE FOG FROM WEST TO EAST. THE BACK EDGE OF THE STEADY RAIN IN THE WARM SECTOR HAD MOVED OFFSHORE LAST EVENING BUT THERE ARE STILL SOME SHOWERS ALONG AND AHEAD OF THE FRONT THAT WILL PRIMARILY IMPACT THE COASTAL PLAIN EARLY THIS MORNING. THERE WILL LIKELY BE A BREAK IN PRECIP FROM LATE THIS MORNING THRU THE AFTERNOON ALTHOUGH A COUPLE OF SHOWERS CANNOT BE COMPLETELY RULED OUT NEAR THE COAST WITH THE FRONTAL BOUNDARY STALLING OFFSHORE. THE REGION WILL START OFF CLOUDY THIS MORNING BUT THERE WILL BE BREAKS IN OUR FAR NW ZONES TODAY ONCE THE FOG/STRATUS ERODES. WITH THE UPPER TROUGH STILL BACK TO OUR WEST, THE MID AND HIGH CLOUDS WILL YIELD MOSTLY CLOUDY SKIES ALONG AND ESPECIALLY EAST OF I-95. DESPITE THE CLOUD COVER, WENT ABOVE STAT GUIDANCE FOR TEMPS TODAY WITH THE GUIDANCE CONTINUALLY BEING BIASED TOO COLD FOR HIGHS OVER THE PAST WEEK AND HALF. THE HIGHS MAY OCCUR EARLIER THAN USUAL SOMETIME THIS MORNING AS POST-FRONTAL CAA IS STRONG ENOUGH TO OFFSET THE DAYTIME HEATING.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... SHORTWAVE ENERGY ASSOCIATED WITH THE UPPER TROUGH WILL PROGRESS TOWARD THE EASTERN SEABOARD TONIGHT. THE MODELS CONTINUE TO SHOW SECONDARY CYCLOGENESIS ALONG THE SOUTHEAST COAST BY EARLY THIS EVENING. THE SURFACE LOW IS EXPECTED TO DEEPEN AS IT MOVES TO THE NE ALONG THE STALLED FRONTAL BOUNDARY OFFSHORE. THE TRACK OF THE LOW IS FORECAST TO BE FAR ENOUGH OFF THE COAST TO SPARE OUR AREA FROM THE GREATEST IMPACTS (I.E., HEAVY PRECIP AND STRONG WINDS) BUT WE WON`T BE COMPLETELY MISSED. THE MODEL GUIDANCE HAS COME INTO GOOD GENERAL AGREEMENT WITH RESPECT TO THE EVOLUTION OF THERMAL PROFILES, THE TIMING OF PRECIP AND THE PLACEMENT OF THE PRECIP SHIELD. WE CAN SAY WITH REASONABLE CONFIDENCE THAT PRECIP SHOULD EXPAND NEWD INTO THE DELMARVA AND COASTAL NJ THIS EVENING. THE WESTERN EDGE OF THE PRECIP SHIELD WILL LIKELY SET UP SOMEWHERE NEAR OR JUST WEST OF THE I-95 CORRIDOR OVERNIGHT. THE THERMAL PROFILES WILL INITIALLY BE WARM ENOUGH FOR IT TO START OUT AS RAIN EVERYWHERE IN THE EVENING. HOWEVER, HIGH PRESSURE BUILDS IN FROM THE WEST AND NW WINDS WILL ADVECT COLDER AIR INTO THE AREA OVERNIGHT. THUS, WE EXPECT THE RAIN TO MIX WITH AND EVENTUALLY CHANGE OVER TO SNOW FROM WEST TO EAST OVERNIGHT. HOWEVER, THERE IS STILL UNCERTAINTY IN SOME OF THE FINER DETAILS WHICH WILL ULTIMATELY DECIDE HOW MUCH OF THE PRECIP WILL FALL AS RAIN VS SNOW AND HOW MUCH OF THE SNOW WILL BE ABLE TO ACCUMULATE WITH MARGINAL BOUNDARY LAYER TEMPERATURES. MOST OF THE UNCERTAINTY RESIDES IN THE 06Z-12Z FRIDAY TIME FRAME AND IS TIED TO THE WILD CARD OF DYNAMICAL COOLING. THE 00Z GUIDANCE HAS TRENDED A LITTLE BIT HIGHER WITH THE QPF FOR THE 06-12Z PERIOD WITH AROUND 0.5 INCH FORECAST ALONG THE COAST. ALSO, THE 03Z SREF MEAN AND 06Z NAM HAS TRENDED WETTER AND SNOWIER. WE TRENDED SLIGHTLY HIGHER WITH OUR FORECAST SNOWFALL AMOUNTS OF 1-2 INCHES (LOCALLY 2-3 INCHES) IN THE COASTAL PLAIN. HOWEVER, THERE IS STILL A REASONABLE WORST- CASE SCENARIO (I.E., OUR MAX SNOWFALL PROBABILISTIC GRAPHIC) THAT SOME LOCATIONS GET DOUBLE THESE FORECAST AMOUNTS IF THE EFFECTS FROM DYNAMICAL COOLING WINDS UP BEING EVEN GREATER AND PRECIP TRANSITIONS TO SNOW MUCH MORE RAPIDLY THAN INDICATED BY THE 00Z GUIDANCE. CONVERSELY, WE`VE SEEN MODELS SOMETIMES BEING TOO BULLISH WITH SNOWFALL ACCUMULATIONS IN RAIN-CHANGING-TO-SNOW EVENTS, ESPECIALLY WHEN THE BOUNDARY LAYER IS WARM AT THE ONSET. THE UNCERTAINTY STILL SEEMS TOO HIGH TO ISSUE ANY WINTER WEATHER ADVISORY THIS FAR OUT BUT ONE MAY NEED TO BE ISSUED LATER TODAY. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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AN OVERALL ACTIVE PATTERN LOOKS TO BE IN PLACE THROUGH THE LONG TERM PERIOD, ESPECIALLY FROM THE LATTER HALF OF THE WEEKEND AND INTO EARLY NEXT WEEK. FOR FRIDAY MORNING, AN AREA OF LOW PRESSURE IS FORECAST TO BE OFF OF THE MID-ATLANTIC COAST, EAST OF VIRGINIA, ALONG AN OLD COLD FRONTAL BOUNDARY. WHILE THIS LOW PRESSURE IS FORECAST TO TRACK NORTHEAST AND FARTHER OUT TO SEA THROUGH THE COURSE OF THE DAY, THE PROXIMITY OF THIS SYSTEM TO THE NEW JERSEY AND DELAWARE COASTS FRIDAY MORNING MAY ALLOW FOR SOME LINGERING LIGHT SNOW ACROSS EASTERN NJ AND SOUTHEAST DE BEFORE THE SYSTEM DEPARTS FARTHER EAST BY LATE MORNING TO MIDDAY. TOTAL ACCUMULATION AMOUNTS FOR THESE AREAS FROM LATE THURSDAY NIGHT THROUGH EARLY FRIDAY MAY REACH BETWEEN ONE TO TWO INCHES, BUT WITH SOME UNCERTAINTY REGARDING TRACK AND QPF AMOUNTS, WE WILL HOLD OFF ON ANY ADVISORY HEADLINES AT THIS TIME. OTHERWISE, THE REMAINDER OF FRIDAY SHOULD BE DRY WITH GRADUAL CLEARING FROM WEST TO EAST ACROSS THE REGION AS AN AREA OF HIGH PRESSURE TO OUR SOUTHWEST BUILDS TOWARD THE MID-ATLANTIC. THIS HIGH PRESSURE IS EXPECTED TO STICK AROUND THROUGH SATURDAY ACROSS THE AREA, YIELDING DRY AND QUIET CONDITIONS WITH JUST SOME CLOUDS ADVANCING IN FROM THE NORTHWEST AS THE DAY WEARS ON. DAYTIME MAXIMUM TEMPERATURES ARE EXPECTED TO BE PRETTY SIMILAR BOTH FRIDAY AND SATURDAY, MAINLY IN THE 40S ACROSS THE REGION, EXCEPT SOME TEMPS MAXING OUT IN THE 30S OVER THE HIGHER TERRAIN IN THE POCONOS. BY EARLY SUNDAY, A WEAK COLD FRONT MAY APPROACH OUR REGION FROM THE NORTHWEST, BUT WITH LIMITED MOISTURE ASSOCIATED WITH THIS BOUNDARY, WE HAVE KEPT A DRY FORECAST FOR SUNDAY, WITH DAYTIME HIGHS REACHING MAINLY IN THE 40S. OF NOTE, THE GFS AND ECMWF CONTINUE TO DEVELOP AN AREA OF LOW PRESSURE OF VARYING INTENSITY OFF THE SOUTHEASTERN SEABOARD SUNDAY, TAKING IT OUT TO SEA LATER SUNDAY NIGHT. LITTLE OR NO IMPACT IS STILL EXPECTED FOR OUR REGION, EXCEPT PERHAPS SOME INCREASING CLOUDINESS, ESPECIALLY OVER THE SOUTHERN HALF OF OUR CWA. THROUGH THE REMAINDER OF THE LONG TERM PERIOD, THERE CONTINUES TO BE SIGNIFICANT MODEL DIFFERENCES WITH REGARDS TO A POSSIBLE LOW PRESSURE SYSTEM PASSING ACROSS THE GREAT LAKES MONDAY AND ANOTHER AREA OF LOW PRESSURE POSSIBLY DEVELOPING OFF THE EAST COAST TUESDAY. WHILE THE TIMING OF PRECIPITATION ACROSS OUR REGION REMAINS A LOW CONFIDENCE FORECAST AT THIS TIME, THE OVERALL PATTERN AND A BROAD LONGWAVE TROUGH OVER THE GREAT LAKES TO NORTHEAST AND MID-ATLANTIC SUGGESTS A COLDER TREND INTO EARLY/MID NEXT WEEK, AND WE GENERALLY FOLLOWED SUPERBLEND AND/OR WPC GUIDANCE WITH REGARDS TO TEMPS AND POPS AT THIS EXTENDED TIME RANGE.
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&& .AVIATION /12Z THURSDAY THROUGH MONDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. A COLD FRONT HAD JUST MOVED THRU RDG AND ABE AS NOTED BY THE W-NW WIND SHIFT. THE FRONT WILL PROGRESS THRU THE I-95 TERMINALS BEFORE 12Z AND ACY/MIV SHORTLY AFTER. LOW CLOUDS AND FOG ALONG AND AHEAD OF THE FRONT HAS RESULTED IN LIFR RESTRICTIONS EARLY THIS MORNING BUT THEY SHOULD IMPROVE IN WAKE OF FROPA FROM WEST TO EAST TOWARD DAYBREAK. A BRIEF SHOWER POSSIBLE EARLY THIS MORNING WITH FROPA. EXPECT VFR CONDITIONS FROM MID MORNING THRU THE AFTERNOON. RAIN WILL MOVE BACK TOWARD ACY/MIV AFTER 23Z AND THEN TOWARD THE PHILA TERMINALS AFTER 03Z. CURRENTLY NOT EXPECTING THE PRECIP TO REACH ABE AND RDG. THE RAIN IS EXPECTED TO MIX WITH AND THEN TRANSITION TO SNOW FROM WEST TO EAST OVERNIGHT INTO EARLY FRIDAY MORNING. IFR OR EVEN RESTRICTIONS POSSIBLE ONCE IT CHANGES TO SNOW. NW WINDS 5-10 KT IN THE EVENING WILL BECOME NLY AND INCREASE TO 10-15 KT LATE. OUTLOOK... FRIDAY...MAINLY VFR, EXCEPT POSSIBLE SUB-VFR IN LIGHT SNOW IN THE MORNING FOR EASTERN SITES, ESPECIALLY KACY/KMIV. SATURDAY AND SUNDAY...MAINLY VFR CONDITIONS ARE EXPECTED. MONDAY...MAINLY VFR, BUT CONDITIONS MAY LOWER AS THE DAY WEARS ON DUE TO POSSIBLE LOW PRESSURE APPROACHING THE REGION. IN ADDITION TO POSSIBLE LOWER CIGS DEVELOPING, LOWER VSBYS MAY ALSO OCCUR IN RAIN/SNOW. && .MARINE... SCA REMAINS IN EFFECT FOR THE ATLANTIC COASTAL WATERS FOR TODAY AND TONIGHT. FOR THE ZONES UNDER A SCA, THE WINDS ARE CURRENTLY SW AND BELOW 25 KT BUT THE SEAS ARE STILL 5-7 FT. THE WINDS MAY BRIEFLY GUST AOA 20 KT AS THEY TURN NWLY BEHIND A COLD FRONT DURING THE EARLY AND MID MORNING. NW WINDS BECOME NLY TONIGHT AND INCREASE AS LOW PRESSURE DEVELOPS OF THE SOUTHERN MID-ATLANTIC COAST. GUSTS 25-30 KT ARE POSSIBLE IN THE ATLANTIC COASTAL WATERS. THE SCA MAY NEED TO BE EXPANDED INTO THE DE BAY FOR LATE THURSDAY NIGHT IF THE LOW STRENGTHENS FURTHER THAN FORECAST OR TRENDS CLOSER TO THE COAST. OUTLOOK... FRIDAY...BREEZY NORTHWEST WINDS ARE EXPECTED, AND GUSTS BETWEEN 25 TO 30 KNOTS ARE EXPECTED FOR THE ATLANTIC COASTAL WATERS. WE HAVE EXTENDED THE SCA THROUGH 6PM FRIDAY. SATURDAY...SUB-ADVISORY CONDITIONS ARE EXPECTED. SUNDAY AND MONDAY...WINDS AND SEAS LOOK TO REMAIN BELOW ADVISORY CRITERIA FOR MUCH OF SUNDAY, BUT THERE IS SOME POTENTIAL FOR OFFSHORE LOW PRESSURE TO PASS EAST OF OUR WATERS SUNDAY NIGHT INTO MONDAY, WHICH COULD ENHANCE SEAS AND WIND GUSTS. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST FRIDAY FOR ANZ450>455.
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&& $$ SYNOPSIS...KLINE NEAR TERM...KLEIN SHORT TERM...KLEIN LONG TERM...KLINE AVIATION...KLEIN/KLINE MARINE...KLEIN/KLINE

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