Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 251805 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 105 PM EST SUN JAN 25 2015 .SYNOPSIS... A STRONG COLD FRONT WILL CONTINUE TO PUSH SOUTHEAST THROUGH OUR REGION TODAY, REACHING A LATE DAY POSITION FROM THE DELMARVA WEST INTO LOW PRESSURE OVER THE LOWER OHIO VALLEY. THAT LOW WILL REACH THE NORTH CAROLINA COAST MONDAY MORNING THEN TURN NORTH NORTHEAST, INTENSIFYING VERY RAPIDLY AS IT NEARS CAPE COD TUESDAY. HIGH PRESSURE FOLLOWS BY LATE WEDNESDAY, THEN ANOTHER LOW WILL REDEVELOP ON THE NEXT COLD FRONTAL PASSAGE OFF THE MID ATLANTIC COAST LATE THURSDAY AND FRIDAY. HIGH PRESSURE FOLLOWS SATURDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... WITH THE 12:30 PM UPDATE, WE HAVE INCREASED TEMPERATURES FROM PHL SOUTH AHEAD OF A COLD FRONT ALONG WITH CLOUD COVER FOR THE REMAINDER OF THE AFTERNOON. THIS CLOUD COVER SHOULD KEEP THE TEMPERATURES IN CHECK FROM WARMING TO MUCH MORE AS THE DAY GOES ON. THE LATEST RAP AND HRRR HOLD OFF ANY PRECIPITATION TILL THIS EVENING, THIS FORECAST UPDATE TAKES OUT AMY MENTION OF PRECIPITATION TILL THIS EVENING. OTHERWISE, AS THE LOW PRESSURE FROM YESTERDAY PULLS FARTHER TO OUR NORTHEAST AN ARCTIC-TYPE COLD FRONT PUSHES THROUGH OUR REGION FROM LATE MORNING AND THROUGH THIS AFTERNOON. WATER VAPOR IMAGERY THIS MORNING SHOWS ONE TROUGH AXIS TO OUR NORTHEAST WHILE ANOTHER SHORTWAVE AXIS PUSHES THROUGH THE GREAT LAKES...THIS IS DRIVING THE ARCTIC FRONT TODAY. WAY BACK ACROSS THE NORTHERN PLAINS IS THE ENERGY THAT WILL BE THE DRIVING FORCE FOR THE CLIPPER SYSTEM LATE TONIGHT AND THEN THE MUCH LARGER COASTAL NOR`EASTER EXPECTED ON MONDAY- TUESDAY. OVERALL A MAINLY DRY AND TRANQUIL DAY IS EXPECTED ACROSS THE REGION. THE AFOREMENTIONED FRONT WILL SLIP THROUGH THE REGION BY THIS AFTERNOON USHERING IN A COOLER AIRMASS. THE MORNING STRATOCU SHOULD LIFT AND MIX OUT A LITTLE AS THE DAY WEARS ON. DECENT DOWNSLOPING COMPONENT SHOULD ALLOW HIGHS TO REACH AROUND 40F THIS AFTERNOON, SLIGHTLY WARMER SOUTH AND EAST OF PHILLY, AHEAD OF THE FRONTAL PASSAGE. BEHIND THE FRONT WEAK MID-LEVEL WARM AIR ADVECTION OCCURS TO OUR SOUTHWEST AS MORE MOISTURE AND CLOUDS ADVECT IN BEGINNING LATER THIS EVENING. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... BROAD SCALE SURFACE LOW PRESSURE, RIDING ALONG THE SAGGING COLD FRONT LATER THIS EVENING, WILL PASS TO OUR SOUTH TONIGHT. HIGH PRESSURE TO OUR NORTH WITH WEAK MID-LEVEL RIDGING WILL ALLOW FOR THE MID-LEVEL SHORTWAVE DRIVING THE SURFACE LOW TO DEEPEN AND TAKE MORE OF A NEGATIVE TILT TONIGHT. STRENGTHENING WAA, IN RESPONSE TO THIS PROCESS, WILL OCCUR ACROSS OUR REGION AS A LIGHT SNOW SHOULD BREAK OUT FROM WEST-EAST. ONSET TIMING IS STILL A BIT OF A QUESTION BUT A MAJORITY OF THE HI-RES GUIDANCE IS SHOWING THE INCREASING CHANCES DURING THE LATE EVENING. PTYPE SHOULD NOT BE MUCH OF AN ISSUE EXCEPT ACROSS OUR EXTREME SOUTHERN ZONES AS LOW-LEVEL TEMPERATURES STRUGGLE TO TRANSITION COLDER (BELOW 0C) JUST AHEAD OF THE APPROACHING LOW...WAA SHOULD KEEP A RAIN/SNOW MIX SOUTH OF DOVER WHILE NORTHWARD IS ALL SNOW. DECENT CONVERGENCE ACROSS OUR CENTRAL ZONES LATE TONIGHT, BOTH THERMALLY AND DYNAMICALLY. GUIDANCE IS PAINTING A NOSE OF A TENTH OF LIQUID FROM A PHL/ABE LINE WEST SO THIS IS WHERE WE SHOULD SEE SLIGHTLY HIGHER SNOW AMOUNTS...ON THE ORDER OF 1-2" IN AND AROUND PHILLY, 2-3" FARTHER WEST TOWARDS RDG...MESOSCALE BANDING POTENTIAL ALSO EXISTS ALBEIT NOT NEARLY AS ROBUST AS SATURDAY MORNING. EVEN THOUGH THIS SNOW WILL AFFECT THE MONDAY MORNING COMMUTE WE DID NOT WANT TO ADD TO ANY CONFUSION WITH MULTIPLE WINTER WEATHER HEADLINES DEALING WITH THE SAME EVENT...JUST TWO DIFFERENT PIECES OF ENERGY. GIVEN WE ARE EXPECTING A MUCH MORE IMPACTFUL STORM BEGINNING LATER ON MONDAY...SEE LONG TERM DISCO...WE DECIDED TO FORGO AN ADVISORY BUT MAKE MENTION OF THE EARLY MORNING SNOWFALL IN THE HWO/WSW PRODUCTS. && .LONG TERM /MONDAY THROUGH SATURDAY/... **MAJOR DISRUPTIVE SNOWSTORM POTENTIAL LATE MONDAY INTO TUESDAY MORNING PHILLY AREA NEWD TO NEW ENGLAND...WINTER STORM WATCH IN PLACE FOR MOST OF THE FORECAST AREA** **BLIZZARD WATCH HAS BEEN ISSUED FOR MONMOUTH, OCEAN, AND MIDDLESEX COUNTIES** 500 MB: A STRONG SHORT WAVE MONDAY MORNING OVER THE CENTRAL APPALACHIANS INTENSIFIES INTO A CLOSED LOW SOUTH OF LONG ISLAND TUESDAY. RIDGING IN THE WAKE OF ITS MARITIMES DEPARTURE FOLLOWS TO THE EAST COAST WEDNESDAY. A SOUTHEASTWARD MOVING SHORT WAVE REACHES THE MID ATLANTIC COAST FRIDAY WITH A TEMPORARILY FLATTENED WESTERLY FLOW NEXT WEEKEND. TEMPERATURES (ENERGY USE): BELOW NORMAL MONDAY THROUGH THURSDAY, POSSIBLY 5 TO 10 DEGREES BELOW MON-WED; NEAR NORMAL FRI, CHILLING AGAIN SATURDAY. FORECAST BASIS: UNLESS OTHERWISE NOTED WITHIN THE DAILIES. THIS FORECAST IS A 50 50 BLEND OF THE 00Z/25 MAV/MET FOR MONDAY-TUESDAY. THE 00Z/25 MEX MOS WAS APPLIED TUESDAY NIGHT AND WEDNESDAY. THE 05Z/25 WPC D4-8 ELEMENTS OF DEWPOINTS/WIND/SKY/POP/MAX-MIN TEMPS WERE NOT USED FOR THE LONGER RANGE DUE TO FOCUS ON THE POTENTIALLY VERY HIGH IMPACT STORM FOR MONDAY NIGHT. THEREFORE...THERE WAS NO UPDATE OF THE FORECAST BEYOND WEDNESDAY IN THE EARLY ISSUANCE TODAY. THE DAILIES... MONDAY-TUESDAY...WSA IN DIFFERING SEGMENTS TO BE REFINED WHEN WATCHES CONVERT TO WARNINGS AND OR ADVISORIES. MODEL DISAGREEMENT FOR THE 00Z/25 CYCLE WITH THE NAM THE MAIN OUTLIER RIGHT NOW. THE UKMET IS LARGE BUT A FASTER DEPARTURE THAN THE ECMWF. THE 00Z/06ZNAM WAS ACCEPTABLE THROUGH MIDDAY MONDAY AND THEREAFTER DID NOT RELY ON THE NAM FOR ITS QPF...INSTEAD THIS FORECAST IS BASED HEAVILY ON NCEP QPF/SNOWFALL AS WELL AS THE 00Z/25 ECMWF AND GFS BLEND. MONDAY: SEVERAL INCHES OF SNOW EXPECTED BUT AN ADVISORY NOT ISSUED SINCE WE DID NOT WISH TO DRAW ATTENTION AWAY FROM THE POTENTIALLY VERY HIGH IMPACT EVENT FOR MONDAY NIGHT. TOO WARM FOR MUCH ACCUMULATION FAR SNJ AND MUCH OF THE DELMARVA. THE ARCTIC FRONT AND ITS SLOWLY DEEPENING BOUNDARY LAYER COLD IS CRUCIAL FOR THE LIFT OF THE SELY 850MB FLOW AND A GENERAL SNOW IN EASTERN PA/MUCH OF NJ. COMMUTES IMPACTED. HIGH CONFIDENCE. MONDAY NIGHT INTO TUESDAY MORNING...UNCERTAINTY ON AMOUNTS ETC ALL HINGING ON INTENSITY AND TRACK OF A COASTAL STORM. OVERALL, THIS LOOKS LIKE A MAJOR STORM FOR US AND POTENTIAL FOR BLIZZARD CONDITIONS IN NE NJ. OUR FORECAST AMOUNTS ARE PROBABLY CONSERVATIVE. BANDING IN THE COMMA HEAD WITH A BENT BACK FRONT ALOFT LOOKS TO BE A MAJOR PLAYER...GENERATING SNOWFALL RATES MONDAY NIGHT POSSIBLY IN EXCESS OF AN INCH AN HOUR ACROSS NJ AND PORTIONS OF E PA. IF THE 00Z/06Z NAM MASS FIELDS ALOFT ARE CORRECT THEN ALL THIS HEAVY SNOW WOULD MISS TO THE EAST. THOSE WITH TRAVEL PLANS IN E PA AND NJ ESPECIALLY FOR MONDAY NIGHT AND TUESDAY SHOULD BE AWARE THAT THOSE PLANS MAY NEED MAJOR ALTERATION/CANCELLATION. BE PREPARED WITH ALTERNATE PLANS. "IF" CONFIDENCE IS VERY HIGH, WE MAY CONVERT TO WARNINGS LATE TODAY. WATCHES DO NOT MEAN A DONE DEAL BUT DO PAY ATTENTION. A DRIER MORE POWDERY SNOW WILL BE EASIER TO ACCUMULATE IN THE COLDER AIRMASS THAN JUST WHAT OCCURRED EARLY SATURDAY. WIND WILL BECOME A FACTOR IN BLOWING/DRIFTING, MAINLY IN NJ/DEL. TUE NIGHT THRU WED NIGHT... HIGH PRESSURE WILL DOMINATE DURING THIS PERIOD WITH FAIR BUT COLD WEATHER EXPECTED. THU INTO FRI...THIS FORECAST WAS NOT UPDATED ON THIS MID SHIFT. MODELS ARE SHOWING ANOTHER CLIPPER TYPE SYSTEM APPROACHING FROM THE WEST AFTER THE MID WEEK PERIOD. TEMPERATURES WILL HAVE BEGUN TO MODERATE BY THE TIME THE PRECIP ARRIVES...SO SOME RAIN/SNOW LINE ISSUES WILL OCCUR. MOSTLY USED CHC POPS FOR NOW. TEMPS WILL STILL BE BELOW NORMAL...BUT NOT AS COLD AS WED. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TODAY...VFR CIGS AOA 4000 FT. STRATOCU DECK WILL REMAIN IN PLACE MOST OF THE DAY UNDER WESTERLY WINDS WITH A FEW GUSTS POSSIBLE TO NEAR 20 KT. TONIGHT...MVFR/IFR IN AREAS OF SNOW. TIMING IS STILL A BIT SUSPECT BUT LIGHT SNOW SHOULD OVERSPREAD FROM THE WEST-EAST BY LATE TONIGHT. MINIMAL RAIN/SNOW MIXING EXPECTED VCNTY KMIV TOWARD 12Z MONDAY. EXPECT SOME LIGHT ACCUMULATIONS THROUGH EARLY MONDAY MORNING...AROUND 1-2 INCHES PHL/ILG/TTN/PNE, MAYBE 2-3 INCHES RDG/ABE. OUTLOOK... MON AND MON NIGHT...IFR/LIFR SOUTH AND MVFR OR INTERMITTENT IFR NORTH IN SNOW OR PERIODS OF SNOW. N-NE WINDS GUSTING 20-30 KT AT TIMES WITH 35 KT GUSTS POSSIBLE VCNTY KACY. VERY HIGH CONFIDENCE. PLOWABLE AMOUNTS AND POTENTIAL FOR AIRPORT CLOSURES AT NIGHT INTO EARLY TUESDAY DEPENDENT ON SNOW AMOUNTS AND RATE OF FALL AS WELL AS DRIFTING. TUE...IFR PROBABLE EARLY IN COMMA HEAD BENT BACK BANDING OF THE BIG NOREASTER THEN PROBABLY BECOMING VFR BY LATE IN THE DAY. NORTHWEST WINDS GUSTING 20-30KT, EXCEPT POSSIBLY STRONGER VCNTY KACY. AVERAGE CONFIDENCE. TUESDAY NIGHT-WED: MOSTLY VFR. N-NW WINDS. HIGH CONFIDENCE: THURSDAY: CONDITIONS MAY DEGRADE IN A PERIOD OF PCPN DURING THE AFTERNOON OR NIGHT. && .MARINE... REST OF TODAY...WE REMOVED THE SCA FROM THE OCEAN FRONT AS WINDS AND SEAS HAVE FALLEN BELOW THRESHOLDS. TONIGHT...SUB-SCA EXPECTED. LOW PRESSURE WILL MOVE BY TO OUR SOUTH LATE AS WINDS VEER TOWARDS THE NORTH-NORTHEAST. SEAS BEGIN TO BUILD ACROSS THE SOUTHERN WATERS LATE AS DO THE WINDS. GALE WARNINGS/STORM WATCHES IN PLACE STARTING MONDAY AFTERNOON. OUTLOOK... MONDAY INTO TUESDAY...MOSTLY GALE CONDITIONS ON THE WATERS BUT POCKETS OF STORM FORCE GUSTS. HAVE FORECAST WHERE THE STORM FORCE 50 KT GUSTS OVER THE NJ WATER WHERE THEY ARE MOST LIKELY TO OCCUR, BUT WITH THE UNDERSTANDING THAT ISOLATED STORM FORCE GUSTS MAY OCCUR IN THE DELAWARE WATERS AS WELL. THE HEADLINES ARE THE MOST LIKELY WORST CASE SCENARIO. TUESDAY AFTERNOON THROUGH THURSDAY...MAINLY SCA CONDITIONS WITH AREAS OF FREEZING SPRAY EXPECTED. && .TIDES/COASTAL FLOODING... ANOTHER NORTHEASTER IS EXPECTED TO AFFECT THE COASTAL WATERS OF DELAWARE AND NEW JERSEY FROM MONDAY NIGHT INTO TUESDAY. MINOR TO POSSIBLY MODERATE TIDAL FLOODING SHOULD OCCUR AROUND THE TIMES OF HIGH TIDE, MAINLY THE MIDNIGHT TUESDAY MORNING HIGH TIDE CYCLE. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...WINTER STORM WATCH FROM MONDAY AFTERNOON THROUGH TUESDAY MORNING FOR PAZ054-055-060>062-070-071-101>106. NJ...WINTER STORM WATCH FROM MONDAY AFTERNOON THROUGH TUESDAY MORNING FOR NJZ001-007>010-015>019-027. WINTER STORM WATCH FROM MONDAY EVENING THROUGH TUESDAY MORNING FOR NJZ021>025. BLIZZARD WATCH FROM MONDAY AFTERNOON THROUGH TUESDAY MORNING FOR NJZ012>014-020-026. DE...WINTER STORM WATCH FROM MONDAY AFTERNOON THROUGH TUESDAY MORNING FOR DEZ001. WINTER STORM WATCH FROM MONDAY EVENING THROUGH TUESDAY MORNING FOR DEZ002>004. MD...WINTER STORM WATCH FROM MONDAY AFTERNOON THROUGH TUESDAY MORNING FOR MDZ008. WINTER STORM WATCH FROM MONDAY EVENING THROUGH TUESDAY MORNING FOR MDZ012-015-019-020. MARINE...STORM WATCH FROM MONDAY AFTERNOON THROUGH TUESDAY MORNING FOR ANZ450>453. GALE WARNING FROM 11 AM MONDAY TO 11 AM EST TUESDAY FOR ANZ431- 454-455. GALE WARNING FROM 5 PM MONDAY TO 11 AM EST TUESDAY FOR ANZ430. && $$ SYNOPSIS...DRAG/KLINE NEAR TERM...GAINES/HEAVENER/KLINE SHORT TERM...HEAVENER LONG TERM...DRAG/KLINE AVIATION...DRAG/HEAVENER/KLINE MARINE...DRAG/HEAVENER/KLINE TIDES/COASTAL FLOODING...

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