434  
FXUS61 KPHI 242117  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
417 PM EST MON NOV 24 2014  
   
SYNOPSIS
 
 
A COLD FRONT WILL MOVE THROUGH THE REGION OVERNIGHT AND STALL JUST  
OFFSHORE THROUGH TUESDAY...ALLOWING HIGH PRESSURE TO BRIEFLY MOVE  
IN FROM THE SOUTHWEST. LOW PRESSURE WILL DEVELOP ALONG THIS STALLED  
FRONT AND AFFECT THE REGION AS A STRONG NOR EASTER ON WEDNESDAY.  
HIGH PRESSURE WILL MOVE IN ON THANKSGIVING AND DOMINATE UNTIL A COLD  
FRONTAL PASSAGE IN THE SUNDAY AND MONDAY TIME FRAME.  
 

 
   
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
 
 
ANY REMAINING WIND GUSTS SHOULD BEGIN TO TAPER OFF THROUGH THE REST  
OF THE AFTERNOON, AND WEAKEN EVERYWHERE AROUND SUNSET. DRY WEATHER  
IS EXPECTED OVERNIGHT, EVEN THOUGH A COLD FRONT IS FORECAST TO MOVE  
ACROSS THE AREA. ALL GUIDANCE IS INDICATING THE RAIN REMAINING TO  
OUR NORTH AND WEST AND DRYING BEFORE IT REACHES OUR AREA. THE DRY  
COLD FRONT WILL PROGRESS THROUGH THE AREA OVERNIGHT FROM WEST TO  
EAST, WITH THE MAIN EFFECT SOUTHERLY WINDS AND AN INCREASE IN CLOUD  
COVER AHEAD OF THE FRONT, WITH PARTIALLY CLEARING SKIES AND WESTERLY  
WINDS BEHIND IT.  
 

 
   
SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/
 
 
ONE LAST FAIR WEATHER DAY EXPECTED ON TUESDAY BEFORE THE UPCOMING  
STORM IN THE LONG TERM. OVERALL DRY WEATHER WITH MID AND HIGH LEVEL  
CLOUDS EXPECTED FOR MOST OF THE DAY. TEMPERATURES WILL BE 10-15  
DEGREES COOLER WITH NORTHWEST FLOW ACROSS THE AREA AND LOWERING  
THICKNESSES AND 925 MB TEMPERATURES. HIGHS WERE A BLEND OF MIXED 925  
MB TEMPS, MAV/MET MOS, AND MOSGUIDE WHICH KEEPS EVERYONE ABOVE  
NORMAL, BUT CLOSER THAN MONDAY.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH MONDAY/
 
 
**WINTER STORM/EVENT OF WET SNOW AT HAND E PA AND NW NJ**  
 
500 MB: THE LEAD SHORT WAVE THAT PRODUCES OUR WINTER STORM WILL  
BE MOVING EASTWARD ALONG THE GULF COAST TUESDAY EVENING THEN UP  
THE EAST COAST LATE WEDNESDAY TO NEW ENGLAND BY THURSDAY MORNING.  
IT PASSES THROUGH NJ AS AN INTENSIFYING 200M 12 HR 500MB HFC NEAR  
06Z THURSDAY.  
 
TEMPERATURES: MIN TEMPS WED MORNING WILL BE ABOUT 5 DEGREES ABOVE  
NORMAL BUT THE PROBLEM IS THE HIGH TEMPERATURES AFTER DAYBREAK  
WEDNESDAY WILL BE 8 TO 12 DEGREES BELOW NORMAL AS WET BULBING  
OCCURS IN THE INCREASING NORTHERLY SFC FLOW. LOWS WEDNESDAY NIGHT  
WILL BE NEAR OR SLIGHTLY BELOW NORMAL BUT NOT A HARD FREEZE SUBSEQUENT  
TO THIS SNOW.  
 
POPS: TUESDAY NIGHT AND WEDNESDAY NIGHT ARE BLENDED 12Z/24 NCEP MOS  
THEN THAT BLENDED WITH THE 09Z/24 SREF AND 00Z-12Z ECMWF 6 HR QPF  
INDICATIONS OF .10 OR GREATER.  
 
THE STORM...  
 
OUR RECOMMENDATION: TO REACH YOUR HOLIDAY DESTINATION ON TIME WITH  
PROBABLY A MINIMUM OF WEATHER RELATED TRAVEL DELAYS...AND ESPECIALLY  
TRAVELING WEST OF I-95 INTO NORTHWEST NJ...EASTERN PA...TRAVEL SHOULD  
BE COMPLETED AT THE LATEST...BY 10 AM WEDNESDAY.  
 
NORMALLY THIS STORM WOULDN'T HAVE GARNERED SO MUCH LEAD TIME ATTENTION  
BUT WE RESPONDED TO THE THE HEIGHTENED PUBLIC INTEREST ON WHAT IS  
USUALLY THE BUSIEST TRAVEL DAYS OF THE YEAR.  
 
THE WATCH WAS EXPANDED TO JUST NW OF I-95 IN THE 330 PM FORECAST.  
 
ITS POSSIBLE THAT THE SNOW AMOUNTS NEAR AND EAST OF I95 ARE A BIT  
TOO LOW AND THAT THE WATCH MIGHT HAVE NEEDED A SLIGHT SEWD EXTENSION  
INTO NE MD AND N DE. DEPENDS HOW FAST RAIN CHANGES TO SNOW THERE.  
 
TUESDAY NIGHT...LEFTOVER WARMTH AND IT APPEARS THE LEADING EDGE OF  
THE PCPN SHIELD WILL BEGIN AS RAIN MOST OF THE AREA EXCEPT WELL TO  
THE NORTHWEST OF I-95 (HIGHER TERRAIN). NO ACCUMULATION ANTICIPATED  
BEFORE 7 AM. LIGHT WEST WIND BECOMING N-NE TOWARD MORNING.  
 
WEDNESDAY THROUGH MIDNIGHT WEDNESDAY EVENING...  
 
THE WEDNESDAY AFTERNOON EVENING COMMUTE SHOULD BE PROBLEMATIC...ESPECIALLY  
HILLS AND OVER THE KITTATINNY RIDGE IN NW NJ-POCONOS OF NE PA.  
 
WEST OF I-95...MAINLY WHERE SOME BANDING AND ASSOCIATED SNOWFALL RATE  
ENHANCEMENT IS EXPECTED ALONG THE SE EDGE OF THE COMMA HEAD (THERMAL  
AXIS OF PIVA AND FGEN). ACCUMULATION HERE MAY BE MORE ON THE ORDER  
OF 12 TO 1? BANDING COULD RESULT IN ISOLATED GREATER THAN 10 INCH  
AMOUNTS IN THE POCONOS AND NORTHERN SUSSEX COUNTY NJ.  
 
I-95 CORRIDOR RAIN MIXING WITH OR CHANGING TO WET SNOW DURING  
MIDDAY OR EARLY AFTERNOON THEN REMAINING AS SNOW BEFORE ENDING  
DURING WEDNESDAY EVENING. WHILE QPF IS GREATER HERE...SNOWFALL  
SHOULD BE NOT BE GREATER THAN 10 TO 1 RATIO. SLOPPY WET SNOW THAT  
COULD CLING TO TREES AND WIRES AND OBSCURE ROAD SIGNS DURING THE  
AFTERNOON-EVENING IN A 32-33F SURFACE TEMPERATURE ENVIRONMENT. IF  
4 TO 6 INCHES OF WET SNOW WERE TO ACCUMULATE ON BRANCHES/WIRES...THE  
RISK OF BROKEN TREE LIMBS SHOULD INCREASE CONSIDERABLY. TOTALS UNKNOWN  
BUT SUSPECT MAINLY 1 TO 5 INCH AMOUNTS.  
 
ADDED A WATCH TO PHILADELPHIA AT THE LAST MINUTE JUST BEFORE 330  
PM DUE TO AUTOMATED PHRASING FROM OUR FORECAST GRIDS.  
 
COAST: RAIN POSSIBLY ENDING AS SNOW WEDNESDAY EVENING. TOTALS NIL TO  
2 INCHES? NO ACCUMULATIONS DURING THE DAY AS PER THE WATER TEMPERATURE  
STILL IN THE MID 50S, THE ONSHORE FLOW AND PROXIMITY OF THE WARMING  
ALOFT NEAR THE SURFACE LOW AND EAST OF THE VORT PATH SHOULD KEEP  
THEM WELL ABOVE FREEZING THROUGHOUT THE DAY. THE CAVEAT TO ALL OF  
THIS IS THAT THE LOCATION OF THE RAIN/SNOW TRANSITION AND EVEN  
SNOW RATIOS IS VERY MUCH DEPENDENT ON THE TEMPERATURE PROFILE.  
THERE IS STILL MODEL DISAGREEMENT, SO SNOW AMOUNTS REMAIN UNCERTAIN  
FROM I95 EASTWARD REMAIN FAR FROM CERTAIN.  
 
THE COAST SHOULD CHANGE TO SNOW OR FLURRIES WEDNESDAY EVENING BEFORE  
ENDING WHEN A SLIGHT ACCUMULATION COULD OCCUR.  
 
PRECIPITATION EVERYWHERE MODERATE TO HEAVY FOR A TIME DURING THE  
DAY WITH TAIL END SNOW IN EASTERN PA AND NW NJ POSSIBLY STILL  
MODERATE DURING THE EVENING.  
 
NORTH TO NORTHEAST WIND GUST 15-25 MPH I95 EASTWARD.  
 
RECORD DAILY SNOWFALL IS FORECAST FOR KABE (VULNERABLE RECORD OF  
1.7 INCHES) AND DITTO AT KILG WHERE THE VULNERABLE DAILY RECORD IS  
0.1 INCHES.  
 
AFTER MIDNIGHT WEDNESDAY NIGHT...JUST A SMATTERING OF FLURRIES AND  
VARIABLE CLOUDINESS WITH LIGHT WIND AND TEMPERATURES NEAR FREEZING.  
 
THURSDAY THROUGH SUNDAY...  
 
* THANKSGIVING DAY WILL BE DRY WITH BELOW NORMAL TEMPERATURES.  
* FRIDAY AND SATURDAY WILL FEATURE DRY WEATHER W/UNSEASONABLY  
COOL TEMPERATURES.  
* A COLD FRONTAL PASSAGE EXPECTED IN THE SUNDAY-MONDAY PERIOD  
W/TEMPERATURES EXPECTED TO MODERATE TO SEASONABLE LEVELS.  
 
THE MAIN CHALLENGE THURSDAY AND BEYOND WILL BE HOW THE MODELS  
RESOLVE A MID-LEVEL SPLIT FLOW REGIME OVER THE EASTERN PACIFIC  
AND THE TRANSITION FROM A MERIDIONAL FLOW ACROSS THE CONUS TO A  
ZONAL FLOW...AS THE NAO BECOMES POSITIVE AND THE PNA BECOMES  
NEGATIVE. WITH THE FLOW BECOMING ZONAL...THE MAIN UNCERTAINTY WILL  
BE W/SHORTWAVE ENERGY RIDING ALONG THE US/CANADIAN BORDER OVER THE  
WEEKEND...WHERE PREDICTABILITY IS LOW. THERE ARE DIFFERENCES IN  
THE AMPLITUDE AND TIMING OF THIS FEATURE...WHICH TRANSLATES INTO  
UNCERTAINTY W/THE TIMING OF A COLD FRONT AND TEMPERATURES...ESP  
LATE IN THE WEEKEND INTO EARLY NEXT WEEK.  
 
THURSDAY...  
FLOW REMAINS CYCLONIC ALOFT WITH X-SECS INDICATING ABUNDANT  
MOISTURE IN THE LOW AND MID-LEVELS...SO EXPECTING CONSIDERABLE  
CLOUDINESS. LOW-LEVEL FLOW WILL BE OUT OF THE NORTHWEST WITH A  
TRAJECTORY OFF THE GREAT LAKES. THE BEST LIFT AND JET DYNAMICS  
WILL BE TO THE SOUTHEAST AND THE DOWNSLOPING FLOW SHOULD KEEP  
ANY -SHSN CONFINED TO THE HIGHER TERRAIN OF THE FAR NW CWA... NOT  
EXPECTING ANY ACCUMULATION. IT WILL BE BRISK WITH MIXING TO 900  
HPA SUPPORTING WIND GUSTS TO AROUND 20 KNOTS.  
 
FRIDAY...  
STRONG MID-LEVEL HEIGHT RISES SIGNAL THE RETURN TO A MORE  
ZONAL FLOW W/SURFACE HIGH-PRESSURE INVOF THE APPALACHIANS.  
THE COLUMN WILL DRY OUT ALONG WITH STRONG SUBSIDENCE AND A  
SURFACE FLOW OUT OF THE NORTHWEST...SO EXPECTING A DRY DAY.  
 
SATURDAY...  
SURFACE RIDGE MOVES OFFSHORE LEADING TO A SOUTHWEST FLOW  
ACROSS THE REGION. THE MODELS INDICATE AN OVERRUNNING REGIME  
IN ADVANCE OF A WEAK SHORTWAVE OVER THE GREAT LAKES. ATTM...  
THE DEEPEST MOISTURE AND BEST DYNAMICS ARE NORTHWEST OF THE  
CWA...THEREFORE ANTICIPATING ANOTHER DRY DAY.  
 
LATE WEEKEND INTO EARLY NEXT WEEK...  
THE MODELS INDICATE A SLOW COLD FRONTAL PASSAGE DURING THIS  
TIME AS THE SURFACE FRONT BECOMES PARALLEL TO THE MID-LEVEL  
FLOW. THIS PRESENTS THE BEST CHANCE OF QPF IN THE LONG TERM  
BUT IT SHOULD BE FAIRLY LIGHT AS THERE IS NO GMEX CONNECTION.  
 

 
   
AVIATION /21Z MONDAY THROUGH SATURDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
ALL TAFS HAVE RETURNED TO VFR, AND SHOULD REMAIN SO THROUGH THE  
REMAINDER OF THE AFTERNOON INTO THIS EVENING. A COLD FRONT WILL MOVE  
THROUGH THE AREA OVERNIGHT. AHEAD OF THE COLD FRONT, MOISTURE MAY  
GET TRAPPED IN THE LOW LEVELS, LEADING TO SOME LOWER CIGS AND/OR  
VSBYS. A TEMPO GROUP HAS BEEN INSERTED FOR A FEW HOURS BEFORE THE  
FRONTAL PASSAGE FROM THE DELAWARE VALLEY TAFS TOWARD THE COASTAL  
TAFS, WITH THE LOWEST CONDITIONS EXPECTED CLOSER TO THE COAST.  
BEHIND THE FRONT, IMPROVING CONDITIONS ARE EXPECTED AND SHOULD  
REMAIN VFR INTO TUESDAY.  
 
GUSTY SOUTHERLY WINDS THIS AFTERNOON WILL BEGIN TO LOSE THEIR GUSTS  
AROUND SUNSET, BUT WILL REMAIN A STEADY FLOW THROUGH THE NIGHT.  
BEHIND THE FRONTAL BOUNDARY, WINDS WILL SWITCH TO WEST/NORTHWEST AND  
REMAIN SO THROUGH TUESDAY. ADDITIONAL GUSTS ARE EXPECTED DURING THE  
DAY TUESDAY AROUND 20 KNOTS.  
 
OUTLOOK....  
 
TUESDAY NIGHT...VFR CIGS LOWER TO MVFR CONDITION RAIN SOUTH OF PHL  
AFTER 06Z/26. LIGHT WNW WIND BECOMING NNE BY DAWN WEDNESDAY AT 5 TO  
15 KT.  
 
WEDNESDAY AND WEDNESDAY EVENING...A COASTAL STORM WILL BRING WIDESPREAD  
MVFR VARIABLE IFR CEILINGS. REDUCTIONS IN VISIBILITY DUE TO RAIN ALONG  
THE COAST (KACY/KMIV), RAIN SNOW MIX EVENTUALLY CHANGING TO ALL SNOW  
IN THE DELAWARE RIVER VALLEY (KTTN KPNE KPHL AND KILG) AND MOSTLY  
SNOW KABE AND KRDG. IN ADDITION, EXPECT PERSISTENT NORTHERLY OR  
NORTHEASTERLY WINDS DURING THE DAY WITH GUSTS 12-25 KT FROM WEST  
TO EAST. PRECIPITATION SHOULD END AS SNOW MOST TAF SITES DURING  
THE EVENING AND BY MIDNIGHT BE DIMINISHED TO A FEW FLURRIES EXCEPT  
POSSIBLY NO SNOW AT KMIV/KACY.  
 
A PLOWABLE...POSSIBLY SLUSHY SNOW ACCUMULATION IS EXPECTED ON ANY  
UNTREATED RUNWAYS-PAVEMENTS AT KRDG AND KABE WEDNESDAY.  
 
THANKSGIVING...CONDITIONS SLOWLY RETURN TO VFR AND WINDS SHIFT TO  
WESTERLY OR NORTHWEST. THERE COULD BE BRIEF MVFR CONDITIONS IN  
SCATTERED SNOW SHOWERS LATER THURSDAY MAINLY JUST N OF KRDG AND  
KABE. WINDS MAY GUST TO 25 KT.  
 
FRIDAY...VFR CONDITIONS EXPECTED.  
 
SATURDAY...VFR CONDITIONS EXPECTED.  
 

 
   
MARINE
 
 
THE GALE WARNING HAS BEEN DROPPED AS WINDS HAVE STRUGGLED TO  
APPROACH GALE FORCE IN THE SOUTHERLY FLOW. WE WILL CONVERT TO A  
SMALL CRAFT ADVISORY, WITH THE BAY ENDING TUESDAY MORNING, AND THE  
OCEAN FRONT EXTENDED THROUGH THE DAY TUESDAY DUE TO ELEVATED SEAS.  
 
OUTLOOK...  
 
TUESDAY NIGHT...DIMINISHING NW TO N WIND WITH WINDS AND SEAS BELOW  
SCA CRITERIA. WINDS TURN NE BY DAWN.  
 
WEDNESDAY...GALE CONDITIONS POSSIBLE WITH STRONG NORTHERLY OR  
NORTHEASTERLY WINDS. A GALE WATCH HAS BEEN ISSUED FOR MOST OF THE  
WATERS....STRONGEST WINDS IN THE ATLANTIC WATERS EAST OF DELAWARE.  
 
WEDNESDAY NIGHT...WINDS WILL SLOWLY DIMINISH TO SCA CRITERIA.  
 
THURSDAY...WINDS ARE EXPECTED TO EVENTUALLY FALL BELOW SCA CRITERIA  
BUT ATLANTIC SEAS MAY NOT DROP BELOW 5 FT TIL AT NIGHT.  
 
FRIDAY...POSSIBLE SCA COLD AIR ADVECTION WEST TO NORTHWEST FLOW.  
 
SATURDAY...WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SCA THRESHOLDS.  
 

 
   
CLIMATE
 
 
FOR OUR EIGHT CLIMATE SITES, HERE ARE THE RECORD HIGH TEMPERATURES  
FOR NOVEMBER 24TH AND THE MOST RECENT YEAR OF OCCURRENCE.  
 
RECORDS HAVE OCCURRED. DETAILS IN THE RER'S.  
 
RECORD HIGHS 11/24:  
 
ACY: 72 SET IN 1999  
PHL: 71 SET IN 1979  
ILG: 73 SET IN 1979  
ABE: 69 SET IN 1931  
TTN: 71 SET IN 1979  
GED: 75 SET IN 1992  
RDG: 69 SET IN 1979  
MPO: 64 SET IN 1931  
 
RECORD HIGHEST TEMP SO LATE IN THE SEASON (NOV 24)...JUST IN CASE WE  
REACH THIS VALUE.  
 
ACY: 77 12/7/1997  
PHL: 73 12/7/1998 AND LAST OF SEVERAL  
ILG: 75 12/4/1998  
ABE: 72 12/29/1984 AND LAST OF SEVERAL  
TTN: 76 12/7/1998 (LATTER OF TWO)  
GED: 77 12/1/1991 (SHORTER POR)  
RDG: 77 12/29/1984  
MPO: 67 11/29/1990  
 
REGARDING THE MIDWEEK COASTAL STORM BRINGING SNOW TO A LARGE  
PORTION OF OUR REGION, WE HAVE INCLUDED DAILY SNOWFALL RECORDS  
BELOW FOR OUR FOUR PRIMARY CLIMATE SITES THAT HAVE A LONG-STANDING  
UNBROKEN PERIOD OF RECORD (POR) WITH RESPECT TO HISTORICAL  
SNOWFALL DATA.  
 
DAILY SNOWFALL RECORDS:  
 
NOVEMBER 26TH: NOVEMBER 27TH: PERIOD OF RECORD:  
 
ACY: TRACE 1977,1957,1955 1.2 INCHES 1978 1874  
 
PHL: 6.0 INCHES 1898 6.9 INCHES 1949,1938 1872  
 
ILG: 0.1 INCHES 1950 4.5 INCHES 1978 1894  
 
ABE: 1.7 INCHES 1925 7.0 INCHES 1938 1922  
 
OTHER COOPERATIVE SITE SHORTER HISTORICAL RECORD CAN BE FOUND AT  
THE NWS MOUNT HOLLY WEBSITE UNDER NOW DATA.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE  
WEDNESDAY NIGHT FOR PAZ054-055.  
WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE  
WEDNESDAY NIGHT FOR PAZ060>062-101-103-105.  
WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE  
WEDNESDAY NIGHT FOR PAZ070-071-102-104-106.  
NJ...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE  
WEDNESDAY NIGHT FOR NJZ001-007-008.  
WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE  
WEDNESDAY NIGHT FOR NJZ009.  
WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE  
WEDNESDAY NIGHT FOR NJZ010-015.  
DE...NONE.  
MD...NONE.  
MARINE...GALE WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY EVENING  
FOR ANZ431-450>455.  
SMALL CRAFT ADVISORY UNTIL 6 PM EST TUESDAY FOR ANZ450>455.  
SMALL CRAFT ADVISORY UNTIL 6 AM EST TUESDAY FOR ANZ430-431.  
 

 
 

 
SYNOPSIS...FRANCK  
NEAR TERM...ROBERTSON  
SHORT TERM...ROBERTSON  
LONG TERM...DRAG/FRANCK 416  
AVIATION...DRAG/FRANCK/ROBERTSON 416  
MARINE...DRAG/FRANCK/ROBERTSON 416  
CLIMATE...416  
 
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