Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 040612
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
112 AM EST WED MAR 4 2015

.SYNOPSIS...
A WARM FRONT WILL LIFT THROUGH THE AREA OVERNIGHT...FOLLOWED BY A
ARCTIC COLD FRONT DURING THE DAY WEDNESDAY. THE FRONT WILL PUSH TO
OUR SOUTH INTO THURSDAY WHILE LOW PRESSURE DEVELOPS AND MOVES
ALONG THE BOUNDARY. HIGH PRESSURE WILL RETURN TO THE MID ATLANTIC
REGION FOR FRIDAY AND FRIDAY NIGHT. A FRONTAL PASSAGE IS EXPECTED
SATURDAY INTO SATURDAY NIGHT...FOLLOWED BY HIGH PRESSURE AGAIN
SUNDAY INTO SUNDAY NIGHT. ANOTHER FRONTAL PASSAGE IS EXPECTED
MONDAY INTO MONDAY NIGHT.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
THE WINTER WEATHER ADVISORY REMAINS IN EFFECT FOR BERKS COUNTY,
UPPER BUCKS COUNTY, SOMERSET COUNTY AND POINTS NORTH. THE ADVISORY
HAS BEEN DISCONTINUED SOUTH OF THAT LINE WHERE TEMPERATURES ARE
ABOVE FREEZING, MAINLY IN THE MIDDLE AND UPPER 30S.

WE CONTINUE TO EXPECT PATCHY LIGHT RAIN AND DRIZZLE OVERNIGHT
THROUGHOUT OUR FORECAST AREA. SOME OF THE LIGHT RAIN AND DRIZZLE
WILL CONTINUE TO FREEZE UPON CONTACT WITH THE GROUND IN THE
ADVISORY AREA WHERE MANY LOCATIONS WILL REMAIN AT OR BELOW 32
DEGREES THROUGH THE BALANCE OF THE NIGHT.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TODAY/...
WINTER WEATHER ADVISORY CONTINUES INTO THE FIRST PART OF
WEDNESDAY MORNING FOR THE POCONO`S AND FAR NORTHWEST NJ, WHERE
POCKETS OF SUB-FREEZING TEMPS AND FREEZING RAIN WILL PERSIST.
OTHERWISE, WEDNESDAY WILL BE A RELATIVELY QUIET PERIOD IN BETWEEN
TWO WINTER EVENTS.

A COLD FRONT WILL APPROACH FROM THE NORTHWEST IN THE MORNING AND
SLOWLY SAG SOUTHEASTWARD THROUGHOUT THE DAY. EXPECT PERIOD OF RAIN
THROUGHOUT THE DAY FOR MUCH OF THE AREA. THE COVERAGE OF RAIN WILL
BE HIGHEST NEAR THIS FRONTAL BOUNDARY. QPF AMOUNTS WILL BE LIGHT-
LESS THAN A HALF INCH. LEANED TOWARD THE COOLER MET GUIDANCE FOR
TEMPS GIVEN THE PERSISTENT CLOUDS AND PRECIP OVER THE AREA, AS
WELL AS THE END TO THE WAA REGIME WITH WINDS VEERING OUT OF THE
SOUTH AND SOUTHWEST. HIGHS WEDNESDAY RANGE FROM THE MID 30S IN THE
POCONO`S TO THE UPPER 40S IN SOUTHERN DE.

18Z/3 NAM THERMAL PROFILE SUGGEST SLEET AND OR SNOW COULD BEGIN
MIXING WITH ANY RAIN FALLING NEAR SUNSET FROM KRDG TO KABE
NORTHWESTWARD.

&&

.LONG TERM /TONIGHT THROUGH TUESDAY/...
S/WV ENERGY ROUNDING THE BASE OF A MID-LEVEL TROUGH SITUATED OVER
GREAT LAKES WILL GRADUALLY VEER LARGE SCALE FLOW TO THE SOUTHWEST
OVER THE MID-ATLANTIC. THIS WILL SLOW THE ADVANCE OF AN ARCTIC
FRONT MOVING THROUGH THE AREA ON WEDNESDAY AND IT WILL BRIEFLY
BECOME STATIONARY TO OUR SOUTH ON THURSDAY. MEANWHILE...CLOSED
MID-LEVEL LOW EJECTS NEWD OUT OF BAJA CALIFORNIA...ACCOMPANIED BY
SEVERAL SOUTHERN STREAM S/WV DISTURBANCES THAT WILL LEAD TO LOW
PRES DEVELOPMENT ALONG THE NOW STATIONARY FRONT TO OUR SOUTH. THIS
WILL PROMOTE A ROBUST OVERRUNNING REGIME OVER THE MID-ATL... FED
BY BAJA/GMEX MOISTURE AND SUPPORTED BY THE LF QUADRANT OF A
VIGOROUS 250 HPA JET.

THE OPERATIONAL MODELS AND THEIR RESPECTIVE ENSEMBLES HAVE
SIGNALED THIS SCENARIO FOR OVER A WEEK NOW...AND FINALLY APPEAR
MUCH CLOSER TO A CONSENSUS ON THE LOW-LEVEL THERMAL PROFILE...BUT
DIFFERENCES REMAIN IN THEIR DEPICTION OF THE QPF BULLSEYE AND
AMOUNTS. AT THIS TIME...WE FAVOR THE NAM/ECMWF QPF...AND FEEL THE
GFS IS OVERDONE. THIS WOULD PLACE THE MAX QPF BULLSEYE IN THE 00Z
WED THRU 00Z THU TIME FRAME ALONG THE I-95 CORRIDOR. AS COLDER AIR
WORKS IN FROM THE NORTHWEST...WE EXPECT RAIN TO GRADUALLY CHANGE
TO SNOW FROM NORTH TO SOUTH WED NIGHT. KEEP IN MIND THERE IS STILL
SOME DISAGREEMENT ON HOW QUICKLY THE LOW-LEVEL THERMAL PROFILE
COOLS...AS SLPR FIELDS INDICATE THE REGION IS IN A SADDLE...WHICH
IS SUPPORTIVE OF A SLOW COLD FROPA. ATTM...WE EXPECT THE RAIN TO
CHANGEOVER TO SNOW IN THE NORTHWEST AROUND 00Z...AND PERHAPS AS
LATE AS 09Z IN THE LOWER DELMARVA.

AS FAR AS PTYPE AND AMOUNTS...WE`RE EXPECTING 6 TO 8 INCHES OF
SNOW IN THE I-95 CORRIDOR WITH 4 TO 6 INCHES NORTH AND SOUTH OF
THIS AREA. IF A MORE ROBUST WARM NOSE WORKS IN ALOFT...AS
SUGGESTED BY THE NAM...THERE WOULD BE MORE SLEET WHICH WOULD CUT
DOWN ON THE SNOWFALL AMOUNTS. ON THE OTHER HAND...ALTHOUGH OMEGA
IN THE DENDRITIC SNOW GROWTH ZONE IS NOT ROBUST...FGEN IS
INDICATED IN THE MID-LEVELS AND THIS COULD BOOST SNOWFALL TOTALS.
FINALLY...IT IS QUESTIONABLE HOW MUCH DRY AIR AND/OR DOWNSLOPING
DUE A NORTHERLY SURFACE FLOW WILL CUT DOWN ON QPF ACROSS THE
NORTHERN PART OF THE CWA. FURTHER TO THE SOUTH OVER THE
DELMARVA...SNOWFALL TOTALS COULD BE LOWER DUE TO A WARMER THERMAL
PROFILE...IMPLYING A LONGER TRANSITION FROM RAIN TO SNOW.

WITH THIS PACKAGE WE HAVE ISSUED A WINTER STORM WATCH FOR THE
ENTIRE CWA FROM WED NIGHT THRU THU EVE...WITH THE GREATEST
UNCERTAINTY IN MEETING SNOWFALL CRITERIA NORTH OF THE I-78
CORRIDOR AND OVER FAR SOUTHEAST NJ AND THE SOUTHERN DELMARVA. WE
EXPECT THE THURSDAY MORNING RUSH HOUR TO BE PARTICULARLY
IMPACTED...ESPECIALLY IN THE I-95 CORRIDOR...WHERE SNOW COULD FALL
MODERATE AT TIMES.

SNOW IS EXPECTED TO END THURSDAY EVENING...AS THE MID-LEVEL
TROUGH APPROACHES FROM THE WEST...AND PUSHES THE SYSTEM OFFSHORE.
MUCH COLDER AIR WILL FILTER IN THU NIGHT WITH MIN TEMPS AROUND 20
DEGREES BELOW NORMAL. OTHERWISE...GENERALLY FAIR WEATHER IS
EXPECTED THRU THE WEEKEND... WITH A WEAK COLD FRONTAL PASSAGE
LIKELY LATER SAT OR EARLY SUNDAY. THE FRONT HAS LIMITED MOISTURE
ATTM...SO THE FORECAST IS KEPT DRY. TEMPS MAY ACTUAL APPROACH
SEASONABLE LEVELS ON SUNDAY. EARLY NEXT WEEK...THERE IS A LOT OF
UNCERTAINTY WITH REGARD TO THE EVOLUTION OF BOTH NORTHERN AND
SOUTHERN STREAM ENERGY...AND THE DEGREE OF PHASING THAT TAKES
PLACE BETWEEN THE TWO OVER THE ERN CONUS. FOR NOW WE KEPT THIS
PART OF THE FORECAST DRY AS WELL.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

OVERNIGHT...MVFR VARIABLE IFR CONDS IN -RA AND -DZ CHANGING WITH
LIGHT SOUTHEAST TO SOUTH SURFACE WINDS BUT LLWS WITH STRONG WINDS
NEAR THE INVERSION AROUND 2000 FT. PLS SEE TAFS FOR DETAILS.

WEDNESDAY...MVFR OR IFR CONDS IN INTERMITTENT RAIN/DRIZZLE/FOG.
POTENTIAL FOR A PERIOD OF LIFR FOG IN THE FRONTAL BOUNDARY DURING
THE MORNING AS WARM AIR TEMPORARILY LAYS CLOSE TO THE NEAR
FREEZING SNOW AND ICE SURFACES. SLEET/SNOW SHOULD BEGIN MIXING
WITH ANY ON GOING RAIN VCNTY KABE AND KRDG AROUND 23Z.

OUTLOOK...
WED NIGHT AND THURSDAY...RAIN WILL GRADUALLY CHANGEOVER TO
SLEET... THEN SNOW ACROSS THE TERMINALS FROM NORTH TO SOUTH. THE
CHANGEOVER IS EXPECTED TO OCCUR AT ABE AND RDG BETWEEN AROUND
23Z/4-01Z/5...AT TTN, PNE, PHL, AND ILG AROUND 03Z/5...AND MIV AND
ACY AROUND 06Z/5. THERE IS STILL SOME UNCERTAINTY AS TO WHAT TIME
THE CHANGE TAKES PLACE. EXPECT MVFR CONDITIONS WITH IFR POSSIBLE
IN SNOW AND LOW CEILINGS...PARTICULARLY AT TTN, PNE, PHL, AND ILG.

THURSDAY NIGHT AND FRIDAY...SNOW WILL GRADUALLY END FROM WEST TO
EAST ACROSS THE TERMINALS THU EVENING. EXPECT MVFR/IFR CONDITIONS
TO IMPROVE TO VFR BY THURSDAY NIGHT AND REMAIN VFR THRU FRIDAY.

SATURDAY AND SUNDAY...MVFR POSSIBLE IN LOW CLOUDS AND SHRA/SNSH
WITH THE PASSAGE OF A COLD FRONT LATE SAT INTO EARLY SUNDAY...
OTHERWISE VFR CONDITIONS EXPECTED.

&&

.MARINE...
SOUTHERLY WINDS WILL INCREASE THIS EVENING. ALTHOUGH STORM-FORCE
WINDS WILL BE LOCATED ONLY 1,000 FT AGL AND GALE-FORCE WINDS 200
FT AGL, A STRONG INVERSION WILL NOT BE FAVORABLE FOR THESE WINDS
TO MIX DOWN TO THE SURFACE. HOWEVER, THE PRESSURE GRADIENT
TIGHTENS ENOUGH FOR SUSTAINED WINDS TO APPROACH SCA CRITERIA
TONIGHT. SEAS ARE ALSO FORECAST TO BUILD TO 4-5 FT OVERNIGHT.
THEREFORE, A SCA WAS ISSUED FOR THE COASTAL WATERS.

THE WINDS TURN MORE WESTERLY ON WEDNESDAY AND DECREASE JUST AHEAD
OF A COLD FRONT. DO NOT EXPECT SCA GUSTS. HOWEVER, ELEVATED SEAS
NEAR 5 FT MAY LINGER INTO THE MORNING. CONFIDENCE WASN`T HIGH
ENOUGH TO EXTEND THE ADVISORY AT THIS POINT.

OUTLOOK...
WED NIGHT THRU FRIDAY...WINDS AND SEAS WILL LIKELY MEET SCA
THRESHOLDS WED NIGHT THRU AT LEAST FRIDAY MORNING.

FRIDAY AFTERNOON THRU SUNDAY...WINDS AND SEAS ARE EXPECTED TO
REMAIN BELOW SCA THRESHOLDS.

&&

.HYDROLOGY...
PLEASE MONITOR LATEST QPF FCSTS FROM WPC AND MARFC.

TUESDAY FORECAST CYCLES CAME IN WETTER FOR WEDNESDAY AFTERNOON
AND WEDNESDAY NIGHT, ESPECIALLY SOUTH OF PHILLY. THE GFS, FOR
INSTANCE, HAS 0.75 TO ABOUT 1.00 OF LIQUID ACROSS THE DELMARVA AND
SOUTHERN NJ, SOUTH OF THE I295 CORRIDOR. WE`RE ONCE AGAIN TAKING
NOTICE.

A CHANGEOVER TO SLEET OR SNOW ISN`T EXPECTED TO OCCUR UNTIL EARLY
THURSDAY MORNING.

WHILE THERE ISN`T MUCH OF A SNOWPACK ACROSS THE SOUTHERN HALF OF
OUR CWA, THE GROUND IS FROZEN, AND ANY RUNOFF WILL BE VERY
EFFICIENT.

IF THE 0.75 TO 1.00 MATERIALIZES, WE FEEL NUISANCE POOR DRAINAGE
AND LOW LYING FLOODING WILL BE THE MOST LIKELY OUTCOME. MODELED
SOLUTIONS SUGGEST WE WOULD NEED ABOUT 2.50 INCHES OF LIQUID,
EITHER IN THE FORM OF ALL RAIN OR RAIN AND MELTING SNOW TO HAVE
OUR SOUTHERN CREEKS AND STREAMS LEAVE THEIR BANKS.

WITH MORE SNOW OR SLEET EXPECTED ACROSS THE NORTHERN HALF OF THE
CWA, WE`RE NOT CONCERNED ABOUT FLOODING THERE.

WITH THE RAINFALL, THE FLOW ON AREA CREEKS AND STREAMS WILL
INCREASE. THIS COULD START TO MOVE ICE, AND IN A WORST CASE
SCENARIO, CREATE RESTRICTIONS OR JAMS.

CONTINUE TO MONITOR THE FORECAST. KEEP IN MIND THAT SNOWMELT AND
THE WARMER TEMPERATURES EXPECTED TOMORROW, BY THEMSELVES, WOULD
NOT CAUSE FLOODING. THE AMOUNT OF RAIN THAT WE RECEIVE WILL BE THE
DETERMINING FACTOR.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...WINTER WEATHER ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR
     PAZ060>062-105.
     WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY EVENING
     FOR PAZ054-055-060>062-101>106.
     WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING
     FOR PAZ070-071.
     WINTER WEATHER ADVISORY UNTIL 9 AM EST THIS MORNING FOR PAZ054-
     055.
NJ...WINTER WEATHER ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR
     NJZ007>010.
     WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY EVENING
     FOR NJZ001-007>010-012-015.
     WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING
     FOR NJZ021>025.
     WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING
     FOR NJZ013-014-016>020-026-027.
     WINTER WEATHER ADVISORY UNTIL 9 AM EST THIS MORNING FOR NJZ001.
DE...WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING
     FOR DEZ002>004.
     WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING
     FOR DEZ001.
MD...WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING
     FOR MDZ015-019-020.
     WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING
     FOR MDZ008-012.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR
     ANZ450>455.

&&

$$

SYNOPSIS...FRANCK
NEAR TERM...DRAG/IOVINO/KLEIN
SHORT TERM...DRAG/KLEIN
LONG TERM...FRANCK
AVIATION...DRAG/FRANCK/KLEIN
MARINE...DRAG/FRANCK/KLEIN
HYDROLOGY...KRUZDLO



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