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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 040115
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
815 PM EST TUE MAR 3 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 WEDNESDAY MORNING/...
-- Changed Discussion --
AFTN FORECAST LOOKS BASICALLY ON TRACK SO LITTLE CHANGE EXPECTED
FOR THE 930 PM ESTF.

ACCUMULATIVE SLEET, ESPECIALLY IN EASTERN PA OF THE LEHIGH VALLEY
DOWN INTO PHILADELPHIA`S WESTERN SUBURBS AND ALSO CENTRAL AND
NORTHERN NEW JERSEY WHERE THERE ARE MANY REPORTS OF 1/2 TO 1 INCH
OF PURE SLEET LATE TODAY WITH ADDITIONAL 1 INCH OR MORE OF SNOW N
OF I78. ASSOCIATED ACCIDENTS SNARLED THE EVENING COMMUTE IN PARTS
OF E PA...AND NORTHERN NJ BASICALLY NW OF I-95.

STRONG WINDS ALOFT WILL NOT PUNCH THROUGH THE STRONG INVERSION OF
TEMPS NEARING 10-11C AT 2000 FT SO OVERNIGHT WARMING WILL BE MINIMAL
AND BASICALLY THE SOUTHERLY FLOW IS DRAWING ON WET BULB MODIFIED
POLAR AIR.

MUCH OF THE RAIN RATE I95 EWD HAS BEEN HEAVY ENOUGH FOR CONSIDERABLE
RUNOFF AND ICE ACCRETION WHILE EXISTING IS NOT MAJOR, SO FAR.

ROAD TEMPS IN DELAWARE AS OF 8 PM ARE GENERALLY 33F OR HIGHER
DESPITE COLDER AIR TEMPS AND ONLY 32F ALONG THE BORDER WITH PA.

MUCH OF THE COASTAL PLAIN IS FORECAST TO RISE INTO THE 40S OVERNIGHT
WITH A LIGHT SOUTHEAST WIND BECOME A SOUTHWEST WIND. READINGS ARE
EXPECTED TO BE MAINLY IN THE UPPER 20S TO LOWER 30S IN AREAS TO
THE NORTHWEST OF THE INTERSTATE 95 CORRIDOR.

OVERALL, IT APPEARS A BREAK IS AT HAND WITH INTMT PCPN OVERNIGHT...
RAIN EXCEPT LIGHT FREEZING RAIN NEAR I78 NORTHWARD.

WILL RESEND THE ADVISORY INFORMATION AT 915 PM AFTER A QUICK LOOK
AT 00Z/4 NAM.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
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 /WEDNESDAY NIGHT 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 /01Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

TONIGHT...ICING LAYER IS THINNING BELOW 5000 FT AS WARMER AIR MOVES
NORTHEAST AND WORKS DOWNWARD. DEICING NEEDS SHOULD CONTINUE FOR
SEVERAL MORE HOURS KRDG/KABE/KTTN AND POSSIBLY EVEN KPHL AREA.

MVFR VARIABLE IFR CONDS IN FZRA CHANGING TO RAIN FROM SOUTH TO NORTH
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.
-- End Changed Discussion --

&&

.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...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...WINTER WEATHER ADVISORY UNTIL 6 AM EST WEDNESDAY FOR
     PAZ060>062-105.
     WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
     EVENING FOR PAZ054-055-060>062-101>106.
     WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
     EVENING FOR PAZ070-071.
     WINTER WEATHER ADVISORY UNTIL 1 AM EST WEDNESDAY FOR PAZ070-
     071-101>104-106.
     WINTER WEATHER ADVISORY UNTIL 9 AM EST WEDNESDAY FOR PAZ054-
     055.
NJ...WINTER WEATHER ADVISORY UNTIL 6 AM EST WEDNESDAY FOR
     NJZ007>010.
     WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
     EVENING FOR NJZ001-007>010-012-015.
     WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR
     NJZ021>025.
     WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
     EVENING FOR NJZ021>025.
     WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
     EVENING FOR NJZ013-014-016>020-026-027.
     WINTER WEATHER ADVISORY UNTIL 1 AM EST WEDNESDAY FOR
     NJZ012>020-027.
     WINTER WEATHER ADVISORY UNTIL 9 AM EST WEDNESDAY FOR NJZ001.
DE...WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR
     DEZ002.
     WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
     EVENING FOR DEZ002>004.
     WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
     EVENING FOR DEZ001.
     WINTER WEATHER ADVISORY UNTIL 1 AM EST WEDNESDAY FOR DEZ001.
MD...WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR
     MDZ015-019-020.
     WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
     EVENING FOR MDZ015-019-020.
     WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY
     EVENING FOR MDZ008-012.
     WINTER WEATHER ADVISORY UNTIL 1 AM EST WEDNESDAY FOR MDZ008-
     012.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST WEDNESDAY FOR ANZ450>455.

&&

$$
SYNOPSIS...FRANCK
NEAR TERM...DRAG/KLEIN 815
SHORT TERM...KLEIN
LONG TERM...FRANCK
AVIATION...DRAG/FRANCK/KLEIN 815
MARINE...DRAG/FRANCK/KLEIN
HYDROLOGY...815