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Area Forecast Discussion
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000
FXUS61 KPHI 021323
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
823 AM EST MON MAR 2 2015

.SYNOPSIS...
A COLD FRONT WAS MAKING ITS WAY THROUGH OUR REGION EARLY THIS
MORNING. HIGH PRESSURE CENTERED OVER IOWA WILL BUILD TO THE EAST
AND IT IS FORECAST TO PASS OFF THE MIDDLE ATLANTIC COAST ON
TUESDAY. A WARM FRONT IS EXPECTED TO LIFT THROUGH OUR AREA ON
TUESDAY EVENING. A COLD FRONT FROM THE NORTHWEST IS ANTICIPATED TO
ARRIVE ON WEDNESDAY AFTERNOON. THE BOUNDARY SHOULD SINK SLOWLY TO
THE SOUTHEAST ON WEDNESDAY NIGHT AND THURSDAY AS LOW PRESSURE
RIDES ALONG IT. ANOTHER ARCTIC HIGH IS FORECAST TO BUILD ACROSS
OUR REGION FROM THE WEST FOR FRIDAY INTO SATURDAY. A WARM FRONT
MAY BEGIN TO APPROACH FROM THE SOUTHWEST ON SUNDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
820 AM UPDATE... WINTER WX ADVISORY FOR THE DELMARVA AND
SOUTHEASTERN NJ WERE CANCELLED WITH PRECIP FINALLY OFFSHORE.
THERE WILL STILL BE SOME ICY SPOTS OVER THE NEXT COUPLE OF HOURS
ON UNTREATED SURFACES. SCT SNOW SHOWERS AND FLURRIES WERE ALSO
ADDED TO THE MORNING FORECAST FOR NORTHEASTERN PA AND NORTHERN NJ.

PREVIOUS DISCUSSION...
A COLD FRONT WILL APPROACH THE AREA FROM THE WEST EARLY THIS
MORNING, AND PROGRESS ACROSS AND OFFSHORE AROUND OR SHORTLY AFTER
SUNRISE. GUIDANCE CONTINUES TO INDICATE SOME LIGHT PRECIPITATION
DEVELOPING ACROSS SOUTHERN NEW JERSEY AND THE SOUTHERN PORTIONS OF
THE DELMARVA THROUGH AROUND SUNRISE AS THE FRONT APPROACHES AND A
SHORT WAVE ALOFT HELPS CREATE SOME SHOWERS. ALSO, SOME PATCHY
FOG/DRIZZLE WILL CONTINUE FOR A FEW MORE HOURS THIS MORNING UNTIL
THE COLD FRONT MOVES THROUGH THE AREA. WE HAVE CANCELLED THE
ADVISORY FOR EVERYONE EXCEPT FOR THE AREAS ACROSS SOUTHERN NEW
JERSEY AND THE SOUTHERN PORTIONS OF THE DELMARVA WHERE THERE
REMAINS THE THREAT FOR SOME FREEZING RAIN/SLEET THIS MORNING.

TEMPERATURES ARE AT OR BELOW FREEZING FOR MOST AREAS THIS
MORNING. TEMPERATURES WILL RISE THROUGH THE DAY WITH SUNSHINE
RETURNING, BUT WILL REMAIN BELOW NORMAL EVERYWHERE.

ONCE THE FRONT MOVES THROUGH THE AREA, ALL PRECIPITATION WILL END
AND SKIES WILL BEGIN TO PARTIALLY CLEAR BEHIND IT. ALSO, WEST-
NORTHWEST WINDS WILL BECOME QUITE GUSTY BEHIND THE FRONT, GUSTING
AROUND 25-30 MPH AT TIMES THROUGH THE DAY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
HIGH PRESSURE BEGINS TO MOVE INTO THE AREA THIS EVENING, BEFORE
CENTERING ITSELF ACROSS THE AREA OVERNIGHT. SKIES WILL CLEAR OUT
THIS EVENING, ALTHOUGH SOME HIGH LEVEL CLOUD COVER MAY RETURN
OVERNIGHT. WIND GUSTS WILL HAVE DROPPED OFF BY THE EVENING,
ALTHOUGH A STEADY BREEZE WILL REMAIN THROUGH THE EVENING, BEFORE
BECOMING LIGHT AND VARIABLE OVERNIGHT. WITH MOSTLY CLEAR SKIES AND
LIGHT WINDS, TEMPERATURES SHOULD BE ABLE TO DROP WELL BELOW NORMAL
OVERNIGHT.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
THERE IS NOT MUCH CHANGE REGARDING THE FORECAST FOR TUESDAY INTO
WEDNESDAY.

PRECIPITATION IS EXPECTED TO OVERSPREAD OUR REGION QUICKLY FROM
THE WEST ON TUESDAY AFTERNOON. THE FORECAST TEMPERATURE PROFILES
SUGGEST THAT THE PRECIPITATION WILL BEGIN AS SNOW IN MOST
LOCATIONS WITH PERHAPS SLEET AT THE START IN OUR FAR SOUTHERN
COUNTIES.

STRONG WARM ADVECTION IS ANTICIPATED ALOFT FROM TUESDAY AFTERNOON
INTO TUESDAY EVENING. WARMING AT THE SURFACE WILL LAG A BIT. THERE
SHOULD BE A GRADUAL TRANSITION FROM A WINTRY MIX TO RAIN FROM
SOUTH TO NORTH. HOWEVER, TRAPPED COLD AIR IN OUR FAR NORTHERN
COUNTIES COULD RESULT IN SEVERAL HOURS OF FREEZING RAIN THERE ON
TUESDAY NIGHT INTO EARLY WEDNESDAY MORNING. OUR LATEST PROJECTIONS
FOR TUESDAY INTO TUESDAY NIGHT BRING 1 TO 3 INCHES OF SNOW ACROSS
OUR NORTHERN COUNTIES AND LESS THAN AN INCH TO OUR CENTRAL AND
SOUTHERN COUNTIES WHERE ACCUMULATION MAY BE CUT DOWN BY THE
PRESENCE OF SLEET. FREEZING RAIN SHOULD CAUSE A PROBLEM ONLY
ACROSS OUR NORTHERN COUNTIES WHERE UP TO A TENTH OF AN INCH OF ICE
MAY ACCUMULATE ON TOP OF THE NEW SNOWFALL.

IT CONTINUES TO APPEAR AS THOUGH THE PRECIPITATION WILL CHANGE TO
ALL RAIN FOR WEDNESDAY. A BIT OF DRYING MAY BEGIN TO WORK ITS WAY
DOWN FROM THE NORTHWEST ON WEDNESDAY AFTERNOON. IT SEEMS POSSIBLE
THAT SOME LOCATIONS, ESPECIALLY IN THE CENTRAL AND SOUTHERN PARTS
OF OUR FORECAST AREA MAY PICK UP A HALF INCH TO AN INCH OF
RAINFALL DURING THE PERIOD. THE RAIN IN COMBINATION WITH SNOWMELT
AND THE FROZEN GROUND, ALONG WITH ICE MOVEMENT IN AREA WATERWAYS
MAY RESULT IN A BIT OF MINOR FLOODING.

THE MODELS ARE COMING TOGETHER ON THE IDEA OF A WAVE OF LOW
PRESSURE RIDING ALONG THE SLOW MOVING COLD FRONT. IT SHOULD BRING
US ANOTHER ROUND OF PRECIPITATION FOR WEDNESDAY NIGHT INTO
THURSDAY. AS COLD AIR FILTERS DOWN INTO OUR REGION FROM THE NORTH
AND NORTHWEST, THE PRECIPITATION TYPE WILL LIKELY TRANSITION TO
SNOW. THERE IS ENOUGH SPREAD IN THE GUIDANCE SOLUTIONS TO MAKE THE
DETAILS A BIT UNCERTAIN AT THIS POINT. HOWEVER, IT IS LOOKING
INCREASINGLY POSSIBLE THAT WE WILL SEE ACCUMULATING SNOW IN MUCH
OF OUR FORECAST AREA AT THAT TIME.

HIGH PRESSURE FROM THE WEST IS ANTICIPATED TO BRING DRY WEATHER
AND BELOW NORMAL TEMPERATURES FOR THURSDAY NIGHT INTO SATURDAY
NIGHT.

THE 0000 UTC GFS AND THE 0000 UTC ECMWF ARE BOTH SUGGESTING THE
POTENTIAL FOR PRECIPITATION TO BE NEARING OUR REGION FROM THE
SOUTHWEST ON SUNDAY DUE TO A WEAK AREA OF LOW PRESSURE ALONG WITH
A WARM FRONT.

&&

.AVIATION /13Z MONDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

IFR CONDITIONS PERSIST ACROSS THE TAF SITES EARLY THIS MORNING.
AS A FRONTAL BOUNDARY MAKES ITS WAY ACROSS THE ARE AROUND
DAYBREAK, CONDITIONS SHOULD IMPROVE TO MVFR THEN VFR. ONCE VFR
CONDITIONS RETURN, THEY SHOULD REMAIN ACROSS THE TAF SITES THROUGH
THE PERIOD.

LIGHT WINDS THIS MORNING WILL INCREASE BEHIND THE FRONTAL
BOUNDARY OUT OF THE WEST-NORTHWEST. GUSTY WINDS ARE EXPECTED TODAY
WITH GUSTS AROUND 20-25 KNOTS EXPECTED. GUSTS SHOULD DROP OFF
AROUND SUNSET, THROUGH A STEADY BREEZE WILL LIKELY REMAIN THROUGH
THE EVENING BEFORE BECOMING LIGHT AND VARIABLE OVERNIGHT.

OUTLOOK...

TUESDAY...CONDITIONS LOWERING TO MVFR AND IFR IN THE AFTERNOON,
AS SNOW AND SLEET BUILD INTO OUR REGION.

TUESDAY NIGHT...MVFR AND IFR CONDITIONS WITH A WINTRY MIX OF
PRECIPITATION CHANGING TO RAIN FROM SOUTH TO NORTH. THE RAIN MAY
BE MODERATE TO HEAVY AT TIMES. LOW LEVEL WIND SHEAR IS POSSIBLE
DUE TO A SOUTHWESTERLY LOW LEVEL JET THAT IS FORECAST TO DEVELOP
OVERHEAD.

WEDNESDAY...MVFR AND IFR CONDITIONS IN RAIN. THE RAIN MAY BE
MODERATE TO HEAVY AT TIMES, ESPECIALLY SOUTH OF KPHL.

WEDNESDAY NIGHT...MVFR AND IFR CONDITIONS IN RAIN, MIXING WITH
THEN CHANGING TO SNOW FROM NORTH TO SOUTH.

THURSDAY...MVFR AND IFR CONDITIONS IN MORNING SNOW. CONDITIONS
IMPROVING GRADUALLY TO VFR WITH A LESSING CHANCE OF SNOW IN THE
AFTERNOON.

THURSDAY NIGHT AND FRIDAY...MAINLY VFR.

&&

.MARINE...
SMALL CRAFT ADVISORY REMAINS IN EFFECT ON THE WATERS FOR TODAY
INTO TONIGHT AS WINDS WILL INCREASE BEHIND A FRONTAL BOUNDARY THAT
WILL CROSS THE WATERS THIS MORNING. AN OCCASIONAL GUSTY AROUND
34/35 KNOTS IS POSSIBLE AROUND MIDDAY, BUT WE ARE NOT CONFIDENT ON
GALE FORCE GUSTS BEING FREQUENT ENOUGH TO NEED A WARNING AT THIS
TIME. AS HIGH PRESSURE BUILDS INTO THE AREA OVERNIGHT, WINDS WILL
DIMINISH BELOW ADVISORY LEVELS.

OUTLOOK..

TUESDAY...NO MARINE HEADLINES ARE ANTICIPATED.

TUESDAY NIGHT AND WEDNESDAY...A SMALL CRAFT ADVISORY MAY BE
NECESSARY DUE TO A GUSTY SOUTH TO SOUTHWEST WIND.

WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...A SMALL CRAFT ADVISORY
MAY BE NEEDED TO DUE TO GUSTY NORTHWEST WIND.

FRIDAY...NO MARINE HEADLINES ARE ANTICIPATED.

&&

.HYDROLOGY...
THE NEXT ROUND OF PRECIPITATION IS FORECAST TO MOVE INTO OUR AREA
ON TUESDAY AFTERNOON AND IT WILL CONTINUE INTO WEDNESDAY AND
THURSDAY.

THIS MIDWEEK EVENT APPEARS TO START AS A WINTRY MIX BEFORE
CHANGING OVER TO RAIN AS TEMPERATURES RISE WELL ABOVE FREEZING ON
WEDNESDAY. THE QPF AMOUNTS FOR TUESDAY INTO WEDNESDAY FAVOR THE
0.25 TO 0.75 INCH RANGE.

THE COMBINATION OF THE BRIEF WARM-UP ON WEDNESDAY, LOCALLY
MODERATE TO HEAVY RAINFALL, MELTING SNOW, A FROZEN GROUND, AND
ABOVE NORMAL ICE IN CREEKS, STREAMS, AND RIVERS COULD LEAD TO
INCREASED RUNOFF AND POSSIBLE FLOODING. WHERE THE DEPTH OF THE
SNOWPACK IS GREATEST (IN NE PA AND N NJ), RAPID SNOWMELT IS NOT
EXPECTED SINCE TEMPS WILL NOT RISE AS SHARPLY AS IN AREAS TO THE
SOUTH.

INCREASED FLOW 0N AREA CREEKS, STREAMS, AND RIVERS COULD ALSO
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
WARMTH BY THEMSELVES TYPICALLY DO NOT CAUSE FLOODING. THE AMOUNT
OF RAIN THAT WE RECEIVE WILL BE THE DETERMINING FACTOR.

THE RAIN IS FORECAST TO CHANGE BACK TO SNOW ON WEDNESDAY NIGHT.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EST TUESDAY FOR ANZ430-431-
     450>455.

&&

$$
SYNOPSIS...IOVINO
NEAR TERM...KLEIN/ROBERTSON
SHORT TERM...ROBERTSON
LONG TERM...IOVINO
AVIATION...IOVINO/ROBERTSON
MARINE...IOVINO/ROBERTSON
HYDROLOGY...STAFF



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