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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
735 PM EST TUE MAR 3 2015

.SYNOPSIS...
MIXED PRECIPITATION WILL CHANGE TO AN EXTENDED PERIOD OF FREEZING
RAIN THIS EVENING THROUGH LATE TONIGHT. THE PRECIPITATION WILL
LIKELY TURN TO RAIN ACROSS SOUTHERN AND FAR WESTERN SECTIONS
EARLY WEDNESDAY. COLDER TEMPERATURES WILL FOLLOW FOR THE LATTER
PART OF THE WEEK...AND STEADY SNOW WILL RETURN WEDNESDAY EVENING
INTO THURSDAY AS A WAVE OF LOW PRESSURE RIPPLES ALONG A NEARLY
STATIONARY FRONT THAT WILL BE DRAPED JUST TO OUR SOUTH. HIGH
PRESSURE AND COLD AIR WILL RETURN FOR FRIDAY INTO THE FIRST PART
OF THE WEEKEND.

&&

.NEAR TERM /UNTIL 10 PM THIS EVENING/...
LL JET AND ASSOC PUSH OF WARM AIR ALOFT HAS CHANGED PRECIP TO
PLAIN RAIN OVR PARTS OF WARREN AND SOMERSET COUNTY AS OF 23Z.
MEANWHILE...MIXED FZRA AND IP CONTINUE TO FALL ACROSS THE REST OF
CENTRAL PA. MDL SOUNDINGS...AS WELL AS LATEST HRRR
OUTPUT...CONTINUE TO INDICATE THE LOW LVL COLD AIR WILL ERODE FROM
WEST TO EAST OVERNIGHT WITH THE LAST OF THE FZRA ENDING ACROSS THE
HIGH TERRAIN NE OF KIPT BTWN 06Z-09Z. 

BASED ON ASOS ICE ACCRETIONS THRU 23Z AND UPSTREAM RADAR
TRENDS...CONFIDENCE IN WARNING TYPE ICE ACCUMS ACROSS THE N MTNS
IS WANING. ACROSS THE LAUREL HIGHLANDS...KJST ALREADY REPORTED 0.36
INCHES OF ICE ACCRETION THRU 23Z...BUT TRANSITION TO RAIN
UNDERWAY WITH TEMP AT 32F. WILL LET THE CURRENT WARNINGS/ADVISORIES
RIDE FOR NOW...BUT WILL LKELY BE ABLE TO CANCEL THE WESTERN
COUNTIES LATER THIS EVENING.

&&

.SHORT TERM /10 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
PRECIP SHOULD TAPER OFF ACROSS THE NORTHERN COUNTIES LATE
TONIGHT...AS COLD FRONT SAGS SOUTH INTO THE REGION. FURTHER
SOUTH...PRECIP WILL CONTINUE TO FALL ALONG AXIS OF LL JET AND
PLUME OF HIGHER PWATS. HOWEVER...ALL NEAR TERM MDL DATA SUGGESTS
A CHANGEOVER TO PLAIN RAIN...AS LOW LVL COLD AIR IS SCOURED OUT.

&&

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
AN ACTIVE LATE-WINTER PRECIPITATION PATTERN WILL IMPACT CENTRAL
PA THROUGH MIDWEEK FOLLOWED BY WHAT IS HOPEFULLY THE LAST SHOT OF
ARCTIC AIR FOR THE SEASON THURSDAY INTO FRIDAY. THE PATTERN SHOULD
DRY OUT LATE IN THE WEEK THROUGH THE UPCOMING WEEKEND WITH HIGH
PRESSURE IN CONTROL MOST OF THE TIME. THE GENERAL MODEL AND ENSEMBLE
CONSENSUS IS TO MAINTAIN A RIDGE IN THE WEST AND TROUGH IN THE
EAST THROUGH THE WEEKEND WITH SOME SIGNS OF A PATTERN SHIFT BY THE
MIDDLE OF NEXT WEEK WITH TROUGHING FCST TO DEVELOP ALONG THE WEST
COAST. BELOW NORMAL TEMPS SHOULD MODERATE CLOSER TO NORMAL EARLY
NEXT WEEK WITH SOME HINTS AT EVEN WARMER TEMPS LATER NEXT WEEK.

MODELS CONTINUE TO SHOW AN AMPLIFIED AND MOIST SW FLOW ALOFT AND
JET ENTRANCE REGION DYNAMICS SUPPORTING A BROAD STRIPE OF PCPN
ALONG A WELL DEFINED BAROCLINIC ZONE AHEAD OF PHASING UPPER LEVEL
ENERGY OVER THE DSW/ROCKIES ON WED AND MOVING EWD THROUGH THE OH
VLY AND MID ATLC ON THURSDAY. SEVERAL WAVES OF LOW PRESSURE ARE
FCST TO DEVELOP AND MOVE ENEWD ALONG A SW-NE ORIENTED COLD FRONT
WHICH SHOULD PROGRESS AND SETTLE SEWD THROUGH THE MID ATLC REGION
BY EARLY THURS...AS ARCTIC HIGH PRESSURE BUILDS INTO THE UPPER
PLAINS. AMPLE MOISTURE IS FCST BY THE MODELS TO MOVE INTO A
DEEPENING COLD SECTOR ALONG/NORTH OF THE SEWD-ADVANCING COLD
FRONTAL BOUNDARY WHICH COULD RESULT IN A LATE SEASON HEAVY SNOW
EVENT FOR SOUTH CENTRAL PA WED NGT INTO THURS. THERE ARE MODEL
DIFFERENCES WITH THE TIMING OF THE FRONT WHICH IS LKLY TIED TO THE
CONSOLIDATION OF SHORTWAVE ENERGY UPSTREAM. THAT SAID...THE
CONSENSUS FCST AXIS OF MAX QPF /0.50 INCH OR GREATER/ HAS BEEN
FAIRLY CONSISTENT PAINTED OVER THE SRN 1/3 OF THE CWA. SIMILAR TO
YESTERDAY...USED A MULTI MODEL BLEND WITH PSEUDO BIAS CORRECTION
FACTOR TO DERIVE GRIDDED QPF AMTS WHICH GENERALLY RANGE FROM 0.25
TO 0.75 INCHES ACROSS THE SRN 1/2 OF THE CWA. THE COLUMN WILL BE
IN A STATE OF TRANSITION AND COOLING DOWN FROM NW TO SE WED-WED
NGT AS THE COLD FRONT PUSHES SOUTHEAST ACROSS THE AREA. THIS
SHOULD SUPPORT A TRANSITION FROM RAIN TO SNOW. A PERIOD OF SLEET
MAY IMPACT FCST SNOW ACCUMULATIONS WITH THE DURATION A KEY FACTOR
IN THIS FCST. WITH INCREASING CONFIDENCE AND GREATEST RISK IN THE
POTENTIAL FOR HEAVY SNOW/6+ INCHES...WHICH IS SUPPORTED BY ROBUST
WPC ENSEMBLE AS WELL AS THE GEFS MEAN...HAVE ISSUED A WINTER STORM
WATCH FOR THE SOUTH-CENTRAL COUNTIES FROM WEDNESDAY EVENING
THROUGH THURSDAY EVENING. 

WHAT IS HOPEFULLY THE LAST SHOT OF ARCTIC AIR THIS SEASON SHOULD
ARRIVE BEHIND THE COLD FRONT. FRIDAY MORNING LOWS ARE LKLY TO BE
20-30F BELOW NORMAL WITH SINGLE DIGIT LOWS +/- ZERO DEGREES. SUCH
READINGS MAY BREAK DAILY RECORDS.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
A WARM FRONT LIFTING NE FROM THE OH VLY WILL KEEP A LARGE
AREA OF FREEZING RAIN AND SLEET ACROSS MOST OF THE AREA THIS
EVENING. JST WARM ENOUGH FOR JUST RAIN...BUT GROUND AND OBJECT
TEMPS LIKELY STILL COLD. THE OTHER FACTOR OVERNIGHT WILL BE LLWS.

THE PRECIPITATION WILL LIKELY GO OVER TO JUST RAIN LATE TONIGHT
FOR A SHORT TIME. MANY AREAS MAY JUST SEE NOTHING ONCE THE
STRONGER WARM ADVECTION SHUTS OFF.

FOR WED...RAIN WILL GO BACK TO SNOW FROM NW TO SE. HARD TO SEE
CONDITIONS BEING VERY GOOD.

VERY COLD LOW LEVEL AIR WILL BE ADVECTED BACK TO THE SOUTH LATE
WED INTO THU. A SERIES OF WEAK LOW PRESSURE SYSTEMS WILL TRACK 
ALONG THE COLD FRONT FROM LATE WED INTO THU...LIKELY GIVING
AT LEAST SOUTHERN PA SOME SNOW. THE COMBINATION OF INCREASING
WINDS...SNOW...AND FALLING TEMPERATURES WILL LIKELY RESULT IN
POOR CONDITIONS FOR AVIATION.

IMPROVING CONDITIONS WILL SET IN FOR FRIDAY INTO MONDAY...AS COLD
HIGH PRESSURE BUILDS INTO THE AREA.

OUTLOOK...

WED NIGHT...SIG REDUCTIONS IN SNOW DEVELOPING MAINLY ACROSS THE
SOUTH.

THU...SLOWLY IMPROVING CONDITIONS...LINGERING MVFR NW AND SE.

FRI-SAT...MAINLY VFR.

SUN...MVFR WITH CHC -SHSN MAINLY NORTH AND WEST. VFR SE.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 7 AM EST WEDNESDAY FOR PAZ004-
010-017-019-024>028-033>036-042-045-046-049>053-056>059-
063>066.
WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY 
EVENING FOR PAZ024>028-033>036-056>059-063>066.
WINTER STORM WARNING UNTIL 7 AM EST WEDNESDAY FOR PAZ005-006-
011-012-018-037-041.

&&

$$
SYNOPSIS...DEVOIR
NEAR TERM...DEVOIR/FITZGERALD
SHORT TERM...DEVOIR
LONG TERM...STEINBUGL
AVIATION...MARTIN

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