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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 031925
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
225 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/...
AT MID AFTERNOON...PRECIPITATION TRANSITION IS WELL UNDERWAY WITH
INITIAL BURST OF SNOW HAVING PUSHED INTO THE MIDDLE TO LOWER SUSQ
RIVER VALLEY. SNOW AND SLEET WILL HAVE CHANGED OVER TO PRIMARILY
FREEZING RAIN BY EARLY EVENING. HRRR HAS VASCILLATED CONSIDERABLY
FROM HOUR TO HOUR...BOTH WITH QPF AND OVERNIGHT TEMPERATURES...AND
THUS AM BASING THE ICE FORECAST AND ITS ASSOCIATED NEAR- TO
SHORT- TERM CHANGES ON SHORT RANGE ENSEMBES AND IN PARTICULAR SREF
THREATS WHICH CONSECUTIVELY HAVE INDICATED 80% OR GREATER
CONFIDENCE IN .25"+ OF ICE ACCRETION FROM LATE THIS AFTERNOON
THROUGH THE EARLY MORNING HOURS (PAST MIDNIGHT) OF WEDNESDAY.
WILL UPGRADE TO WINTER STORM WARNINGS (THERE IS STILL SOME
SNOW/SLEET BEFORE THE COMPLETE CHANGEOVER) FOR ICE ACROSS THE
NORTH CENTRAL MOUNTAINS...WHERE GREATER THAN 0.25" OF ICE IS
EXPECTED. FARTHER WEST...A CHANGEOVER TO RAIN IS EXPECTED OVER
WARREN AND ELK COUNTIES...HOLDING DOWN AMOUNTS ALONG THE WESTERN
BORDERS OF THOSE COUNTIES. THE WARNING AREA MAY NEED TO BE
EXPANDED FARTHER SOUTH INTO THE CENTRAL MOUNTAINS IN TIME...BUT
CONFIDENCE IN DOING SO SOUTH OF INTERSTATE 80 WAS LOW GIVEN
CONFLICTING HRRR LLVL TEMPERATURE READINGS AND QPF DISTRIBUTION
THROUGH LATE TONIGHT.

THE REST OF THE SOUTHERN THIRD OF CENTRAL PA IS SEEING A SEVERAL
HOUR LULL IN PRECIP AT MID AFTERNOON AS A RESULT OF A DRY SLOT
WHICH FOLLOWED THE INITIAL WAA BURST. PRECIP FILLING IN BEHIND IS
FZRA OVER THE LAURELS AND HEADING INTO THE CENTRAL MOUNTAINS WITH
A FEW REPORTS STILL OF SOME SLEET PELLETS MIXED IN.

NEAR TERM DETAILS APPEAR TO BE IN GOOD SHAPE. EVE SHIFT WILL CONT
TO MONITOR EVOLUTION OF QPF AND ADJUST ICE AMOUNTS AS NECESSARY.

&&

.SHORT TERM /10 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
PROLONGED ICE ACCRETION IS THE MAIN THREAT LATE TONIGHT INTO
WEDNESDAY MORNING THROUGHOUT THE CENTRAL AND NRN MTNS OF THE
STATE. BY LATE TONIGHT...WARM AIR WILL BE FLOODING THE SOUTH AND
CHANGING FZRA OVER TO PLAIN RAIN. THE NORTH MAY NOT COMPLETELY
MIX OUT THE SHALLOW AND INITIALLY QUITE COLD AIR...SO EXPECT
AREAS OF FREEZING RAIN TO PERSIST THERE THROUGH THE PRE DAWN HOURS
ON WEDNESDAY. ICE ACCUMS SHOULD BE ON THE ORDER OF 0.20-0.30 OF
AN INCH ACROSS THE NCENT MTNS OF PA WHERE ADVISORIES ARE BEING
UPGRADED TO WARNINGS...WITH LESSER AMOUNTS IN MOST PLACES TO THE
SOUTH OF INTERSTATE 80.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
AN ACTIVE LATE-WINTER PATTERN WILL AFFECT 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 CONSENSUS IS TO
MAINTAIN A RIDGE IN THE WEST AND TROUGH IN THE EAST...LIMITING
TEMPERATURE MODERATIONS TO NO BETTER THAN CLIMATE NORMALS.

MODELS SHOW AN ACTIVE PCPN ZONE EXTENDING FROM THE SRN PLAINS
ENEWD INTO THE NRN MID ATLANTIC STATES...IN BTWN A POSITIVELY
TILTED TROUGH PUSHING THROUGH THE PLAINS/MIDWEST/GREAT LAKES AND
ABOVE NORMAL RIDGING FROM THE GOMEX INTO THE WRN ATLANTIC OCEAN.
SEVERAL WAVES OF LOW PRESSURE ARE FCST TO MOVE ALONG A SW-NE
ORIENTED COLD FRONT WHICH SHOULD SLOWLY PROGRESS EWD TOWARD THE
COAST WED-THUR AS NRN STREAM ENERGY CROSSES THE GREAT LAKES. THERE
ARE SOME DIFFERENCES WITH MODEL QPF BUT THE CONSENSUS POINTS
TOWARD THE SRN PA FOR THE HIGHEST PCPN AMTS. USED A MULTI MODEL
BLEND WITH PSEUDO BIAS CORRECTION FACTOR TO DERIVE GRIDDED QPF
AMTS WHICH CONSERVATIVELY 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 FROM NW TO SE WED-WED NGT AS THE COLD FRONT
PUSHES EAST. THIS SHOULD SUPPORT A GENERAL TRANSITION FROM RAIN TO
SNOW ACROSS THE CWA. WITH A DECENT AMOUNT OF MSTR AVAILABLE/STRIPE
OF ABOVE NORMAL PW LOCATED JUST SOUTH OF PA...THE POTENTIAL EXISTS
FOR MODERATE TO HEAVY SNOW OVER THE SRN PORTIONS OF THE AREA.
HOWEVER GIVEN THE UNCERTAINTY AT DAY 3-4 RANGE IN THE FRONTAL
WAVES AND THERMAL PROFILES IN A STATE OF FLUX GOING FROM WARM TO
COLD...CONFIDENCE IN BIG AMOUNTS IS QUESTIONABLE. FOR NOW THE DAY
3+4 NUMBERS RANGE FROM 0-2" NORTH OF I-80...2-4" FROM I80 TO THE
PA TURNPIKE/I-81 AND AMOUNTS IN EXCESS OF 4" POSSIBLE ALONG/S OF
THE TURNPIKE/I-81. THIS IS SUBJECT TO CHANGE AS ANY SLIGHT SHIFT
IN THE QPF AXIS IS PLAUSIBLE AT THIS POINT. THE TAKEAWAY HERE IS
THAT WINTER WX WILL LKLY CONTINUE TO IMPACT THE AREA THROUGH
MIDWEEK WITH THE GREATEST RISK FOR HEAVY SNOW OVER THE SRN
PORTIONS OF THE CWA.

WHAT IS HOPEFULLY THE LAST SHOT OF ARCTIC AIR SHOULD ARRIVE BEHIND
THE COLD FRONT THURSDAY WITH SINGLE DIGIT LOWS +/- OF FRIDAY
MORNING. MAY BE THE COLDEST MORNING UNTIL NEXT WINTER. SOME SNOW
SHOWERS ARE POSSIBLE OVER THE WEEKEND WITH A REINFORCING COLD
FRONT. TEMPS WILL REMAIN AT OR BELOW AVG THROUGH THE PERIOD.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
WARMER AIR SURGING IN ON INCREASING SW FLOW WILL BRING A PROLONGED
WINTRY MIX/FREEZING RAIN EVENT THIS AFTERNOON THROUGH EARLY
WEDNESADY MORNING ACROSS MUCH OF CENTRAL PA. SNOW/SLEET WILL
CHANGE TO FREEZING RAIN SOUTH THIS AFTERNOON...AND EVEN PLAIN RAIN
ACROSS THE LAUREL HIGHLANDS AND SOUTH CENTRAL MOUNTAINS AND LOWER
SUSQUEHANNA RIVER VALLEY BY THIS EVENING. FARTHER NORTH...COLD AIR
WILL REMAIN LOCKED OVER THE NORTH CENTRAL MOUNTAINS MAINTAINING
FREEZING RAIN THROUGH EARLY WEDNESDAY MORNING.

AS A RESULT...WIDESPREAD SIGNIFICANT RESTRICTIONS TO CIGS/VSBYS
WILL ACCOMPANY THIS STORM AT ALL TERMINALS FOR AN EXTENDED PERIOD
FROM THIS AFTERNOON THROUGH LATE TONIGHT. LLWS WILL ALSO BE
PREVALENT AS 850MB WINDS INCREASE TO AROUND 50 KTS.

LATE WED/EARLY THURS AS COLDER AIR WORKS BACK TO THE SOUTH...LOW
PRESSURE MOVING NE ALONG THE FRONT WILL LIKELY RESULT IN A NASTY
MIXTURE OF PRECIPITATION. POTENTIAL IS THERE FOR HEAVY WET SNOW
AND SIGNIFICANT FREEZING RAIN AS WELL.

OUTLOOK...

WED...SOME IMPROVEMENT TO CONDITIONS BUT SOME REDUCTIONS WILL
CONTINUE /ESP SOUTH/ IN RAIN TRANSITIONING BACK TO SNOW LATER IN
THE DAY.

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.

&&

.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 WARNING UNTIL 7 AM EST WEDNESDAY FOR PAZ005-006-
011-012-018-037-041.

&&

$$
SYNOPSIS...DEVOIR
NEAR TERM...DEVOIR
SHORT TERM...LAMBERT
LONG TERM...LAMBERT/STEINBUGL
AVIATION...DEVOIR/RXR