Area Forecast Discussion
Issued by NWS State College, PA

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000
FXUS61 KCTP 032144
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
444 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 VACILLATED 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 ENSEMBLES 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 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 /22Z TUESDAY THROUGH SUNDAY/...
A LARGE AREA OF SLEET AND FREEZING RAIN OVER THE AREA AS OF LATE
AFT.

MINOR ADJUSTMENTS MADE TO 21Z TAFS.

EARLIER DISCUSSION BELOW.

WARMER AIR SURGING IN ON INCREASING SW FLOW WILL BRING A PROLONGED
WINTRY MIX/FREEZING RAIN EVENT THIS AFTERNOON THROUGH EARLY
WEDNESDAY 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 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
SHORT TERM...DEVOIR
LONG TERM...STEINBUGL
AVIATION...DEVOIR/MARTIN/RXR


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