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Area Forecast Discussion
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000
FXUS61 KCTP 030743
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
243 AM EST TUE MAR 3 2015

.SYNOPSIS...
HIGH PRESSURE CENTERED OVER THE REGION WILL DRIFT EAST TO THE
SOUTHERN NEW ENGLAND COAST BY THIS AFTERNOON. AN AREA OF LOW
PRESSURE OVER THE CENTRAL PLAINS STATES WILL MOVE QUICKLY NORTHEAST
TO THE UPPER GREAT LAKES BY TONIGHT. A SURGE OF DEEP MOISTURE
AHEAD OF THIS LOW WILL RIDE UP AN OVER THE COLD AIR IN PLACE
ACROSS PENNSYLVANIA AND LEAD TO ANOTHER ROUND OF SIGNIFICANT
WINTRY/MIXED PRECIPITATION THIS AFTERNOON INTO EARLY TONIGHT. THE
PRECIPITATION WILL LIKELY TURN TO RAIN ACROSS SOUTHERN SECTIONS
EARLY WEDNESDAY. COLDER TEMPERATURES WILL FOLLOW FOR THE LATTER
PART OF THE WEEK...AND 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 AM THIS MORNING/...
SFC HIGH PRESSURE /1032 MB/ WAS CENTERED OVER THE WESTERN SOUTHERN
TIER OF NEW YORK AT 07Z AND WILL BE DRIFTING EAST ALONG THE
PENN/NEW YORK BORDER THROUGH SUNRISE. 

THIN CIRRUS STREAMING TWD THE WRN MTNS OF PENN WILL QUICKLY
LOWER AND THICKEN UP DURING THE MID TO LATE MORNING HOURS
TODAY...BUT NOT BEFORE THE DAMAGE HAS BEEN DONE WITH RESPECT TO
SOLIDIFYING A VERY COLD BOUNDARY LAYER PRIMED FOR SUPPORTING SNOW
THIS AFTERNOON...THEN AN EXTENDED PERIOD OF MIXED PRECIP LATE
TODAY AND TONIGHT. MORE DETAILS ON THAT BELOW IN THE SHORT TERM
SECTION OF THE DISCUSSION.

EARLY MORNING LOWS WITH WINDS GOING LIGHT AND VARIABLE WILL BE IN
THE SINGLE DIGITS BELOW ZERO ACROSS THE NW MTNS...IN THE LOWER TO
MID TEENS THROUGHOUT THE CENTRAL RIDGE AND VALLEY REGION OF THE
STATE...AND UPPER TEENS TO AROUND 20F IN THE SOUTHEAST.

STILL EXPECT PRECIP ONSET FROM THE SOUTHWEST TO HOLD OFF UNTIL
AFTER 15Z/10AM.

&&

.SHORT TERM /10 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
CONDITIONS WILL GO DOWNHILL FAIRLY QUICKLY ON TODAY WITH MOISTURE
FROM BAJA MONSOONAL FLOW ADVECTING THROUGH THE OHIO VALLEY AND
ARRIVING INTO THE ALLEGHENIES BY LATE MORNING IN THE FORM OF SNOW
INITIALLY...SPREADING EASTWARD ACROSS MY CWA THROUGH THE MIDDAY
AND EARLY AFTERNOON HOURS.

VERY MILD BOUNDARY LAYER FLOW WILL BRING A QUICK MIX AND EVENTUAL
CHANGEOVER TO FREEZING RAIN FOR ALL AS THE DAY PROGRESSES. THERE
MAY BE A COMPLETE CHANGEOVER TO RAIN ACROSS THE FAR SOUTH AND
SOUTHEAST. CONSENSUS BLEND OF 12Z OPERATIONAL MODELS AND ENS 
GUIDANCE IS CONSISTENT WITH PREVIOUS SOLUTIONS FOR AN INITIAL FEW
TO SEVERAL HOUR PERIOD OF SNOW/SLEET THIS AFTERNOON...FOLLOWED BY
A SIGNIFICANT BOUT OF MIXED PRECIP/FREEZING RAIN LATER THIS
AFTERNOON THROUGH EARLY TONIGHT. 

OVERALL IT APPEARS THAT PROLONGED ICE ACCRETION IS THE MAIN
THREAT...PRECEDED BY THE COATING TO 1 INCH OF SNOW FAR SOUTH AND 1
TO 2 INCHES OF SNOW IN MOST AREAS (WITH UP TO 3 INCHES NORTH). THE
NORTH MAY NOT COMPLETELY MIX OUT...AND EXPECT AREAS OF FREEZING
RAIN TO PERSIST THERE THROUGH THE PRE DAWN HOURS ON WEDNESDAY. ICE
ACCUMS SHOULD BE ON THE ORDER OF 0.10-0.20 OF AN INCH ACROSS THE
NCENT MTNS OF PA...WITH LESSER AMOUNTS IN MOST PLACES TO THE SOUTH
OF INTERSTATE 80.

WINTER WEATHER ADVISORIES CONTINUE FOR A PERIOD OF SNOW/SLEET
ACCUM...FOLLOWED BY FREEZING RAIN...GENERALLY FROM MIDDAY TODAY
THROUGH THE EARLY MORNING HOURS ON WEDNESDAY.

&&

.LONG TERM /WEDNESDAY NIGHT 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 /07Z TUESDAY THROUGH SATURDAY/...
MINOR ADJUSTMENTS MADE TO 03Z TAFS.

EARLIER DISCUSSION BELOW.

LOOKING AT JUST A FEW CLDS OVERNIGHT WITH VFR CONDITIONS.

WINDS WILL DIE DOWN IN ANOTHER HOUR OR TWO.

A FAST MOVING SYSTEM MOVING ACROSS THE GREAT LAKES WILL
PULL WARM AIR INTO THE AREA LATE TUE. SNOW WILL QUICKLY
MOVE IN DURING THE AFTERNOON AND MIX WITH AND CHANGE TO
A MIXTURE OF FREEZING RAIN...SNOW...AND SLEET BY LATE 
TUE AFT AND EARLY EVENING...BEFORE CHANGING TO RAIN LATE
TUESDAY NIGHT INTO EARLY WED. 

A FEW RAIN SHOWERS WILL BE ACROSS THE AREA ON WED. 

AS COLDER AIR WORKS BACK TO THE SOUTH LATE WED INTO EARLY
THU...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.

IMPROVING CONDITIONS FOR LATE THU.

OUTLOOK...

WED...CIG/VIS REDUCTIONS CONTINUE IN WINTRY MIX/RAIN.

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

FRI-SAT...MAINLY VFR.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 7 AM EST 
WEDNESDAY FOR PAZ006-011-012-018-037-041-042.
WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 4 AM EST 
WEDNESDAY FOR PAZ004-005-010-017-024>026-033>035.
WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 4 AM EST 
WEDNESDAY FOR PAZ019-027-028-036-045-046-049>053-056>059-
063>066.

&&

$$
SYNOPSIS...LAMBERT/DANGELO
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT/DANGELO
LONG TERM...STEINBUGL 
AVIATION...MARTIN



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