Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 051003
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
503 AM EST THU MAR 5 2015

.SYNOPSIS...
A WAVE OF LOW PRESSURE WILL TRACK SOUTH OF PENNSYLVANIA THIS
MORNING. HIGH PRESSURE WILL BUILD SOUTHEAST INTO THE STATE FRIDAY
AND SATURDAY. A STRONG UPPER-LEVEL RIDGE WILL BUILD INTO THE
REGION EARLY NEXT WEEK. THIS SHOULD PROVIDE GENERALLY FAIR WEATHER
AND SEVERAL DAYS OF NEAR NORMAL TEMPERATURES AND RELATIVELY DRY
WEATHER.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WATER VAPOR/SATL DERIVED PWAT IMAGERY SHOWING AN ATMOSPHERIC RIVER
OF ANOMALOUS PWATS EXTENDING FROM THE S PACIFIC OCEAN NEWRD INTO
THE MISS VALLEY AND EVENTUALLY PA AND THE NEW ENGLAND STATES.
THIS DEEP MOISTURE PLUME IS OVERRUNNING AN EXPANSIVE ARCTIC HIGH
PRES TO THE NORTH. ASIDE FROM SOME RAIN OR SLEET BEING MIXED IN
FOR ANOTHER HOUR ACROSS FAR SOUTHERN YORK AND LANCASTER
COUNTIES...BANDS OF LIGHT TO MDT SNOW WERE SEEN ON REGIONAL 88D
MOSAIC ACROSS SOUTHERN PENN.

AS A WEAK WAVE OF LOW PRESSURE AT THE SFC MOVES EAST ALONG THE
NC/VA BORDER THIS MORNING /AND BANDS OF LOW-MID LEVEL FGEN
TIGHTEN UP/STRENGTHEN BENEATH THE RIGHT ENTRANCE REGION OF A
POWERFUL...165 KT UPPER JET/ SNOWFALL RATES ACROSS THE ADVISORY
AND WARNING AREAS WILL INCREASE FOR SEVERAL HOURS...WITH BRIEF
PERIODS OF 1/4-1/2SM VBSYS LIKELY ACROSS THE LOWER SUSQ REGION
SOUTH OF THE I-81/I-78 CORRIDOR.

EMPLOYING A HOST OF 00/03Z OPERATIONAL AND ENSEMBLE DATA...ALONG
WITH HOURLY HIGH RES MODELS...WE TRIMMED THE WINT WEATHER
ADVISORIES FROM MOST OF THE COUNTIES BORDERING INTERSTATE 80
/EXCEPT FOR NORTHUMBERLAND WHERE ITS NWD EXTENDING CHIMNEY WILL
SEE MUCH LESS SNOW THAN SOUTHERN PORTIONS OF THE COUNTY WHERE 2-3
INCHES IS LIKELY/.

OTHERWISE...A CONSENSUS BLEND OF LATEST HIGH RES AND ENS MODELS
CONTINUE TO POINT TOWARD A GENERAL 2-4 INCH STORM TOTAL SNOWFALL
ACROSS THE SOUTHERN COUNTIES BY THIS AFTERNOON...WITH PERHAPS A
FEW AMTS UP TO 6 OR 7 INCHES TO THE SOUTH OF THE TURNPIKE IN THE
LOWER SUSQ VALLEY...AND ON THE RIDGES OF SOMERSET COUNTY.

09Z TEMPS RANGED FROM THE MID TO UPPER TEENS OVER THE NW MTNS...TO
THE LOWER 30S THROUGHOUT THE LOWER SUSQ VALLEY. COLDER AIR WILL
CONTINUE TO FILTER INTO THE REGION ON NW FLOW...AND TEMPS WILL
SLOWLY FALL ALL DAY THROUGHOUT CENTRAL PENN AND THE SUSQ VALLEY.

BLEND OF LATEST MDL DATA INDICATE SNOW WILL TAPER OFF BY LATE AM
ACROSS THE CENTRAL COUNTIES...AND MAY LAST UNTIL LATE AFTN ACROSS
YORK/LANCASTER COUNTIES. ARCTIC HIGH AND ASSOC DRY AIR MASS WILL
ARRIVE EARLY OVR THE NW COUNTIES...RESULTING IN DRY/COLD WX THE
ENTIRE DAY UP THERE.

SOME PARTIAL CLEARING APPEARS LIKELY ACROSS THE NW COUNTIES LATE
IN THE DAY. ELSEWHERE...MDL SOUNDINGS INDICATE A MID LVL CLOUD
DECK WILL LINGER EVEN AFTER THE SNOW ENDS. OVERCAST SKIES AND COLD
ADVECTION WILL LIKELY BLUNT ANY DIURNAL WARMING AND RESULT IN
STEADY TEMPS THRU EARLY AFTN...THEN FALLING TEMPS LATE.

CONSALL OUTPUT SUPPORTS DAYTIME TEMPS FROM ONLY ARND 10F ACROSS
THE NW MTNS...TO THE L20S ACROSS THE SOUTHEAST COUNTIES...ANOTHER
EXCEPTIONALLY COLD DAY FOR THE TIME OF YEAR.


&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
HIGH PRESSURE AND BELOW NORMAL LOW-LEVEL TEMPERATURES WILL
DOMINATE THE REGION TONIGHT INTO LATE FRIDAY. UNSEASONABLY COLD
AIR...PERHAPS THE LAST OF THE SIGNIFICANT ARCTIC SURGES OF OUR
ENDLESS WINTER.

BASED ON THE LOW TEMPERATURES NEAR AND BELOW 0F AND THE
WINDS...THE POTENTIAL EXISTS FOR SOME AREAS TO EXPERIENCE WIND
CHILLS LOW ENOUGH LATE TONIGHT INTO FRIDAY WHICH MIGHT REQUIRE AN
ADVISORY ACROSS THE NORTHERN TIER COUNTIES /AND PERHAPS EVEN THE
LAUREL HIGHLANDS/.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
SFC HIGH PRESSURE RIDGE WILL SAG JUST TO THE SOUTH OF THE MID
ATLANTIC REGION FRIDAY NIGHT...ALLOWING FOR AN INCREASE IN SWRLY
SFC WINDS AND CLOUDS ACROSS THE NW HALF OF THE CWA...WITH MAINLY
CLEAR SKIES AND LIGHTER WIND PERSISTING ACROSS THE LOWER SUSQ
VALLEY...MUCH CLOSER TO THE SFC RIDGE. COLD TEMPS IN THE LOW-MID
TEENS ACROSS THE NW MTNS FRIDAY WILL STAY NEARLY STEADY OR EVEN
RISE A FEW DEG F FRIDAY NIGHT...WHILE A MORE NORMAL NOCTURAL TEMP
DROP OF 12-15F IS EXPECTED ACROSS THE LOWER SUSQ VALLEY.

SATURDAY THE TEMPERATURES AT 850 MB RETURN CLOSER TO NORMAL AND
HIGH PRESSURE DRIFTS TO OUR SOUTH. PENNSYLVANIA SHOULD REMAIN
NORTH OF THIS WEAK HIGH....CUTTING OFF ANY MOISTURE TO THE
SOUTH...KEEPING THE REGION IN WEAK WESTERLY FLOW INTO MONDAY. THE
PERIOD SHOULD BE RELATIVELY DRY WITH ANY FRONTAL PRECIPITATION
SUPPRESSED TO OUR SOUTH AND ONLY WEAK NORTHERN STREAM WAVES TO OUR
NORTH TO GENERATE ANY PRECIPITATION.

SO...KEPT THE POPS LOW THROUGH THE PERIOD AND ANY LIGHT
PRECIPITATION WOULD LIKELY BE SNOW AS 850 HPA TEMPS STAY BELOW 0C.
BEST CHANCE OF ANY PRECIPITATION WOULD BE IN NORTHERN AREAS SHOULD
ONE OF THE NORTHERN STREAM WAVES PROVE TO BE STRONGER THAN
GUIDANCE IMPLIES.

A RIDGE IS FORECAST TO BUILD OVER THE REGION TUESDAY INTO
WEDNESDAY AND OUR LOWER TROPOSPHERE TEMPERATURES SHOULD GET AT
LEAST SLIGHTLY....ABOVE NORMAL....BOTH TUESDAY INTO WEDNESDAY.
THIS SHOULD PROVIDE AT LEAST 2 DAYS OF NEAR SEASONAL TEMPERATURES
FOR A CHANGE. RELATIVELY WARM DAYS AND COLD NIGHTS...A GOOD SLOW
WAY TO MELT SNOW WITHOUT FLOODING.

THE NAEFSBC AND GEFSBC SUGGEST A FRONTAL PASSAGE THURSDAY WITH
SLIGHTLY COLDER TEMPERATURES AS ANOTHER HIGH PRESSURE SYSTEM IS
FORECAST TO MOVE OVER THE NORTHEASTERN UNITED STATES THURSDAY INTO
SATURDAY NEXT WEEK.

&&

.AVIATION /10Z THURSDAY THROUGH MONDAY/...
MOISTURE OVERRUNNING A WAVY COLD FRONT TO THE SOUTH OF PA WILL
BRING ANOTHER ROUND OF RAIN/SNOW MAINLY TO AREAS SOUTH OF I-80
OVERNIGHT INTO THURSDAY MORNING.

WIDESPREAD MVFR/IFR WILL CONTINUE ACROSS SRN AIRFIELDS OVERNIGHT
THROUGH AT LEAST MID DAY THURSDAY BEFORE DRIER AIR BEGINS MOVING
INTO THE REGION FROM THE WEST AND NORTH BRINGING IMPROVING
CONDITIONS. NORTHERN SITES...ESPECIALLY KBFD MAY STAY MVFR OR
HIGHER.

TRANSITION FROM RAIN TO SNOW OCCURRING ACROSS KMDT ATTM. THIS
SHOULD BE COMPLETE OVER THE NEXT 2 TO 3 HOURS WITH SNOW THEN
CONTINUING THROUGH THE NIGHT.

OUTLOOK...

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

FRI-SAT...MAINLY VFR.

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

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR
PAZ024>028-034-035-050-052-056>059-063.
WINTER STORM WARNING UNTIL 4 PM EST THIS AFTERNOON FOR PAZ033-
036-064>066.

&&

$$
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...GRUMM/LAMBERT
AVIATION...GARTNER



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