Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 262120
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
420 PM EST THU FEB 26 2015

.SYNOPSIS...
AN UPPER LEVEL TROUGH AND YET ANOTHER PUSH OF ARCTIC AIR WILL
MOVE EAST ACROSS THE STATE LATE TODAY THROUGH EARLY FRIDAY...
ACCOMPANIED BY MORE SNOW SHOWERS...WITH A SEVERAL HOUR PERIOD OF
STEADY SNOW ACROSS THE LAUREL HIGHLANDS LATE TODAY AND THIS
EVENING. A LARGE AREA OF HIGH PRESSURE WILL BUILD ACROSS THE AREA
FOR THE FIRST PART OF THE WEEKEND. THE PATTERN WILL THEN BECOME
RATHER STORMY WITH A FRONTAL BOUNDARY WAGGLING NORTH AND SOUTH
OVER THE AREA INTO MID WEEK.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
APPROACHING UPPER LEVEL SHORT WAVE AND ANOTHER ARCTIC CFRONTAL
BOUNDARY WILL BRING A FEW-SVRL HOUR PERIOD OF STEADY LIGHT SNOW TO
THE LAURELS LATE THIS AFTERNOON AND EVENING...WHILE SOME
INTERMITTENT LIGHTER SNOW AND SNOW SHOWERS DEVELOPS AND FALLS
THROUGH EARLY TONIGHT TO THE EAST OF THE INTERSTATE 99/RT220
CORRIDOR.

ACCUMS WILL RANGE FROM JUST A LIGHT COATING AT LOWER ELEVATIONS
ACROSS THE SOUTHERN THIRD TO HALF OF THE CWA...TO BETWEEN 1 AND 2
INCHES ACROSS THE LAUREL HIGHLANDS.

AS WINDS BACK AROUND FROM THE NORTH TO NW THROUGH TONIGHT...A
BETTER LLVL UPSLOPE COMPONENT AND STEEPER LOW-MID LEVEL LAPSE
RATES WILL MEAN THAT SNOW SHOWERS WILL CONTINUE ACROSS THE
LAURELS...WHILE THE LIGHT SNOW EARLY ON...TRANSFORMS TO FLURRIES
AND ISOLATED -SHSN TO THE SE OF THE ALLEGHENY FRONT.

LOW TEMPS TONIGHT WILL RANGE FROM THE SINGLE DIGITS BELOW ZERO
ACROSS THE NW MTNS...TO THE TEENS IN THE SE. THE GENERALLY LIGHT NORTH
TO NW WIND WILL REDUCE THE APPARENT TEMP BY ABOUT 7-10F FROM THE
ACTUAL AIR TEMPS.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
THE UPPER TROUGH AXIS FLATTENS OUT AN MOVES ACROSS THE REGION
FRIDAY. AREAS OF STRATO CU AND ISOLATED TO SCTD MORNING SNOW
SHOWERS WILL DISSOLVE AS ANOMALOUSLY STRONG 1040-1045 MB SFC HIGH
PRESSURE BUILDS EAST INTO THE COMMONWEALTH FROM THE OHIO VALLEY.

HIGH TEMPS FRIDAY WITH A WEST TO NW WIND OF 5-10KTS WILL VARY
FROM JUST 8-12F ACROSS THE NW MTNS AND LAURELS...TO THE LOWER AND
MID 20S ACROSS THE LOWER SUSQ VALLEY.

CLEAR SKIES AND LIKELY THE COLDEST NIGHT UNTIL NEXT WINTER WILL
OCCUR FRIDAY NIGHT AS THE CENTER OF HIGH PRESSURE MOVES OVER PENN.

LOW TEMPS EARLY SATURDAY WILL BE 10-15F BELOW ZERO ACROSS THE
WESTERN MTNS...AND 5 BELOW TO 5 ABOVE ELSEWHERE. THE COLDEST RURAL
VALLEYS IN NW AND NCENT PENN COULD SEE THE MERCURY SETTLE TO
AROUND -20F AT 11-12Z SATURDAY.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
A RELATIVELY MILD/ACTIVE SOUTHWEST FLOW ALOFT SHOULD PREVAIL
THROUGH THE PERIOD AS THE PERSISTENT UPPER RIDGE OVER THE WRN
U.S. TEMPORARILY BREAKS DOWN. AN ARCTIC HIGH PRESSURE SYSTEM OVER
CENTRAL PA AT THE START OF THE PERIOD WILL RETREAT INTO ATLANTIC
CANADA BY SUNDAY NIGHT. THE COMBINATION OF SHORTWAVE ENERGY IN THE
SRN STREAM EJECTING FROM A DSW TROUGH AND A DIGGING NRN STREAM
TROUGH MOVING SEWD FROM SOUTH CENTRAL CANADA TOWARD THE UPPER
MIDWEST SEEMS TO DRIVE AN EXPANDING AREA OF WAA TYPE SNOWFALL
SPREADING EASTWARD SUN-MON BEHIND THE SOUTHERLY RETURN FLOW INTO
A RETREATING COLD SECTOR ASSOCD WITH THE DEPARTING ARCTIC HIGH.
THE PCPN SHOULD BE ENHANCED ALONG AN EXPANDING BAROCLINIC ZONE
ACROSS THE CENTRAL AND EASTERN US...AS UPPER RIDGING BUILDS OVER
THE SE U.S.

WHILE THERE APPEARS TO BE LITTLE INDICATION OF A STRONG SURFACE
LOW...MODELS STILL GENERATE 0.25-0.50 INCH QPF AMTS ALONG THE
BAROCLINIC ZONE. THERMAL PROFILES SEEM TO FAVOR SNOW ACROSS THE NW
1/2 OF CENTRAL PA WITH MIXED PTYPES IN THE SOUTH/SOUTHEAST.
PRELIMINARY 24HR SNOW/ICE AMOUNTS WERE DERIVED USING A MULTI
MODEL QPF BLEND WITH PSEUDO INTERNAL BIAS CORRECTION FACTOR AND
WPC WWD. THIS RESULTS IN ADVY LEVEL SNOWFALL OVER THE NW 1/2 AND
0.10 INCH ICE/ZR OVER THE LWR SUSQ VLY. CONFIDENCE IN THE AMTS IS
AVG AT BEST GIVEN UNCERTAINTY IN QPF AND LOW-LEVEL TEMPERATURES.
THE LACK OF A DEFINED SFC CYCLONE ALSO RAISES SOME REG FLAGS.

ANOTHER COLD HP SYSTEM BUILDS INTO THE REGION MON-TUE WITH ANOTHER
SW FLOW WAA MSTR SURGE ALONG BAROCLINIC FRONTAL ZONE LKLY
IMPACTING THE AREA INTO THE MIDDLE OF NEXT WEEK. TIMING
DIFFERENCES ARE EVIDENT WITH THE GFS MORE BULLISH ON PCPN
RETURNING EARLY TUE VS. SLOWER ECMWF (TUE NGT). MIXED PTYPE ISSUES
ARE EXPECTED AGAIN WITH THIS NEXT SYSTEM.

&&

.AVIATION /21Z THURSDAY THROUGH TUESDAY/...
EXPECT MAINLY VFR CLOUD BASES AND VSBYS ACROSS THE CENTRAL MTNS
AND SUSQ VALLEY TAF SITES TO DIP ONCLY DOWN INTO THE MVFR RANGE AS
AN UPPER LEVEL DISTURBANCE /AND ANOTHER PUSH OF ARCTIC AIR/
CROSSES THE REGION LATE TODAY AND EARLY TONIGHT WITH SCT-NUMEROUS
-SHSN DEVELOPING IN THE 20-23Z PERIOD.

MORE PERSISTENT MVFR CIGS AND VSBYS IN LIGHT SNOW WILL OCCUR ACROSS
THE WESTERN MTNS...WITH PERIODS OF IFR LATE THIS AFTERNOON
THROUGH EARLY TONIGHT. CONDITIONS WILL IMPROVE JUST A BIT AFTER
MIDNIGHT TONIGHT ACROSS THE LAURELS...WITH MAINLY VFR VSBYS AND
MVFR TO VFR CIGS DEVELOPING THROUGHOUT THE CENTRAL RIDGE AND
VALLEY REGION AND SUSQ VALLEY.

OUTLOOK...

FRI...EARLY AM LGT SNOW/VIS REDUCTIONS POSSIBLE...OTHERWISE VFR
WITH A 5-10KT WEST TO NW WIND.

FRI NIGHT AND SAT...NO SIG WX EXPECTED.

SUN...SNOW LIKELY NW MTNS. MIXED PRECIP POSSIBLE ELSEWHERE.

MON...MIXED PRECIP WITH CIG/VIS REDUCTIONS POSSIBLE...MAINLY AM.

&&

.CLIMATE...
THE COLDEST FEBRUARY ON RECORD IS STILL LOOKING LIKELY. MONTHLY
MEAN TEMPERATURES THROUGH THE 25TH...IPT 18.0...MDT 20.7.

THE CURRENT RECORD COLDEST FEBRUARY..IPT 19.3...MDT 21.4 BOTH SET
IN 1934.

SO FAR...THIS MONTH IS THE THIRD COLDEST EVER AT IPT...AND FOURTH
COLDEST EVER AT MDT.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

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



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