Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 271258
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
758 AM EST FRI FEB 27 2015

.SYNOPSIS...
A LARGE AREA OF HIGH PRESSURE WILL BUILD ACROSS THE AREA THROUGH
THE FIRST HALF OF THE WEEKEND. A LOW PRES SYSTEM WILL LIFT OUT OF
THE MIDWEST LATE IN THE WEEKEND...PASSING OVER THE REGION SUNDAY
NIGHT. A STRONGER AREA OF LOW PRESSURE WILL LIKELY TRACK WEST OF
PENNSYLVANIA LATE TUESDAY OR EARLY WEDNESDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AT 11Z RADAR CONTINUES TO SHOW PATCHY LIGHT SNOW FALLING FROM
ARND KUNV SEWRD INTO THE LOWER SUSQ VALLEY ALONG AXIS OF INVERTED
SFC TROF. RETURNS SHOULD CONTINUE TO DIMINISH...AS DRIER AIR
WORKS IN. BLEND OF LATEST HRRR AND 4KM NAM INDICATE ANY ACCUMS
AFTER 12Z WILL BE NEGLIGIBLE. SATL IMAGERY SHOWS CLEARING SKIES
ACROSS NORTHWEST PA EARLY THIS AM...AS DRY...ARCTIC AIR MASS
OVERSPREADS THE AREA. EXPECT THIS PARTIAL CLEARING TO PROGRESS
INTO THE EASTERN HALF OF THE STATE LATER THIS MORNING.

UPSTREAM OBS SUGGEST SKIES MAY BECOME MOSUNNY FOR A WHILE THIS
MORNING. HOWEVER...DIURNAL HEATING...COMBINED WITH COLD POOL
ALOFT...SHOULD YIELD A FAIR AMT OF STRATO CU THIS AFTN...ESP OVR
THE ALLEGHENY PLATEAU. GEFS MEAN 925MB TEMPS ARND -15C SHOULD
TRANSLATE TO HIGHS NO BETTER THAN ARND 10F ACROSS THE HIGHER
TERRAIN OF THE ALLEGHENIES...TO THE L/M20S ACROSS THE SUSQ VALLEY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
CLEARING SKIES...A CALM WIND AND SNOW COVER WILL LIKELY RESULT IN
THE LOWEST TEMPS UNTIL NEXT WINTER TONIGHT AS THE CENTER OF HIGH
PRESSURE MOVES OVER PENN.

THE IDEAL RADIATIONAL COOLING CONDS SHOULD ALLOW READINGS TO
BOTTOM OUT FROM 10-15F BELOW ZERO ACROSS THE WESTERN MTNS...TO
0-5F ABV ZERO ACROSS THE LOWER SUSQ VALLEY. THE COLDEST RURAL
VALLEYS IN NW AND NCENT PENN COULD SEE THE MERCURY SETTLE TO
AROUND -20F AT 11-12Z SATURDAY. SOME LOCATIONS ACROSS THE NW MTNS
ARE LIKELY REACH WCHILL ADVISORY CRITERIA...DESPITE A LIGHT/CALM
WIND. HOWEVER...CONFIDENCE IN WIDESPREAD APPARENT TEMPS BLW -15F
NOT THERE YET FOR AN ADVISORY.

FAIR AND STILL COLD WEATHER EXPECTED SATURDAY...AS SFC HIGH
DRIFTS OVR THE AREA. A FAST-MOVING MID LVL SHORTWAVE IS PROGGED BY
ALL MDLS TO TRACK ACROSS THE AREA LATE IN THE DAY. LOW PWAT AIR
MASS WILL PRECLUDE ANY PRECIP CONCERNS. HOWEVER...CIRRUS MAY DIM
THE SUNSHINE AT TIMES. ENS MEAN 850/925MB TEMPS REMAIN WELL BLW
NORMAL FOR THE DATE...LIKELY SUPPORTING HIGHS ONLY IN THE 20-25F
RANGE.

&&

.LONG TERM /SATURDAY NIGHT 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 /13Z FRIDAY THROUGH TUESDAY/...
PATCHY LIGHT SNOW CONTINUES TO QUICKLY ERODE FROM KUNV SEWRD INTO
THE LOWER SUSQ VALLEY ALONG AXIS OF INVERTED SFC TROF...AS DRIER
ARCTIC AIR WORKS IN FROM THE WEST.

CLEARING SKIES ACROSS NORTHWEST PA EARLY THIS AM SHOULD FILL BACK
IN WITH COLD POOL STRATOCU MVFR CIGS FOR SEVERAL HOURS THIS
MORNING THROUGH EARLY AFTERNOON...WITH OROGRAPHIC FLOW ALSO
KEEPING LIGHT SNOW AND LOW CIGS/VSBYS IN KJST THROUGH AT LEAST
EARLY AFTERNOON. REMAINDER OF THE AREA WILL BE OR TRANSITION TO
VFR CONDITIONS OVER NEXT FEW HOURS AS ANOMALOUSLY STRONG
1040-1045 MB SFC HIGH PRESSURE BUILDS IN FROM THE OHIO VALLEY.
WINDS WILL BE W/NW AT AROUND 10 MPH.

OUTLOOK...

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.

TUE...VFR AM. MIXED PRECIP WITH CIG/VIS REDUCTIONS POSSIBLE LATE.

&&

.CLIMATE...
THE COLDEST FEBRUARY ON RECORD IS STILL LOOKING LIKELY. MONTHLY
MEAN TEMPERATURES THROUGH THE 26TH...IPT 18.2...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...FITZGERALD
NEAR TERM...FITZGERALD
SHORT TERM...FITZGERALD
LONG TERM...FITZGERALD/STEINBUGL
AVIATION...RXR
CLIMATE...



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