Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 271143 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 643 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 /12Z FRIDAY THROUGH TUESDAY/... LARGE-SCALE FORCING AHEAD OF A SHORTWAVE OVER THE GREAT LAKES BRINGING SOME LIGHT SNOW TO PORTIONS OF CENTRAL MTNS EARLY THIS MORNING. THIS WILL REDUCE VSBYS/CIGS TO MVFR /OCCASIONAL IFR/ PRIMARILY OVER THE WESTERN HIGHER TERRAIN THROUGH 12Z. BRIEF PERIOD OF MVFR CIGS POSS FURTHER EAST THROUGH 10Z. ANOTHER PUSH OF ARCTIC AIR ARRIVES IMMEDIATELY BEHIND THE SHORTWAVE FOR FRI. OROGRAPHIC FLOW WILL KEEP MVFR CONDITIONS IN WESTERN HIGHER TERRAIN THROUGH MIDDAY...WITH IMPROVING CONDITIONS IN THE AFTERNOON AS ANOMALOUSLY STRONG 1040-1045 MB SFC HIGH PRESSURE BUILDS INTO THE COMMONWEALTH FROM THE OHIO VALLEY. VFR WILL BE THE RULE IN CENTRAL AND EAST. 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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