Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 192007 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 307 PM EST FRI DEC 19 2014 .SYNOPSIS...
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HIGH PRESSURE CENTERED OVER THE WESTERN GREAT LAKES WILL SLIDE EAST ACROSS PENNSYLVANIA THIS WEEKEND...BRINGING DRY WEATHER WITH LIGHTER WIND. A DEEP UPPER TROUGH AND ASSOCIATED SFC LOW WILL LIFT NORTHEAST THROUGH THE GREAT LAKES DURING THE MIDDLE OF NEXT WEEK LIKELY BRINGING US RAIN AND WIND FOR CHRISTMAS EVE...THEN BLUSTERY AND COLDER CONDITIONS FOR CHRISTMAS DAY WITH SCATTERED SNOW SHOWERS.
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&& .NEAR TERM /THROUGH TONIGHT/...
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STUBBORN...ALBEIT SHALLOW STRATO CU CLOUD DECK TRAPPED BELOW A MODERATELY STRONG SUBSIDENCE INVERSION /BASED AT AROUND 2-3KFT AGL/ WILL PERSIST ACROSS MUCH OF NORTHERN AND WESTERN PENNSYLVANIA LATE TODAY INTO SATURDAY...WHILE PARTIAL CLEARING OCCURS ACROSS THE LOWER SUSQ VALLEY AND SURROUNDING AREAS. TEMPS WILL REMAIN STEADY THROUGH LATE THIS AFTERNOON UNDER THE 10-15 KT NWRLY FLOW. READINGS WILL VARY FROM THE MID TO UPPER 20S ACROSS THE NORTHERN AND WESTERN MOUNTAINS...TO THE LOWER 40S IN THE SOUTHEAST. A WEAK SFC RIDGE WILL MOVE TO NEAR THE PENN/OHIO BORDER BY 12Z SATURDAY...BUT THE WEAK WESTERLY ISENTROPIC LIFT ALONG THE 285K THETA SFC...AND SOME SHALLOW MOISTURE BEING ADVECTED SWD INTO THE NRN MTNS OF PENN FROM LAKE ONTARIO...WILL MAINTAIN MOSTLY CLOUDY TO CLOUDY SKIES. LITTLE MORE THAN A FEW FLURRIES OR SPOTTY -FZDZ WILL FALL FROM THIS THIN CLOUD LAYER ACROSS THE HIGHER TERRAIN OF THE LAURELS AND INVOF KBFD. AFTER A PTLY CLOUDY LATE AFTERNOON AND EVENING IN THE SE PART OF THE CWA...A BKN LAYER OF STRATO CU IS EXPECTED TO DRIFT SE /OR FORM/ ACROSS THE REGION OVERNIGHT. DUE TO THE NW-SE GRADIENT OF DECREASING CLOUDS...LOW TEMPS AT DAYBREAK SAT WILL BE IN A RATHER TIGHT RANGE...FROM THE UPPER TEENS TO LOWER 20S ACROSS THE MOUNTAINS...TO THE LOWER 20S IN THE SE
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&& .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
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A RIDGE OF HIGH PRESSURE...LIGHTER WIND...AND ASSOC DRIER AIR MASS WILL BUILD EAST ACROSS THE STATE SATURDAY...PROVIDING THE AREA WITH FAIR WEATHER. HIGH RES MODEL DATA CONTINUES TO PAINT A MOSTLY CLOUDY PICTURE FOR MUCH OF THE REGION SATURDAY INTO SATURDAY NIGHT...THOUGH PERIODS OF SUNSHINE ARE LIKELY THROUGHOUT THE CENTRAL RIDGE AND VALLEY REGION...AND SUSQUEHANNA RIVER VALLEY. WAA ALOFT IN ADVANCE OF SHORTWAVE LIFTING OUT OF THE MISS VALLEY WILL LIKELY SPREAD SOME THIN CIRRUS OVER THE LOWER/THIN STRATO CU CLOUD DECK PRESENT ACROSS THE REGION SATURDAY. ALL 12Z OPERATIONAL MODEL DATA CONTINUES TO SUPPORT A DRY DAY WITH SFC RIDGE AND LOW PWAT AIRMASS OVR THE STATE. MAX TEMPS SHOULD BE FAIRLY CLOSE TO SEASONAL NORMS NEAR 30 ACROSS THE MTNS...AND MID TO UPPER 30S IN THE SE. MOSTLY CLOUDY SKIES WITH LIGHT WIND SAT NIGHT WILL YIELD LOWS IN THE LOWER 20S ACROSS THE MTNS...AND GENERALLY THE MID 20S ELSEWHERE.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/... HIGH PRESSURE WILL SHIFT SLOWLY EASTWARD FROM THE GREAT LAKES INTO NORTHERN NEW ENGLAND BY 12Z MONDAY. A MOISTURE-STARVED NRN STREAM SHORTWAVE SHOULD PRODUCE A PERIOD OF CLOUDINESS SAT NIGHT...BUT LIKELY NOT PRODUCE ANY PRECIP. LATEST MDL SOUNDINGS POINT TOWARD A RELATIVELY BRIGHT SUNDAY IN THE WAKE OF THIS FEATURE WITH NEAR SEASONAL TEMPS. SPLIT FLOW REGIME ACROSS THE LOWER 48 WILL TRANSITION TO A HIGHLY AMPLIFIED PATTERN BY EARLY NEXT WEEK ACROSS THE LOWER 48...WITH A DEEP NEGATIVELY TILTED TROUGH EVOLVING OVER THE EASTERN 1/3RD OF THE CONUS. THE MODELS SEEM TO BE FORMING A CONSENSUS ON THE PESKY LOW THAT REFUSES TO BE WELL FORECAST...LIFTING IT SLOWLY FROM FL PANHANDLE NNEWD JUST OFF THE EAST COAST SUN-MON ALONG A LOW LEVEL BAROCLINIC ZONE THAT MAY NOT BUDGE PAST THE GULF STREAM AS THE FLOW ALOFT TURNS SOUTHWESTERLY/PARALLEL TO THE COASTAL FRONT. INCREASED POPS FOR MONDAY OVER THE SE BASED ON MULTI-MODEL/WPC BLEND. COMPLEX SFC PATTERN WITH SOME HINTS AT LOW LEVEL CAD ALONG WITH WAA ALOFT VIA SLY FLOW COULD MAKE FOR A MESSY MIXED PTYPE TRANSITION. AN INTENSE TRIPLE POINT SYSTEM DEVELOPING ON DEC 23-24 WILL LIKELY STEAL THE HEADLINES GIVEN ITS TIMING AND LARGE PORTION OF REAL ESTATE THAT WILL BE AFFECTED. WHILE THE DETAILS REMAIN UNCLEAR AT THIS POINT...TEMPERATURES SHOULD BE WARM ENOUGH TO SUPPORT RAIN ON THE FRONT SIDE OF THE SYSTEM BEFORE BRISK WNW WINDS DRIVE STRONG CAA EAST OF THE APPALACHIANS. THE TIMING OF THE COLD/OCCLUDED FRONT WILL BE KEY FOR PRECIPITATION TRANSITION FROM RAIN TO SNOW SHOWERS. AS THE SYSTEM SPINS UP INTO EASTERN CANADA...THE STRONG CAA CIRCULATING THROUGH THE GREAT LAKES AND OH VLY SHOULD LEAD TO LAKE EFFECT/UPSLOPE/WRAP AROUND SNOW SHOWERS OVER THE WESTERN ALLEGHENIES BY CHRISTMAS DAY. A PERIOD OF STRONG GUSTY WINDS ARE HIGHLY PROBABLE AS THE DYNAMIC SYSTEM INTENSIFIES SHIFTING NWWD FROM NEW ENGLAND INTO ONTARIO/QUEBEC. THE TAKE HOME MESSAGE IS THAT A VOLATILE PERIOD OF WEATHER WILL IMPACT THE AREA THROUGH CHRISTMAS DAY WITH POTENTIAL WIND...RAIN AND SNOW IMPACTS ALL ON THE TABLE. STAY TUNED. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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LLVL NWRLY FLOW AND OROGRAPHIC FORCING OF A SHALLOW MOIST LAYER WILL CONTINUE TO PRODUCE PLENTY OF CLOUDS ACROSS THE NW 1/2 TO 2/3RDS OF THE STATE WITH MAINLY MVFR BKN-OVC CIGS THROUGH TONIGHT. KJST AND KBFD MAY TEETER ON THE UPPER END OF IFR FOR A FEW HOURS LATER TONIGHT /AFTER 06Z/. IN CONTRAST...THE SE PENN AIRFIELDS SUCH AS KMDT...KTHV AND KLNS WILL SEE MAINLY VFR...WITH SKY CONDITIONS VARYING SCT-BKN030-040. NORTHWEST WINDS OF 10-15 KTS WITH HIGHER GUSTS WILL DECREASE TO 8 KTS OR LESS LATER TONIGHT AND SATURDAY. HIGH PRESSURE BUILDS EAST ACROSS PENN SATURDAY...WITH BKN-OVC CIGS VARYING BETWEEN MVFR OVER THE HIGHER TERRAIN OF THE NORTH AND WEST...TO SCT-BKN VFR IN THE VALLEYS. OUTLOOK... SUN...NO SIG WX EXPECTED. MON...LOW CIGS WITH LGT RAIN/SNOW POSSIBLE. BECOMING BREEZY. TUE...LOW CIGS WITH RAIN LIKELY. BREEZY. WED...MILD WITH PERIODS OF RAIN OF VARYINGY INTENSITY...LEADING TO MVFR TO IFR. ALSO...WINDY WITH LLWS.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...FITZGERALD/STEINBUGL AVIATION...LAMBERT

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