Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 260024 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 724 PM EST SUN JAN 25 2015 .SYNOPSIS... A VIGOROUS UPPER LEVEL STORM WILL SPREAD LIGHT SNOW OVER PENNSYLVANIA TONIGHT...BEFORE AN INTENSE SECONDARY COASTAL LOW IS SPAWNED OFF OF THE CAROLINA COAST ON MONDAY AND BLASTS MUCH OF THE NORTHEAST WITH NEAR BLIZZARD CONDITIONS MONDAY NIGHT AND TUESDAY. PERIODS OF LIGHT SNOW AND SNOW SHOWERS WILL PERSIST OVER CENTRAL PA THROUGH TUESDAY BEFORE BEFORE HIGH PRESSURE BUILDS OVER THE REGION MID WEEK...FOLLOWED BY ANOTHER CLIPPER LATE THURSDAY. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... SFC OBS INDICATE COLD FRONT AT MID AFTERNOON TO BE BETWEEN KLBE AND KIDI...EXTENDING EASTWARD THROUGH THE CENTRAL MOUNTAINS AND EASTWARD TO THE MIDDLE SUSQ RIVER VALLEY. DRY LLVL AIR BLEEDING SOUTHWARD AS SFC HIGH NOSES INTO N CENTRAL PA...EVIDENCE BY SFC TD OF 15F AT KIPT...WHILE KSEG TD IS 27F. MEANWHILE...MOISTURE FLUX AND WAA ARE INCREASING OVER OHIO AND INTO SOUTHWEST PA AHEAD OF VIGOROUS CLIPPER ADVANCING FROM THE MIDDLE MISSISSIPPI RIVER VALLEY. THE SNOW THERE WILL SPREAD EASTWARD AND OVERSPREAD SOUTHWEST AND CENTRAL PA LATE THIS AFTERNOON THROUGH THE EVENING HOURS. SNOWFALL OVERSPREADS MOST OF CENTRAL PA BY LATE EVENING...WITH TIMING OVER THE LAURELS BETWEEN 5PM AND 7 PM...CENTRAL MOUNTAINS BETWEEN 8 PM AND 10 PM...AND AREAS NORTH OF I80 BETWEEN 10 PM AND MIDNIGHT...ALTHOUGH SPOTS ALONG THE NY BORDER MAY WAIT UNTIL WELL AFTER MIDNIGHT. NO MAJOR CHANGES IN QPF OR SNOW AMOUNTS...BUT WITH 24 HOUR EVENT CRITERIA IN EFFECT...WE EXPECT WIDESPREAD 3 TO 6 INCH AMOUNTS OVER ALL OF CENTRAL PA. 6"+ EXPECTED OVER THE LAUREL HIGHLANDS...BUT REMAINING BELOW THE 24 HR WARNING CRITERIA OF 8"/24 HOURS...WHICH IS WHY ADVISORIES ARE POSTED FOR THOSE AREAS AS WELL. SNOW/WATER RATIOS BTWN 11/1 AND 13/1 WERE USED WITH WPC QPF AS A BASIS FOR SNOW AMOUNTS...AND THEN EDITED FOR CONSISTENCY. BANDING AND FLUFF FACTOR MAY INFLUENCE TOTALS UPWARD SLIGHTLY FROM WHAT WE CURRENTLY HAVE. IT APPEARS MOST OF THE ACCUMULATION OCCURS LATE TONIGHT THROUGH MID MORNING MONDAY...BEFORE UPPER LEVEL TROF AND TRANSFER TO COASTAL LOW TAKES PLACE. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... WEAKENING PRIMARY CLIPPER LOW OVER THE CENTRAL APPALACHIANS TRACKS SOUTH OF PA MONDAY MORNING WHILE IMPRESSIVE SECONDARY DEVELOPMENT TAKES PLACE OFF OF THE VA/NC COAST AND RACES NE LATER MONDAY. STILL CONCERNED FOR WESTERN EDGE OF HEAVY SNOW FALL TO BRUSH MY FAR SOUTHEAST COUNTIES...WE MAINTAIN A WINTER STORM WATCH FOR YORK LANCASTER AND LEBANON COUNTIES AS A RESULT FOR AN ADDITIONAL 4-6"+ LATER MONDAY INTO TUESDAY. BUT DURING MONDAY...PERIODS OF LIGHT SNOW AND SNOW SHOWERS WILL PERSIST THROUGH MOST OF THE DAY. DEEP EAST FETCH AND UPSLOPE INTO THE LAURELS KEEPS THE SNOWFALL GOING THROUGH THE AFTERNOON HOURS...WITH DEFORMATION BANDING LIKELY SETTING UP OVER THE SOUTHEAST LATE IN THE DAY. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... HELD ONTO THE WATCH FOR THE FAR SE. OUR EASTERN AREAS WILL BE CLOSE TO THE HEAVIER SNOW FROM THE COASTAL STORM MONDAY NIGHT AND TUESDAY MORNING. STRONGEST WINDS WILL BE EAST OF OUR AREA...BUT GUSTY WINDS WILL BE LIKELY BY TUESDAY MORNING. AS NOTED YESTERDAY...THERE WILL BE A LARGE TEMPERATURE GRADIENT FROM NY TO MD INTO TUE. FRONTAL ZONE RIGHT OVER THE STATE COLLEGE AREA MUCH OF THE MORNING HERE. FIRST CONCERN IS THE INVERTED TROUGH TO THE WEST THAT LINGERS INTO MONDAY NIGHT. DID UP POPS SOME ACROSS THE NW. SECOND CONCERN IS THE DEEP COASTAL THAT FORMS LATE MONDAY AND TRACKS NE. WATCH POSTED FOR THE FAR SE. DID EDGE QPF AND SNOWFALL AMTS UP SOME ACROSS THE FAR EAST AND SE FOR MONDAY NIGHT AND EARLY TUE. WINDS A LITTLE HIGH ON TUE...DID EDGE WIND GUSTS DOWN SOME. WIND CHILLS MAY REACH ADVISORY LEVELS AT TIMES THIS WEEK...BUT REAL CONCERN MAINLY STAYS NE OF OUR AREA. WED STILL LOOKING MAINLY DRY. ANOTHER FRONT FOR LATE THU INTO EARLY FRIDAY. SECONDARY LOW FORMS...BUT SITUATION AT THIS POINT NOT LIKE WHAT WE HAVE AT THE CURRENT TIME. MORE DETAIL BELOW... MAIN FOCUS IN THE EXTENDED FCST WILL BE EVOLUTION OF RAPIDLY DEVELOPING COASTAL LOW EAST OF PA MON NITE AND TUESDAY. MDL DATA SHOWING A FAIRLY TIGHT RANGE OF SOLUTIONS. 12Z GFS MAY BE A LITTLE OFF...FROM 12P CHAT ROOM DISC. ANYWAY...MOST OF THE DATA PLACE OUR EXTREME EASTERN COUNTIES FROM LANCASTER NORTH THRU SCHUYLKILL CO ON THE WESTERN PERIPHERY OF THE SIGNIFICANT DEFORMATION BAND SNOW. MDL 7H FGEN FIELDS SEEM TO IMPLY THE HEAVY SNOW WILL REMAIN JUST EAST OF THE CWA. HOWEVER...GIVEN COMPLEXITY OF CRITERIA DIFFERENCES ACROSS OUR BORDERS...AND 40% CONFIDENCE OF AN ADDITIONAL 6 INCHES OR MORE OVER LEBANON/LANCASTER/E YORK COUNTIES WITH THE SECONDARY LOW...OPTED TO ISSUE WINTER STORM WATCH FOR THESE THREE COUNTIES FOR MONDAY AFTERNOON THROUGH TUESDAY MORNING. ACROSS THE REST OF CENTRAL PA...LIGHT SNOW EXPECTED MONDAY NIGHT AND TUESDAY ASSOC WITH NEXT SHORTWAVE DIVING INTO DEEPENING UPPER TROF AXIS OVR PA. TIGHT PRES GRADIENT WEST OF COASTAL LOW SHOULD RESULT IN A BLUSTERY DAY TUESDAY...BLOWING/DRIFTING SNOW A POSSIBILITY. BUFKIT SOUNDINGS INDICATE GUSTS TO ARND 30KTS LIKELY. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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KJST AND AOO SOCKED IN WITH VERY LOW CIG/VSBY AND LIGHT TO MODERATE PRECIP. DOWNSLOPING FARTHER TO THE EAST SHOULD BE ENOUGH TO KEEP SERN AIRFIELDS /KMDT AND KLNS/ IN VFR/HIGH MVFR CONDS. AN ALBERTA CLIPPER WILL TRACK JUST SOUTH OF PENNSYLVANIA TONIGHT INTO MONDAY...BRINGING ANOTHER ROUND OF SNOW WITH IFR CONDS. THIS WILL IMPACT MOST TERMINALS AFTER 00Z MONDAY...BUT SOME AFFECTS POSSIBLE EARLIER AT KJST. SNOW RAPIDLY OVERSPREADING FROM SW TO NE...BRINGING IFR CONDS TO THE ENTIRE REGION OVERNIGHT. SNOW/SNSH CONTINUES MONDAY INTO TUES. NW WINDS PICK UP MON NIGHT INTO TUES AS LOW PRES SPINS UP OFF NEW ENGLAND COAST. QUIET WX WEDNESDAY BETWEEN SYSTEMS...BEFORE ANOTHER CLIPPER DROPS ACROSS THE AREA LATE THU INTO FRI. OUTLOOK... MON-MON NIGHT...WIDESPREAD IFR/MVFR IN SNOW/SNSH. TUE...AREAS MVFR IN SHSN WEST...AND POSS LINGERING SNOW IN THE EAST. WED...VFR WITH NO SIG WEATHER EXPECTED. THU...VFR TO START...WITH LATE DAY RESTRICTIONS SPREADING IN FROM THE WEST. THU NIGHT- FRI...WIDESPREAD IFR/MVFR IN SNOW.
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&& .CTP WATCHES/WARNINGS/ADVISORIES...
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WINTER WEATHER ADVISORY UNTIL 7 PM EST MONDAY FOR PAZ017>019- 024>028-033>036-050-056-057-063-064. WINTER WEATHER ADVISORY UNTIL 7 PM EST MONDAY FOR PAZ010>012- 041-045-046-049-051>053-058. WINTER WEATHER ADVISORY UNTIL 1 PM EST MONDAY FOR PAZ059-065- 066. WINTER STORM WATCH FROM MONDAY AFTERNOON THROUGH TUESDAY MORNING FOR PAZ059-065-066.
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&& $$ SYNOPSIS...DEVOIR/FITZGERALD NEAR TERM...DEVOIR/FITZGERALD SHORT TERM...DEVOIR/FITZGERALD LONG TERM...FITZGERALD/MARTIN AVIATION...DEVOIR/CERU/EVANEGO

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