Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 251954 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 254 PM EST SUN JAN 25 2015 .SYNOPSIS...
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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.
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&& .NEAR TERM /THROUGH TONIGHT/...
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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.
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&& .SHORT TERM /MONDAY/...
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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.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... 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...NEARLY ALL OF WHICH 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. THE MORE LKLY SCENARIO ATTM APPEARS TO BE ONCL LIGHT SNOW CONTINUING ACROSS THE REST OF CENTRAL PA 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. FAIR AND CHILLY WED EXPECTED WED...AS HIGH PRES BUILDS OVR THE AREA. MED RANGE GUIDANCE STILL INDICATES NEXT CHANCE OF SNOW THURS/THU NIGHT WITH NEXT IN SERIES OF CLIPPERS. ECENS SHOWS A DEEPENING UPPER LVL TROF OVR THE EASTERN CONUS BY NEXT WEEKEND...OFFERING NO RESPITE FROM THE COLD WX. && .AVIATION /19Z SUNDAY THROUGH FRIDAY/... COLD FRONT SAGGING SOUTHWARD ACROSS PA. NRN PA SEEING SOME IMPROVEMENT NORTH OF THE FRONT...WHILE LOWS CIGS AND LIGHT PRECIP PERSIST ALONG AND SOUTH OF THE FNT ACROSS SRN PA. KJST SOCKED IN WITH VERY LOW CIG/VSBY AND LIGHT 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/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... SUN NIGHT...SNOW RAPIDLY OVERSPREADING FROM SW TO NE...BRINGING IFR CONDS TO THE ENTIRE REGION OVERNIGHT. 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. && .CTP WATCHES/WARNINGS/ADVISORIES...
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WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 7 PM EST MONDAY FOR PAZ017>019-024>028-033>036-050-056-057-063-064. WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 7 PM EST MONDAY FOR PAZ010>012-041-045-046-049-051>053-058. WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 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 NEAR TERM...DEVOIR SHORT TERM...DEVOIR LONG TERM...FITZGERALD/MARTIN AVIATION...DEVOIR/EVANEGO

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