Area Forecast Discussion
Issued by NWS State College, PA

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365 FXUS61 KCTP 082239 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 539 PM EST MON FEB 8 2016 .SYNOPSIS... A LONG-DURATION PERIOD OF SNOW WILL LIKELY RESULT IN A WIDESPREAD LIGHT TO MODERATE ACCUMULATION FOR MUCH OF CENTRAL PA TONIGHT INTO EARLY WEDNESDAY. LAKE EFFECT AND UPSLOPE SNOW SHOWERS WILL FOLLOW FROM MID WEEK INTO THE FIRST PART OF THE WEEKEND...WITH ADDITIONAL ACCUMULATION LIKELY IN THE FAVORED NORTHWEST SNOWBELT AND HIGHER TERRAIN ALONG THE ALLEGHENIES AND LAURELS. THE COLDEST AIRMASS OF THE WINTER IS POISED TO BRING FRIGID TEMPERATURES AND DANGEROUS WIND CHILLS FOR VALENTINES WEEKEND. && .NEAR TERM /UNTIL 10 PM THIS EVENING/...
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AS OF 22Z...SOME LIGHT SNOW HAS OVERSPREAD SOMERSET CO. HOWEVER...MOST OF CENTRAL PA REMAINS IN REGION OF NIL WEATHER...THE CALM BEFORE THE EXTENDED PERIOD OF UNSETTLED WEATHER. HARD TO CALL IT A STORM PER SE AS A SLOW-MOVING AND AMPLIFYING UPPER TROUGH TAKES ON A NEGATIVE TILT ACROSS THE MID ATLANTIC REGION LATE TONIGHT. WHILE THE PRECIP COULD BRIEFLY BEGIN AS LGT RAIN IN THE LOWER ELEVS OF SOUTHERN PA THIS EVENING...WET BULB ZERO ELEVATION CLOSE TO THE SFC PAINTS A SNOW...RATHER THAN RAIN/SNOW MIX BY ARND 03Z.
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&& .SHORT TERM /10 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
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AFTER DISCUSSION WITH PHI AND LWX...ALONG WITH NEW WPC GRAPHICS...HAVE ISSUED WINTER WX ADVISORY FOR MUCH OF SOUTHERN PA AND A WARNING FOR THE ADAMS/YORK/LANCASTER...WHERE WPC GUIDANCE NOW SUPPORT TOTALS TO ARND 6 INCHES BY TUES NIGHT. A PAIR OF WELL-DEFINED SHORTWAVES ROTATING ARND BASE OF UPPER LOW OVR THE GRT LKS WILL PRODUCE PERIODS OF MAINLY LIGHT SNOW ALONG NEG TILTED INVERTED SFC TROUGH AXIS AND ASSOC PLUME OF HIGHER PWATS ACROSS CENTRAL PA TONIGHT THRU TUE EVENING. FIRST SHORTWAVE SHOWS UP CLEARLY IN WV LOOP THIS EVENING OVR S OHIO. AS THIS FEATURE LIFTS NE...A PERIOD OF LIGHT SNOW WILL OVERSPREAD CENTRAL PA THIS EVENING FROM SW TO NE. BLEND OF MDL DATA SUPPORT OVERNIGHT SNOW TOTALS OF 1-3 INCHES...WITH THE HIGHEST AMTS OVR THE HIGHER ELEVS OF SOUTHERN PA. MARGINAL BLYR TEMPS COULD LIMIT ACCUMS IN THE VALLEYS. AFTER AN EXPECTED LULL IN THE SNOW /ROUGHLY BTWN 09Z-15Z/ EXPECT STEADIER SNOW TO REDEVELOP UPON APPROACH OF SECOND SHORTWAVE LIFTING OUT OF THE OHIO VALLEY. BEST LG SCALE FORCING...AS INFERRED BY MDL 500-300MB QVEC CONV FIELDS...WILL BE FOCUSED ACROSS SOUTHERN PA...WHERE MDL BLENDED QPF SUPPORTS SEVERAL INCHES OF ADDITIONAL ACCUM BTWN MIDDAY TUES AND TUES EVENING. MARGINAL BLYR TEMPS MAY CONTINUE TO HINDER SNOW ACCUMS IN THE VALLEYS...AS NCAR MESO ENSEMBLE AND SPC SSEO BOTH SUGGEST. SO...CONFIDENCE IN WARNING TYPE SNOW IN THE POPULATION CENTERS OF SOUTHERN PA IS NOT NEARLY AS HIGH AS FOR THE RIDGETOP LOCATIONS. EXPECT A TRANSITION TOWARD A LAKE EFFECT/UPSLOPE SNOW PATTERN LATE TUES NIGHT INTO WEDNESDAY NIGHT...AS INVERTED SFC TROUGH LIFTS NE AND BLYR FLOW TURNS TO THE WEST.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/... *IMPACT WEATHER HIGHLIGHTS INCLUDE ADDITIONAL LAKE EFFECT AND UPSLOPE SNOW ACCUMULATIONS THURSDAY-SATURDAY...FOLLOWED BY FRIGID TEMPERATURES AND DANGEROUSLY COLD WIND CHILLS FOR VALENTINES WEEKEND. ANOMALOUS WESTERN RIDGE/EASTERN TROUGH PATTERN WILL REMAIN IN PLACE THROUGH THE WEEKEND. THE GLOBAL ENSEMBLE MEANS GENERALLY KEEP THIS PATTERN CONFIGURATION INTACT INTO NEXT WEEK BUT AT A DECREASING AMPLITUDE. AS THE BROAD UPPER LEVEL CIRCULATION DEPARTS OVER THE NORTHEAST TOWARD THE END OF THE WEEK...IT WILL BE REPLACED BY A POLAR VORTEX DROPPING SOUTH ACROSS HUDSON BAY INTO SE CANADA. COLD AIR WILL BEGIN SPILLING SOUTHWARD LATER IN THE WEEK...REINFORCED INITIALLY BY A SECONDARY FRONT ON THURSDAY. CONFIDENCE CONTINUES TO INCREASE IN A SIGNIFICANT ARCTIC AIR INTRUSION/COLD OUTBREAK FOR VALENTINE`S WEEKEND. LAKE EFFECT/UPSLOPE SNOWS FOR SEVERAL DAYS THU-SAT WILL BRING ADDITIONAL LGT-MDT ACCUMULATION OVER THE FAVORED NORTHWEST SNOWBELT DOWNWIND OF LAKE ERIE AND IN THE HIGHER TERRAIN OF THE ALLEGHENIES/LAURELS. A NEW ELEMENT IN THE FCST IS DEVELOPING LOW PRESSURE OFF THE MID-ATLANTIC/NORTHEAST COAST BY EARLY SATURDAY. AT THIS TIME THE 08/00Z ECMWF LIES ON THE WESTERN EDGE OF THE GUIDANCE ENVELOPE. CONFIDENCE IS HIGH IN THE FCST COLD PATTERN/WELL-BELOW NORMAL TEMPERATURES THROUGH THE PERIOD. THE COLDEST AIRMASS OF THE WINTER APPEARS POISED TO ARRIVE THIS WEEKEND WITH GFS/EC BOTH BRINGING -30C AIR AT 850MB INTO PA. MAX/MIN TEMPERATURE DEPARTURES OF -20 TO -25 DEGREES BELOW CLIMO ARE PROBABLE SATURDAY AND SUNDAY. WIDESPREAD SINGLE DIGIT TEMPERATURES +/- ZERO ARE FCST SATURDAY NIGHT INTO EARLY SUNDAY. A STRONG GRADIENT BETWEEN LOW PRESSURE OFF THE NEW ENGLAND COAST AND 1040+MB ARCTIC HIGH DROPPING INTO THE UPPER MS VALLEY WILL PRODUCE GUSTY WINDS AND DANGEROUSLY COLD WIND CHILLS -10F TO -25F DEGREES BELOW ZERO. && .AVIATION /22Z MONDAY THROUGH SATURDAY/... FLYING CONDS OVER CENTRAL PA AIRSPACE EXPECTED TO REMAIN VFR INTO THE LATE AFTN/EARLY EVENING HOURS. LOWERING CLOUDS AND LIGHT PCPN WILL OVERSPREAD THE REGION FROM THE WEST THIS EVENING AS AREA OF SFC LOW PRESSUR DEVELOPS AND DEEPENDS ACROSS THE REGION. THE COMPLEX WEATHER PATTERN WILL RESULT IN WIDESPREAD... BUT MAINLY LIGHT TO OCCASIONALLY MODERATE... SNOW TONIGHT INTO TUESDAY NIGHT. WHILE THERE MAY BE BREAKS FROM TIME TO TIME...EXPECT FAIRLY WIDESPREAD SNOW/SNOW SHOWERS AND ASSOCIATED RESTRICTIONS OVER MUCH OF THE REGION THROUGH THAT PERIOD. LOOKING AHEAD...SNOW SHOWERS BECOME CONFINED TO WESTERN HIGHER TERRAIN MID/LATE WEEK AS SHOT OF QUITE COLD AIR ARRIVES ON NW FLOW. OUTLOOK... TONIGHT INTO TUE NIGHT...PERIODS OF LIGHT SNOW. IFR CONDITIONS. WED...IFR/MVFR IN SHSN WRN AIRSPACE. MVFR-VFR CIGS CENTRAL/EAST. SFC WIND GUSTS 20+KT FROM 270-300. THU-SAT...MVFR IN -SHSN W MTNS. VFR ELSEWHERE. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 7 PM EST WEDNESDAY FOR PAZ024- 033. WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 5 AM EST WEDNESDAY FOR PAZ025>028-034>036-056-057-059-063. WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 5 AM EST WEDNESDAY FOR PAZ064>066. && $$ SYNOPSIS...STEINBUGL NEAR TERM...FITZGERALD/GARTNER SHORT TERM...GARTNER/FITZGERALD LONG TERM...STEINBUGL AVIATION...GARTNER/RXR

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