Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 310056 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 756 PM EST FRI JAN 30 2015 .SYNOPSIS... ARCTIC AIR WILL BRING BITTER COLD TEMPERATURES AND SUB-ZERO WIND CHILLS TO MUCH OF CENTRAL PENNSYLVANIA TONIGHT INTO EARLY SATURDAY. CONFIDENCE IS INCREASING FOR A HIGH IMPACT WINTER WEATHER EVENT SUNDAY INTO MONDAY WITH THE POTENTIAL FOR SIGNIFICANT SNOW ACCUMULATION AND SOME MIXED WINTRY PRECIPITATION. ANOTHER SHOT OF ARCTIC AIR SHOULD FOLLOW FOR TUESDAY. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... THE SUBSIDENCE INVERSION BASE WILL BE CRASHING BY 3-4 KFT OVER THE NEXT SEVERAL HOURS AS HIGH PRESSURE NEAR KORD BUILDS EAST AND THE MEAN...850-700MB THERMAL TROUGH DRIFTS TWD EASTERN PENN. PRIOR TO THAT...NARROW BANDS OF LIGHT TO MODERATE SHSN WILL AFFECT THE NRN AND WRN MTNS OF PENN THROUGH 02Z WITH ADDITIONAL LIGHT ACCUMS OF AROUND 1/2 INCH IN A FEW LOCATIONS. ELSEWHERE ACROSS THE CENTRAL RIDGE AND VALLEY REGION..SCATTERED FLURRIES WILL OCCUR. WIND CHILLS WILL RANGE FROM 10 TO 20 BELOW ZERO OVER WESTERN HIGHER ELEVATIONS...AND FROM ZERO TO 10 BELOW THROUGHOUT THE CENTRAL RIDGE AND VALLEY REGION. SKIES WILL CLEAR ACROSS MOST OF THE REGION LATER TONIGHT. WESTERN UPSLOPE AREAS AND MY FAR NORTHEASTERN ZONES MAY KEEP CLOUDS AND LINGERING FLURRIES THE LONGEST...BUT FORECAST SOUNDINGS SHOW THE INVERSION HEIGHTS COMING DOWN SO THE CHANCES FOR ACTUAL MEASURABLE SNOW WILL BE DWINDLING QUICKLY. WINDS REMAINING IN THE 10-15 MPH RANGE LATE TONIGHT...WITH HIGHER GUSTS WILL KEEP WIND CHILLS IN THE 10-20 BELOW ZERO RANGE OVER MUCH OF THE REGION. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... SATURDAY WILL START BRIGHT IN MOST AREAS AS THE HIGH CRESTS JUST TO OUR SOUTH. HIGH CLOUDS MAY BEGIN TO INVADE FOR THE LAST HALF OF THE AFTERNOON...BUT THEY SHOULD DO LITTLE TO MAR AN OTHERWISE FAIR ALBEIT COLD MID WINTER`S DAY. HIGHS FROM THE MID TEENS TO MID 20S NORTH TO SOUTH WILL BE ABOUT 15 DEG BELOW NORMAL ON AVERAGE. && .LONG TERM /SUNDAY THROUGH FRIDAY/... *SIGNIFICANT WINTER WEATHER/SNOW EVENT POSSIBLE SUNDAY-MONDAY *BITTER COLD TEMPERATURES AND DANGEROUS WIND CHILLS POSSIBLE MONDAY NIGHT INTO TUESDAY A POTENTIALLY WIDESPREAD HIGH IMPACT WINTER WX EVENT APPEARS TO BE SHAPING UP ACROSS CENTRAL PENNSYLVANIA FOR SUNDAY INTO MONDAY. A WINTER STORM WATCH HAS BEEN ISSUED FOR ALL CENTRAL PA COUNTIES AND IS VALID FROM 12PM SUNDAY THROUGH 12 PM MONDAY. CONFIDENCE IN THE EVENT OCCURRING IS AVERAGE WITH SLIGHTLY LOWER CONFIDENCE IN THE DETAILS SUCH AS LOCATION AND SNOW ACCUM NUMBERS GIVEN THE UNCERTAINTY IN THE TRACK OF THE SYSTEM...AND POTENTIAL FOR MIXED PCPN/WARMER TEMPS IN THE SRN 1/3 OF THE AREA. A SHORTWAVE NOW ENTERING CENTRAL BRITISH COLUMBIA WILL BE DIGGING SOUTHEAST DOWN INTO THE NORTHERN/CENTRAL PLAINS LATER SAT AND INTO SUN. THIS ENERGY COUPLED WITH A MORE SUBTLE SHORTWAVE ON ITS HEELS DROPPING DOWN FROM THE NORTHWEST TERRITORIES WILL PLAY A KEY ROLE IN THE EVOLUTION OF SURFACE LOW PRESSURE THAT IS CURRENTLY FORECAST TO DEVELOP OVER THE LOWER MO AND MID MS VALLEY REGION BY EARLY SUN BEFORE THEN AIMING EAST TOWARD THE OH VALLEY AND MID- ATLANTIC STATES SUN NIGHT AND MON. AS THIS STORM DEVELOPS...MUCH COLDER AIR WILL BUILD NOT ONLY BEHIND THE SYSTEM AS A LARGE ARCTIC ANTICYCLONE HEADS SOUTHWARD INTO THE NORTHERN PLAINS...BUT COLDER AIR WILL ALSO BLEED EASTWARD AS PRESSURES RISE OVER SOUTHEASTERN CANADA AND NORTHERN NEW ENGLAND IN ASSOCIATION WITH A PRONOUNCED UPPER CONFLUENCE ZONE. THE COMBINATION OF THESE TWO SYSTEMS WILL HELP GENERATE A INCREASINGLY TIGHT BAROCLINIC ZONE UPON WHICH THE DEVELOPING SURFACE LOW WILL MOVE ALONG. THE PREVAILING SHIFT IN THE 12Z MODELS WAS TO CONTINUE A MORE NORTHERLY TRACK WITH THIS SYSTEM...WHICH IS REFLECTED IN THE WPC FORECAST WHICH WAS WEIGHTED HEAVILY IN THE FINAL GRIDDED SNOW/ICE ACCUMULATIONS. HOWEVER FORECAST CONFIDENCE IS TEMPERED BY THE RUN- TO- RUN INCONSISTENCIES THE MODELS HAVE SHOWN ALONG THE WITH DISTINCT POSSIBILITY THAT THE MODELS MAY REVERSE TRENDS IN SUBSEQUENT RUNS. WITH SEVERAL FORECAST CYCLES COMING UP ANTICIPATE SOME CHANGES REGARDING NUMBERS AND LOCATIONS OF SNOWFALL TOTALS. A SHOT OF ARCTIC AIR IS FORECAST TO SURGE INTO THE AREA BEHIND THE EARLY WEEK STORM WITH POTENTIAL FOR DANGEROUS WIND CHILLS MONDAY NIGHT INTO TUESDAY. THIS COULD ADD TO STORM-RELATED IMPACTS. HIGH PRESSURE SHOULD BRING COLD BUT QUIET WEATHER INTO MIDWEEK. MODELS AND ENSEMBLES SHOW A COASTAL TYPE SYSTEM SOMETIME NEXT WED-FRI BUT IT IS WAY TOO EARLY TO SPECULATE ON THIS SYSTEM. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... PREDOMINANTLY IFR AT BFD AND JST WILL CONTINUE INTO THE AFTERNOON AS POST FRONTAL SNOW SHOWERS CONTINUE TO FAVOR THE HIGH TERRAIN TERMINALS OF THE WEST AND NORTH. THROUGH THE CENTRAL AREAS THE CONDITIONS WILL SLOWLY IMPROVE AS THE DAY CONTINUES BEFORE BECOMING VFR BY MID TO LATE AFTERNOON. EASTERN AND SOUTHEASTERN TERMINALS WILL BE MAINLY VFR WITH PERHAPS A BRIEF REDUCTION IN A PASSING SNOW SHOWER. GUSTY WINDS WILL CONTINUE INTO THE OVERNIGHT BUT DIMINISHING SOMEWHAT TO BETWEEN 15-20KT. OUTLOOK... SAT...VFR. SUN...WIDESPREAD IFR/MVFR DEVELOPING ASSOCIATED WITH A STORM MOVING TOWARD THE REGION. MON...REDUCED CONDS EARLY...IMPROVING AS THE STORM MOVES AWAY FROM THE AREA. TUE-WED...NO SIG WX. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY MORNING FOR PAZ004>006-010>012-017>019-024>028-033>037-041-042- 045-046-049>053-056>059-063>066. WIND CHILL ADVISORY UNTIL 11 AM EST SATURDAY FOR PAZ004>006- 010>012-017>019-024-033-037-041-042-045-046-049-051>053-058. && $$ SYNOPSIS...LA CORTE/LAMBERT NEAR TERM...LA CORTE/LAMBERT SHORT TERM...LA CORTE LONG TERM...STEINBUGL AVIATION...LA CORTE/GARTNER

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