Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 310847 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 347 AM EST SAT JAN 31 2015 .SYNOPSIS...
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ARCTIC AIR AND SUBZERO WIND CHILLS WILL IMPACT CENTRAL PENNSYLVANIA FOR MUCH OF THE DAY. A LARGE WINTER STORM WILL TARGET THE AREA ON SUNDAY...WITH THE POTENTIAL INCREASING FOR A WIDESPREAD HEAVY SNOWFALL ACROSS CENTRAL AND NORTHERN SECTIONS... AND THE COMBINATION OF SNOW AND MIXED PRECIPITATION ACROSS THE SOUTH. ANOTHER SHOT OF ARCTIC AIR WILL FOLLOW FOR MONDAY AFTERNOON INTO TUESDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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INVERSION HEIGHTS FALLING RAPIDLY EARLY TODAY AS HIGH PRESSURE BUILDS FROM EASTERN KY AND WV. WIND CHILLS IN THE -10F TO -20F RANGE ARE COMMON ACROSS WESTERN AND NORTHERN SECTIONS...AND ADVISORY RUNS THROUGH 16Z. A MOSTLY SUNNY AND CHILLY DAY IS IN STORE FOR MOST...AS THE SFC RIDGE AXIS EXPANDS AND OVERSPREADS ALL OF PA ON UP INTO UPSTATE NEW YORK AND SOUTHERN QUEBEC. HIGH CLOUDS EVIDENT IN THIS MORNINGS IR LOOP OVER THE CENTRAL AND WESTERN GLAKS MAY STREAM OVERHEAD THIS AFTERNOON...BUT WON`T DIMINISH BRIGHT SKIES WHICH SHOULD HELP DIMINISH THE NIP OF THE AFTERNOON. HIGHS FROM THE MID TEENS TO MID 20S NORTH TO SOUTH WILL BE ABOUT 15 DEG BELOW NORMAL ON AVERAGE.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
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DIRTY RIDGE AXIS BUILDS EASTWARD FROM THE OHIO VALLEY TONIGHT AND SUNDAY...AS A VIGOROUS NORTHERN STREAM TROF DROPS ACROSS THE ROCKIES AND INTO THE UPPER PLAINS BY MIDDAY SUNDAY. THIS CONFLUENCE IS IMPORTANT AS IT WILL AID IN LOCKING COLD AIR OVER THE REGION AS THE AFOREMENTIONED TROF ADVECTS INCREASINGLY MOIST AND MILD AIR TOWARDS THE REGION SUNDAY AFTERNOON AND NIGHT... STARTING AS SNOW FOR ALL. SNOW SHOULD BEGIN FROM THE ALLEGHENY CREST WESTWARD BY NOON BEFORE STEADILY OVERSPREADIN THE REMAINDER OF CENTRAL PA DURING THE EARLY TO MID AFTERNOON.
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&& .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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*SIGNIFICANT WINTER WEATHER/SNOW EVENT POSSIBLE SUNDAY-MONDAY *BITTER COLD TEMPERATURES AND DANGEROUS WIND CHILLS POSSIBLE MONDAY NIGHT INTO TUESDAY LATEST MODEL SIMULATIONS AND ENSEMBLES CONTINUE TO SHOW VERY HIGH POTENTIAL FOR HEAVY SNOWFALL AND MIXED PRECIPITATION (SOUTH) TO IMPACT CENTRAL PA SUNDAY NIGHT THROUGH MONDAY. LATEST ECMWF SOLUTION DEPICTS A MILLER-B TYPE SFC LOW EVOLUTION...WITH PRIMARY LOW TRACKING TO SOUTHWEST CORNER OF PA BY 12Z MON...WHILE SECONDARY FORMS OVER THE DELMARVA AND SCOOTS RAPIDLY OUT TO SEA BY MONDAY AFTERNOON. THIS WILL PRODUCE A PERIOD OF MODERATE TO HEAVY SNOWFALL ACROSS MOST OF CENTRAL AND NORTH CENTRAL PA...WHILE A MIX AND CHANGEOVER TO SLEET AND FREEZING RAIN IS LIKELY ALONG AND SOUTH OF THE TURNPIKE. A WINTER STORM WATCH CONTINUES IN EFFECT FOR ALL CENTRAL PA COUNTIES AND IS VALID FROM NOON EST SUNDAY THROUGH NOON EST MONDAY. WPC FORECAST IS WEIGHTED HEAVILY IN THE FINAL GRIDDED SNOW/ICE ACCUMULATIONS...AS BEFORE. CONFIDENCE IS NOW 80% OR GREATER FOR 4 INCHES OR MORE OF ACCUMULATION IN 24 HOURS BY 12Z MON OVER ALL BUT THE SOUTHERN 1/5 OF CENTRAL PA WHERE MIXTURE IS EXPECTED. KEEPING RECENT INCONSISTENCIES IN MIND...DO ANTICIPATE SOME CHANGES REGARDING NUMBERS AND LOCATIONS OF SNOWFALL TOTALS...BUT WITH UPPER WAVE OVER BC NOW ONSHORE AND PRESUMABLY BETTER INITIALIZED THAN SOLUTIONS FROM 48 HOURS AGO...CONFIDENCE HAS MARKEDLY INCREASED FOR AN IMPACTFUL WINTER STORM TO VISIT THE COMMONWEALTH SUNDAY AFTERNOON THROUGH MONDAY. 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.
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&& .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... IFR AT KJST WILL CONTINUE INTO THE EARLY MORNING HOURS AS SNOW SHOWERS AND LOW CIGS PERSIST IN THE NWRLY UPSLOPE FLOW. UPSLOPE WINDS ALSO CONTINUE TO SUPPORT MVFR CIGS AT KBFD AND KAOO. VFR HAS RETURNED ELSEWHERE AND SHOULD PREVAIL INTO TOMORROW...THOUGH A STRAY REMAINING SNOW SHOWER COULD BRING SOME TEMP REDUCTIONS OVERNIGHT. GUSTY WINDS WILL CONTINUE AT MOST TAF LOCATIONS OVERNIGHT. MOST HAVE SOMEWHAT DIMINISHED...BUT REMAIN BETWEEN 15-20KTS WITH GUSTS AS HIGH AS 25 TO 30KTS. UNV IS ONE OF THE FEW LOCATIONS THAT IS CALM WINDS DUE TO DECOUPLING. 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 THIS MORNING FOR PAZ004>006-010>012-017>019-024-033-037-041-042-045-046-049- 051>053-058. && $$ SYNOPSIS...DEVOIR NEAR TERM...DEVOIR SHORT TERM...DEVOIR LONG TERM...DEVOIR/STEINBUGL AVIATION...LA CORTE/CERU

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