Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 011518 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1018 AM EST SUN FEB 1 2015 .SYNOPSIS... LOW PRESSURE WILL CROSS THE CENTRAL MISSISSIPPI RIVER VALLEY TODAY AND MOVE INTO THE OHIO VALLEY TONIGHT...AND CROSS THE STATE ON MONDAY. THIS WILL PRODUCE WIDESPREAD WINTRY PRECIPITATION ACROSS THE AREA THIS AFTERNOON INTO MONDAY. A PERIOD OF FREEZING RAIN IS LIKELY ACROSS THE SOUTH AND CENTRAL SECTIONS TONIGHT. ANOTHER SHOT OF ARCTIC AIR WILL FOLLOW FOR MONDAY AFTERNOON INTO TUESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... BROKEN SHIELD OF LIGHT SNOW DEVELOPING WELL OUT AHEAD OF SFC LOW OVER EASTERN KANSAS THIS MORNING...ALONG A COLD FRONTAL BOUNDARY DROPPING SOUTHWARD ACROSS THE EASTERN GREAT LAKES AND OHIO VALLEY. THE AFOREMENTIONED LOW PRESSURE CENTER WILL TRACK ALONG THIS BOUNDARY THIS AFTERNOON AND TONIGHT...AND ACROSS THE SOUTHERN TIER OF PENNSYLVANIA BY MONDAY MORNING. EXPANDED POPS SLIGHTLY EARLY THIS MORNING AS RADAR TRENDS INDICATE A FEW POCKETS OF LIGHT SNOW WILL REACH INTO THE LOWER SUSQ FOR A TIME THIS MORNING. BACK EDGE OF INITIAL SNOWFALL LIES ACROSS CENTRAL OH/IN THIS MORNING...AND EXPECT THIS LULL TO REACH INTO AT LEAST PORTIONS OF CENTRAL AND SOUTHERN PA FOR A GOOD PART OF THIS AFTERNOON. ALL HEADLINES RETAINED FOR THIS FORECAST CYCLE. MAIN CONCERNS ARE THAT POPS WERE TOO HIGH TO BEGIN THE STORM THIS AFTERNOON...WHERE ONLY VERY LIGHT AMOUNTS OF QPF AND SNOW ARE EXPECTED. IN FACT...HI RES HRRR AND HRW-ARW CONTINUE TO SHOW FRACTURED MOTHEATEN PRECIP SHIELD DECREASING BY AFTERNOON...WITH A FEW TO SEVERAL HOURS IN BETWEEN IN AND MAIN PRECIP EVENT SPINNING UP THIS EVENING AS SFC LOW PUSHES INTO THE OHIO VALLEY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... LOW PRESSURE MOVES UP THE OHIO RIVER TONIGHT. BY MONDAY MORNING IT SHOULD BE OVER KPIT...AND ROLL OVER THE SOUTHERN HALF OF THE LOCAL AREA. MAIN QPF FALLS IN THE 03Z TO 09Z TIMEFRAME FOR MANY... AND THIS SIX HOUR PERIOD WILL BE CRITICAL FOR SNOW ACCUMS OVER THE CENTRAL MOUNTAINS...JUST NORTH OF THE CHANGEOVER ZONE. FASTER/ GREATER MIXING WILL DECREASE SNOW AMOUNTS SUBSTANTIALLY. FOR NOW HAVE NUDGED THE MIXING ZONE NORTH AND DECREASED SNOW AMOUNTS SOUTH OF INTERSTATE 80 INTO THE 4-6" RANGE. AS A RESULT...GREATER FZRA POTENTIAL EXISTS WITH THIS SOLUTION THAN PREVIOUS THINKING. WHILE THE FARTHER NORTH/WARMER SOLUTION WILL CUT DOWN THE SNOW AMOUNTS IN THE CENTRAL ZONES...WARNING CRITERIA SNOWFALL IS EXPECTED NORTH OF INTERSTATE 80. ADVY AND SUB ADVISORY SNOW AMOUNTS ARE EXPECTED ACROSS THE SOUTHERN THIRD OF CENTRAL PA... BUT THE CHANCE FOR ICING IS ENOUGH TO WARRANT AT LEAST AN ADVY FOR THEM. SFC LOW RAPIDLY TRACKS EAST OF THE AREA BY MIDDAY MONDAY...WITH COLDER AIR POURING BACK INTO THE COMMONWEALTH ON THE BACKSIDE OF THE LOW. EXPECT LITTLE IF ANY ADDITIONAL SNOW ACCUMULATION BY MON AFTERNOON ACROSS THE NORTH. PRECIP WILL HAVE SHUT OFF ACROSS CENTRAL AND SOUTHERN AREAS BY MIDDAY. SHARPLY COLDER AIR IS POISED TO OVERSPREAD CENTRAL PA AGAIN ON MONDAY NIGHT. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... MAIN IMPACTS FROM WINTER STORM WILL HAVE MOVED AWAY FROM REGION BY MON NIGHT...BUT ARCTIC AIR PUSHING IN WILL BRING A VERY COLD NIGHT WITH LOWS BOTTOMING OUT IN THE SINGLE DIGITS SOUTH AND BELOW ZERO NORTH. THOUGH STRONGER WINDS IN THE EVENING WILL BE GRADUALLY DIMINISHING OVERNIGHT...ENOUGH OF A BREEZE WILL REMAIN TO DROP WIND CHILL VALUES BELOW ZERO FOR ALL...WITH NORTHERN MTNS AND LAUREL HIGHLANDS LIKELY NEEDING A WIND CHILL ADVISORY /-15F/ MON NIGHT INTO EARLY TUE. THIS COULD ADD TO STORM-RELATED IMPACTS...INCLUDING POTENTIAL FOR PATCHY BLACK ICE. HIGH PRESSURE WILL BRING COLD BUT GENERALLY QUIET WEATHER INTO MIDWEEK. A WEAK SYSTEM MOVES THROUGH WED THAT MAY BRING LIGHT ACCUMS TO THE NW HALF /BEFORE THE SYSTEM DEEPENS MORE RAPIDLY OVER NEW ENGLAND/...WHICH WILL BE FOLLOWED BY A SHOT OF MORE ARCTIC AIR AS COLD HIGH PRESSURE BUILDS IN FOR THU INTO FRI - INCLUDING A RETURN OF BELOW ZERO WIND CHILLS. TEMPS MODERATE A BIT...BUT REMAIN BELOW NORMAL...ON SAT. ANOTHER LOW PRESSURE AREA MAY IMPACT THE REGION ON SUNDAY...BUT AT THIS TIME IT LOOKS TO BE ON THE WEAKER SIDE. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/... DETERIORATING FLYING CONDS EXPECTED THIS AFTN AND EVENING...AS LOW PRES APPROACHES FROM THE MIDWEST...SPREADING SNOW AND LOWERING CIGS ACROSS CENTRAL PA. AT 15Z...IFR CONDS ALREADY NOTED ACROSS WESTERN PA. UPSTREAM RADAR RETURNS AND LATEST HRRR OUTPUT SUGGESTS IFR CONDS WILL DEVELOP AT KAOO/KUNV ARND 16Z AND AT KIPT ARND 18Z. ACROSS THE SOUTHEAST COUNTIES...SOME MINOR VIS REDUCTIONS APPEAR LIKELY THIS AFTN IN LGT SNOW. HOWEVER...IFR CONDS WILL LKLY HOLD OFF AT KMDT/KLNS UNTIL LATE THIS EVENING. WARMER AIR WORKING INTO THE STATE WILL CHANGE SNOW TO EITHER RAIN OR FZRA ACROSS THE SOUTHERN HALF OF THE STATE LATE TONIGHT. HOWEVER....WIDESPREAD IFR TO LIFR CONDS EXPECTED EVERYWHERE IN CONTINUING PRECIP AND LOW CIGS RESULTING FROM MOIST SE FLOW ASCENDING THE HIGHER TERRAIN OF CENTRAL PA. LLWS REMAINS A POSSIBILITY LATE TONIGHT ACROSS THE S/SE AS LOW LEVEL JET ROTATES THROUGH. MARKED IMPROVEMENT IS EXPECTED BTWN 15Z-18Z MONDAY...AS LOW PRES PASSES EAST OF THE AREA...AND DRIER NW FLOW DEVELOPS. OUTLOOK... MON...REDUCED CONDS EARLY...GRADUALLY IMPROVING AS THE STORM MOVES AWAY FROM THE AREA. LLWS POSS MON AFT/NIGHT. TUE...NO SIG WX. WED...MVFR IN SHSN NW...VFR SE. THU...NO SIG WX. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER STORM WARNING UNTIL 1 PM EST MONDAY FOR PAZ004>006- 010>012-017>019-037-041-042-045-046-049>053-058. WINTER WEATHER ADVISORY UNTIL 8 AM EST MONDAY FOR PAZ033>036- 064>066. WINTER STORM WARNING UNTIL 8 AM EST MONDAY FOR PAZ024>028-056- 057-059-063. && $$ SYNOPSIS...DEVOIR NEAR TERM...DEVOIR SHORT TERM...DEVOIR LONG TERM...RXR AVIATION...FITZGERALD/CERU

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