Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 291641 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1141 AM EST THU JAN 29 2015 .SYNOPSIS... AN ALBERTA CLIPPER WILL CROSS THE AREA THIS AFTERNOON AND TONIGHT. HIGH PRESSURE WILL RETURN FOR LATE FRIDAY INTO SATURDAY. A NEW STORM MAY BRING A ROUND OF WINTRY WEATHER FOR LATER SUNDAY INTO MONDAY...BEFORE ANOTHER SURGE OF COLD AIR WORKS INTO THE AREA EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... CLOUDS CONTINUE TO THICKEN OVER THE REGION AS OF LATE MORNING...WITH THE FIRST PRECIPITATION REACHING THE GROUND OVER FAR WESTERN PA IN THE FORM OF SOME SLEET OR FREEZING RAIN. THE MAIN AREA OF PRECIP IS SHOWN BY THE HRRR TO BE ENTERING MY WESTERN ZONES BY 18Z/1PM. STILL SOME CONCERN FOR A BRIEF PERIOD OF LIGHT FREEZING RAIN OR SLEET AT THE ONSET...EVEN OUTSIDE THE CURRENT ADVISORY AREAS. SNOWFALL TOTALS IN OUR GRIDDED FORECASTS LOOK REASONABLE AND WE ARE NOT EXPECTING MORE THAN A TRACE OF ICE...BUT IF IT SHOULD COINCIDE WITH THE EVENING COMMUTE UNTREATED ROADS COULD POSE TRAVEL PROBLEMS. AT THIS STAGE WE PLAN TO HANDLE THIS EXPECTED BRIEF PERIOD OF ICE WITH SPECIAL WEATHER STATEMENTS AND NOWCASTS...AND WILL MONITOR FOR THE POSSIBLE NEED FOR A HEADLINE PRODUCT. A STRONG SHOT OF WAA ALOFT AND MODERATELY STG UPPER LEVEL DIVERGENCE ASSOCIATED WITH THE RIGHT ENTRANCE REGION OF AN UPPER LVL JET MAX ACROSS SRN ONTARIO WILL LEAD TO PERIODS OF LIGHT TO BRIEFLY MDT SNOW FOCUSED ACROSS THE NW HALF OF THE STATE THIS AFTERNOON INTO TONIGHT. GUIDANCE IS CONSISTENT IN SHOWING WARM AIR SURGING IN ALOFT TODAY...THEN BEING PINCHED OFF QUICKLY AS PRECIP DEVELOPS AND THE COLUMN EVAPORATIVELY COOLS. HOWEVER...THE RAP/HRRR HOURLY DATA SHOW THE WARM AIR ACTUALLY PUSHING BACK NORTH BETWEEN 21-00Z OVER THE SWRN ZONES...WHICH IF IT COINCIDES WITH ONGOING PRECIP WILL COMPLICATE THE PRECIP TYPE SCENARIO OVER THE LAURELS AND SOME MARYLAND BORDER COUNTIES. THE POTENTIAL FOR THE WINTRY MIX IS THE LOW PROBABILITY OUTCOME AT THIS POINT. REST FROM EARLIER... MODEL CONSENSUS REMAINS UNCHANGED TO A LARGE DEGREE WITH RESPECT TO THE QPF FROM THE CLIPPER SYSTEM MOVING BY JUST TO OUR NORTH ACROSS LAKES ERIE AND ONTARIO LATE TODAY AND TONIGHT. A GENERAL 2-4 INCH SNOWFALL IS LIKELY OVER THE ALLEGHENIES OF WRN PENN WHERE A WINTER WEATHER ADVISORY IS IN EFFECT FROM LATE THIS MORNING THROUGH 12Z FRIDAY. THE CENTRAL RIDGE AND VALLEY OF THE STATE WILL 1-2 INCHES BY MIDNIGHT TONIGHT...WHILE COUNTIES THROUGHOUT THE LOWER SUSQ VALLEY RECEIVE GENERALLY LESS THAN 0NE INCH. A BIT OF SLEET AND EVEN PATCHY ICE FROM LIGHT FREEZING RAIN IS POSSIBLE ACROSS SOUTHERN PENN LATE TODAY AND THIS EVENING AS THE RATHER SHALLOW WEDGE OF WARMER AIR ALOFT DRIFTS EAST. HIGHS THIS AFTERNOON WILL REACH THE UPPER 20S TO AROUND FREEZING IN THE INCREASING/BRISK SW FLOW AHEAD OF THE CLIPPER/ARCTIC FRONT. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... THE BRUNT OF THE CURRENT STORM SYSTEM WILL OCCUR LATE THIS AFTERNOON AND EARLY TONIGHT...WITH SOME BRIEF PERIODS OF MDT SNOW LIKELY AS ONE OR MORE N/S BANDS OF ENHANCED 850-700 MB UVVEL CROSSES THE REGION. 03Z SREF INDICATES THAT AN AXIS OF ANOMALOUS /2-3 SIGMA/ 850MB MOISTURE FLUX AND SIMILARLY ANOMALOUS /50 KT/ SWRLY LLJ WILL BE GRADUALLY WEAKENING AS IT CROSSES PENN BETWEEN 21Z AND 06Z FRI. SFC COLD FRONT EXTENDING SOUTH FROM THE LOW...PUSHES ACROSS OUR WESTERN ZONES LATE THIS EVENING...THEN CLEARS THE SUSQ VALLEY BETWEEN 07-09Z FRIDAY. SNOW WILL TAPER TO SNOW SHOWERS BY LATE TONIGHT...MAINLY IN THE ISOLATED FORM ACROSS THE CENTRAL AND SOUTHERN VALLEYS. LOW TEMPS TONIGHT WILL RANGE FROM THE MID TO UPPER TEENS ACRS THE WRN MTNS...TO THE MID AND UPPER 20S ACROSS THE SUSQ VALLEY. A SLIGHTLY EARLIER TIMING OF THE CFROPA WILL KNOCK THESE VALUES DOWN BY A FEW DEG F. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... PERIODS OF GENERALLY LIGHTER SNOW WILL LINGER INTO EARLY FRIDAY...AS THE MAIN COLD FRONT DROPS SE. A TIGHT LLVL PRESSURE GRADIENT IN THE WAKE OF THE COLD FRONT WILL BRING GUSTY NORTHWEST WINDS AND SLOWLY FALLING TEMPS ACROSS THE REGION DURING THE DAYLIGHT HOURS FRIDAY. WIND GUSTS WILL BE IN THE MID TO UPPER 20 KT RANGE FOR MOST AREAS CREATING A WIND CHILL IN THE SINGLE DIGITS TO LOW TEENS IN THE SUSQ VALLEY....AND 5 BELOW TO 15 BELOW ACROSS THE NRN AND WRN MTNS. FRIDAY NIGHT WILL BE BITTERLY COLD...AS SKIES CLEAR AND WINDS DIE DOWN. LOW TEMPS WILL VARY FROM THE SINGLE DIGITS BELOW ZERO ACROSS THE NORTH...TO SINGLE DIGITS ABOVE ZERO IN THE SOUTH. A BRIGHT DAY ON SAT...BUT NOT REAL WARM. STILL HAVE CHC POPS ON SUNDAY. A LOT OF SPREAD IN THE MODEL OUTPUT THE LAST FEW DAYS. 12Z MODELS BACKING OFF SOME NOW. PATTERN SUPPORTS LOW PRESSURE SYSTEMS THAT ARE FAST MOVING AND WEAK. WOULD STILL EXPECT SOME LIGHT SNOW INTO MONDAY MORNING. A COLD NIGHT MONDAY NIGHT...AS THE NEXT HIGH BUILDS INTO THE AREA. SOME HINTS AT ANOTHER FAST MOVING LOW FOR MID WEEK...FOR NOW WENT WITH CHC POPS. MINOR CHANGES TO THE PACKAGE MADE. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... VFR WILL CONTINUE INTO EARLY AFTERNOON BEFORE RAPIDLY DETERIORATING TO MVFR/IFR AS SNOW OVERSPREADS THE FLYING AREA FROM WEST TO EAST. SNOW WILL BEGIN AROUND OR SHORTLY AFTER NOON IN BRADFORD. EXPECT IFR CONDITIONS TO DEVELOP RAPIDLY WITH THE SNOW...SPREADING EAST 18-00Z. REDUCED CONDITIONS SHOULD IMPROVE OVERNIGHT WITH THE PASSAGE OF THE COLD FRONT...AROUND 06Z FRIDAY OVER THE WEST. MORE LIKE 09-12Z OVER THE SERN AREAS. THE CONDITIONS AT BFD AND JST WILL LIKELY REMAIN MVFR/IFR INTO FRIDAY. OUTLOOK... SAT...VFR. SUN...RESTRICTIONS DEVELOPING WITH SNOW OVERSPREADING FROM THE WEST. MON...REDUCED CONDS EARLY IN SNOW. IMPROVING FROM WEST TO EAST AFTERNOON ONWARD. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 7 AM EST FRIDAY FOR PAZ004>006- 010-011-017-024-033. && $$ SYNOPSIS...LA CORTE/LAMBERT NEAR TERM...LA CORTE/LAMBERT SHORT TERM...LAMBERT LONG TERM...LAMBERT/MARTIN AVIATION...CERU/GARTNER

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