Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 240914 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 414 AM EST MON NOV 24 2014 .SYNOPSIS...
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NEAR-RECORD WARM TEMPERATURES ARE EXPECTED OVER MUCH OF THE AREA TODAY...BEFORE COLD AIR ARRIVES TONIGHT BEHIND A DEPARTING LOW PRESSURE SYSTEM. ANOTHER AREA OF LOW PRESSURE WILL MOVE ALONG THE MID ATLANTIC COAST WEDNESDAY INTO THURSDAY... BRINGING A CHANCE OF SIGNIFICANT SNOW TO THE EASTERN HALF OF PENNSYLVANIA. ANOTHER SHOT OF COLD AIR WILL FOLLOW FOR NEXT WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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STEADY OR SLOWLY RISING TEMPERATURES ARE THE NORM THIS MORNING AS WARM FRONT LIFTS ACROSS CENTRAL PA. STEADIEST AND HEAVIEST RAINFALL HAS STREAKED NORTH AND EAST OF MY AREA AT THIS TIME ON THE NOSE OF A 55-65KT 850 MB JET LIFTING INTO NY STATE. LIGHTER SHOWERS STILL TRAVERSING THE HIGHER TERRAIN OF WESTERN PA AS WELL AS THE LOWER SUSQ RIVER VALLEY...BUT THESE WILL DECREASE LATER THIS MORNING AS THE WARM FRONT CONTINUES TO LIFT NORTH UPSTATE NY. SHORT TERM CONCERN IS FOR STRONG GUSTY WINDS ACROSS THE HIGHER ELEVS OF THE ALLEGHENIES LATER TODAY. STRONGLY COUPLED SOUTHWEST WINDS SHOULD EASILY CREATE IN THE UPPER 30KT RANGE...LIKELY INCREASING TO OCNLY 40-43 KTS IN THE LATE AFTERNOON AND NIGHT. WIND ADVISORY REMAINS IN EFFECT 17Z-09Z TUESDAY FOR THE NW MTNS AND LAUREL HIGHLANDS. CLEARING AND STRONG MIXING WILL PUSH AFTERNOON TEMPS TO NEAR- RECORD LEVELS. THE BIGGEST TEMP BUST POTENTIAL AREA /STAY TOO COOL VS FCST/ WILL BE THE NORTHEASTERN MTNS. COLD FRONT TIMED TO CROSS THE REGION LATE THIS AFTERNOON AND EVENING...BUT COOLING WILL NOT BE SHARP AS DEEP NEARLY PARALLEL FLOW PROMOTES ONLY SLOW SOUTHEAST PROGRESSION OF POST FRONTAL AIR MASS. AFTER A ROUND OF EVENING SHOWERS...EXPECT THE REMAINDER OF TONIGHT TO BE DRY AS COLD ADVECTION PERSISTS ON WSW FLOW. MINS WILL NOT BE VERY COLD... ONLY RANGING FROM AROUND 30F NORTH TO THE LOWER 40S SOUTHEAST.
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&& .SHORT TERM /TUESDAY/...
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BOUNDARY LAYER FLOW WILL SLOWLY BACK AND WEAKEN ON TUESDAY...WHILE A WEAK AREA OF HIGH PRESSURE DRIFTS INTO THE OHIO VALLEY AND INTO THE WRN PA TUESDAY NIGHT. TUESDAY WILL BE THE CALM BEFORE THE STORM AS ALL EYES SHIFT SOUTHWARD FOR THE EVOLUTION OF WHAT COULD BE THE FIRST WIDESPREAD SIGNIFICANT SNOWFALL ACROSS MUCH OF THE EASTERN HALF OF CENTRAL PA WEDNESDAY. COLD AIR WILL CONTINUE TO FILTER IN ALOFT...AND HIGHS TUESDAY WILL BE SOME 20 DEGREES COOLER THAN THE NEAR RECORD READINGS OF MONDAY AFTERNOON.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... POTENTIAL FOR SIG WINTER IMPACTS FROM LOW PRESSURE MOVING UP THE EAST COAST ON WED/WED NIGHT. WILL CONTINUE TO INJECT INTERPRETATION OF THE LATEST MODEL GUIDANCE WITH EACH 3-HOURLY UPDATE TO GUIDE DECISION SUPPORT LEADING UP TO THE PRIME TRAVEL PERIOD FOR THE THANKSGIVING HOLIDAY. HIGHLY AMPLIFIED AND ACTIVE UPPER AIR PATTERN WILL BRING A PERIOD OF ACTIVE WEATHER THROUGH THE COMING WEEK. THE 500MB CONFIGURATION WILL FEATURE ANOMALOUS RIDGING ALONG THE WEST COAST AND IN THE WESTERN ATLANTIC WITH A FULL-LATITUDE PERSISTENT TROUGH EBBING AND FLOWING OVER THE CENTRAL AND EASTERN U.S. AFTER THE EXIT OF MONDAY/S LOW PRESSURE AREA...COLDER TEMPS RETURN ON BRISK W/SW FLOW FOR TUE DROPPING HIGHS SOME 20-25F FROM PREV DAYS READINGS. WE/LL ALSO SEE THE RETURN OF LIGHT SNOW SHOWERS IN THE WESTERN HIGHER TERRAIN. THEN FOCUS WILL TURN TO A WAVE CURRENTLY DROPPING SE FROM BRITISH COLUMBIA AND WASHINGTON STATE...WHICH WILL SPAWN AN AREA OF LOW PRESSURE OVER THE SE US TUESDAY NIGHT...THAT WILL LIKELY MOVE NORTH NORTHEASTWARD JUST OFF THE EAST COAST WEDNESDAY INTO THURSDAY. 12Z/18Z OPERATIONAL AND GEFS RUNS ALONG WITH THE 21Z SREF ARE BECOMING FAIRLY WELL CLUSTERED WITH RESPECT TO THE LOCATION OF THE NEAR...TO SUB-1000 MB SFC LOW EARLY WED EVENING /NEAR...AND UP TO ABOUT 200 NM EAST OF DELMARVA PENINSULA/. THERE IS STILL MUCH UNCERTAINTY AT THIS 60-72 HOUR TIMEFRAME BEFORE THE EVENT...WITH RESPECT TO THE EXACT TRACK OF THE SFC LOW AND ASSOCIATED SNOW/RAIN AMOUNTS. COLD AIR WILL BE IN PLACE WED MORNING AS A /WEAK/ HIGH PRESSURE RIDGE RETREATS TO THE NORTH AHEAD OF THE APPROACHING LOW. NORTHERLY FLOW OVER CENTRAL PA NOT PARTICULARLY STRONG IN ANY MODEL...BUT A SHORTWAVE LOOKS POISED TO SLIDE IN FROM THE GREAT LAKES ON WED TO ADD SOME SYNOPTIC LIFT TO A RAPIDLY DEEPENING AND FAST MOVING SURFACE LOW. THE 12Z ECMWF AND IT`S ENSEMBLE ARE VERY SIMILAR HUGGING THE SFC LOW ALONG THE SHORELINE...WHILE US/CANADIAN MODELS AND THEIR ENSEMBLES ARE FURTHER EAST BY 100-200 NM. EXPERIENCE SHOWS THAT THE LACK OF A SIGNIFICANT BLOCKING HIGH TO OUR NORTH OR NORTHEAST...FAVORS A MORE WESTERN TRACK /SIMILAR TO THE EC AND ITS ENSEMBLE/. SHOULD THE WWD TREND CONTINUE EVEN FURTHER WITH AN EARLIER INJECTION OF NRN STREAM ENERGY INTO THE SOUTHERN STREAM SYSTEM...IT/S CONCEIVABLE THAT OUR FAR SE ZONES /NEAR KLNS AND KMDT/ COULD EVEN SEE A MIX WITH SLEET AND RAIN FOR A PERIOD THAT WOULD HOLD DOWN ACCUMULATIONS. PRECIP MAY START OFF EARLY WED AS A MIX OF RAIN AND SNOW IN THE SE...BUT COOLING TEMPS ALOFT SHOULD CONVERT ALL PRECIP OVER TO SNOW BY MIDDAY. AS IS A GENERAL RULE WITH THESE TYPES OF EVENTS... THERE WILL LIKELY BE A SHARP DROP OFF IN ACCUMULATIONS ON THE NW EDGE OF THE HEAVIER SNOWS. BIGGEST POTENTIAL IMPACTS IN OUR CWA WILL BE THE CENTRAL MTNS AND SUSQ VALLEY...WHERE POTENTIAL FOR A SEVERAL HOUR PERIOD OF HEAVY ACCUMULATING SNOW WILL EXIST. BUT AGAIN...SMALL CHANGES IN THE ULTIMATE TRACK COULD LEAD TO MODIFICATIONS OF SNOWFALL FORECASTS. THE TAKE AWAY...THOUGH THE DETAILS REMAIN UNCERTAIN...THERE WILL BE SIG IMPACTS TO TRAVEL ALONG THE U.S. EAST COAST ON ONE OF THE BUSIEST DAYS OF THE YEAR /WED/. PLAN ACCORDINGLY. COLDER AIR REMAINS IN PLACE LATE IN THE WEEK AS SCT SNOW SHOWERS RETURN TO THE WESTERN HIGHER TERRAIN. TEMPS LOOK TO GRADUALLY MODIFY LATE WEEKEND HEADING INTO NEXT WEEK...WITH NO BIG STORM SYSTEMS EXPECTED AFTER THANKSGIVING. && .AVIATION /09Z MONDAY THROUGH FRIDAY/... A LOW PRESSURE SYSTEM TRACKING NORTHWARD INTO THE GRT LKS WILL SPREAD LOWERING CIGS AND RAIN ACROSS CENTRAL PA TONIGHT. REGIONAL RADAR AT 06Z SHOWS A DRY SLOT BEGINNING TO ENTER SOUTHWEST PA. THIS WILL CAUSE CIGS AND VSBYS TO INCREASE...AND SHOULD LIFT RESTRICTIONS SLOWLY. THE LOW LEVEL MOISTURE REMAINS HIGH AND SOUTHERLY WINDS IN THE 1-2 KFT LAYER WILL BECOME VERY STRONG OVERNIGHT...MAKING LLWS A NEAR CERTAINTY. SFC GUSTS OVERNIGHT WILL BE HIGHEST AT KJST DUE TO IT/S RIDGETOP LOCATION. HRRR OUTPUT SUGGESTS GUSTS BTWN 25-35KTS ARE POSSIBLE THERE UNTIL 09Z. MUCH LIGHTER SFC WINDS EXPECTED ELSEWHERE...WHICH WILL LEAD TO THE LLWS. THE CONDITIONS LOOK TO IMPROVE QUICKER THAN PREVIOUSLY MODELED...WHICH MEANS THE LOW CIGS AND LINGERING DRIZZLE WILL GIVE WAY TO IMPROVING CONDS BY MID MONDAY AM...AS WARM FRONT LIFTS NORTH OF THE REGION. GENERALLY VFR CONDS ARE ANTICIPATED MONDAY AFTERNOON. A COLD FRONT MOVING FROM THE WEST WILL BE ACCOMPANIED BY SCT LATE DAY SHRA ACROSS THE W MTNS...POSSIBLY PRODUCING A BRIEF VSBY REDUCTION AT KBFD OR KJST. OUTLOOK... TUE...NO SIG WX EXPECTED. WED...SNOW/LOW VSBYS POSS EASTERN PA. THU...-SHSN/REDUCED VSBYS POSS NW MTNS. FRI...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... WIND ADVISORY FROM NOON TODAY TO 4 AM EST TUESDAY FOR PAZ004>006-010-011-017-024-033. && $$ SYNOPSIS...DEVOIR NEAR TERM...DEVOIR SHORT TERM...DEVOIR LONG TERM...DEVOIR/RXR AVIATION...FITZGERALD/CERU

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