Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 240544 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1244 AM EST MON NOV 24 2014 .SYNOPSIS... STRONG LOW PRESSURE WILL PUSH NORTHWARD THROUGH THE GREAT LAKES LATE TONIGHT AND MONDAY. IT WILL BRING A SLUG OF RAIN THROUGH THE STATE TONIGHT. VERY WARM AND EVEN NEAR-RECORD WARM TEMPERATURES ARE EXPECTED OVER MUCH OF THE AREA MONDAY...BEFORE THE COLD AIR FOLLOWING THE GREAT LAKES LOW MOVES ACROSS LATE MONDAY AND MONDAY NIGHT. A DEEPENING AREA OF LOW PRESSURE WILL MOVE NORTHWARD ALONG THE MID ATLANTIC COAST WEDNESDAY. THERE IS A LOW CONFIDENCE AS TO WHAT THE EXACT PATH OF THIS STORM WILL BE. HOWEVER...THE EASTERN THIRD TO HALF OF THE STATE COULD HAVE A SIGNIFICANT SNOWFALL. COLD AIR WILL FOLLOW FOR NEXT WEEKEND. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... WARM FRONT LIFTING THROUGH THE VIRGINIAS EARLY THIS MORNING WITH STRONG SOUTHERLY FLOW ALOFT. VIGOROUS UPPER TROF LIFTING THROUGH CENTRAL AND EASTERN OHIO WITH WIDESPREAD LIGHT TO MODERATE RAIN SHIELD EXTENDING FROM NORTHEAST OHIO THROUGH ALL BUT FAR SOUTHWEST PA. BACK EDGE OF RAIN SHIELD MAKING STEADY PROGRESS NNE AS PREVIOUSLY MENTIONED...FAST NORTHWARD PROPOGATION OF RAIN PRECLUDES ANY CONCERNS FOR HEAVY RAIN. GENERAL 0.50 INCHES QPF IS EXPECTED...BUT SOME HEAVIER AMOUNTS ARE POSSIBLE FAR SOUTHEAST WHERE CONVECTIVE INSTABILITY IS PREVENT. KEPT MENTION OF T THERE FOR THE OVERNIGHT. WINDS ALOFT GET UP TO 50 KTS OVER THE CENTRAL MTNS...BUT THE GENERAL STABILITY OVER THE BULK OF THE AREA SHOULD KEEP GUSTS DOWN DURING THE NIGHT. THE EXCEPTION COULD BE THE HIGHER PEAKS IN THE WEST WHICH COULD BE GUSTY /INTO THE 20 PLUS KT RANGE/ THROUGH THE NIGHT. TEMPS WILL LIKELY LEVEL-OFF OR EVEN RISE LATER TONIGHT. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/... SUBSIDENCE/DRYING IMMEDIATELY BEHIND THE OVERNIGHT WAVE WILL START THE BREAK-UP OF THE CLOUDS FROM S-N. HOWEVER...THE AMBIENT MOISTURE WILL BE HIGH IN THE LLVLS AND FLOW OUT OF THE SOUTH THROUGH THE COLUMN WILL MAKE IT DIFFICULT TO CLEAR THE NORTHERN HALF OF THE AREA TOO RAPIDLY. THE SOUTH WILL LIKELY GET SOME DECENT CLEARING AND THE WARM AIR AHEAD OF THE COLD FRONT WILL PUSH TEMPS TO NEAR-RECORD LEVELS ON MONDAY AFTERNOON. WILL KEEP THE NUMBERS SLIGHTLY LOWER THAN RECORDS...THOUGH. THIS IS DUE TO THE UNCERTAINTY OF HOW MUCH SUN TIME WE WILL HAVE. THE BIGGEST TEMP BUST POTENTIAL AREA /STAY TOO COOL VS FCST/ WILL BE THE NORTHEASTERN MTNS. THEY COULD STAY TOO CLOUDY. THE INSTABILITY COULD ALSO TOUCH OFF A FEW SHOWERS -MAINLY IN THE CENTRAL AND NORTH. THE COLD FRONT SHOULD MOVE THROUGH LATER IN THE DAY AND EARLY EVENING. THE WINDS WILL BE THE OTHER STORY - ALONG WITH THE TEMPS. THE WESTERN MOUNTAINS/ALLEGHENIES WILL BE THE GUSTIEST PLACE. MIXED- WINDS WITH LITTLE DIRECTIONAL SHEAR OFF BUFKIT SOUNDINGS MAKE FOR WIND GUSTS EASILY INTO THE UPPER 30KT RANGE...LIKELY INCREASING TO OCNLY 40-43 KTS IN THE LATE AFTERNOON AND NIGHT. A WIND ADVISORY WAS RECENTLY ISSUED FOR 17Z MONDAY - 09Z TUESDAY FOR THE NW MTNS AND LAUREL HIGHLANDS. THE PERIOD OF LIKELY HIGHEST GUSTS APPEAR TO BE NEAR...AND FOR SEVERAL HOURS IN THE WAKE OF THE CFROPA /OR FROM 21Z MONDAY TO 05Z TUESDAY/. && .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 DROPOFF 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 /06Z MONDAY THROUGH FRIDAY/... A LOW PRES SYSTEM TRACKING NORTHWARD INTO THE GRT LKS WILL SPREAD LOWERING CIGS AND RAIN ACROSS CENTRAL PA TONIGHT. REGIONAL RADAR AT 00Z SHOWS THE RAIN ABOUT TO ENTER SOUTHERN PA AND LINEAR EXTRAPOLATION SUGGESTS THE RAIN WILL OVERSPREAD ALL CENTRAL PA AIRFIELDS BTWN 02Z-04Z. A BLEND OF LATEST LAMP GUIDANCE...SREF AND HRRR MDL OUTPUT IMPLY CIGS WILL DROP TO IFR BTWN 04Z-06Z...JUST A COUPLE HOURS AFTER THE RAIN BEGINS. 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 POSS THERE BTWN 03Z-07Z. MUCH LIGHTER SFC WINDS EXPECTED ELSEWHERE...WHICH WILL LEAD TO THE LLWS. EARLY LOW CIGS AND LINGERING DRIZZLE WILL GIVE WAY TO IMPROVING CONDS BY LATE MONDAY AM...AS WARM FRONT LIFTS NORTH OF THE REGION. GENERALLY VFR CONDS ARE ANTICIPATED MON AFTN. HOWEVER...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...DANGELO/LAMBERT NEAR TERM...DANGELO/DEVOIR/LAMBERT SHORT TERM...DANGELO/LAMBERT LONG TERM...RXR AVIATION...FITZGERALD

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