Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 311203 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 803 AM EDT FRI OCT 31 2014 .SYNOPSIS... A WEAK RIDGE OF HIGH PRESSURE WILL DRIFT EAST ACROSS THE APPALACHIANS EARLY TODAY. A VIGOROUS UPPER LEVEL TROUGH DIGGING THROUGH THE CAROLINAS WILL SUPPORT THE DEVELOPMENT OF A STRONG COASTAL STORM EXPECTED TO TRACK JUST OFF THE EAST COAST THIS WEEKEND. THIS WILL LEAD TO MUCH COOLER AIR BEING USHERED INTO THE REGION ON A BRISK NORTHERLY WIND. HIGH PRESSURE WILL RETURN TO THE AREA BEHIND THE DEPARTING STORM SYSTEM ON MONDAY WITH MODERATING TEMPERATURES INTO THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... CURRENT FORECAST ON TRACK. MOSTLY CLOUDY CONDITIONS THROUGHOUT CENTRAL PA TODAY. WEAK SHORTWAVES ROUNDING THE BASE OF SHARP 5H TROF OVER LAKE MICHIGAN THIS MORNING ARE LIFTING ACROSS CENTRAL AND EASTERN PA IN THE BROAD UPPER SOUTHWEST FLOW. BROKEN LOW TO MID CLOUD DECK COVERS ALL THE WAY THROUGH THE LOWER SUSQ EARLY TODAY. WILL KEEP CONTINUITY WITH PREVIOUS FORECAST AND MAINTAIN DRY CONDITIONS FOR THE SE HALF OF THE CWA...WHILE INITIALLY ISOLATED SHOWERS ACROSS THE NW MTNS...SPREAD TO THE SE AND EXPAND IN COVERAGE THIS AFTERNOON AND EVENING AS THE POTENT UPPER TROUGH /OVER THE WRN GLAKES THIS MORNING/ DIVES SE TWD THE SMOKEY MOUNTAINS AND UPPER DIFFLUENCE GREATLY INCREASES OVER CENTRAL AND WESTERN PENN ATOP AN INVERTED SFC TROUGH. THE PRIMARY FCST PROBLEM FOR TODAY IS DETERMINING JUST HOW FAR EAST THE SHOWERS WILL MOVE AS THE UPPER LOW TO OUR WEST DEVELOPS RAPIDLY AND DROPS SOUTH. THE TRACK OF THE LOW WELL TO OUR WEST AND THEN SOUTH OF THE AREA SUGGESTS THERE WILL BE SOME MEASURE OF SHORTWAVE RIDGING/SUBSIDENCE TO THE EAST OF THE SYSTEM...OVER PARTS OF THE MID ATLANTIC AND NORTHEAST. HIGH TEMPS TODAY WILL VARY FROM THE LOW-MID 40S ACROSS THE NW MTNS...TO THE MID 50S THROUGHOUT THE LOWER SUSQ REGION. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... MODELS ARE IN GOOD AGREEMENT WITH THE DEVELOPMENT OF A SHARP/HIGHLY AMPLIFIED UPPER TROUGH OVER THE EASTERN U.S. DURING THE UPCOMING 24-36 HOURS. THE UPSTREAM ENERGY CAN BE SEEN CLEARLY ON WATER VAPOR IMAGERY AS A POTENT UPPER TROUGH OVER NERN WISC MOVES SE AND FROM LEAST A PAIR OF SYSTEMS. THE PRIMARY CHUNK OF UPPER ENERGY IS CURRENTLY MOVING SSE ACROSS NERN WISCONSIN. THE UPPER FLOW OVER THE LOCAL AREA IS EXPECTED TO BACK QUICKLY TO THE SOUTHWEST AND EVENTUALLY SOUTH AS A POTENT LOW CLOSES OFF AND DIVES SOUTH-SOUTHEAST FROM THE LOWER GLAKES TOWARD THE CAROLINA COAST. AT THIS POINT IT LOOKS LIKE MOST OF MY EASTERN FCST AREA COULD REMAIN DRY INTO TONIGHT...WHILE THE BEST CHANCE OF RAIN SHOWERS WILL BE OVER ABOUT THE WESTERN HALF OF THE CWA. THE LACK OF DEEP MOISTURE SHOULD RESULT IN FAIRLY LIGHT RAINFALL WITH THIS FEATURE...PERHAPS UP TO A QUARTER INCH OVR THE W MTNS. RISK OF SNOW OVER THE HIGHER ELEVATIONS OF THE LAURELS BY LATER FRIDAY APPEARS LOW GIVEN LATEST MODEL SOUNDINGS. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... FRIDAY NIGHT INTO SATURDAY THE LARGE UPPER LEVEL LOW WILL DROP DOWN SOUTH AS ALL MEDIUM RANGE GUIDANCE CUTS OFF UPPER LOW SOUTH OF PA AND MOVES IT DOWN INTO THE CAROLINAS. LATE FRIDAY NIGHT...EARLY SATURDAY MORNING AS REMNANTS OF AN ASSOCIATED CLIPPER LOW SHOULD DIE OVR THE CENTRAL APPALACHIANS AS ENERGY IS TRANSFERRED TO DEVELOPING COASTAL LOW NR CAPE HATTERAS. HOWEVER GIVEN THE MOISTURE...THE ADVECTION OF COLDER AIR...AND THE UPSLOPE FLOW...THERE IS A GOOD CHANCE FOR SNOW SHOWERS OVER THE SW ALLEGHENIES EARLY SATURDAY MORNING. THIS IS REINFORCED BY WWD GRAPHICS AND MODEL SOUNDINGS. HAVE ADJUSTED WX GRIDS ACCORDINGLY. AS THE LOW DROPS SOUTH IT WILL BECOME A COASTAL STORM AND LIFT NE. THIS WILL CAUSE A TIGHTENING PRESSURE GRADIENT AND BRING STRONG NW FLOW DRAWING MUCH COLDER/DRIER AIR INTO PA. OPERATIONAL RUNS AND NEARLY ALL ENSEMBLE MEMBERS KEEP COASTAL LOW FAR ENOUGH OUT TO SEA TO NOT DIRECTLY IMPACT CENTRAL PA. HOWEVER...COLD NW FLOW WILL LIKELY PRODUCE SCT LAKE EFFECT SNOW SHOWERS ACROSS THE ALLEGHENY PLATEAU AND PARTS OF THE CENTRAL MOUNTAINS SATURDAY NIGHT. GIVEN DRYNESS OF AIR MASS MOVING IN...DON/T EXPECT ANY SIG ACCUMS...BUT A COATING OF SNOW DOES APPEAR POSSIBLE OVR THE W MTNS. TEMPS THIS WEEKEND WILL ALMOST CERTAINLY BE THE COLDEST YET THIS SEASON. ENSEMBLE MEAN 8H TEMPS POINT TOWARD DAYTIME HIGHS FROM THE U30S-L40S OVR THE ALLEGHENIES TO 45-50F ACROSS THE LOWER SUSQ VALLEY. THE COLDEST NIGHT OF THIS OUTBREAK WILL LIKELY BE SUNDAY NIGHT...WHEN SFC HIGH BUILDS OVR THE REGION. THOSE LOCATIONS THAT HAVE YET TO SEE A FREEZE WILL LIKELY GET IT BY MONDAY AM. HIGH CONFIDENCE IN A PERIOD OF DRY WEATHER SUNDAY/MONDAY...WHEN ALL GUIDANCE BUILDS SFC HIGH AND ASSOC DRY AIR MASS ACROSS PA. AN APPROACHING COLD FRONT WILL BRING THE NEXT CHC OF SHRA BY MIDWEEK. DEEP UPPER TROF WILL LIFT OUT QUICKLY EARLY NEXT WEEK...ALLOWING A MUCH MILDER RETURN SW FLOW TO OVERSPREAD THE REGION. TEMPS LIKELY TO RETURN TO ABV NORMAL READINGS BY TUESDAY. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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31/12Z IR SAT AND SFC OBS CONTINUE TO SHOW A FAIRLY UNIFORM OVERCAST LOW VFR CLOUD DECK /WITH BASES GENERALLY AOB 050/ BLANKETING THE AIRSPACE. STAYING MORE OPTIMISTIC THAN GUIDANCE WAS A GOOD BET FOR THE PAST 6 HOURS AND WILL FOLLOW PERSISTENCE TREND THROUGH 18Z. LOWERED CIGS TO MVFR AT THE WRN TAFS AFTER 00Z WITH RAIN ARRIVING AROUND THE SAME TIME. SFC LOW PRES WILL TRACK ESEWD FROM SERN MI ACROSS OH/WV TO THE CAROLINAS. GUIDANCE STILL FAVORS REDUCED CONDS TONIGHT INTO EARLY SATURDAY WITH PCPN COVERAGE INCREASING OVER THE WRN INTO CNTRL AREAS. WINDS WILL SHIFT TO THE N-NW AND INCREASE THROUGH SATURDAY. OUTLOOK... SAT...MVFR/IFR WITH SCATTERED RAIN/SNOW SHOWERS WEST. VARYING CONDS FROM VFR-MVFR CENTRAL/EAST WITH OCNL -SHRA. N-NW WINDS INCREASING SATURDAY NIGHT. SUN...GUSTY NW WINDS. RAIN/SNOW SHOWERS ENDING WEST. LOW CIGS WEST BECOMING VFR. MON-TUE...NO SIG WX.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...DEVOIR/LAMBERT SHORT TERM...LAMBERT LONG TERM...LAMBERT/CERU AVIATION...STEINBUGL

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