Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 010306 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1106 PM EDT FRI OCT 31 2014 .SYNOPSIS... A STRONG UPPER-LEVEL TROUGH DROPPING SOUTHWARD FROM THE GREAT LAKES WILL DEEPEN A LOW PRESSURE SYSTEM OFF THE MID-ATLANTIC COAST ON SATURDAY. THIS LOW WILL EVENTUALLY TRACK SOUTHEAST OF CAPE COD SATURDAY NIGHT AND SUNDAY. FOR PENNSYLVANIA...THIS WILL LEAD TO MUCH CHILLIER AIR ARRIVING ON A BRISK NORTH TO NORTHWEST WIND SATURDAY INTO SUNDAY. HIGH PRESSURE WILL RETURN TO THE AREA BY MONDAY...WITH MODERATING TEMPERATURES INTO THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... SHOWERS ARE DISSIPATING ACROSS WESTERN PA LATE THIS EVENING...AS UPPER-LEVEL LOW PRES SWINGS SOUTHWARD THROUGH THE OHIO VALLEY. FATHER EAST...LLVL EASTERLY FLOW PICKING UP AND SOME LIGHT RAIN DEVELOPING AS OFFSHORE LOW BEGINS TO STRENGTHEN. THE HIGHER TERRAIN OF NRN AND WRN PA COULD SEE SOME SNOWFLAKES MIX IN WITH ANY RAIN SHOWERS OVERNIGHT...AS COLDER AIR IS PULLED INTO THE AREA. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... DEEP EASTERLY FLOW AROUND OFFSHORE SFC LOW SHOULD DELIVER A DAMP MORNING TO MUCH OF EASTERN AND SOUTH-CENTRAL PA. DESPITE RELATIVELY LOW DEEP LAYER MOISTURE...ANOMALOUS EASTERLY FLOW OF THIS SORT TYPICALLY PRODUCES FAIRLY WIDESPREAD ALBEIT LIGHT RAIN. POPS BEGIN TO DECREASE LATER IN THE DAY AS THE LOW PULLS NORTHEASTWARD TOWARDS CAPE COD. MARGINALLY COLD AIR MOVING INTO THE REGION SHOULD PROMOTE A MIXTURE OF RAIN AND SNOW SHOWERS OVER THE LAURELS AND NORTHERN MOUNTAINS...WITH LITTLE IF ANY ACCUMULATION EXPECTED DURING THE DAYLIGHT HOURS. BACKING LOW LEVEL FLOW WILL ADVECT COLDER AIR INTO THE REGION LATE SATURDAY AFTERNOON AND NIGHT. EARLY AFTERNOON TEMPERATURES IN THE 40S WILL DROP SLOWLY ACROSS WESTERN AND CENTRAL AREAS BY EVENING TO THE UPPER 30S TO LOWER 40S. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... LARGE UPPER TROUGH WILL BECOME MORE NARROW AS IT DIGS SOUTHWARD SAT NIGHT INTO SUN...WITH COASTAL LOW TO THE EAST LIFTING NORTHEASTWARD. 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. ENSEMBLE MEAN 8H TEMPS THIS WEEKEND POINT TOWARD DAYTIME HIGHS FROM THE U30S-L40S OVR THE ALLEGHENIES TO 45-50F ACROSS THE LOWER SUSQ VALLEY. THE COLDEST NIGHT WILL BE SUNDAY NIGHT...WHEN SFC HIGH BUILDS OVR THE REGION AND SKIES CLEAR OUT. 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 INTO TUE...WHEN ALL GUIDANCE BUILDS SFC HIGH AND ASSOC DRY AIR MASS ACROSS PA...ALONG WITH MODERATING TEMPS. AN APPROACHING COLD FRONT WILL BRING THE NEXT CHC OF SHRA LATE TUE INTO WED. FOLLOWED BY A CLIPPER SYSTEM FOR LATE WEEK /MODELS DIVERGE ON TIMING/. BUT LATE WEEK TREND WILL BE A RETURN BACK TO COOLER TEMPERATURES. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
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SOME VARIATION WITH CONDITIONS AT BFD AND JST. WILL CONTINUE TO UPDATE TAFS AS NEEDED. EARLIER DISCUSSION BELOW. ONE LOW OVER THE OH VLY...WITH NEW SYSTEM FORMING OFF THE SE COAST. RAIN WILL CONTINUE TO SLOWLY EDGE EASTWARD OVERNIGHT. IFR AND MVFR CONDITIONS WILL DEVELOP FROM WEST TO EAST AND PERSIST INTO SAT. IT WILL BECOME WINDY ON SAT. CONDITIONS WILL SLOWLY IMPROVE LATE SATURDAY INTO SUNDAY...AS DRIER AND COLDER AIR WORKS SOUTHWARD FROM QUEBEC. WINDS WILL REMAIN GUSTY INTO SUNDAY. IT MAY BE COLD ENOUGH AT TIMES FOR RAIN TO MIX WITH SOME SNOW AT SPOTS LIKE BFD AND JST. OUTLOOK... SUN...GUSTY NW WINDS. RAIN/SNOW SHOWERS ENDING WEST. LOW CIGS WEST BECOMING VFR. MON-TUE...NO SIG WX. WED...MVFR WITH CHC SHRA.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...EVANEGO NEAR TERM...EVANEGO SHORT TERM...DEVOIR/EVANEGO LONG TERM...RXR AVIATION...MARTIN

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