Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 271939 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 339 PM EDT FRI MAR 27 2015 .SYNOPSIS... A DEEP UPPER LEVEL TROUGH WILL SWING EAST ACROSS PENNSYLVANIA THIS WEEKEND...BRINGING UNSEASONABLY COLD WEATHER. THE UPPER LEVEL FLOW WILL BECOME MORE ZONAL NEXT WEEK LEADING TO A SLOW MODERATION IN TEMPERATURES. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... RIGHT ENTRANCE REGION OF A 300 HPA JET AND THE BACK EDGE OF AN ASSOCIATED NE/SW BAND OF 850-700 HPA FGEN CONTINUES SLIDING SLOWLY EAST OF THE LOWER SUSQ VALLEY THIS AFTERNOON. NOTHING MORE THAN SOME LIGHT SPRINKLES OF RAIN /OR HIGHER ELEVATION FLURRIES/ IS EXPECTED TO OCCUR TO THE EAST OF A KTHV TO KMUI LINE FOR THE REMAINDER OF THE DAYLIGHT HOURS. OVER THE NORTHWEST MTNS AND LAUREL HIGHLANDS...AN APPROACHING UPPER TROUGH WITH -2 TO -3 SIGMA 850-500 HPA TEMP ANOMALIES AND DEEPENING COLD AIR WILL COMBINE WITH A WELL-ALIGNED NWLY LLVL FLOW TO PRODUCE AN INCREASING TREND IN SNOW SHOWERS...WITH LIGHT SNOW ACCUMS POSSIBLE ACROSS THE HIGHER TERRAIN OF THE NW WHERE TEMPS WILL STRUGGLE TO REACH 32F FOR A HIGH TODAY. A FEW BREAKS IN THE MULTI-LAYERED CLOUD COVER SHOULD OCCUR LATE THIS AFTERNOON THROUGH EARLY TONIGHT ACROSS THE CENTRAL RIDGE AND VALLEY REGION...ALONG WITH THE FEW FLURRIES FALLING FROM NARROW BANDS OF THICKER/LOWER STRATO CU. HIGHS THIS AFTERNOON WILL BE MUCH BELOW NORMAL...MAXING OUT NEAR FREEZING IN THE NORTH...AND IN THE MID 40S OVER THE SE. LOW LEVEL COLD ADVECTION AND UPSLOPE FLOW WILL CONTINUE TO FAVOR SCATTERED-NUMEROUS SNOW SHOWERS TONIGHT...WITH AN INCH OR TWO SO FALLING ACROSS THE NORTHWEST PART OF WARREN COUNTY...AND A COATING TO AN INCH ELSEWHERE ACROSS THE NRN AND WRN MTNS. PARTLY-MOSTLY CLOUDY SKIES WILL PREVAIL SE OF THE ALLEGHENIES WITH SOME FLURRIES AND ISOLATED LIGHT SNOW SHOWERS EARLY ON. THE APPROACH OF A SHORTWAVE EMBEDDED IN THE LARGER SCALE TROUGH WILL BRING AN AREA OF STEEPER LOW-MID LEVEL LAPSE RATES AND A BETTER CHC FOR SNOW SHOWERS /EVEN ACROSS THE CENTRAL MTNS AND SUSQ VALLEY/ LATE TONIGHT INTO SATURDAY MORNING. LOWS IN THE TEENS AND 20S EARLY SATURDAY WILL AVERAGE SOME 5 TO 15 DEG BELOW NORMAL. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... THE COLDEST 850 AIR WILL SLIDE THROUGH THE AREA FOR THE FIRST PART OF SATURDAY...ACCOMPANIED BY A FEW-SVRL HOUR PERIOD OF SNOW SHOWERS THAT WILL BRING AN ADDITIONAL LIGHT COATING /EVEN TO SOME LOWER ELEVATIONS THROUGHOUT THE CENTRAL RIDGE AND VALLEY REGION/. AFTERWARD...HIGH PRESSURE BUILDING IN FROM THE OHIO VALLEY BRINGING BRIGHTENING SKIES FOR THE AFTERNOON. SATURDAY WILL BE THE COLDEST DAY WE/LL SEE UNTIL LATER THIS COMING FALL...WITH HIGHS FROM ONLY AROUND 20F IN THE KBFD AREA...TO BETWEEN 35-40F IN THE SUSQ VALLEY. THESE HIGH TEMPS WILL BE 15-18 DEGREES BELOW NORMAL. THE UNSEASONABLY COLD TEMPS AND GUSTY NW WIND IN THE LATE MORNING/AFTERNOON HOURS WILL FEEL MORE LIKE MID WINTER THAN EARLY SPRING WITH WIND CHILLS ONLY AROUND 10F ACROSS THE NW MTNS...AND 20S THROUGHOUT MUCH OF THE SUSQ RIVER VALLEY. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
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THE RETURN OF THE LARGE SCALE UPPER TROUGH WILL PUNCTUATE THE BEGINNING OF THE EXTENDED FORECAST. TEMPERATURES WILL BEGIN THE PERIOD ABOUT 10 TO 15 DEGREES BELOW NORMAL WITH A FEW RECORD LOWS POSSIBLE SUNDAY MORNING. AS WE MOVE TOWRD THE END OF MARCH...GENERAL UPPER LEVEL TROUGHINESS WILL CONTINUE OVER THE EASTERN CONUS BUT THE AXIS WILL MOVE OFFSHORE. THIS WILL ALLOW FOR A RELAXATION OF THE LOW HEIGHTS FOR A TIME. ALTHOUGH...ONLY ENOUGH TO BRING US BACK TO NORMAL TEMPS BY MIDWEEK. BUT THIS WILL FEEL RELATIVELY MILD. BECAUSE WE ARE STILL IN THE EFFECTS OF THE UPPER TROUGH...SCATTERED BOUTS OF PRECIPITATION ARE LIKELY THROUGH LATE WEEK. AS TEMPERATURES FALL NEAR OR BELOW FREEZING OVER NORTHERN PENNSYLVANIA EACH NIGHT...A DIURNAL FLUCUATION BETWEEN DAYTIME RAIN TO NIGHT TIME RAIN/SNOW OR SNOW SHOWERS IS POSSIBLE THROUGH MIDWEEK.
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&& .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... NW FLOW IN THE WAKE OF THE COLD FRONTAL PASSAGE THURSDAY AFTERNOON AND EVENING AFTERNOON WILL COMBINE WITH AN APPROACHING DEEP UPPER TROUGH AND EMBEDDED SHORTWAVE TO PRODUCE NUMEROUS SNOW SHOWERS ACROSS THE NW MTNS AND LAUREL HIGHLANDS WITH HIGH CONFIDENCE FOR MVFR CIGS AND OCNL MVFR VSBYS. NARROW BANDS OF HEAVIER SNOW SHOWERS AND PERIODS OF ENHANCED OROGRAPHIC LIFT ACROSS THE LAUREL HIGHLANDS WILL BRING BRIEF DECREASES INTO THE IFR RANGE. GENERALLY VFR CONDITIONS UNDER A MULTIPLE LAYER OF STRATO CU AND ALTOCU/CIRRUS WILL PREVAIL THROUGH EARLY TONIGHT /04Z/ ALONG AND TO THE EAST OF A LINE FROM KAOO...TO KUNV AND KELM. AFTERWARD... EXPECT CIGS AND VSBYS TO GENERALLY LOWER AS AN UPPER AIR DISTURBANCE TRACKS EAST TWD THE REGION AND INCREASES THE AREAL COVERAGE OF SNOW SHOWERS THROUGH SATURDAY MORNING. NW WINDS WILL AVERAGE AROUND 10 MPH THIS AFTERNOON AND TONIGHT...WITH GUSTS INTO THE MID TEENS. WIND SPEEDS WILL INCREASE BY ABOUT 5 KTS SATURDAY AS THE LLVL PRESSURE GRADIENT TIGHTENS UP...HELPING TO CREATE GUSTS TO AROUND 20 KTS. OUTLOOK... SAT...MVFR/IFR WITH SNOW SHOWERS NORTH/WEST. VFR TO MVFR CENTRAL AND EAST WITH SCHC OF -SHRA. SUN...NO SIG WX/VFR. MON...CHANCE OF LIGHT RAIN /LIGHT SNOW EARLY/ ACROSS NW HALF WITH MVFR REDUCTIONS. VFR SE. TUE...CHANCE OF LIGHT RAIN ACROSS NW HALF WITH MVFR REDUCTIONS. VFR SE. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...LA CORTE/TYBURSKI AVIATION...LAMBERT

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