Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 271012 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 612 AM EDT MON APR 27 2015 .SYNOPSIS... AN UPPER TROUGH OF LOW PRESSURE WILL DRIFT SOUTH ACROSS THE MID ATLANTIC STATES TODAY AND EARLY TONIGHT...RESULTING IN SCATTERED RAIN SHOWERS...THAT COULD BE MIXED WITH WET SNOW AT TIMES ACROSS THE NORTHERN AND WESTERN MOUNTAINS OF THE STATE. MAINLY DRY CONDITIONS WITH MODERATING TEMPERATURES WILL OCCUR TUESDAY AND WEDNESDAY. LATE THIS WEEK...A SLOW MOVING AND DEEPENING UPPER LOW DROPPING SOUTHEAST FROM THE UPPER GREAT LAKES...WILL CAPTURE AN AREA OF SURFACE LOW PRESSURE MOVING NORTHEAST NEAR THE NORTH CAROLINA COAST. THIS COMBINATION OF WEATHER FEATURES WILL BRING MUCH OF CENTRAL PENNSYLVANIA UNSEASONABLY CHILLY AND SHOWERY CONDITIONS THURSDAY INTO AT LEAST EARLY FRIDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A SPRAWLING UPPER LOW OVER THE CANADIAN MARITIMES WILL PUSH A DISTINCT EAST-WEST TROUGH SOUTH ACROSS PENN TODAY. STRATO CU DECK HAS EXPANDED SOUTH TO COVER MOST OF THE CWA AS OF 09Z. WEAK RIDGING ALOFT /AHEAD OF THE SFC TROUGH DRIFTING OUT OF SOUTHERN NEW YORK/ HAS KEPT THE CLOUD COVER RATHER SHALLOW AND NON-PRECIPITATING SO FAR...BUT THIS WILL CHANGE OVER THE COURSE OF THE NEXT SEVERAL HOURS. LOW TEMPS AROUND SUNRISE WILL RANGE FROM THE LOWER TO MID 30S ACROSS THE NRN AND WRN MTNS...TO AROUND 40 IN THE SE. A FEW POCKETS OF ANOMALOUSLY COLD AIR ALOFT WITH MDTLY STEEP 850-700 MB LAPSE RATES ON THE ORDER OF 6-6.5C/KM WILL HELP TO SPARK SCATTERED RAIN SHOWERS...ESP ACROSS THE NRN MTNS AND MIDDLE SUSQ VALLEY THROUGH MID AFTERNOON. 00Z/06Z OPER MODELS AND LATEST SREF SOUNDINGS REMAIN MARGINALLY COLD ENOUGH FOR SNOW THIS MORNING ACROSS THE NW MTNS...SO HAVE MIXED RAIN/SNOW SHOWERS MENTIONED UP THERE THRU ARND 14Z. LOW PWATS SHOULD TRANSLATE TO ONLY VERY LIGHT RAINFALL AMTS MONDAY...ON THE ORDER OF A FEW HUNDRETHS AT BEST. HEIGHTS WILL RISE A BIT /BY JUST 10-20 DECAMETERS/ LATE TODAY AND TONIGHT. COMBINE THIS WITHE DECREASING MID LEVEL LAPSE RATES...AND FORMATION OF A NEAR ISOTHERMAL LAYER BETWEEN 650 AND 600 MB...AND WE SHOULD SEE A GRADUAL DECREASE IN CLOUDS...AND SHOWERS IN MOST LOCATIONS. THE BEST CHC FOR SHOWERS LATE TODAY APPEARS TO BECOME FOCUSED ACROSS THE WRN POCONOS AND LOWER SUSQ VALLEY. MAX TEMPS WILL BE 8 DEG F OR SO BELOW NORMAL ACROSS THE CENTRAL MTNS AND SUSQ VALLEY...AND AROUND 10 DEG BELOW NORMAL ACROSS THE NRN AND WRN MTNS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... ISOLATED LIGHT SHOWERS WILL BECOME CONFINED TO THE NRN AND WESTERN MTNS OF THE STATE TONIGHT...AS A 2-4 KFT THICK ISOTHERMAL LAYER IN THE MID LEVELS CAPS OF THE CLOUD DEPTH ELSEWHERE. WHILE A FEW SPRINKLES ARE POSSIBLE ACROSS THE CENTRAL MTNS...THE LOWER SUSQ VALLEY AND SCENT MTNS OF PENN WILL BECOME PARTLY CLOUDY TONIGHT WITH A NORTH TO NWRLY BREEZE OF 6-8 KTS. LOWS EARLY TUESDAY WILL BE IN THE MID 30S ACROSS THE NRN AND WRN MTNS...AND L40S IN THE LOWER SUSQ VALLEY. TUESDAY WILL FEATURE MORE SHALLOW...AND LESS COVERAGE OF THE STRATO CU CLOUDS THAN MONDAY. A FEW SPRINKLES ARE POSSIBLE EARLY TUESDAY ACROSS THE CENTRAL AND NW MTNS. HIGH TEMPS TUESDAY AFTERNOON WILL CLIMB BACK TO NEAR NORMAL FOR THIS TIME IN LATE APRIL. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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SLOWLY RISING HEIGHTS/APPROACH OF HIGH PRESSURE AT THE SFC AND ALOFT WILL BRING A FEW DAYS OF DRY AND NOTICEABLY MILDER CONDITIONS FOR TUESDAY AND WED. A SLOW MOVING SRN STREAM UPPER LOW WILL EMERGE INTO THE SERN TO MID ATLC STATES DURING THE MIDWEEK PERIOD. A DISTINCT AND RATHER POTENT SHOT OF UPPER ENERGY...IN THE FORM OF A CLOSED LOW DROPPING SSE FROM THE UPPER GLAKES REGION SHOULD CAPTURE THE SFC LOW /PROGGED BY MOST 00Z-06Z MODEL AND ENS GUIDANCE TO BE NEAR THE OUTER BANKS OF NC THURSDAY MORNING/. PHASING OF THESE FEATURES WILL COINCIDE WITH THE DEVELOPMENT OF HIGHLY ANOMALOUS EAST-NERLY FLOW IN THE 925-850 MB LAYER LATE THUR INTO FRIDAY ACROSS SOUTHERN AND ERN PENN. PWATS IN EXCESS OF OVER 1 INCH NEAR THE DELMARVA AND SRN NJ COAST WILL BE TRANSPORTED NWWD UP/OVER THE SHALLOW COLD AIR ENTRENCHED ACROSS CENTRAL PENN AND THE SUSQ VALLEY. COORDINATED WITH SURROUNDING WFOS TO BOOST POPS /AND THE NORTHEAST TO NORTHERLY WIND/ FOR THURSDAY AFTERNOON AND NIGHT. WE EVEN SPECKLED IN SOME WET SNOW MIXING IN LATE THURSDAY/FRIDAY MORNING ACROSS THE LAURELS AOA 2400 FT MSL. THE MUCH COOLER GFS/GEFS TEMPS APPEAR MORE REALISTIC AT THIS POINT AS CLOUDS THICKEN.../AS RAIN DEVELOPS ACROSS THE REGION FORM THE SOUTH AND WEST/ AND FALLS THROUGH THE WEDGE OF RELATIVELY DRIER/COOLER AIR NEAR THE SFC.
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&& .AVIATION /10Z MONDAY THROUGH FRIDAY/... 27/09Z... NO CHANGES FOR INTERMEDIATE UPDATE AT 09Z. REGIONAL RADAR SHOWS SHOWER ACTIVITY INCREASING OVER LAKE ERIE/WRN NY WHICH SHOULD REACH THE NW AIRSPACE BY 12Z. 27/06Z... AN UPPER LEVEL DISTURBANCE EMBEDDED WITHIN A BROADER CYCLONIC/CCW CIRCULATION OVER THE NERN U.S. WILL MOVE SWD THROUGH NY STATE AND ACROSS CENTRAL PA AIRSPACE TODAY. THIS WILL RESULT IN DIURNALLY FAVORED SHOWER ACTIVITY /POSSIBLY MIXED WITH SHSN EARLY THIS MORNING AT BFD/ AND BKN TO OVC MVFR TO LOW- END VFR CIGS. WINDS FROM 290-320 WILL GUST UP TO 20KTS AT TIMES THIS AFTN. LOOK FOR SHOWERS TO DISSIPATE AFTER 00Z WITH LITTLE TO NO CHANGE IN FCST CIGS FOR THE OVERNIGHT PERIOD. HIGHEST CONFIDENCE IN MVFR CIGS IS OVER THE WRN HIGH TERRAIN TAF SITES IN ZOB SECTOR. OUTLOOK... TUE...MVFR CIGS WEST/LOW-END VFR CIGS CENTRAL AND EAST. WED...NO SIG WX. THU-FRI...MVFR POSSIBLE IN SCATTERED RAIN SHOWERS. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...LAMBERT AVIATION...STEINBUGL

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