Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 302012 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 412 PM EDT MON MAR 30 2015 .SYNOPSIS... A POTENT BUT RELATIVELY FAST MOVING AREA OF LOW PRESSURE WILL MOVE SOUTHEAST FROM THE WESTERN GREAT LAKES TONIGHT AND RIDE ALONG THE MASON-DIXON LINE TUESDAY...BRINGING HIGHLY ELEVATION DEPENDENT SNOW ACCUMULATION OF A FEW TO SEVERAL INCHES ACROSS THE NORTHERN HALF TO TWO THIRDS OF PENNSYLVANIA. MIXED PRECIPITATION OR RAIN WILL FALL ACROSS THE SOUTHERN TIER OF PENNSYLVANIA. A SHARP MODERATION IN TEMPERATURES WILL OCCUR THURSDAY BEFORE A NEW COLD FRONT APPROACHES FOR FRIDAY WITH RAIN SHOWERS...POSSIBLY CHANGING TO A PERIOD OF SNOW AT NIGHT ACROSS MUCH OF CENTRAL AND NORTHERN PENN. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... GUSTY WNW WINDS WITH MSTLY CLOUDY TO CLOUDY SKIES AND A FEW BANDS OF BRIEF RAIN SHOWERS...AND MTN SNOW SHOWERS WILL PREVAIL THROUGH SUNSET. BRIEF CLEARING WILL OCCUR EARLY TONIGHT WITH WINDS TAILING OFF TO LIGHT AND VARIABLE IN MANY LOCATIONS AFTER MIDNIGHT. THIS WILL ALLOW MIN TEMPS TO SETTLE INTO THE MID 20S TO LOWER 30S. THE STAGE WILL BE SET FOR YET ANOTHER EARLY SPRING /WINTRY/ WEATHER EVENT FOR MUCH OF CENTRAL AND NORTHERN PENN BEGINNING AROUND OR SHORTLY BEFORE DAYBREAK TUESDAY ACROSS THE WESTERN MTNS...THEN SPREADING ACROSS THE REMAINDER OF THE REGION DURING THE MID TO LATE MORNING HOURS. MORE TO FOLLOW IN THE SHORT TERM SECTION BELOW. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... MODELS ARE IN GOOD AGREEMENT ON THE TRACK OF A POTENT CLIPPER ALONG THE MASON-DIXON LINE DURING THE DAY TUESDAY. THREE OR FOUR FACTORS GREATLY COMPLICATE THE FORECAST FOR SNOWFALL AMOUNT ACROSS THE REGION TUESDAY. THE FIRST BEING THE EXACT TRACK AND QPF...SECOND IS THE TIMING OF THE HEAVIEST SNOWFALL RATES DURING THE MORNING /A FEW HOURS FASTER MEAN MORE SNOW/...AND THIRD BEING A LARGE DEGREE ELEVATION DEPENDENCY. IN ANY CASE...A SEVERAL HOUR PERIOD OF MODERATE TO STG UVVEL ASSOCIATED WITH THE LEFT EXIT REGION OF A 100 KT UPPER JET WILL BRING A MODERATE TO BRIEFLY HEAVY SNOW TUESDAY MORNING...GRADUALLY TAPERING TO AREAS OF LIGHTER SNOW/SNOW SHOWERS FOR THE MID TO LATE AFTERNOON. LIKELY SNOWFALL WILL VARY FROM 1-3 INCHES IN THE VALLEYS...AND UP TO 4 OR 5 INCHES OF HEAVY WET SNOW ACROSS THE HIGHER TERRAIN NEAR AND TO THE NORTH OF THE RT 322 CORRIDOR. THERE MAY BE LITTLE OR NO SNOW SOUTH OF THE TURNPIKE AND WEST OF INTERSTATE 81...ALONG AND JUST SOUTH OF THE LOW TRACK. AFTER COORDINATION WITH SURROUNDING OFFICES...WE WANTED TO WAIT FOR AT LEAST ONE MORE RUN TO CONFIRM THE TIMING TRACK AND QPF AMOUNTS BEFORE COORDINATING AN ADVISORY FOR A BORDERLINE AND HIGHLY ELEVATION INFLUENCED EVENT. MULTI MODEL TEMPS FOR TUESDAY/S MAXES ARE IN THE MID 30S ACROSS THE NRN MTNS...AND UPPER 30S TO MID 40S IN CENTRAL PENN...WITH HIGHS AROUND 50F IN THE SOUTH. UNLESS IT SNOWS FAIRLY HARD...MOST ACCUMS AFTER 15Z WILL LIKELY BE ON GRASSY SURFACES. OVER CENTRAL AREAS WHERE A RAIN-SNOW MIX IS LIKELY FOR A TIME...IT SHOULD BE TOO WARM TO STICK. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
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SFC LOW WILL EXIT THE NJ/DELMARVA COAST TUESDAY NIGHT WITH HIGH PRESSURE ARRIVING FROM THE GREAT LAKES. DRY WEATHER WILL PERSIST THROUGH MIDWEEK BEFORE THE PATTERN TURNS INCREASINGLY UNSETTLED FROM THURSDAY INTO EASTER WEEKEND. THE 12Z MODEL AND ENSEMBLE DATA SEEMS TO BE COMING AROUND TO THE IDEA THAT ONE OR TWO FRONTAL WAVES WILL BRING PCPN TO THE AREA FROM THURSDAY INTO SATURDAY. THERE IS STILL SOME SPREAD IN BOTH THE TRACK AND STRENGTH OF THE TRAILING FRONTAL WAVES WITH THE LAST TWO RUNS OF THE EC COMING IN MUCH STRONGER THAN THE GFS. THE CANADIAN IS IN THE MIDDLE IN TERMS OF POSITION BUT LEANS TOWARD THE STRONGER EC. AT ANY RATE THE DETAILS ARE STILL UNCLEAR BUT A MEAN BLEND/CONSENSUS SOLUTION INCORPORATING WPC GUIDANCE SUPPORTS INCREASING POPS INTO THE LKLY RANGE FOR AT LEAST TWO 12-HOUR PERIODS. A SHORTWAVE TROUGH ROTATING THROUGH THE MID ATLC AND NORTHEAST STATES WILL BRING A REINFORCING SHOT OF COOL AIR ON SATURDAY...PRECEDED BY ABOVE NORMAL TEMPS AHEAD OF THE COLD FRONT. THE COOL DOWN SHOULD BE BRIEF WITH MODERATING TEMPS INTO EARLY NEXT WEEK.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/... GUSTY WNW WINDS AVERAGE 10-15 KTS FOR THE NEXT SEVERAL HOURS...WITH GUSTS OF 25 TO 30 KTS AT TIMES WILL BE THE RULE IN THE WAKE OF THE COLD FRONT THROUGH THE REST OF THE DAYLIGHT HOURS. VFR WILL CONTINUE ACROSS ALL CENTRAL PA AND SUSQ VALLEY TAF SITES...WHILE MVFR CIGS WILL BE FOUND FOR THE REST OF TODAY ACROSS THE HIGHER ELEVATION AIRFIELDS OF KJST...KFIG AND KBFD. A FAST MOVING CLIPPER TYPE LOW WILL SPREAD A SHIELD OF STEADY LIGHT TO MDT SNOW ACROSS THE NORTHERN THIRD TO HALF OF PENN VERY LATE TONIGHT AND TUESDAY MORNING WITH CONDITIONS DROPPING TO IFR/LIFR FROM BFD TO POINTS EAST TWD KIPT AND KAVP. IFR IN MIXED PRECIP OR SNOW APPEARS LIKELY FOR THE CENTRAL THIRD OF THE STATE TUESDAY MORNING/EARLY AFTERNOON...WHILE A FEW PERIODS OF LIGHTER RAIN/SNOW SHOWERS WILL OCCUR ACROSS THE SOUTHERN TIER COUNTIES OF PENNSYLVANIA. SOME BRIEF AND LIGHTER RAIN AND SNOW SHOWERS FOR LATE TUESDAY AFTERNOON INTO EARLY WEDNESDAY...IN THE WAKE OF THE LOW PRESSURE AREA. LOOKING COLD BUT DRY ON WED. A SHARP...BUT BRIEF WARMING FOR THURSDAY...WITH A GUSTY SW WIND OF 20-30KTS. OUTLOOK... TUE...CHANCE OF LIGHT SNOW/RAIN...MAINLY ACROSS THE NW HALF WITH MVFR REDUCTIONS. WED-THU MORNING...MAINLY VFR...AS HIGH PRESSURE BUILDS ACROSS THE AREA. THU PM-FRI...LOWERING CONDITIONS TO MVFR WITH SCATTERED RAIN SHOWERS...AS A COLD FRONT MOVES EASTWARD. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LA CORTE/LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...STEINBUGL AVIATION...LAMBERT/MARTIN

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