Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 201444 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1044 AM EDT MON APR 20 2015 .SYNOPSIS...
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ANOTHER ROUND OF SHOWERS AND SCATTERED STRONG TO POTENTIALLY SEVERE THUNDERSTORMS WILL DEVELOP THIS AFTERNOON AHEAD OF A STRONG COLD FRONT...WHICH WILL PUSH ACROSS THE STATE MONDAY EVENING. A LARGE UPPER LEVEL LOW WILL SET UP OVER ONTARIO AND QUEBEC FOR THE MIDDLE AND LATTER PART OF THE WEEK...USHERING IN UNSEASONABLY COOL AIR WHICH WILL LAST INTO THE WEEKEND OR LONGER.
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&& .NEAR TERM /UNTIL 7 PM THIS EVENING/...
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INITIAL SHORT WAVE THAT BROUGHT A SUBSTANTIAL 0.5-1.5 INCH RAINFALL ACROSS MUCH OF THE REGION OVERNIGHT AND EARLY THIS MORNING WAS HEADING NE INTO THE NEW ENGLAND STATES LATE THIS MORNING. MINOR RIDGING AT THE SFC AND ALOFT WILL BE OVER THE CWA THROUGH EARLY THIS AFTERNOON...BEFORE ANOTHER POTENT SHORTWAVE ROARS NE UP THE OHIO VALLEY AND IGNITES ONE OR MORE LINES/CLUSTERS OF STRONG TO LOCALLY SVR TSRA. SPC RECENTLY UPGRADED THE PREVIOUS SLIGHT RISK...TO AN ENHANCED RISK ACROSS THE SE HALF OF OUR CWA...WHERE THE PRESENCE OF A SLOWLY LIFTING/MEANDERING WARM FRONTAL BOUNDARY AND PRESENCE OF A SOUTH-SOUTHWESTERLY LLJ OF 30-35KTS WILL ENHANCE LLVL SPEED AND DIRECTIONAL SHEAR ENOUGH TO PROMOTE DVLPMT OF A FEW SUPERCELLS AND A LOW THREAT FOR AN ISOLATED TORNADO OR TWO. NRN AND WESTERN PARTS OF THE STATE REMAIN UNDER A SLIGHT RISK WHERE THE PRIMARY SVR WEATHER THREAT WILL COME IN THE FORM OF LOCALIZED STRAIGHT LINE WIND DAMAGE INVOF BOW ECHOES/BKN-S SIGNATURES IN SHORT LINES. VIS SAT LOOP SHOWS PLENTY OF CLEARING UPSTREAM ACROSS SWRN PENN...WVA AND WRN VA. POCKETS OF SFC BASED CAPES OF 500 J/KG ARE ALREADY DEVELOPING TO OUR SW...AND THIS INSTABILITY WILL QUICKLY RAMP UP OVER THE NEXT SVRL HOURS...AND COMBINED WITH THE INCREASED LARGE SCALE LIFT AHEAD OF THE SHORT WAVE AND EWD ADVANCING CFRONT TO FIRE OFF THE TSRA. CONTINUE TO LEAN TWD EARLIER THINKING THAT NOT MUCH /IF ANY/ OF THE CONVECTION WILL BE ABLE TO ATTAIN NEAR-SEVERE INTENSITY AS IT MOVES INTO THE N-CENTRAL MTNS WHERE SCOURING OF THE MORNING MOISTURE IS LEAST LIKELY AND CLOUDS WILL LIKELY HANG ON THROUGHOUT THE DAY. AGAIN...TSRA THAT OCCUR SOUTH OF RTE 22 SHOULD BE ABLE TO GROW/INTENSIFY AS IT IS DRIVEN EASTWARD AND PERHAPS A LITTLE NORTH OF EAST. ONSET TIMING OF THE LINES OF TSRA...AND THE WINDOW OF THEIR GREATEST IMPACTS...WILL BE ABOUT 17-20Z ACROSS THE LAURELS...19-23Z ACROSS MUCH OF CENTRAL PENN...AND 20Z MON-01Z TUES ACROSS THE SUSQ VALLEY. MAX TEMPS THIS AFTERNOON WILL VARY FROM THE LOWER 60S ACROSS THE NCENT MTNS /NORTH OF THE WARM FRONT/...TO THE LOWER-MID 70S ACROSS SCENT PENN AND THE ADJACENT LOWER SUSQ VALLEY.
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&& .SHORT TERM /7 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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THE INITIAL STORMS SHOULD PUSH EAST OF MOST OF THE AREA IN THE EARLY EVENING. THEY WILL PROBABLY DRAG ON IN LANCASTER COUNTY AFTER SUNSET. THE COLD FRONT/OCCLUSION WILL MOVE IN TO THE WEST AROUND SUNSET...AND WILL BE ACCOMPANIED BY ADDITIONAL SHOWERS AND PERHAPS SOME THUNDER GIVEN THE MOIST ATMOS. THE FRONT SHOULD BE OFF TO THE EAST BY 06 OR 07Z. CLEARING IS LIKELY IN THE SE HALF OF THE AREA DUE TO THE ADVECTION OF DRY AIR. TEMPS DROP QUICKLY AND 0C LINE IS TO UNV BY 09Z. THE COLD ADVECTION AND UPSLOPE WILL LEAD TO SCT SHRA OVER THE NW LATE AT NIGHT AND INTO THE DAY ON TUESDAY. MAXES TUES WILL BE SHY OF 50F IN THE NW AND PERHAPS THE LAURELS AS WELL. THE LOWER SUSQ WILL PROBABLY TOUCH 60F.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... THE PATTERN WILL BE DOMINATED BY A LARGE UPPER LEVEL LOW MOVING THROUGH THE NORTHERN GREAT LAKES...AND THROUGH SOUTHERN CANADA MIDWEEK TO THE WEEKEND. THERE IS GOOD MODEL CONSENSUS THROUGH THE MID RANGE PERIOD. AFTER THE FRONT LIFTS OUT BY TUESDAY MORNING THE UPPER LOW HANGS AROUND S CANADA/NEW ENGLAND FOR SEVERAL DAYS KEEPING FAIRLY BRISK W/NW FLOW ACROSS PA. THIS WILL BRING A STEADY STREAM OF COLDER AIR AS TEMPS SLOWLY SLIP A BIT LOWER EACH DAY WITH BELOW NORMAL READINGS FOR A SEVERAL DAY PERIOD LINGERING INTO NEXT WEEKEND. PROXIMITY OF UPPER LOW WILL ALSO KEEP MENTION OF SCT SHOWERS IN THE FORECAST. A SHORTWAVE SHOULD DROP THROUGH THE REGION WEDNESDAY AFTERNOON INTO THURSDAY MORNING. THIS COULD DROP EVEN COLDER AIR INTO THE REGION BRINGING THE POSSIBILITY OF SNOW TO THE NW TO THE CENTRAL REGIONS OF PA. THE MODELS THEN DIVERGE ON A SOLUTION BUT THE UPPER LEVEL LOW SHOULD CONTINUE ITS EASTWARD TREK...WITH ONLY A SLIGHT CHANCE FOR PRECIPITATION NEXT WEEKEND. && .AVIATION /14Z MONDAY THROUGH FRIDAY/...
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CIGS WILL STAY IN THE IFR TO LOW MVFR RANGE FOR THE NEXT FEW HOURS ACROSS NWRN PENN...AND MUCH OF THE CENTRAL MTNS AND SUSQ VALLEY AS A WARM FRONT MEANDERS/SLOWLY LIFTS NORTH TWD CENTRAL PENN. CONDITIONS WILL SLOWLY IMPROVE THIS AFTERNOON TO HIGH END MVFR OR VFR AROUND THE WESTERN AND SOUTHERN EDGES OF THIS MORE PERSISTENT AND LOWER STRATUS DECK FROM THE WEAK EAST TO SE LLVL FLOW. THE POOREST FLYING CONDITIONS MAY LINGER THE LONGEST FROM KUNV TO KIPT AND POINT NORTH. TSRA IMPACTS /BRIEF IFR CIGS AND IFR VSBYS/ LIKELY AT MANY AIRFIELDS THIS AFTERNOON INTO EARLY THIS EVENING AS A FEW LINES...CLUSTERS OF STRONG TO POTENTIALLY SVR TSRA FORM TO OUR SW AND RACE FAIRLY QUICKLY TO THE ENE AT 35-45 KTS. ISOLATED AND BRIEF OCCURRENCES OF STRONG SW-WESTERLY WIND GUSTS OF 40-50KTS ARE POSSIBLE TOO. A STRONG SFC COLD FRONT PUSHES EAST ACROSS ALL AIRFIELDS LATE TODAY /WEST/ AND EARLY TONIGHT /ACROSS THE CENTRAL MTNS AND SUSQ VALLEY REGION/. COLDER AND MOIST WESTERLY UPSLOPE FLOW IN THE WAKE OF THE FRONT WILL QUICKLY LOWER CIGS AT KJST AND KBFD BACK DOWN INTO THE IFR OR LIFR RANGE TONIGHT AND EARLY TUESDAY WITH AREAS OF MVFR LINGERING DURING THE DAY TUESDAY. FOR THE CENTRAL VALLEYS AND SUSQ VALLEY AIRFIELDS...VSBYS WILL EB VFR TO BRIEF MVFR IN SHRA TONIGHT...WHILE CIGS IN THE MVFR RANGE SHOULD BE FAIRLY WIDESPREAD AS THE MUCH COOLER AIR PUSHES IN. BKN CIGS IMPROVE TO MAINLY VFR BY LATE MORNING TUESDAY ACROSS THIS SAME REGION. OUTLOOK... TUE-FRI...PERSISTENT NW FLOW PATTERN EACH DAY WILL FAVOR MVFR CIGS OVER THE NW AIRSPACE IN ZOB SECTOR...WITH MAINLY VFR CONDITIONS PREVAILING IN ZNY DOMAIN. SCT SHOWERS WILL BE POSSIBLE ACROSS ALL OF THE AIRSPACE THROUGH THE REMAINDER OF THE WEEK.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...DANGELO/LAMBERT LONG TERM...CERU/RXR AVIATION...LAMBERT

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