Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 031932 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 332 PM EDT MON AUG 3 2015 .SYNOPSIS... A LARGE UPPER LOW CENTERED OVER NORTHERN ONTARIO WILL TRANSLATE EASTWARD OVER THE NEXT FEW DAYS. A COLD FRONT WILL PUSH SOUTHEAST AND THROUGH THE STATE LATE TODAY AND EARLY TONIGHT...TRIGGERING A FEW AREAS OF SHOWERS AND THUNDERSTORMS. LARGELY CONFLUENT NORTHWEST FLOW ALOFT OVER THE GREAT LAKES DURING THE MID WEEK WILL HELP HIGH PRESSURE SETTLE IN BEHIND THE FRONT. HOWEVER...THE FRONT WILL HANG UP JUST TO THE SOUTH OF THE REGION AND MAY RETURN NORTHWARD AS A WARM FRONT LATER THIS WEEK. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... WAITING GAME IS ON FOR CONVECTION TO BEGIN FIRING DURING THE NEXT FEW HOURS IN THE MODERATELY UNSTABLE/MDTLY SHEARED ENVIRONMENT OVER THE SUSQ VALLEY...AND LATER ON ACROSS THE NW MTNS AND LAUREL HIGHLANDS OF PENN. THE EARLIER AREA OF CONVECTIVE DEBRIS/LAYERED MID AND HIGH CLOUDS HAS LARGELY DISSOLVED. A DISTINCT PRE...COLD FRONTAL TROUGH SLID EAST ACRS THE ALLEGHENIES AND CENTRAL MTNS DURING THE MIDDAY HOURS...AND LLVL RIDGING AND SEVERAL DEG F OF DEWPOINT DRYING IN ITS WAKE HAS GREATLY NEGATED THE CHC FOR CONVECTION FOR THE NEXT SEVERAL HOURS ACROSS THE CENTRAL AND WESTERN MTNS. LAST FEW RUNS OF THE HRRR INCLUDING THE MOST RECENT 17Z VERSION CONTINUES TO FIRST DEVELOP SHRA/TSRA ACROSS THE MIDDLE SUSQ VALLEY ALONG THE AFOREMENTIONED LEE TROUGH...AND THEN WITH A SURGE OF HIGHER PWAT AIR BENEATH INCREASING DYNAMICS/RE REGION OF AN 80 KT UPPER JET. ALTHOUGH THE SPC DAY ONE OUTLOOK KEEPS THE SLIGHT RISK OVER ALMOST ALL OF CENTRAL PA...WILL MAKE SOME MODIFICATIONS TO THE AREAL DISTRIBUTION AND TIMING OF CONVECTION INTO TONIGHT. MIXED LAYER CAPES OF 1-2K JOULES AND GOOD DEEP LAYER SHEAR WILL CREATE AN ENVIRONMENT WHERE STORMS WILL GROW MODERATELY TALL AND MOVE FAIRLY QUICKLY W-E. 0-3KM BULK SHEAR WILL INCREASE TO 30-35 KTS...WITH 0-6KM VALUES ABOUT 10 KTS FASTER. THE MAIN SEVERE WEATHER THREAT SHOULD BE SEVERAL...EMBEDDED ORGANIZED BOWS WITHIN THE FEW BKN LINES OF SHOWERS/TSRA...CONSIDERING THE NEARLY UNI- DIRECTIONAL VERTICAL WIND PROFILE. IN ADDITION...DOWNDRAFT CAPE PER SPC MESO ANALYSIS PAGE HAS INCREASED TO 1000-1200 J/KG ACROSS ROUGHLY THE SERN HALF OF THE CWA AT 16Z. MARGINALLY LARGE HAIL IS THE SECONDARY SEVERE THREAT IN THIS CASE. HEAVY RAIN DOES NOT SEEM TO POSE MUCH OF A THREAT LATE TODAY/TONIGHT BASED ON THE AMT OF SHEAR NOTED ABOVE...AND LACK OF BACK BUILDING. MESO BETA ELEMENT VECTORS VIA BUFKIT HOURLY SOUNDINGS IMPLY MUCH MORE FORWARD PROPAGATION OF STORMS FROM THE WSW. TEMPS WILL CLIMB ANOTHER 2-4 DEG F THROUGH 21Z REACHING MAXES IN THE U70S NW...L-M 80S CENTRAL ZONES AND U80S TO AROUND 90F ACROSS THE LOWER SUSQ VALLEY. SEVERAL CLUSTERS OF SHRA/TSRA WILL DEVELOP OVER/MOVE EAST INTO THE CWA THIS EVENING WITH THE CFRONT PUSHING SE THROUGH THE STATE OVERNIGHT. COVERAGE OF THE CONVECTION IS MAINLY SCATTERED...BUT A FEW LOCATIONS...ESPECIALLY OVER THE MID SUSQ VALLEY WARRANT LOW LIKELY POPS TO COVER DEVELOPING CONVECTION THERE AND THE ASSOCIATED TRANSITION BETWEEN THE TWO...12 HOUR PERIODS THIS EVENING/OVERNIGHT. LOWS EARLY TUESDAY WILL GET INTO THE 50S IN THE NW BUT FOG MAY NOT BE A PROBLEM DUE TO SOME AIR MOVEMENT. THIS USUALLY SPELLS AREAS OF LOW CLOUDS IN CONTRAST TO FOG. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... A RATHER STRONG UPPER TROUGH AND SECONDARY CFRONT WILL BE DIVING SE FROM THE UPPER GLAKES REGION. ALTHOUGH THE LLVL ENVIRONMENT WILL BE DRIER AND SLIGHTLY COOLER IN THE WAKE OF MONDAY NIGHT/S CFROPA...STG FORCING BENEATH THE L.E. REGION OF A 95 KT JET WILL LIKELY SPARK AT LEAST ISOLATED TO SCATTERED TSRA ACROSS THE CENTRAL AND NRN MTNS. MAX TEMPS WILL VARY FROM THE 70S ACROSS THE NW HALF OF THE CWA...TO THE 80S IN THE SE HALF. CLOSE TO NORMAL FOR LATE SUMMER. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
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THE UPPER LOW OVER NORTHERN QUEBEC SHOULD CONTINUE TO DRIFT TO THE NORTHEAST AND ZONAL TO SLIGHTLY NORTHWEST FLOW IS EXPECTED TO FOLLOW AS A QUASI-STATIONARY BOUNDARY HANGS OUT JUST TO THE SOUTH OF THE STATE. UNCERTAINTY REMAINS IN THE PLACEMENT OF THE BOUNDARY SO WILL KEEP SOME POP IN THE SRN PART OF THE STATE...BUT MOST LOCATIONS WILL BE DRY UNTIL THURSDAY INTO THURSDAY NIGHT. THEN A STACKED LOW WILL SLIDE EASTWARD FROM THE MID MISSISSIPPI VALLEY AND MAY MAKE A MORE-OR- LESS CONSTANT RAIN INSTEAD OF SHOWERY/CONVECTIVE PRECIP. THE UPPER LEVEL LOW WILL FINALLY MOVE OFF LATE NEXT WEEKEND WHICH WILL BE A HERALD FOR QUIETER WEATHER. TEMPERATURES SHOULD TREND COOLER LATER IN THE WEEK BEFORE WARMING UP INTO NEXT WEEK.
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&& .AVIATION /19Z MONDAY THROUGH SATURDAY/... AN APPROACHING COLD FRONT AND PRECEDING SFC/LEE TROUGH OVER THE SUSQ VALLEY WILL ACT AS TWO AREAS OF FOCUS FOR LATE AFTERNOON/EVENING SHRA TSRA WITH SCT/BRIEF MVFR CIGS AND VSBYS. A FEW OF THE STORMS MAY BE STRONG TO SEVERE...WITH VERY BRIEF IFR VSBY IN +RA AND HIGHLY-LOCALIZED WESTERLY SFC WIND GUSTS AOA 40KTS. WILL CONTINUE TO USE -SHRA WITH VCTS BTWN 20-22Z TO SHOW TSTM IMPACT RISK AT ALL TERMINALS. OUTLOOK... TUE...VFR. ISOLD-SCT P.M. SHRA/TSRA CENTRAL AND NRN PENN. WED...VFR. NO SIG WX. THU-FRI...VFR/MVFR WITH RAIN PSBL AS LOW PRES TRACKS SOUTH OF CENTRAL PA. SAT...VFR WITH A LOW CHC OF MVFR IN ISOLATED AFTERNOON SHRA. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...DANGELO/CERU AVIATION...LAMBERT

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