Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 301542 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1142 AM EDT WED JUL 30 2014 .SYNOPSIS... THE UPPER LEVEL LOW OVER THE UPPER GREAT LAKES AND EASTERN CANADA WILL PERSIST INTO THE WEEKEND. WHILE THE UPPER LOW MAY OPEN UP AND LIFT A BIT NORTHWARD...AN OFF SHORE HIGH PRESSURE AREA WILL DIRECT MORE GULF AND ATLANTIC MOISTURE INTO THE REGION OVER THE WEEKEND. TEMPERATURES WILL REMAIN COOLER THAN NORMALS. && .NEAR TERM /UNTIL 8 PM THIS EVENING/... 11 AM UPDATE... MID LEVEL CLOUDS WERE SPREADING EAST ACROSS NRN AND WRN PENN /AND ABOUT TO SPILL OVER INTO THE CENTRAL RIDGE AND VALLEY REGION/ AS A RESULT OF WEAK WESTERLY ISENTROPIC UPGLIDE WITHIN THE 300-310K THETA LAYER. BREAKS IN THIS CLOUD DECK WILL COMBINE WITH BLYR HEATING AND WEAK LARGE SCALE LIFT AHEAD OF AN APPROACHING UPPER LEVEL SHORT WAVE TO BRING A BKN LINE OR TWO OF SHOWERS AND ISOLATED LOW-TOPPED TSRA TO THE NW HALF OF THE CWA THIS AFTERNOON AND EARLY THIS EVENING. THE LOWER SUSQ VALLEY MAY STAY DRY RIGHT THROUGH THE DAYLIGHT HOURS BEFORE A FEW WEAKENING SHOWERS DRIFT INTO THE AREA AROUND DUSK...AS THE LEADING EDGE OF THE POOL OF SLIGHTLY STEEPER MID LEVEL LAPSE /6-6.5C PER KM/ APPROACHES. HIGH TEMPS THIS AFTERNOON VARY FROM THE MID AND UPPER 60S ACROSS THE NW MTNS...TO THE LOWER AND MID 70S IN THE CENTRAL VALLEYS...AND AROUND 80F THROUGHOUT THE LOWER SUSQ VALLEY. THESE READINGS ARE STILL WELL BELOW NORMAL IN MOST LOCATIONS /ESPECIALLY ACROSS THE NW MTNS WHERE THE EARLIER DVLPMT OF THE CLOUD COVER HAS FLATTENED THE DIURNAL TEMP CURVE/. && .SHORT TERM /8 PM THIS EVENING THROUGH THURSDAY NIGHT/... THE DIURNAL CONVECTION SHOULD SLIDE TO THE EAST THIS EVENING WHILE DYING OUT. THE COLD AIR ALOFT AND CYCLONIC FLOW WILL LIKELY KEEP A FEW SHOWERS AROUND THROUGH THE NIGHT IN THE NW. CHC POPS FOR SCT COVERAGE SHOULD BE FINE THERE. MINS WILL BE BACK CLOSER TO NORMALS TONIGHT...BUT 40S STILL POSSIBLE IN THE HIGHER ELEVATIONS. THE UPPER LOW THROWS ONE MORE UPPERCUT ON THURSDAY MORNING...AND SCT/NMRS SHOWERS EXPECTED IN THE FORE-NOON. THE AFTERNOON MIGHT BE MAINLY DRY...BUT THE TEMPS ALOFT ARE STILL COOL AND DAYTIME INSTABILITY SHOULD BE GOOD ENOUGH FOR ISOLD-SCT SHOWERS IN THE WEST/NORTH. HIGHS ON THURSDAY DO HAVE THE POTENTIAL TO GET BACK TO NORMAL IN THE SE...BUT THE N/W WILL PROBABLY STILL BE 8-10 DEGS BELOW SEASONAL NORMALS. FOR NOW...THE 12-18 HOURS AROUND THE THURSDAY NIGHT PERIOD SEEM LIKE THE LEAST LIKELY TIME FOR ANY SHOWERS TO DEVELOP. THE BIG SHORT WAVE WILL HELP TO HEAVE THE UPPER LOW A BIT TO THE NORTH. HEIGHTS RISE ABOUT 12DAM FROM THURSDAY MORNING TO FRIDAY MORNING. LOWS THURSDAY NIGHT WILL PROBABLY BE SIMILAR TO THE PREV FEW WITH SKIES TRYING TO CLEAR AND WINDS LIGHT/VARIABLE. && .LONG TERM /FRIDAY THROUGH TUESDAY/... A DEEP UPPER LEVEL TROUGH WILL BE PRESENT ACROSS SOUTHEASTERN CANADA EARLY IN THE LONG TERM PERIOD...BUT WILL RELOAD WITH A SIGNIFICANT CHUNK ENERGY DIGGING INTO IT/S SW FLANK ACROSS THE MID MISS AND OHIO RIVER VALLEYS LATE THIS WEEK AND OVER THE UPCOMING WEEKEND /AS THE CANADIAN PORTION SHEARS OUT TO THE NE/. THIS POTENT SHORTWAVE TROUGH /AND AN ASSOCIATED WELL-DEFINED RIGHT ENTRANCE REGION OF A 90-95 KT 300 MB JET/ WILL LIFT NORTHEAST ACROSS THE MID ATLANTIC REGION FRIDAY THROUGH SUNDAY BEFORE SHIFTING TO THE SOUTHERN NEW ENGLAND COAST BY THE START OF NEXT WEEK. A SLOW MOVING /AND LIKELY STRENGTHENING/ BAROCLINIC ZONE... AND ONE OR MORE WAVES OF WEAK LOW PRESSURE MVG NE ALONG IT WILL BE LOCATED ACROSS CENTRAL OR ERN PENN DURING THIS 2-3 DAY PERIOD. PERIODS OF UNSETTLED WEATHER /SHOWERS AND TSTMS/ WILL OCCUR LATER FRIDAY...SATURDAY AND SUNDAY. THE STRENGTH OF THE LARGE SCALE FORCING AND INCREASINGLY ANOMALOUS HIGH PWAT AIR BENEATH THE NORTHWARD MIGRATING JET AND ITS THERMALLY DIRECT BRANCH WILL BRING THE POTENTIAL FOR SOME LOCALLY HEAVY/TRAINING SHOWERS AND TSRA... ESP ACROSS THE EASTERN HALF OF THE STATE/. MODEL DETAILS DIFFER SLIGHTLY WITH RESPECT TO THE TIMING AND LOCATION OF THE STRONGEST MESO/LARGER SCALE FORCING. BUT ALL GUIDANCE AGREES ON THE BASIC EVOLUTION AND NE MOVEMENT OF THIS TROUGH AND AXIS OF HIGH 40-50MM PWAT AIR RIDING NWD UP ALONG THE MID ATLANTIC PIEDMONT AND SPREADING ACROSS THE EASTERN HALF OF OUR CWA. AS A RESULT OF THESE TIMING/LOCATION DIFFERENCES...POPS WERE CAPPED OFF IN THE HIGH CHC CATEGORY. BUT AS THE FINER DETAILS UNFOLD WITH HIGHER RES MODEL GUIDANCE OVER THE NEXT FEW DAYS...POPS WILL UNDOUBTEDLY TREND HIGHER FOR SEVERAL PERIODS BETWEEN LATE FRIDAY AND SUNDAY. GRADUAL IMPROVEMENT WITH NEAR NORMAL TEMPS IS EXPECTED FOR EARLY NEXT WEEK. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... INCREASING /BUT MAINLY VFR CLOUDS/ WILL OCCUR EAST OF THE I-99/ROUTE 22 CORRIDOR IN CENTRAL PENN THIS AFTERNOON. THE NW MTNS AND LAUREL HIGHLAND AIRFIELDS WILL SEE A DUAL LAYER OF STRATO CU AND ALTO CU CLOUDS WITH CONVECTIVE BASES AROUND 3-4 KFT AGL WITH THE MID LEVEL BASES AROUND 7 KFT AGL. SKC OVER MUCH OF THE SE THIRD OF PENN WILL BECOME DOTTED WITH SCATTERED CU THIS AFTERNOON. THE APPROACH OF A WEAK COLD FRONT AND UPPER TROUGH WILL SPARK SCATTERED SHOWERS AND ISOLATED TSRA WITH BRIEF MVFR RESTRICTIONS POSSIBLE THIS AFTERNOON AND EARLY THIS EVENING...MAINLY TO THE NW OF A LINE FROM KAOO TO KIPT. MAINLY VFR FOR TONIGHT WITH LINGERING BKN ALTO CU CLOUDS...AND PERHAPS A FEW STRAY LIGHT SHOWERS. A STRONGER 500 MB TROUGH WILL ROTATE ACROSS THE AREA ON THU...THUS SHOWERS AND STORMS WITH SMALL HAIL WILL LIKELY BE MORE WIDESPREAD THAN TODAY. PERHAPS A SMALL BREAK IN THE ACTION FOR FRIDAY. MODELS SHOW SOME CHC OF SHOWERS ACROSS THE SOUTH BY LATE IN THE DAY. SOME MODEL SPREAD. WITH THE LONGWAVE TROUGH TO THE WEST...NOT SEEING MUCH CHANCE FOR ANY ONE DAY BEING DRY PRIOR TO NEXT MONDAY...IF THEN. OUTLOOK... THU...SCT TSRA IMPACTS POSSIBLE. FRI-SUN...SCT PM TSRA IMPACTS POSSIBLE. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DANGELO/LAMBERT NEAR TERM...LAMBERT SHORT TERM...DANGELO LONG TERM...LAMBERT/STEINBUGL AVIATION...LAMBERT

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