Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 290829 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 429 AM EDT WED JUL 29 2015 .SYNOPSIS... SUMMERTIME HEAT AND HUMIDITY WILL BE THE MAIN WEATHER STORY TODAY ACROSS CENTRAL PENNSYLVANIA. A COLD FRONT WILL MOVE THROUGH THE KEYSTONE STATE ON THURSDAY...WITH ISOLATED SEVERE THUNDERSTORMS POSSIBLE NEAR THE LOWER SUSQUEHANNA VALLEY. FRIDAY WILL BE SEASONABLY WARM AND DRY WITH MUCH LOWER HUMIDITY TO CLOSE OUT JULY 2015. && .NEAR TERM /THROUGH TONIGHT/... PATCHY FOG EARLY THIS MORNING WILL BURN OFF BY 10AM AND GIVE WAY TO HAZY SUNSHINE. TODAY WILL BE ONE OF THE WARMEST DAYS SO FAR THIS YEAR WITH MAX TEMPERATURES RANGING FROM THE MID-UPPER 80S IN THE HIGHER ELEVATIONS OF THE WESTERN ALLEGHENIES TO THE LOW 90S FROM THE CENTRAL RIDGE/VALLEY REGION TO THE SUSQUEHANNA RIVER VALLEY. HEAT INDEX VALUES SHOULD REACH 90F IN MOST LOCATIONS AND APPROACH 100F THIS AFTERNOON IN THE MIDDLE AND LOWER SUSQUEHANNA VALLEY. THE VERY WARM AND HUMID AIRMASS WILL ALSO SUPPORT A LOW/ISOLATED RISK OF A LATE AFTERNOON-EVENING SHOWER OR TSTM ACROSS THE FAR SOUTH CENTRAL ZONES. ABOVE AVERAGE PW VALUES WILL POOL ALONG A DIFFUSE BOUNDARY WAVERING NEAR THE MASON DIXON LINE. A CONSENSUS OF HIGH RES MODEL DATA TARGETS THE ELEVATED TERRAIN ALONG THE CENTRAL APPALACHIANS /ERN TN TO SW VA TO WV-MD PNHDLS/ WITH THE BEST OPPORTUNITY FOR SCT CONVECTION. THE HIGHEST POPS LOCALLY ARE AOB 20 PCT FROM SOMERSET TO FRANKLIN COUNTY. THE BEST H85 MSTR FLUX ANOMS/LOW-MID LEVEL THETA-E ADVECTION CROSSES THE AREA LATE TONIGHT INTO EARLY THURSDAY MORNING...IN ASSOCIATION WITH WSWLY LLJ PRECEDING THE PROGRESSIVE SFC COLD FRONT ADVANCING EWD THRU THE GREAT LAKES/OH VALLEY...REACHING THE PA/OH BORDER BY 12Z THU. WILL CARRY LOW CHC POPS INTO THE SECOND HALF OF TONIGHT. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... SHORT TERM MODEL DATA OVER THE LAST TWO CYCLES ARE A TAD FASTER WITH THE EWD MVMT OF THE SFC COLD FRONT FCST TO SWEEP ACROSS SERN CANADA AND THE NORTHEAST/MID ATLANTIC STATES ON D2/THURSDAY. WEAK HEIGHT FALLS ARE STILL EXPECTED TO OVERSPREAD CENTRAL PA ON THE SRN PERIPHERY OF STRONG UPPER TROUGH AMPLIFYING OVER ERN CANADA. EARLY-DAY CLOUD COVER W/ISOLD SHOWERS ALONG EWD-ADVANCING COLD FRONT SHOULD EXTEND FURTHER INTO THE INTERIOR CENTRAL ZONES. WHILE THE BEST LARGE SCALE FORCING FOR ASCENT/0-6KM SHEAR AND MID-LEVEL LAPSE RATES WILL BE DISPLACED FURTHER TO THE NORTH OVER THE NEW ENGLAND STATES...STILL THINK THAT THE SERN 1/3 TO 1/4 OF THE CWA STANDS AT BETTER THAN 50/50 ODDS TO SEE A SCT TSTMS AHEAD OF THE COLD FRONT...A FEW OF WHICH MAY BE STRONG TO MARGINALLY SEVERE WITH LOCALIZED WIND DAMAGE POTENTIAL GIVEN STEEP LOW-LEVEL LAPSE RATES AND DCAPE VALUES IN EXCESS OF 1000 J/KG. PREVIOUS SPC D3 MRGL RISK HAS BEEN SHIFTED SOUTH/EAST NOW COVERING ONLY PORTIONS OF THE LWR SUSQ VLY. DRIER LOW PWAT AIR QUICKLY SPREADS INTO THE AREA BEHIND THE FROPA AND ENDS THE PCPN RISK IN THE FAR SE COUNTIES BY LATE THURSDAY EVE/00Z FRI. && .LONG TERM /FRIDAY THROUGH TUESDAY/... LITTLE CHANGE IS ANTICIPATED IN THE LARGE SCALE FLOW PATTERN ACROSS THE EASTERN U.S. THROUGH THE MEDIUM RANGE PERIOD...WITH A MEAN RIDGE IN THE WEST AND BROAD TROUGH EXTENDING SWD FROM HUDSON BAY VORTEX AND EAST OF THE CONTINENTAL DIVIDE. CONVECTIVE PCPN SHOULD BE RATHER SPARSE AND FOCUSED ALONG WEAKENING NRN STREAM FRONTAL SYSTEMS PROGRESSING SEWD FROM THE GREAT LAKES ABOUT EVERY 1-2 DAYS STARTING ON SATURDAY. CONFIDENCE IN TIMING IS LOW ESPECIALLY INTO EARLY NEXT WEEK GIVEN INCREASING MODEL SPREAD. TEMPERATURES SHOULD COOL BACK TO SEASONAL AVERAGES INTO THE BEGINNING OF AUGUST. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... AS OF 2 AM ONLY TRICKLES OF MVFR ARE BEGINNING TO OCCUR. CURRENTLY ONLY THV AND SEG ARE MVFR WITH DEWPOINT DEPRESSIONS OF 4 OR MORE AT LNS...MDT...IPT AND JST. AS THESE SITES ARE STILL FAIRLY DRY...EVEN CONSIDERING CALMING WINDS AND CLEARING SKIES...ANY FOG/LOW STRATOCU WILL TAKE LONGER TO DEVELOP. THE BEST CHANCE FOR IFR CIGS AND VSBYS WILL BE AT UNV...AOO AND BFD. HERE DEWPOINT DEPRESSIONS ARE 3 OR LESS AND TEMPERATURES ARE FORECASTED TO CONTINUE TO FALL. LIKEWISE WINDS ARE CALM AND SKIES ARE CLEARING. SO EXPECT MVFR PATCHY FOG/MIST TO BEGIN TO FORM BETWEEN 07Z TO 09Z AND INCREASE TO IFR BETWEEN 09Z AND 11Z. MDT AND LNS AND IPT SHOULD GO MVFR WITH IPT HAVING THE POTENTIAL OF IFR JUST BEFORE SUNRISE. FOG AND LOW CLOUDS WILL BURN OFF RAPIDLY EARLY WEDNESDAY LEADING TO ANOTHER VFR/SUNNY DAY UNDER HIGH PRESSURE. CLOUDS WILL START TO ADVANCE WED NIGHT AHEAD OF A COLD FRONT APPROACHING FROM THE WEST. SHOWERS IN ADVANCE OF THE FRONT MAY NUDGE INTO BFD BEFORE SUNRISE THURSDAY. THE FRONT SHOULD PASS EARLY THURSDAY BRINGING DRIER CONDITIONS AND A DECREASE IN THE COVERAGE OF SHOWERS AND THUNDERSTORMS. OUTLOOK... FRI...MAINLY VFR. SAT...MAINLY VFR...PM TSRA POSS W. SUN...MAINLY VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...STEINBUGL NEAR TERM...STEINBUGL SHORT TERM...STEINBUGL LONG TERM...STEINBUGL AVIATION...LA CORTE/CERU

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