Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 270542 AFDCTP Area Forecast Discussion National Weather Service State College PA 142 AM EDT Thu Apr 27 2017 .SYNOPSIS... A strong subtropical ridge over the western Atlantic will dominate our weather through Monday. A front will weaken as it moves into the ridge late Thursday triggering thunderstorms. Then ridge will build westward over the weekend. We will be on the warm, moist western side of the ridge most of the weekend. A classic dirty warm up with warm moist air and potential diurnal thunderstorms. Alas, a strong trough should bring cooler drier weather to the region for the second part of next week. && .NEAR TERM /UNTIL 9 AM THIS MORNING/... GOES-16 3.9-11.2um loop at 05Z showing stratus over eastern Lancaster and Schuylkill counties making little progress westward and latest HRRR 925mb RH fields suggest this will remain the case through dawn, with skies remaining mclear across the bulk of the CWA. A light southerly breeze should keep fog at bay over most of the region. However, a lighter gradient across the Lower Susq Valley will allow patchy fog to remain an issue over that part of the state early this morning. Temps on track to bottom out in the mid to upper 50s around dawn. && .SHORT TERM /9 AM THIS MORNING THROUGH FRIDAY NIGHT/... Other than the morning fog/stratus across eastern Pa, it should turn out to be a very nice/warm day with many areas topping out near 80F. The POP, CAPE, and PWAT fields all suggest a front approaches from the west in the afternoon. Noted the 12Z GFS is slower and our superblend is drier than previous runs. No real QPF in our region until around 2100 UTC and by 0000 UTC it gets to central PA and dies. The GEFS is not in yet. Clearly any showers/thunderstorms will most likely be in the late afternoon or evening hours. Only modest CAPE where the LLJ is the strongest. In the 600-900JKG-1 range. Better CAPE in some models/members to southeast where there is less lift and weaker winds. The front is moving into a strong ridge and it is a bit moisture starved. Overnight Thursday into Friday showers end or die out in central areas. A bit cooler and drier overnight Friday into Friday AM. The PW is normal to below normal and the 850 hPa temps are closer to normal to a tad above normal. There is no CAPE to speak of. Friday looks potentially like a really nice warm late April day. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... High amplitude upper pattern to start the period will become more zonal by Days 2/3 as a vigorous trough and strong cold front swing through the region on Monday, bringing cooler conditions through the middle of next week. The region remains on the western periphery of a strong western Atlantic upper ridge, which leaves us susceptible to daily mainly diurnally driven shwr and tstm chances Saturday and Sunday. Continued to utilize a NBM/ECENS/WPC blend for max/min temps and POPS which maintained good continuity with previous fcst. While both weekend days feature a chance of showers and thunderstorms, most of the time will be dry and warm with highs both days ranging through the 70s in most places. Saturday may crack 80 over much of the southeast third of central PA. Max POPS during the extended period remain centered on Monday/May 1st as the aforementioned cold front crosses the Appalachians and continues toward the Atlantic seaboard. A severe weather threat may evolve downstream from the OH Valley into the Mid Atlantic late Monday before temperatures decline to near normal behind the cold front for next Tuesday and Wednesday. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... As of 11 PM, starting to see stronger and faster return flow than I expected. Also some lower clouds at LNS for a few minutes. Did adjust 03Z TAF package some for the above factors, but did not want to back off fog and lower clouds later too much. Earlier discussion below. A nice evening outside. VFR conditions this evening will prevail. However, some lower CIGS and visibilities later, given clear skies, recent wet conditions, and light winds. Expect poor conditions to burn off by mid to late morning, as winds pick up and the strong late April sun prevails. Did not go quite as high as guidance with winds at IPT Thursday afternoon, this area not quite in the gradient yet at 00Z. Also strong winds often pick up there just after 00Z until late evening. Some showers and perhaps a thunderstorm across western areas by 00Z Friday, as a cold front moves eastward. Outlook... Fri...No significant weather. Sat-Sun...A few showers possible. Mainly dry with VFR conditions for much of the time. Mon...Showers and thunderstorms likely. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Grumm NEAR TERM...Fitzgerald SHORT TERM...Grumm LONG TERM...DeVoir AVIATION...Martin

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