Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 250337 AFDCTP Area Forecast Discussion National Weather Service State College PA 1137 PM EDT WED AUG 24 2016 .SYNOPSIS... A seasonably warm and humid late-summer weather pattern will continue across Central Pennsylvania through the weekend. The best chance for scattered showers or thunderstorms will come on Thursday and early next week. && .NEAR TERM /UNTIL 8 AM THURSDAY MORNING/... Still up in the air as to if the current convection in nwrn OH will make it into the wrn mtns w/o falling apart. New NAM does bring it through wetting the entire area in some measure. But, the HRRR and RAP runs of late are less bullish on keeping the area so solid. Both of these rapid update CAMs seem very well-initialized, and appear to have a good handle on things. We have lost what instability we had earlier, and source-region/sfc dewpoints are only in the l-m60s over WV and PA instead of the l-m70s over wrn OH/nrn KY. Will stick with current fcst of high chc POPs in the W before sunrise and drop them into the low chc range as the morning commences. Prev... Tweaks to near term temps and sky cover are all that is needed at this point. Blowoff from convection over IN/OH will make it gradually cloudier through the night. This might keep temps up a little. Prev... Deep layer moisture continues to increase over central PA early this afternoon as return southwest flow has commenced west of the 850 mb ridge moving offshore south of Long Island. Sct fair weather cumulus has slightly more vertical extent than Tuesday as a result...but mid to upper trop is stable and not expecting any diurnal activity this afternoon or evening. Tonight will be fair as deep layer moisture continues to increase. Late night convective complex over the Ohio Valley will be weakening as it makes a dive towards southwest PA in the pre dawn hours...which could bring the West Central Mountains and Laurel Highlands some showers early Thursday morning before complete dissipation. Earlier ARW-E depicted more of a classically right turning complex dissipating as it reached the MD panhandle Thu morning...while latest HRRR is indicating a line of showers and thunderstorms extending from southwest trip of Lake Ontario to southeast Ohio by 07z tonight. Think the latter is more likely to occur...as good moisture convergence along the elongated 850 mb jet advancing from the eastern GLAKS should maintain convection through late tonight before slowly weakening in the pre dawn hours Thu morning. Will adjust pops accordingly for late tonight into Thursday morning. && .SHORT TERM /8 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Have further refined skycover and POPs - allowing for a dry slot behind the early morning scattered showers. However, the guidance keeps high llvl moisture (low clouds) around in the NW after the overnight/morning showers. If those NWrn areas can break out, it will likely allow some heating/instability for the aftn and evening over the NW and sct tsra have a good chc of forming in NW PA and trying to slide into the central mtns. Model CAPEs of 1000 in the NW and 1500 central areas and 06km shear of 30-40kts are respectable. However, there will be some CIN to overcome. MRGL risk seems well- placed at this point. Prev... Did adjust clouds up and temps down slightly for the daytime on Thursday. While precip still looks scattered, the initial cloud cover may delay/hinder heating. Curr POPs and timing of front looking fine. How much/strong convection will be is the question. Prev... Decaying frontal boundary will feed on 2"+ PW Thursday leading to scattered coverage of showers and thunderstorms on Thursday. Main problem may be developing sufficient CAPE as overnight convective remnants from the Ohio Valley may plague a good portion of central PA into Thu afternoon. Latest SPC Day 2 has western portion of my CWA in MRGL risk for Thu afternoon...as setup is far from ideal. Still...the moist and unstable air mass will support scattered convection ahead of the weakening front. Sfc dewpoints will make a run at or exceed 70 in many areas...so it will be noticeably stickier than Wed afternoon. Highs central and north should be a few degrees lower due to cloud cover...while southern areas will warm another degree or two over Wed highs. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... The high pressure over the southeast will weaken the trough moving through and it will become very diffuse on Friday as it slips south toward the Mason Dixon line. Temperatures and humidity will be on the rise with 90F heat likely returning to the Lower Susquehanna Valley by Friday and through the weekend. A drier air mass will reside over the area through most of Sunday. The deep-layer ridge will gradually slide off the Mid Atlantic coast this period, which allows another frontal boundary to sink southward from the Lower Lakes and become quasi-stationary over PA early next week. This will favor unsettled conditions Mon-Tue with POPs trending upward following a mainly dry weekend. Temps will remain above normal by late August standards. && .AVIATION /04Z THURSDAY THROUGH MONDAY/...
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03Z TAFS sent. Minor adjustments made. Earlier discussion below. 00Z TAFS sent. Satellite showing cooling tops north of Lake Erie and near Lake Huron. Remains of this activity and activity over Ohio will likely spread toward the western portion of central PA late. Went VCSH in the western sites. Dewpoints not real high, and there is a breeze out. Thus did not hit the fog or haze hard. Expect winds to pick up at IPT for the next few hours. For Thursday, went with mainly a dry fcst. Did go with VCSH across the east. A warm but mainly dry period Friday into Sunday, as slightly drier builds in from the north. Outlook... Fri...Morning low cigs possible with showers and storms. Improving conditions late. Sat-Sun...No sig wx expected. Mon...A chance of showers and thunderstorms.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...DeVoir NEAR TERM...Dangelo/DeVoir SHORT TERM...Dangelo/DeVoir LONG TERM...Ceru/Steinbugl AVIATION...Martin

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