Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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416 FXUS61 KCTP 010701 AFDCTP Area Forecast Discussion National Weather Service State College PA 301 AM EDT Mon Jul 1 2024 .SYNOPSIS... A large high pressure system will build into the region tonight and Monday, followed by a dying cold front pushing in from the Great Lakes and stalling out over the area by the middle of next week. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... Much drier air advecting into the region this evening with mainly clear skies noted over the Bulk of Scent PA and the Susq Valley at 0130Z. Cooler air and steep llvl lapse rates advecting SE beneath a moderately strong subsidence inversion based at 4-5 kft agl was producing a very rare case of lake effect clouds over and SE of Lake Erie (850 mb temps around +2-3C at KBFD) with fairly widespread high end MVFR and low end VFR OVC cigs across about the NW 1/2 of the state attm and this cloud deck will continue to advance just a bit more south and east overnight, but greatly break up to sct- bkn VFR (>3000 FT agl) across the Central Ridge and Valley region. Aside from some patchy drizzle or a few periods of very light rain from the 2-3 kft thick strato cu layer across the Northern Mtns overnight (with QPF generally a few hundredths of and inch or less), POPs over the Central Ridge and Valley Region and SE PA (where skies will be mainly clear) will be essentially zero. Low temps will vary from the upper 40s throughout the perennial cold rural valleys of the NW Mtns and Somerset Cty, to around 60 in the SE Metro Areas. && .SHORT TERM /8 AM THIS MORNING THROUGH 6 PM TUESDAY/... High pressure (1026 mb or +2 Sigma) builds in over the next 30 hrs and becomes centered near the PA/NY border late tonight. Today should be sunny after the clouds over the Northern and Western Mtns dissipate (for the most part). Wind continues to veer to the N and the dewpoints should drop even more in the deepest mixing of the day. Td in the m40s should be common in the wrn half of the CWA in the aftn. Tonight should be foggy in the nrn and central valleys despite the dewpoints in the 40s as the air temp should get a bit lower than the river/creek water temps. Otherwise, light/no wind under the center of the 1025 high pressure area will help temps down into the m40s to l50s. Fair and warmer weather is expected Tuesday into at least the first half of Wednesday, as upper level ridging builds over the state and surface high drifts offshore. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Central US upper ridge will drift east and maintain fairly good amplification until Wednesday night/Thursday when a weakening shortwave passes well north of PA late Wed into Thursday. The dying cold front is likely to sag into the state Thursday and stall out in the vicinity of PA through Friday. Falling heights/surging low level moisture ahead of the front could support scattered convection as early as Wednesday afternoon over the northwest half of PA. However, a better chance of showers/tsra areawide will come with the arrival of the front Thu into Friday. Early best guess of late week rainfall based on ensemble plumes ranges from 0.25 to 0.75 inches, with the highest amounts over the N Mtns and least in the south. Heat and humidity should peak ahead of the front Wed-Thu. Ensemble mean 850mb temps surging to near 20C indicate max temps could reach the low to perhaps mid 90s in the Lower Susq Valley Thursday, with high humidity pushing heat indices into the mid and upper 90s. Ensemble plumes suggest slightly cooler daytime temps late in the week, due to more clouds and scattered mainly afternoon and early evening showers and TSRA. However, high pwats in the vicinity of the stalling front should result in warm and humid days followed by muggy nights and above normal min temps the entire second half of this week. Models begin to diverge as we head into the weekend. Most guidance suggests that rain chances stick around through at least Saturday as another cold front approaches the area. && .AVIATION /07Z MONDAY THROUGH FRIDAY/... High pressure building in from the Grt Lks will bring VFR and breezy conditions to most of Central PA tonight. However, residual low level moisture ascending the Alleghenies will result in predominantly MVFR cigs from KBFD southward through KJST, with tempo IFR cigs in vicinity of KBFD through around 06Z. MVFR is also possible at AOO and UNV. A downsloping flow should keep conditions VFR east of the Alleghenies tonight. Mixing of much drier air aloft should cause any early stratocu to dissipate by late Monday morning, with widespread VFR conditions expected the rest of the day. A fairly tight pressure gradient should result in gusty north winds for much of the day with gusts in the 20-25kt range for most of the region. Expect winds to diminish toward evening, as the center of the high pressure system pushes into PA. Outlook... Tue...Patchy AM valley fog N Mtns. Wed...Evening tsra impacts possible NW Mtns. Thu...AM low cigs possible W Mtns. Sct PM tsra impacts possible. Fri...Sct tsra impacts possible, mainly PM. && .CLIMATE... At the Altoona Airport, a daily record rainfall of 0.77 inches was set on Sat, Jun 29. This total breaks the old record of 0.53 inches set back in 1972. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/DeVoir NEAR TERM...Lambert/Dangelo SHORT TERM...Dangelo LONG TERM...Lambert/Bauco AVIATION...Fitzgerald/Colbert CLIMATE...Evans/Steinbugl