Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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172 FXUS61 KCTP 302331 AFDCTP Area Forecast Discussion National Weather Service State College PA 731 PM EDT Sun Jun 30 2024 .SYNOPSIS... A cold front will push across south-central Pennsylvania accompanied by scattered showers and thunderstorms. Severe thunderstorms are possible, mainly east of I-99. 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 11 PM THIS EVENING/... Severe to near-severe storms are just ahead of the real dry air and front. While small showers will pop up on the front over the next few hours, these will be passing over already-cooled sfcs. Have started to trim the watch off as the storms move to the south. CAPE is reaching near 2500 in the sun to the south of the line of storms. But, there isn`t much convergence with the hodographs nearly straight lines over the wrn half of the CWA, now. We should start to see cells over the SErn half of the area in advance of the main line, and these may have a little directional shear. All the storms should be off to the SE of the area around 6-7PM, right around or slightly before ending time of the watch. Wind is gusting into the 20s as the dry air invades and temps have even dropped a little in the NW, and significantly over wrn NY where JHW is into the 50s with help from the clouds thickening there. && .SHORT TERM /11 PM THIS EVENING THROUGH 6 PM MONDAY/... The wind should stay up at least 5KT thru the night everywhere. Cloud cover should expand a little into the rest of the Alleghenies early tonight. The dewpoints will be dropping to 45-50F thru the night NW and 50-53F in the SE. Refreshing. Not much clearing is expected for the wrn highlands, either, so fog is not a real concern. Mins will be about 50F in the west with a spot or two in the u40s. High pressure builds in over the next 30 hrs. Mon should be sunny after the clouds in the NW 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. Monday night 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. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... Canadian high pressure builds to southern Ontario by Monday night, bringing a fair and cool night with the high moving directly overhead. This will result in efficient radiational cooling and min temps several degrees below normal. 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. All medium range guidance tracks a weakening shortwave well north of PA late Wednesday 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 week, due to more clouds/showers. However, high pwats in the vicinity of the stalling front should result in muggy nights and above normal min temps the entire second half of next 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 /00Z MONDAY THROUGH FRIDAY/... High pressure building in from the Grt Lks will bring VFR and breezy conditions to most of Central PA tonight. However, upstream observations and latest model soundings indicate residual low level moisture ascending the Alleghenies will result in MVFR cigs from KBFD southward through KJST. The MVFR stratocu has overspread the NW Mtns as of 23Z and model guidance suggests it will reach KJST by 01Z-02Z. 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. Bufkit soundings support 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...DeVoir NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...DeVoir/Bauco AVIATION...Fitzgerald CLIMATE...Evans/Steinbugl