Area Forecast Discussion
Issued by NWS State College, PA
Issued by NWS State College, PA
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849 FXUS61 KCTP 301535 AFDCTP Area Forecast Discussion National Weather Service State College PA 1135 AM EDT Sun Jun 30 2024 .SYNOPSIS... A cold front will push across central Pennsylvania later today, accompanied by scattered showers and thunderstorms. Severe thunderstorms are possible. 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 7 PM THIS EVENING/... Main cold front has likely cleared LE, but dewpoints not dropping yet behind the best wind shift and lowest overall pressures. BFD pressure went down a little this hour vs last. But, it could be coming up right now (after last ob (old mets call that a check rise)). There must be more than one wave of cooler/drier air pushing in. That means we should hold onto PoPs for the nrn tier into the aftn. Showers starting to climb in intensity a little, but still rather tame at 1030 AM. Still expecting SVR to occur this aftn and early evening, and have made minor changes to timing. SPC did nudge the SLGT risk back west just a hair, but not a significant amount/distance. Anticipate a watch close to or over the CWA in the next hr or so. Prev... Sfc cold front is bisecting OH at this time and crossing Lake Erie this morning, and much drier air is filtering in behind it across Michigan where sfc dewpoints drop through the 60s near Detroit to the mid to upper 40s over northern Lower Michigan. Mid level clouds have kept areas of fog from becoming too widespread or dense after the widespread rainfall Saturday afternoon and evening. Additionally, deep layer moisture has decreased substantially over the past 24 hours, with 1 to 1.5" PW across my northern tier this morning where a plume of 2"+ PW resided yesterday at this time. Isolated coverage showers (and still a few lightning strikes over southwest PA) has increased the last hour or so in general moisture convergence ahead of approaching sfc cold front over central OH. Passage of upstream surface cold front later today will bring the chance for another round of deep convection later today, with best severe threat over eastern portions of central PA, coinciding with peak heating of the late afternoon. CAMs are indicating the best likelihood of strong storms later today over my eastern counties where moisture and instability will be greatest and timing of FROPA corresponds with max afternoon heating. Still, a trend towards lesser coverage and intensity of deep convection has been noted from the last few to several CAM runs overall, shifting the greatest coverage and organization of afternoon storms into eastern PA and the Catskills. We do expect a sw-ne aligned line of convection to drop southeastward across central PA from later this morning through the afternoon, and some storms can contain strong gusty winds, heavy downpours and small hail. The reward will be nicely falling dewpoints through the 50s by day`s end across the northern tier. && .SHORT TERM /7 PM THIS EVENING THROUGH 6 PM MONDAY/... Showers and thunderstorms will extend into the early evening hours over the Lower Susq before the front clears my eastern counties. It will be breezy and cooler tonight into Monday as a refreshing air mass similar to last Monday`s drops into the region. Mins tonight will drop into the upper 40s north and Alleghenies and through the 50s elsewhere. Highs Monday will feel even coolish across the north, with some areas struggling to reach 70, and highs farther south will range through the 70s to around 80 southeast with breezy conditions persisting into early Monday evening. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... 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 /16Z SUNDAY THROUGH THURSDAY/... Much of today will be mostly cloudy with MVFR cigs persisting across central and western airfields through early afternoon. A cold front will slide south through the day. Scattered SHRA/TSRA are expected along and ahead of this boundary, with JST, AOO, and UNV having the highest chance of seeing vsby restrictions in brief downpours this morning, and then MDT and LNS this afternoon. Conditions are expected to improve later Sunday, as the winds shift to the northwest and much less humid air moves into the area. The HREF does suggest MVFR cigs are possible at BFD into Sunday night given upslope flow off Lake Erie. Monday and Tuesday look dry at this point with VFR conditions, as high pressure builds into the area. Some valley fog is possible in the north both mornings. Outlook... Wed...PM TSRA moving across from W-E. Thu...A chance of showers and storms. && .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...DeVoir/Dangelo SHORT TERM...DeVoir/Fitzgerald/Steinbugl LONG TERM...DeVoir/Bauco AVIATION...Martin/Colbert CLIMATE...Evans/Steinbugl