Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 220715 AFDCTP Area Forecast Discussion National Weather Service State College PA 315 AM EDT FRI JUL 22 2016 .SYNOPSIS...
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Pennsylvania will be on the northern edge of a subtropical ridge into next week. An upper level disturbances and associated weak cold front across the northern great lakes will move southeast and cross Pennsylvania late today and tonight accompanied by isolated to scattered, mainly afternoon and evening showers and thunderstorms. Mostly sunny, very warm, and generally dry conditions will follow for the upcoming weekend.
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&& .NEAR TERM /UNTIL 8 AM THIS MORNING/...
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Very warm temps aloft (around 8C at 700 mb) residing over the state at 07Z, with even warmer mid-level temps upstream to our northwest, will combine with only weak to mdt llvl positive theta-e advection to bring just very minimal chances for a shower or TSRA through the mid morning hours. The rest of the overnight will stay mainly dry, with just a very low (20 percent chc of less) POP painted across the NWS mtns of the state. Low temps around sunrise will vary from the lower 60s over the Laurel highlands, to the mid and upper 60s elsewhere.
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&& .SHORT TERM /8 AM THIS MORNING THROUGH 6 AM SATURDAY/...
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Shortwave topping the ridge into the nw flow aloft will advect increasing moisture/instability into the region today. Ensembles point to an increase in the PWATs ahead of the shortwave and associated weakening cold front (that should make it to the the intersection with a developing lee trough somewhere across north-central PA or the Susq Valley. After the early day activity fades, diurnal heating and weak convergence with the dying front will bring the chance for additional showers/thunder mainly during the mid day and afternoon hours and mainly over northern areas. Deterministic guidance shows mid level temperatures on the order of 9-11C which will act as a convective deterrent, limiting the extent of development and doing little to break the recent extended period of widespread dry conditions we have been experiencing. 00Z NCAR ensemble data indicates the best chance for late day thunderstorms will be across northeast PA, closest to trailing shortwave tracking across upstate NY. SPC has placed nearly all of central Pa in a marginal risk area Friday, but with the expected warm mid levels, thinking is that convective activity will be widely scattered with the very far north being most susceptible to a few strong storms. 8h temps rising to near 20C should translate to max temps this afternoon ranging from the m/u80s over the Alleghenies, to 90-95F elsewhere. The heat, combined with rising dewpoints, should result in widespread heat indices in the 90s.
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&& .LONG TERM /SATURDAY THROUGH THURSDAY/... Big story in the extended fcst is expected heat wave lasting into early next week, as axis of subtropical ridge briefly shifts from the plains to the northeast conus. Anomalous upper lvl ridging building over PA should bring hot and mainly dry wx this weekend, as warm temps aloft suppress convection. Next chance of shra/tsra for most of the area comes Monday ahead of shortwave working across the Great Lakes. However, any rainfall Monday is likely to do little to stem the dry pattern we have been in. Latest GEFS mean qpf is up to a half an inch at most. 12Z ECENS/NAEFS mean 8h temps are near 22C Saturday through Monday, indicating the potential of several days in a row with highs in the 90s in the valleys. The hottest temps look to be on Saturday as latest GEFS gives high temperature anomalies in the +4 standard deviation and have slightly backed off on Sunday. Have adjusted Max temperatures accordingly. Heat indices around 100F appear possible by Mon across the Susq Valley, as higher dewpoints are advected into the area. Overnight lows are also a concern as the area doesn`t cool off at night through the weekend with Southern PA lows in the 70s with highest readings Monday morning. Some modest cooling appears likely by Tue/Wed of next week behind weak cold front. However, temps still likely to remain somewhat abv normal within a generally zonal flow. && .AVIATION /07Z FRIDAY THROUGH TUESDAY/... Little changes to evening TAF update. VFR conditions continue to prevail across central Pennsylvania airfields. As expected, convective line has dissipated before moving into Pennsylvania. Upper lakes MCS making a significant dive southward, and also not expected to affect central Pennsylvania overnight. Isolated to widely scattered thunderstorms are possible across the entire airspace Friday into Friday night, but coverage and certainty too low to include in any TAFS at this point. Highest risk would likely be across northern and central areas. OUTLOOK... SAT-SUN...Early morning fog possible...otherwise no sig wx. MON-TUE...Restrictions possible with a chance of SHRA/TSRA. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert/Martin SHORT TERM...La Corte/Lambert LONG TERM...Fitzgerald/Ceru AVIATION...Jung

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