Area Forecast Discussion
Issued by NWS State College, PA

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406 FXUS61 KCTP 211416 AFDCTP Area Forecast Discussion National Weather Service State College PA 1016 AM EDT THU JUL 21 2016 .SYNOPSIS... Pennsylvania will be on the northern edge of a subtropical ridge through next week with shortwave passages likely late Friday and late Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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High pressure will move off the Mid Atl coast today...allowing return sw flow to advect warmer and eventually more humid air into the state. Large scale subsidence and still low pwats should ensure another dry day with abundant sunshine. GEFS mean 8h temps arnd 18C should translate to max temps from the m80s over the high terrain, to near 90F in the valleys.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
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Shortwave and assoc swrly ll jet will advect increasing moisture/instability into northwest Pa late tonight. 00Z NCAR ensemble output supports the idea of a dying line of tsra working into the nw mtns arnd dawn Friday, as parent shortwave and best lg scale forcing pass well north of the state. A swrly breeze and rising dwpts should result in a much warmer night than those recently, with min temps in the m60s across much of the region. After a lull in activity during late am/early aftn, a second opportunity for sct tsra appears possible late in the day across mainly northern Pa, as diurnal heating results in moderate CAPES along axis of anomalous PWATs extending from the lower lakes into southern New Eng. 00Z NCAR ensemble data indicates the best chc of late day tsra 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 the mdl thermodynamic/kinematic profiles suggest the northern tier is most susceptible to a few strong storms. 8h temps rising to nr 20C should translate to max temps from the m-u80s over the Alleghenies, to 90-95F elsewhere. The heat, combined with rising humidity, should result in widespread heat indices in the 90s.
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&& .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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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. Any rainfall Monday is likely to do little to stem the dry pattern we have been in. Latest GEFS mean qpf is only a couple tenths of an inch Monday. 00Z ECENS/NAEFS mean 8h temps are near 20C Saturday through Monday, indicating the potential of several days in a row with highs in the 90s in the valleys. 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. 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.
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&& .AVIATION /14Z THURSDAY THROUGH MONDAY/...
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Widespread VFR expected through most of tonight. TS may cross Lake Erie and impact the far northwest airspace between 06-12z Friday. Isolated to widely scattered TS are possible across the entire airspace Friday into Friday night. OUTLOOK... SAT-SUN...Early morning fog possible...otherwise no sig wx. MON...Restrictions possible with chance of TS.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Fitzgerald/La Corte NEAR TERM...Fitzgerald/La Corte SHORT TERM...Fitzgerald LONG TERM...Fitzgerald/Ceru AVIATION...La Corte/Steinbugl

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