Area Forecast Discussion
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042 FXUS61 KPBZ 202151 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 551 PM EDT WED JUL 20 2016 .SYNOPSIS...
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Hot and dry weather is expected tomorrow. Hot and humid weather with periodic thunderstorm chances are expected Friday though the weekend.
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&& .NEAR TERM /THROUGH THURSDAY/...
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High pressure will continue to settle in overhead tonight with cirrus clouds advecting out of the region. Very low dewpoints in place should allow for strong radiational cooling. This will allow lows to drop into the 50s on a widespread basis tonight due to dewpoints largely in the mid 40s to lower 50s. As a side bar, the dewpoint of 39 at PIT currently is clearly not an accurate observation and has been discounted for this forecast. Likewise with dry air in place in the morning and a surface high with its accompanying subsidence shifting to the east during the day, abundant sunshine into the dry boundary layer and dry soils below will be exceedingly efficient in raising temperatures due to the fact that little incoming radiation will be going into latent heating. Additionally, boundary layer flow will turn to the southwest after 18z, which while not likely a long enough duration to bring dewpoints up very much will be enough to increase vertical mixing. This will result in highs jumping toward and into the 90s on a fairly widespread basis by afternoon. Fries
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... A shortwave is progged to approach and cross the region late Thursday night through Friday in northwest flow aloft, resulting in scattered showers and thunderstorms with it`s passage. Instability and shear parameters appear sufficient for a few strong storms, and the SPC marginal risk over the area seems reasonable. Will hold off on an HWO mention for now with uncertainty in the details. Upper ridging is progged to build in across the region from the central CONUS Saturday, with areas north of I 70 expected to stay capped. Diurnally driven instability/thunderstorms are possible to the south, though the ridging should limit the potential. Building heat and humidity is also expected through the weekend, with many locations reaching 90 or above, with heat indices in the mid to upper 90s. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... The ridge is expected to remain across the region through the rest of the weekend, though sufficient instability could result in diurnally driven thunderstorms. The ridge should break down by early next week with better shower/thunderstorm chances associated with a crossing shortwave/surface front. Ridging is progged to redevelop by mid week. Hot and humid conditions should diminish by early next week, though temperatures should still remain a few degrees above seasonal levels. && .AVIATION /22Z WEDNESDAY THROUGH MONDAY/... VFR conditions and light winds can be expected through the TAF period as high pressure remains the dominant feature. Fog at northern TAF locations were not included in the latest TAF issuance based on latest model soundings, however, it is not out of the question as there should be slightly stronger radiational cooling overnight. There will be higher confidence in this later after determining this afternoon`s crossover temperatures and observing dewpoint trends. .OUTLOOK /WEDNESDAY THROUGH MONDAY/... Scattered restrictions in thunderstorms are possible Friday through Monday. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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