Area Forecast Discussion
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856 FXUS61 KPBZ 251715 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 115 PM EDT Mon Sep 25 2017 .SYNOPSIS... High pressure will bring dry and warm weather through mid-week before the passage of a cold front heralds a return to seasonably-cool conditions. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Upper-level moisture on the outskirts of Maria (off the Carolinas) will maintain a veil of occasional cirrus today as the clouds continue to move nwd. Otherwise, the region will remain in a generally-subsident ridging pattern, with strong insolation leading to afternoon temp maxima approaching 90F (given the pre-existing warm airmass evident in the 12Z PIT RAOB). No rain is expected today given the dry air in the mid levels of the atmosphere and a lack of lift. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/... One weak jet streak that advected cirrus northward into our area will peel off to the east by Tuesday. This will allow for skies to clear yet again. Better insolation likely will be offset by a fall off of about 1C in 850 mb temperatures and loss of about 10 dam in 500 mb heights. Thus, highs will trend toward the same numbers on Tuesday as Monday, which will continue the trend of temperature above seasonal levels. By Wednesday, the pattern looks set to finally start to break down as an upper trough starts to shear off to the northeast as it lifts through the Great Lakes. Moisture below the upper levels is exceedingly modest with the diffuse H5 wave that moves across the area largely beyond the diurnal maximum on instability. Thus, while fairly impressive temperature falls will be noted with the front, an utter dearth of moisture in the column combined with forcing anywhere beyond the boundary layer pushing well to the north of the area will mean what looks like a largely dry frontal passage. Some slight chance PoPs were added for the northern fringe of the area, but it would seem most areas should remain dry through the frontal passage. By Thursday, cyclonic flow and constant cold advection will have dropped 850 mb temperatures roughly 10C from their levels earlier in the week. As such, highs will be struggling to reach 70F even as dry weather continues. Fries && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... Further changing of the pattern looks likely in the long term. While post-frontal cyclonic flow will continue through the remainder of the week, a much deeper upper level system will arrive for the weekend. Substantial cooling seems likely with this system in the mid-levels as it transits the Great Lakes and heads into the northeastern CONUS. As a result, instability will increase markedly and mid-level moisture will finally arrive. Shower chances maximize with its passage on Saturday likewise. Saturday`s system and increase in clouds will drop temperatures back toward their coldest point of recent memory. Without much in the way of sunshine and 850 mb temperatures dropping toward +3 or +4C in the daytime, highs much beyond the mid 60s in the lower elevations seem unrealistic. Even still, this will only be a couple of degrees above normal for one day after a stretch of above-normal days that will have been going on since September 13. Fries && .AVIATION /17Z MONDAY THROUGH FRIDAY/...
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High pressure will maintain light southeast wind and VFR through the TAF period. In the early morning hours of Tuesday morning some non-VFR visibility restrictions possible from patchy morning fog. .Outlook... Restrictions are possible with cold fronts Wed night and Fri.
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&& .CLIMATE... While we will not be quite as warm as over the weekend, temperatures will still be 15 or more degrees above normal this afternoon. Here are the local record high temperatures for Monday: PIT: 92 (1881, 1900) ZZV: 94 (1908) MGW: 93 (1930) DUJ: 87 (2007) HLG: 91 (1934) PHD: 91 (2007) && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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