Area Forecast Discussion
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000 FXUS61 KPBZ 240104 AAB AFDPBZ Area Forecast Discussion...UPDATED National Weather Service Pittsburgh PA 904 PM EDT Mon Apr 23 2018 .SYNOPSIS... Slow- moving low pressure will return rain chances late tonight through mid-week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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Showers spreading north and east ahead of a surface low are finding it difficult to reach the ground, as a very dry atmosphere is in place across the region. 00Z PIT sounding shows a very dry atmosphere below 700mb, with only some modest increase in moisture above 700mb up to 500mb. Would think that showers that swing through the area tonight would use most of their available moisture to slowly saturate the layers below 500mb. Have kept PoPs mainly in the chc category overnight.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... Better rain chances are expected Tue with increasing deep- layer moisture and dynamic support as the closed upper low drifts newd, despite downsloping, shallow sely low-level flow. The sely wind is expected to become gusty on the lee side of the ridges, though model sounding progs indicate the strongest winds capped above an inversion with gusts of 20-30 kt expected. Although the closed low will decay into an open wave, new models suggest that the wave may not phase as effectively as previously thought with an approaching nrn-stream wave. As a result, there may come a precipitation gap in wrn PA Tue night before greater coverage returns with the arrival of the nrn wave on Wed. By Wed afternoon, moisture will be shunted ewd, with any rain showers quickly shifting to the ridges and nrn lake-enhancement zones. Lowering inversion heights and eroding moisture should lead to a rapid decrease in precipitation. && .LONG TERM /THURSDAY THROUGH MONDAY/... The last in a series of shortwave troughs will impact the region on Fri as it drives a cold front across the Great Lakes. Increasing rain chances can be expected to end the work week, but the track of the wave may preclude a widespread wet day. Thereafter, an overall pattern shift appears to be in the offing, with a strong wrn-CONUS trough and amplifying ern-CONUS ridge. This pattern of rising heights and a strengthening upper ridge spells a general warming trend for the region, with dry wx and a return to seasonal temperature over the weekend. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... VFR conditions are expected to continue at most ports through the night. Clouds will thicken and lower from the west late tonight, with ZZV expected to lower to MVFR after 06z. Non- restrictive light rain will arrive overnight, with its intensity hindered as it encounters a very dry atmosphere. Widespread MVFR cig and vis is expected after dawn on Tuesday. Winds will increase once again on Tuesday, with gusts of 20 to 30 knots expected areawide by late morning and through the afternoon. OUTLOOK... MVFR/IFR conditions are likely Tuesday through Wednesday for all sites with slow moving low pressure. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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