Area Forecast Discussion
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339 FXUS61 KPBZ 232320 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 720 PM EDT Thu Mar 23 2017 .SYNOPSIS... A period of above-normal temperature and increasing chances for rain is expected through early next week. && .NEAR TERM /THROUGH FRIDAY/...
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Looking at the latest model guidance and surface observations, it appears precipitation generated by a lifting warm front will be minimal, at best, south of I-80. This is supported by the hi-res guidance and the latest nam/sref, and the fact that much of the shower activity that is out in Illinois and Indiana now is diminishing as the warm front lifts northeastward. Still, a shortwave that is expected to ride along the building upper level ridge will help generate a few showers to our north later tonight. With clear skies expected and light wind ahead of this wave, temperatures should fall off early, which could lead to a p-type issue initially depending on the exact arrival of the showers. However, even with some wet-bulbing, the threat for freezing rain appears low, with warm air surging aloft. Any glazing that would occur would be brief and on elevated surfaces given the warm daytime temperatures. Thus, have opted to take out the hwo mention. Any rain showers should end shortly after sunrise as we shift into the warm sector. Southwest wind and strong warm advection should support temperatures above average, despite mostly cloudy skies.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... A series of compact shortwave troughs will develop in the swrn CONUS and eject newd beginning Saturday. As the first wave acquires a negative tilt, shortwave ridging will amplify over the Great Lakes region, leading to a likely-nwd displacement of precipitation on Saturday and Saturday night. Steady height falls will begin to spread across the region Sunday morning as the ejecting wave nears. By afternoon, the associated H5 jet maximum will cross the forecast area, likely invigorating deeper convection with its passage amid modest instability. This wave will be exiting the region by Monday morning, with a downward trend in precipitation expected by late Sunday night as shortwave ridging develops in its wake. && .LONG TERM /MONDAY THROUGH THURSDAY/... In the wake of the Sunday wave, a brief respite can be expected on Monday amid shortwave ridging before a second trough ejects from the Plains. This second wave will be favorable for widespread rain showers as it crosses on Tuesday as warm, moist air is drawn poleward ahead of the system. Behind the wave, seasonable air is expected to arrive mid-week with highs in the 50s and lows in the 30s. Given ensemble spread, there is considerable spread with the placement of the pattern of upper-level troughs and ridges across the country during this time, so the forecast details during this time remains lower-confidence. && .AVIATION /23Z THURSDAY THROUGH TUESDAY/...
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VFR ceilings and visibilities are expected in the main through tonight, although clouds will thicken overnight as a warm front lifts through. FKL/DUJ have a chance to get a brief MVFR shower, otherwise VCSH will handle the situation in an initially very dry atmosphere. An increasing low-level jet may bring low level wind shear concerns overnight into Friday morning before the low levels can mix. Ceilings may lower into prevailing MVFR range north of PIT during the day Friday as moisture continues to increase, although most rain showers should remain off to our north. Winds will swing to the southwest on Friday and start to strengthen. Outlook... The next chance for widespread restrictions is not expected until the approach of low pressure early on Sunday.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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