Area Forecast Discussion
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725 FXUS61 KPBZ 232246 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 646 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/... Looking at the latest model guidance and surface observations, it appears precipitation generated by a lifting warmfront 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. && .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 /22Z THURSDAY THROUGH TUESDAY/... High pressure will keep a majority of clouds at bay through tonight. A shortwave trough crossing along a warm front will bring an increase in clouds and eventually light rain showers by Friday morning. Kept VCSH mention for Pittsburgh and south while northern ports stand the best chance to see borderline MVFR restrictions. Light wind will shift around to the south and gradually increase through the period. An increasing low-level jet will bring a chance for LLWS before mixing commences Friday morning. Outlook... The next chance for widespread restrictions is not expected until the approach of low pressure early on Sunday. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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