Area Forecast Discussion
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000 FXUS61 KPBZ 220220 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 920 PM EST Wed Feb 21 2018 .SYNOPSIS... Periodic rain chances will continue through Sunday. && .NEAR TERM /THROUGH THURSDAY/...
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A surface cold front is shifting southeast of the last vestiges of the CWA at the moment with cold advection well underway wall-to-wall, although cold air is really lagging getting into the SE portion of the area to this point. This has resulted in temperatures rapidly falling toward the 30s. That said, southwest flow off the deck continues and thus moisture will again return into the colder boundary layer as it gets established overnight. With southwesterly flow off the deck and a modestly-curved upper jet streak entrance region set to traverse the area toward morning, precipitation is again starting to blossom from the SW. Problems continue to be revealed, however, in terms of precipitation type. The NAM continues to be far more aggressive with cold advection than the GFS, which yields a more frozen/freezing profile for precipitation along the I-80 corridor from the NAM than the GFS. Further looking at the HREF and a handful of other ensemble guidance, it does suggest that a window of freezing precipitation is plausible in the corridor where the Winter Weather Advisory was previously issued. While all the caveats of warm ground (from recent record warmth) remain, a few areas in the far north may end up with some ice on power lines or trees (probably not much in the way of transportation impacts, however), so the advisory will remain in place. Everywhere warms up efficiently above freezing on Thursday as rainfall continues with the wave moving east. Thus, all freezing rain/snow potential should be over early in the day. Fries
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... After a brief dry spell Thursday evening, rain will move back in from the west with a warm front approaching the region. This will keep rain in the forecast through the weekend. There could be hydrologic concerns through the weekend with the amount of rain in the forecast, but with the heavier rainfall not expected to move into the region until at least Friday, felt it was still a touch early to nail down a particular location to put in an areal flood watch. Highs will be in the 50s and 60s, well above normal. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Low pressure will move across the western Great Lakes Saturday night into Sunday and sweep a cold front across the Ohio Valley, providing some definitive clearing for the local area. This should allow for a dry forecast from Sunday night through Wednesday. One more day of temperatures in the 60s can be expected on Sunday, before temperatures fall to slightly above normal values for the start of the next work week. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... A brief improvement to VFR is expected for most ports this evening before low pressure tracks across the TN and OH Valley regions overnight and Thu. Rain and deterioration to MVFR and eventual IFR is expected. Sfc temperatures are expected to drop below freezing N of I 80, where freezing rain is expected. FZRA should change back to rain with warming temperatures by Thu aftn. The rain should taper off from W-E during the aftn, with some limited improvement to low MVFR possible late. OUTLOOK... Periodic restrictions are expected through Sunday with a series of crossing low pressure areas. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...Winter Weather Advisory from 1 AM to 1 PM EST Thursday for PAZ007>009-013>016. WV...None. && $$

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