Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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302 FXUS61 KPBZ 150935 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 535 AM EDT Wed May 15 2024 .SYNOPSIS... Isolated to scattered showers expected today as an upper trough crosses the region. A few rumbles of thunders will be possible during the afternoon north and west of Pittsburgh. Showers and storms will be possible again Friday and Saturday after a dry Thursday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... KEY MESSAGES: - Isolated to scattered light showers possible. - Thunderstorm chances remain low, with no severe threat. - Near-normal temperatures. ______________________________________________________________ Upper troughing over the Middle Ohio Valley will slowly transition east over the course of the day as a surface low passes south of the Mason-Dixon line. This will support isolated to scattered showers today across the region with better coverage north and west of PGH, where a slow-approaching surface boundary. Any thunder should largely also be north and east of PGH. NBM 6hr prob thunder tops out at 40% and the HREF 10th-90th percentile CAPE spread ranges from double digits to near 800J/kg. Latest shear profiles do not promote and organization. Total precipitation amounts will range from a few hundredths east of PGH up to 0.4-0.5" over eastern Ohio counties. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... KEY MESSAGES: - Ridging provides drier weather tonight through Thursday. - Near to above normal temperature expected. ______________________________________________________________ Precipitation coverage should wane this evening as the trough axis shifts east of the region and heights rise aloft. With ridging the dominant feature, warmer temperatures and dry conditions are then forecast through Thursday night, although some showers may begin to show up in the western CWA prior to 12Z Friday ahead of the next shortwave. && .LONG TERM /FRIDAY THROUGH TUESDAY/... KEY MESSAGES: - Forecast uncertainty increases during the extended period. - Another trough is likely to provide unsettled weather at least for Friday and Saturday, although rain amounts are iffy given the uncertainty. - Temperatures near or above normal are expected. ______________________________________________________________ Uncertainty creeps upward in the extended period. The mid-level ridge will be departing the Appalachians Friday morning, with moisture increasing once again ahead of the next trough, which ensembles have crossing the Mississippi River Friday evening and reaching the Upper Ohio Valley by Saturday. Thereafter, speed and timing differences arise in the models with the handling of this trough. GEFS/GEPS members are favoring a quicker departure and a weaker trough, while ENS favors the opposite outcomes. Differences then continue to get larger from there, with cluster analysis indicating anything from strong ridging to the presence of a closed upper low is on the table by early next week. A good example is looking at NBM 10th/90th 72hr QPF percentiles for the weekend....ranging from 0.04" to 1.38" for the Pittsburgh metro area. Will continue to roll with the NBM suggestions for the extended period and wait for increased model clarity. This would suggest a return of unsettled, but likely not overly impactful weather Friday and Saturday, with lower rain chances during the early part of next week. Near to slightly above normal temperatures are currently forecast, but again, there is a sizable range of outcomes here. && .AVIATION /10Z WEDNESDAY THROUGH SUNDAY/... Low pressure near the OH/KY border (with an inverted surface trough extending north) will continue to drift eastward today, eventually weakening into a trough as a new surface low develops off the Mid Atlantic coast. MVFR should become widespread this morning as cigs lower with increasing low level moisture around the low. The exception will be FKL and DUJ, where moist easterly flow should maintain IFR cigs. Scattered showers and MVFR cigs (IFR at FKL/DUJ) will continue today as the low moves eastward. Some improvement to low VFR is expected through the afternoon with surface heating and mixing. The greatest amount of destabilization is expected near the inverted surface trough, which is expected to be near DUJ-FKL- ZZV this afternoon. A band of MU CAPE around 500 j/kg is depicted on the latest HREF output in this vicinity. Maintained a prob30 for thunderstorms for those ports affected, with showers mentioned just to the east of this boundary where less instability is progged. A thunderstorm is possible at PIT, though confidence was too low for TAF inclusion. Cigs should lower to MVFR again this evening as the trough dissipates across the Upper Ohio Valley region, but low level moisture remains. .Outlook... VFR should return Thursday under a ridge of high pressure. Periodic restrictions and showers are expected Friday through Sunday with another slow moving low pressure system. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...88 NEAR TERM...88 SHORT TERM...88 LONG TERM...CL/88 AVIATION...WM