Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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019 FXUS61 KPBZ 261130 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 730 AM EDT Wed Jun 26 2024 .SYNOPSIS... Strong to severe thunderstorms are expected this afternoon and evening ahead of a cold front. Isolated flooding is also possible with heavy rainfall. Temperatures will trend upwards into the weekend. && .NEAR TERM /THROUGH TONIGHT/... KEY MESSAGES: - Strong to severe storms are expected between 1pm to 8pm. Damaging winds will be the main threat. An isolated tornadoes and hail as large as a quarter can`t be ruled out. - Storm Prediction Center (SPC) has expanded the Slight Risk for severe weather across the region, and Weather Prediction Center (WPC) has continued the Marginal risk for flooding. ------------------------------------------------------------------- 7am Update: The Ohio River Valley is waking up to warm, moist conditions across the region. Overnight low temperatures ranged from upper-60s to low-70s. With mostly clear conditions, diurnal heating will help build instability throughout the day. GOES-16 and ACARS soundings currently suggest elevated instability of 500J/kg between 700mb to 400mb at 7am with effective shear of only 20kts to 25kts. However, progression of a trough over the Midwest will enhance vertical wind shear from the southwest across southern Ohio after 15Z. Previous Discussion: Pre-frontal showers and thunderstorms will rapidly increase in coverage to our west early afternoon and track into our region after 1pm. The primary threat will likely be damaging winds with lingering dry air aloft producing strong cool downdrafts. However, hail (dime to quarter in size) and tornadoes can`t be ruled out. SPC has removed the 2% TOR outlook for the day, but several machine learning outputs still indicate the potential. By late evening, the severe threat will likely evolve into a heavy rain threat, especially for urban areas that experience training or rainfall rates ranging from 2-4 inches per hour. With PWATS well above the climatological average (1.65" to 1.90") and training showers and storms under quasi-zonal flow, swaths of 1 to 2 inches are not out of the question. The severe weather and flash flood threat will decrease after midnight as the shortwave tracks east. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... KEY MESSAGES: - Dry weather returns. - Temperatures increase Friday into the weekend. ------------------------------------------------------------------- Dry conditions resume Thursday as high pressure builds in across the region. A warming trend in temperatures is forecasted Friday and into the weekend as h500 heights approach 890dm. This combined with increasing low-level moisture will result in apparent temperatures back up in the mid 90s by the weekend. && .LONG TERM /SATURDAY THROUGH TUESDAY/... KEY MESSAGES: - Shower and thunderstorm chances return Saturday into Sunday with the next low pressure system. ------------------------------------------------------------------- Ensembles show about a 50% chance in general of highs hitting 90F on Saturday. There`s a good chance most locations will see apparent temperatures back in the 90s with Tds back up in the upper 60s / low 70s. Shower and thunderstorm chances return with increased instability and the approach and passage of another frontal system Saturday into Sunday. Dry conditions and near to slightly above normal temperatures are forecast early next week as high pressure resumes control. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... VFR is expected through the morning ahead of an approaching shortwave trough and associated surface cold front. Mid and high level clouds will continue to stream across the area ahead of the wave. Expect a scattered cumulus layer to develop by late morning/early afternoon with a flux of low-level moisture and diurnal heating. Pre-frontal showers and storms will increase in coverage from west to east after 17Z. However, it appears the most favorable timing for thunderstorms to impact terminals will be between 20Z and 00Z; TEMPO groups have been included with this morning update. Strong wind gusts and hail are possible in these storms, and additional details can be added to the tafs as uncertainty decreases later in the day. MVFR is expected as the thunderstorms end, with a period of showers. Eventual IFR is possible overnight with low level moisture in place. .Outlook... Restrictions in stratus/fog are possible through early Thursday; especially between 06Z to 12Z. VFR is then expected through Friday under high pressure. Restriction and showers/thunderstorm potential returns Friday night with a crossing warm front. Restrictions are expected at times Saturday and Saturday night with showers and thunderstorms ahead of and along a crossing cold front. VFR returns Sunday under high pressure. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Hefferan NEAR TERM...Hefferan/88 SHORT TERM...88 LONG TERM...88 AVIATION...WM/Hefferan