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Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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212 FXUS61 KPBZ 250526 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 126 AM EDT Sat May 25 2024 .SYNOPSIS... Dry weather is expected through the morning. The chance for showers and strong to severe thunderstorms will increase this afternoon and evening. Sunday is expected to be mostly dry under high pressure, with rain returning Sunday night into Monday. && .NEAR TERM /THROUGH TODAY/... KEY MESSAGES: -A crossing shortwave will return the risk of strong to severe storms Saturday afternoon/evening; hail, damaging wind, and excessive rainfall will be the main threat. _____________________________________________________________ Update... The last of the lingering showers near Morgantown have collapsed. The remainder of the overnight through most of Saturday morning is expected to be dry. Overnight low temperatures will remain roughly 10 degrees above normal. Previous... A weak ridge will continue to break down across the Ohio River Valley early Saturday as an ejecting low out of the northern Dakotas tracks into the Great Lakes. With a flux of low-lvl moisture Saturday morning, a few showers and storms may evolve along the moisture boundary. However, scattered to widespread organized convection is expected to develop mid-afternoon as a cold front slowly advances into Ohio. During peak heating, where temperatures will range from low to mid-80s and low-lvl moisture is widespread across the region (dew points in the mid-60s), MUCAPE values will climb between 1500J/kg to 2000J/kg just before sunset. There will be small window of opportunity, based on atmospheric profiles, that hail and strong downdrafts could develop in a few storms. && .SHORT TERM /TONIGHT THROUGH 6 PM SUNDAY/... KEY MESSAGES: -Storm coverage will wane Saturday evening, but flooding may still pose a threat. -Sunday looks dry through most of the day, with thunderstorms returning in the evening. _____________________________________________________________ By 8pm to 10pm, ongoing convection will likely shift from hail/wind threat to a excessive rainfall threat and areas that have training storms with prolong periods of 2 to 3 inch rainfall rate will be vulnerable to flooding. Flood-prone and urban areas will need to be closely monitored into the overnight hours. Hi-Res models suggest the probability of all threats will be low between 2am to 4am Sunday. While precipitation wraps up across the Ohio River Valley, all eyes are focused on a new low pressure system developing in the Great Plains early Sunday morning. Hi-Res models and long range models have been consistent on the track of the low advancing through the Great Lakes region by late Sunday/early Monday morning. The GFS and some of the Hi-Res models have some discrepancy on how far north moisture will advance under southwest flow Sunday night into early Monday morning. Vertical wind shear will not be the primary problem with organized convection, it is mainly a destabilization issue. The Storm Prediction Center has portions of eastern Ohio under a Marginal threat for now, however the threat may shift further north, towards Pittsburgh, if the CAMs come to an agreement on the overall pattern in the next 24 hours. Along with damaging wind, hail, and/or tornadoes, flooding will once again be a concern; especially to hard hitting areas from anticipated convection on Saturday. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... KEY MESSAGES: - The potential for strong to severe storms may continue into Monday. - Near normal to below average temperatures are expected under an elongated trough over the Northeast. ____________________________________________________________ With ensemble members suggesting a slow progression of the upper-level low over the Great Lakes Sunday into Monday, the threat for strong to severe storms may continue for portions of the region. Long range suggests a shift to a cooler pattern by the middle of next week as upper troughing develops over the Great Lakes. Expect temperature to fall below the seasonal average, with Wednesday potentially being the transition day from shower activity to dry weather. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... VFR expected through at least 15z Saturday under the influence of high pressure, with increasing southwesterly surface wind Saturday afternoon. Shortwave passage Saturday afternoon and evening will offer more widespread thunderstorm chances (lowered vsbys and gusty, erratic winds possible). However, uncertainty remains high as initiation, timing and evolution are fairly dependent on progression of convective activity across the lower Ohio River Valley tonight. Thus, most convection should hold off until between 21Z - 00Z. This will be associated with MVFR conditions at times, although instances should be few and far between. .Outlook... High pressure and subsidence should promote VFR and dry weather late Saturday night into Sunday. Fog may develop before dawn Sunday in rain-soaked locales that experience overnight clearing. Thunderstorm probabilities increase overnight Sunday into Monday as a more robust low pressure system moves through the Great Lake region. A pattern shift thereafter will introduce periodic precipitation chances and potential for more prolonged cig restrictions. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Rackley NEAR TERM...Hefferan/Rackley/CL SHORT TERM...Hefferan/22 LONG TERM...Hefferan AVIATION...Frazier/Shallenberger