Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
796 FXUS61 KPBZ 311815 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 215 PM EDT Fri Jul 31 2026 .WHAT HAS CHANGED... No significant changes were made to the forecast. && .KEY MESSAGES... 1) Continued dry through part of Saturday 2) Showers and thunderstorms return late Saturday and Sunday, with unsettled weather next week. && .DISCUSSION... KEY MESSAGE 1... Dry weather is expected through at least early Saturday as high pressure moves east across the region. Rising 500 mb heights under shortwave ridging should result in high temperatures to slightly above seasonable levels today. A digging shortwave trough is expected to begin to advance out of the Midwest tonight into Saturday. Expect an increase in mid and high level clouds tonight through Saturday morning in advance of the trough. KEY MESSAGE 2... The shortwave trough is expected to continue to deepen as it tracks toward the Upper Ohio Valley region late Saturday and Sunday. At the same time, an associated surface low is progged to track NE across the Upper Ohio Valley/eastern Great Lakes region. Increasing moisture and ascent with an initial lead shortwave should return shower and thunderstorm chances Saturday afternoon across Ohio, overspreading the remainder of the area Saturday night. Periods of showers and scattered thunderstorms are expected on Sunday as the main trough axis approaches, and the surface low tracks across the region. Clouds could limit instability, with ML CAPE currently progged at 1000 J/kg or less, however, there is increased amount of vertical wind shear (up to 30kts). Current model runs are hinting at the chance for dry slots to develop in between periods of rain on Sunday. If these dry periods are accompanied by some clearing, there would be an increase in CAPE which combined with 30kts of vertical wind shear would improve the probability for severe weather to develop. Locally heavy rain will also be possible as PWATs approach 1.8 inches, though the potential dry slot Sunday afternoon ahead of the surface low could limit this potential. The surface cold front is currently expected to cross the area late Sunday/Sunday night. Model ensembles then indicate a persistent trough across the Eastern Great Lakes and Ohio Valley region early in the week. This trough should weaken some through the week, though significant uncertainty exists in exact placement and strength. Overall, expect daily, diurnally driven shower and thunderstorm chances under this pattern. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... High confidence VFR continues through the TAF period as surface high pressure slides east across the region. Scant boundary layer moisture will preclude more than a few diurnal cumulus clouds this afternoon giving way to increasing high clouds later today/tonight ahead of the next approaching shortwave trough. Wind will be light at 5 knots or less. Expect clouds to thicken and lower into the daytime hours on Saturday as the column saturates. Rain will approach from the west in the late evening hours with current most likely arrival time to PIT among REFS members after 3am, though notable uncertainty still exists with distribution as wide as an arrival time around midnight and as late as daybreak. Outlook... A lingering trough could maintain restriction potential Monday and Tuesday with shower/thunderstorm chances, though much timing uncertainty arises into early next week with evolution of the trough. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ DISCUSSION...WM/Lupo AVIATION...MLB