071 FXUS61 KPBZ 130019 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 819 PM EDT Tue Aug 12 2025 .SYNOPSIS... A cold front crossing the Great Lakes tonight will push across the Upper Ohio River Valley Wednesday and Wednesday night. Showers and thunderstorms will increase late tonight over Ohio and then spread across the area Wednesday and Wednesday evening. As the front pushes south of area Thursday a few showers are possible mainly south of Pittsburgh. High pressure will build in Friday bringing quiet and less humid weather. && .NEAR TERM /THROUGH WEDNESDAY/... KEY MESSAGES: - Thunderstorms should increase in coverage late tonight over Ohio portion of area. --------------------------------------------------------------- Increasingly moist southwest flow tonight will transport rather high precipitable water values of 1.75-2.00" into Ohio area after midnight. This higher moisture content can be seen in low level water vapor channel with strong dry pocket over western PA and surge of moisture crossing into western half of Ohio. RAP shows increasing instability with this feature and along with modest moisture transport and warm advection in 850-700 mb layer expect an increasing in shower and thunderstorm activity despite loss of diurnal heating. Upper trough does cross area late tonight with 20-30 meter height falls so forcing will be maximized by the end of the night. Given the forcing there is a marginal risk for excessive rainfall per WPC and a couple Ohio Counties could pick up 1-2". && .SHORT TERM /WEDNESDAY NIGHT/... KEY MESSAGES: - Shower and thunderstorms spread across the eastern part of the forecast area through Wednesday, and linger Thursday in the south - Marginal Risk of Excessive Rainfall across area - Dry weather returns Thursday night ---------------------------------------------------------------- Evolution of thunderstorms Wednesday will be complicated by ongoing convection with short wave trough early in the morning. That activity will likely move east and/or dissipate by midday and partial clearing and diurnal destabilization will likely result in renewed storms by early/mid afternoon. With Precipitable Water Values of 1.75-2.00", localized heavy rainfall is expected with a few locations picking up a quick 1-2". Dry antecedent conditions and relatively low point probabilities preclude issuance of flash flood watch. NBM 72 hour PQPF indicates lower end amounts (10th to 25th percentile) of about 0.25", and higher end amounts (75th percentile) of 1.00". Maximum QPF is near 2", and amounts near or above that value would likely occur in just a couple of locations. Heights build over the Great Lakes and Ohio Valley on Thursday, but lingering moisture over the south could result in another round of diurnal showers. && .LONG TERM /THURSDAY THROUGH TUESDAY/... KEY MESSAGES: - Dry weather to continue much of the period - Hot weather returns Sunday - Thunderstorms can`t be ruled out Sunday and Monday with warm and humid northwest flow pattern. - Uncertainty increases by Tuesday in evolution of next trough digging into Great Lakes area. ------------------------------------------------------------------- Ensemble Guidance is confident in a strong upper High building over the Middle Mississippi Valley Friday and Saturday and remaining in place through Monday. WNW flow aloft with high heights will be mainly dry but vulnerable to convective complexes riding the edge of the capping ridge and into Great Lakes and Upper Ohio Valley. Rather low confidence on this for now but something to keep an eye out for. Hot and humid weather returns by Sunday and Heat Index values well into the 90s expected. Confidence drops by Tuesday on precipitation chances as the key question will be the interaction of mid latitude digging trough with recurving Hurricane Erin. Ensemble uncertainty in this evolution is high, ranging from little impact from this trough over Upper Ohio Valley to a potential significant rain event. While ensembles have been mostly confident that Erin recurves well out to sea, the amplitude of the digging trough could be significant enough to generate much needed rainfall for a recently dry Upper Ohio River Valley area. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... Spotty evening showers remain possible across the region, especially near the ridges. High res modeling and ensemble probabilities highlight the possibility of lingering convection moving into the region early tomorrow morning from the west. PROB30s have been included at many ports due to this possibility. Restrictions are not expected to be widespread in this activity. Another round of storms seems likely along a sagging weak cold front crossing the region tomorrow afternoon. MVFR restrictions for CIGs seem likely as moisture rises ahead of the front, but the degree of ceiling drops may be slower and weaker than models indicate with a relatively dry start and top down moistening. Storms can bring gusty winds and heavy downpours. By the evening, ceilings will become VFR as the precipitation moves out of the region. Outlook... Thursday, a chance for MVFR ceilings and a chance for showers return as the weak cold front slowly moves through our region. By Thursday evening, a downward trend in rain potential is favored to end the week as high pressure develops near New England. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Craven NEAR TERM...Craven SHORT TERM...Craven LONG TERM...Craven AVIATION...Lupo/AK