Area Forecast Discussion
Issued by NWS Pittsburgh, PA

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533 FXUS61 KPBZ 101135 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 735 AM EDT Thu Jul 10 2025 .SYNOPSIS... A typical warm and moist summer airmass will remain in place this week and allow scattered afternoon and evening thunderstorms to develop over the Upper Ohio River Valley each day. Thunderstorm chances will be a bit higher this weekend as a weak cold front sags into the area from the Great Lakes. && .NEAR TERM /THROUGH TONIGHT/... KEY MESSAGES: - Patchy dense fog lifting this morning. - Isolated showers and thunderstorms. - Main threats are wind and flash flooding. - Patchy fog possible again tonight. --------------------------------------------------------------- A stabilized airmass is noted near and north of a stalled surface boundary across eastern OH to southwestern PA. The airmass is currently characterized by cool temps and dew points in the mid to upper 60s. Areas of low visibility have been reported at various airports across the region along with satellite confirming areas of fog. Areas of patchy fog will lift with diurnal heating by 8AM/9AM. An upper level trough over the eastern Great Lakes will bring moist and unstable environment to the region. This results in diurnal thunderstorms that are isolated in nature and poorly organized. With the upper level flow weakening, these storms are expected to be slow moving in nature. Precipitable water values are forecast around 1.5" which will be high enough to support locally heavy rain. With the slow-moving storms and the moisture, there is the possibility for localized areas of flash flooding. Mid levels are forecast to be drier today. With some additional DCAPE, there is a slightly higher potential for wet microbursts. Strong wind is possible with thunderstorms today. After sunset, the probability for showers and storms will significantly decrease. With the moisture expected to remain stationary, there is a chance for patchy fog to develop again tonight. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... KEY MESSAGES: - Weak troughs moving along northern edge of subtropical high will support scattered diurnal thunderstorm development - Low probability of severe and flash flooding at any one point but a couple spots could see significant weather each day - Temperatures a bit above normal with a gradual warming trend peaking out on Saturday around 90FF ---------------------------------------------------------------- Currently, the region is seeing a common summer pattern with an upper-level high over the southwestern U.S. and an upper-level trough over the Great Lakes. Combined with a westerly flow aloft, seasonably moist and unstable airmass settles in the area with daily rounds of diurnal thunderstorms that will be poorly organized/more isolated with weak shear. Upper level flow is expected to remain weak through the weekend, so expect slow moving storms. Precipitable water values around 1.5" on Friday and Saturday, will be high enough to support locally heavy rain. This combined with the slow moving storms could result in localized flash flooding. Not much organization for the thunderstorms and coverage will be scattered with very sparse coverage of heavy rainfall and damaging winds each day. It is likely that only 1-2 locations each day are impacted by significant weather while most locations will remain dry. Expect a gradual warming trend into this weekend with maximum temperatures peaking around 90F on Saturday. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... KEY MESSAGES: - Weak front brings better chance of thunderstorms Sunday - Not much cooling with temperatures remaining about 5 degrees above normal ------------------------------------------------------------------- The pattern is not expected to change a lot. Even with weak summer flow regime, a good bit of spread on the timing and intensity of weak troughs drifting through the Ohio Valley and Great Lakes. Looks like best shot for a weak front to enhance thunderstorm chances will be on Sunday. Probabilities for severe weather, based on the ECMWFE, are highest on Sunday. Precipitable water values will increase from about 1.5" to the 1.75-2.00" range, which will also bring a higher threat of heavy rain and flash flooding. Pattern for Monday thru Wednesday becomes a bit more complex and uncertain as we could see a series of weak trough/ridge couplets. There is chance for a dry day or two in that time range, however, there is low confidence at this time. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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Fog is timed to dissipate in the 12Z to 14Z timeframe as satellite imagery shows some morning clearing which may lend to mixing of lingering fog issues. Guidance has some ports hanging on longer than others which may lend to about 1hr of timing uncertainty with dissipation. Mixing of moisture will lend to the quick daytime development of a fair weather cu deck with light southwest flow. The most recent convective guidance shows the highest chances of isolated daytime storms is 30% for all ports save LBE,DUJ, and MGW which only maximize around 15%. Hence, PROB 30s were maintained for afternoon storms when justified. Storm chances decrease after 00Z, with an abrupt increase in fog chances yet again tonight. In a very similar environment to the day prior, TAFs followed a persistence forecast with some small adjustments, tracking closer to HREF 5th percentile vis. Outlook... A weakly forced but warm/humid environment is favored through the end of the week that will allow for intermittent periods of showers/thunderstorms. Confidence is likely to be lower on timing various rounds of precipitation as well as the resultant cig/vsby impacts they could have during the morning hours. More significant upper-level and surface boundary movement appears to arrive over the weekend, which will create a better focused period for convection and restriction development.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Craven NEAR TERM...Lupo SHORT TERM...Craven/Lupo LONG TERM...Craven/Lupo AVIATION...Milcarek