Isolated thunderstorms managed to form in a hot and humid pattern. Weak steering flow led to some localized flash flooding in Allegheny County, and steep lapse rates/high instability combined with dry air aloft to produce hail and wind damage in a few instances.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS PBZ wrote it up.
Isolated thunderstorms managed to form in a hot and humid pattern. Weak steering flow led to some localized flash flooding in Allegheny County, and steep lapse rates/high instability combined with dry air aloft to produce hail and wind damage in a few instances.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Pittsburgh, PA wrote its last area forecast discussion before the first event at Aug 5, 12:41 PM EST, 25 minutes earlier.
Area Forecast Discussion National Weather Service Pittsburgh PA 141 PM EDT Sun Aug 5 2018 ...UPDATED AVIATION DISCUSSION... .SYNOPSIS... Scattered afternoon and early evening showers and storms are expected today and Monday, with otherwise hot and humid conditions prevailing. Seasonable warmth and humidity will be interrupted by likely storms with a Tuesday cold frontal approach. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... With early afternoon update, primary change was to add slight chance pops in all locations slightly sooner than the previous forecast, considering isolated showers and thunderstorms have already developed at this time. Previous discussion follows. 12Z KPIT sounding shows steep low level lapse rates beneath a narrow warm and very dry nose centered around 750mb. Strong surface heating should allow any boundary layer inhibition to be overcome once temperatures break 80 degrees, which should lead to fairly widespread Cu development beneath the aforementioned mid level inversion. The big question is whether sufficient forcing exists for deep moist convection this afternoon/early evening given the large low-mid level cul present in the 12Z height field analysis. Given the "ready and waiting" sounding present this morning, and despite the erratic/weak vertical wind profile, feel the isolated chances mention by the previous forecast are warranted. Pulse slow/erratic moving storm motion can be expected, but given the very large theta-e lapse rates, any "beefy" storm with even modest updraft longevity could produce microbursts given the available dry air present aloft. Otherwise, an uncomfortable afternoon ahead with upper 80s max temps looking kosher, yielding heat indices into the low 90s and almost no wind to speak of. Bookbinder && .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/... A shortwave trough ploughing across the Nrn Plains and Wrn Great Lakes today is progged to shunt the aforementioned shortwave ridge eastward on Monday. This scenario should support isolated afternoon convection once again with persistent inhibition from warm mid levels and an overall lack of immediate forcing. Rain chances will then slowly increase Monday night with the approach of the main trough and associated cold front, which is likely to generate showers and storms on Tuesday. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Ern CONUS troughing is then forecast to maintain daily/periodic rain chances and near average temperature into the weekend. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... Convective temperatures breached easily this afternoon, and shower/thunderstorm coverage growing quickly. As of 18Z, the PIT-HLG corridor has the most activity although airports themselves remain dry. This could change here and eslewhere, with isolated microbursts, occasional lightning and brief IFR restrictions to visibility in heavy rain in the strongest storms. Otherwise, VFR conditions expected with caveats for pre-dawn fog, in and around river valleys (BVI, DUJ in particular). OUTLOOK... The next chance for general restrictions is likely with a Tuesday cold front. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. &&
Hazardous Weather Outlook National Weather Service Pittsburgh PA 317 AM EDT Sun Aug 5 2018 MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023- 029-031-073>076-WVZ001>004-012-021-509>514-060730- Garrett-Tuscarawas-Carroll-Columbiana-Coshocton-Harrison-Jefferson- Muskingum-Guernsey-Belmont-Noble-Monroe-Mercer-Venango-Forest- Lawrence-Butler-Clarion-Beaver-Allegheny-Armstrong-Indiana- Washington-Greene-Westmoreland-Westmoreland Ridges-Fayette- Fayette Ridges-Hancock-Brooke-Ohio-Marshall-Wetzel-Marion-Monongalia- Ridges of Eastern Monongalia and Northwestern Preston-Preston- Eastern Preston-Western Tucker-Eastern Tucker- 317 AM EDT Sun Aug 5 2018 This Hazardous Weather Outlook is for western Maryland, east central Ohio, northwest Pennsylvania, southwest Pennsylvania, west central Pennsylvania, western Pennsylvania, northern West Virginia and northern panhandle of West Virginia. .DAY ONE...Today and Tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Monday through Saturday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to Standard Operating Procedures.
Special Weather Statement National Weather Service Pittsburgh PA 144 PM EDT SUN AUG 5 2018 WVZ001-051800- Hancock- 144 PM EDT SUN AUG 5 2018 ...A STRONG THUNDERSTORM CAPABLE OF PRODUCING SMALL HAIL AND GUSTY WIND WILL AFFECT EAST CENTRAL HANCOCK COUNTY... At 144 PM EDT, a strong thunderstorm was located over New Cumberland, or near Weirton, moving east at 15 mph. Wind gusts up to 55 mph and small hail are possible with this storm. This storm will remain over mainly rural areas of east central Hancock County. LAT...LON 4047 8059 4053 8059 4052 8052 4045 8052 TIME...MOT...LOC 1744Z 276DEG 11KT 4050 8055 Bookbinder
The Pittsburgh radar (KPBZ), 21 km away, was scanning. The volume nearest the first event began at 18:03 UTC.
3 thunderstorm wind, 2 hail, 1 flash flood. Local standard time, as filed.
County 911 officials reported that a tree fell on a residential porch on Grandin Avenue.
County 911 officials reported that a number of trees were down near Edgehill Avenue and Windermere Avenue.
County law enforcement reported flooding near the intersection of Becks Run Road and Raven Street. One vehicle was stuck in the water.
Citizens of Washington County reported hail.
Citizens of Washington County reported hail.
County 911 officials reported that trees were blown down along Garvers Ferry Road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2018Every state in 2018This day in weather historyWarnings in Pennsylvania, August 2018
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 778191, 778192, 778188, 778189, 778190, 778193.