77 at PIT), which was just below daily records but in the upper 1-2% of observations at this time of year, created the ideal environment for flash flooding to occur in isolated regions of western PA.
Every event with a place to put it. Tap one for its entry below.
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.
Weak flow aloft and high PWATs (1.77 at PIT), which was just below daily records but in the upper 1-2% of observations at this time of year, created the ideal environment for flash flooding to occur in isolated regions of western PA.
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 28, 3:34 PM EST, 1 hour 22 minutes earlier.
Area Forecast Discussion National Weather Service Pittsburgh PA 434 PM EDT Sat Aug 28 2021 .SYNOPSIS... Thunderstorm chances continue today and tomorrow under a warm, humid air mass and shortwave activity. The track of Hurricane Ida will need to be monitored closely, heavy rainfall may occur Tuesday into Wednesday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Warm, humid conditions will continue as the Upr OH rmns undr the primary influence of a broad ern CONUS ridge. Sct, to isold showers and thunderstorms will continue into the evening though as an embedded shortwave tracks eastward acrs wrn PA. Severe potential looks to be limited to isolated wind gusts on the strength of heavy pcpn loading. High rain rates are expected with a deepening warm cloud layer and above average PWATs. Weak flow aloft will also support isolated areas of heavy rainfall; flooding may occur if storms training over a region for a long period of time. Showers and storms may continue into portions of the overnight time period with elevated instability available. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... An incoming trough over the northern Great Lakes will flatten the ridge over the East Coast tomorrow afternoon; zonal flow will likely prevail. With no change to our warm, moist air mass over the Ohio River Valley, thunderstorms should once again develop early afternoon into the late evening. Shear should remain generally weak until the late evening but DCAPE values are expected to grow with incoming dry air in the mid to upper-levels; a few isolated strong storms can't be ruled out. Localized flooding in training clusters of heavy downpours can't be ruled out as well. By Monday, the aforementioned trough and its associated frontal boundary will advance south into the Pittsburgh area. The front should lose forward motion a bit as the trough lifts back towards Quebec, placing the Upper Ohio Valley in quasi-zonal flow aloft... or nearly parallel to the frontal boundary / baroclinic zone. Thunderstorms and showers are likely to develop along this area of convergence. A narrow band of localized flooding, orientated west to east, could develop if the boundary remains stationary for a long period of time. && .LONG TERM /TUESDAY THROUGH SATURDAY/... By Tuesday night, remnants of Ida will progress up through the TN Valley and over central Appalachia. The system will begin to phase with the northern stream as it approaches our area late Tuesday and into Wednesday. The worst case scenario if the track continues to hold is a swath of heavy rainfall as the tropical remnant interacts with the cold core trough/cold front. The timing of the Ida and the front remain in question. Slightly cooler and drier conditions are anticipated late week and into the Labor Day Weekend with building high pressure. && .AVIATION /21Z SATURDAY THROUGH THURSDAY/... Isolated to scattered convection could result in brief restrictions but otherwise, general VFR is expected. Given uncertainty in any particular location, have opted to use VCTS in latest TAFs. .Outlook... Little pattern change through Monday will result in continue isolated to scattered afternoon thunderstorms and potential patchy morning fog and low stratus. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. &&
Hazardous Weather Outlook National Weather Service Pittsburgh PA 540 AM EDT Sat Aug 28 2021 OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-029- 031-073>076-WVZ001>004-012-021-509>514-290945- Tuscarawas-Carroll-Columbiana-Coshocton-Harrison-Jefferson OH- Muskingum-Guernsey-Belmont-Noble-Monroe-Mercer-Venango-Forest- Lawrence-Butler-Clarion-Jefferson PA-Beaver-Allegheny-Armstrong- Indiana-Washington-Greene-Westmoreland- Higher Elevations of Westmoreland-Fayette- Higher Elevations of Fayette-Hancock-Brooke-Ohio-Marshall-Wetzel- Marion-Monongalia- Ridges of Eastern Monongalia and Northwestern Preston-Preston- Eastern Preston-Western Tucker-Eastern Tucker- 540 AM EDT Sat Aug 28 2021 This Hazardous Weather Outlook is for east central Ohio, western Pennsylvania, and northern West Virginia. .DAY ONE...Today and tonight. Hazardous weather is not expected at this time. .DAYS TWO THROUGH SEVEN...Sunday through Friday. The potential for heavy rainfall and flooding will increase Tuesday and Wednesday as the remnants of tropical system Ida move into the Ohio Valley. .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
234 PM EDT Sat Aug 28 2021
PAZ023-281900-
Indiana PA-
234 PM EDT Sat Aug 28 2021
...A STRONG THUNDERSTORM WILL IMPACT EASTERN INDIANA COUNTY THROUGH
300 PM EDT...
At 233 PM EDT, Doppler radar was tracking a strong thunderstorm 8
miles northeast of Indiana, moving southeast at 10 mph.
HAZARD...Wind gusts up to 50 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Indiana, Clymer, Chevy Chase Heights, Ernest, Marion Center,
Creekside, Dixonville, Commodore, Brush Vly, and Yellow Creek State
Park.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
&&
LAT...LON 4057 7888 4047 7908 4075 7923 4084 7903
4067 7883
TIME...MOT...LOC 1833Z 328DEG 10KT 4073 7908
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPHThe Pittsburgh radar (KPBZ), 93 km away, was scanning. The volume nearest the first event began at 21:55 UTC.
1 flash flood. Local standard time, as filed.
Multiple areas experienced flooded due to back building storm. Richey Run broke from its banks and flooded Route 208, Route 338 was closed between Ritts Station Road to Blairs Corners Road, and roadways near the county line was affected.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2021Every state in 2021This day in weather historyWarnings in Pennsylvania, August 2021
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: 981666.