Hot and humid weather persist on July 9th under persistent ridging. Increased shortwave ascent and surface moisture in light, southerly flow supported the development of scattered thunderstorms.
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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.
Hot and humid weather persist on July 9th under persistent ridging. Increased shortwave ascent and surface moisture in light, southerly flow supported the development of scattered thunderstorms. The greatest risk of the day was downburst wind;DCAPE values were near 1000J/kg.
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 Jul 9, 11:46 AM EST, 4 hours 36 minutes earlier.
Area Forecast Discussion
National Weather Service Pittsburgh PA
1246 PM EDT Thu Jul 9 2020
.SYNOPSIS...
Hot and humid weather with afternoon and evening scattered thunderstorms
will continue through Friday. A cold front will increase rain chance
for the weekend, but will cool temperature back to seasonable
levels. Another stretch of heat and humidity return next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
Hot and humid weather will persist again today under persistent ridging.
This ridging is expected to weaken across western portions of the
forecast area with the encroachment of a Midwest longwave trough.
Increased shortwave ascent and sfc moisture in light, srly flow
should support the development of scattered afternoon and evening
thunderstorms across this region where better convergence is hinted.
Isolated convection is expected elsewhere, including the eastern
ridges, along the lake breeze north of I-80, and along lingering
outflow boundaries from yesterday's convection. Overall, convection
will be slow moving supported by lack of steering flow within the
boundary layer. It is also this lack of shear that should preclude
widespread severe concerns, with the greatest risk potential for
downburst wind across east-central Ohio where DCAPE values near 1000
J/kg are forecast.
High temperature 10 to 13 degrees above the average is on track
again today, continuing the ongoing stretch of temperature at or
above 90F for the week. Those readings in conjunction with lower 70s
dewpoints will drive heat index values to near the 100 degree mark
for lowland areas generally along and south of the PA turnpike. As
such, a Heat Advisory remains in effect through this evening.
&&
.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Further encroachment of the aforementioned trough will support
higher precipitation probabilities on Friday in continued warmth and
humidity. Scattered thunderstorms are expected during the afternoon,
becoming widespread Friday evening as the trough axis treks across
the region. BUFKIT forecast soundings suggest a deep warm cloud layer
over 10,000ft, precipitable water values over 1.70 inches, and the
presence of a low level jet should support efficient rainfall rates
during this relatively short timeframe. Though widespread flooding is
not a concern due to progressive shortwave movement, precipitation
should provide a welcome reprieve from the relatively dry and hot
stretch of weather.
Further escalation of precipitation chances is expected
again Saturday with a crossing cold front. Upper troughing with
clouds and rain chance will keep temperature around the calculated-
normals for the weekend.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Ern CONUS upr troughing will maintain seasonable temperature with
convective weather through Monday. Ridging is indicated thereafter in
response to troughing over the nwrn CONUS/wrn Canada. Precip. probs
will thus drop and temperature will rise with 90s expected once again
by mid week.
&&
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
General VFR expected outside of any afternoon/early evening
convection. Confidence in coverage/location is relatively low so
have maintained VCTS mention.
.Outlook...
Restrictions are likely Friday night and Saturday with the advn and
passage of a cdfnt.
&&
.CLIMATE...
Based on the 30-year climatological average, here is the "normal"
number of 90-degree days per year at each of the local climatic
sites:
Pittsburgh: 6.9 days
Morgantown: 8.0 days
Wheeling: 5.0 days
Zanesville: 10.0 days
Dubois: 1.0 day
90+F temperatures are still forecast through Friday. Here is a
summary of the most-recent 90+F stretches at each site:
Pittsburgh (7/3-7/10/2020): prior 8-day stretch ended 8/20/1995
Morgantown (7/2-7/10/2020): prior 9-day stretch ended 8/4/1995
Wheeling (7/4-7/10/2020): prior 7-day stretch ended 7/27/2016
Zanesville (7/4-7/10/2020): prior 7-day stretch ended 7/8/2012
Dubois (7/5-7/10/2020): would be longest 90F stretch at DUJ.
Dubois most recently had a 5-day stretch of 90F days ending
7/23/2011. Dubois also is the site with the greatest potential
variability in the forecast maximum during this forecast period, and
therefore the most likely not to reach 90F on any given day.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...None.
OH...Heat Advisory until 8 PM EDT this evening for OHZ039>041-048>050-
057>059-068-069.
PA...Heat Advisory until 8 PM EDT this evening for PAZ020-021-029-031-
073-075.
WV...Heat Advisory until 8 PM EDT this evening for WVZ001>004-012-021-
509.
&&Hazardous Weather Outlook National Weather Service Pittsburgh PA 112 PM EDT Thu Jul 9 2020 MDZ001-PAZ007>009-013>016-022-023-074-076-WVZ510>514-101715- Garrett-Mercer-Venango-Forest-Lawrence-Butler-Clarion-Jefferson PA- Armstrong-Indiana-Westmoreland Ridges-Fayette Ridges- Ridges of Eastern Monongalia and Northwestern Preston-Preston- Eastern Preston-Western Tucker-Eastern Tucker- 112 PM EDT Thu Jul 9 2020 This Hazardous Weather Outlook is for western Maryland, northwest Pennsylvania, southwest Pennsylvania, western Pennsylvania and northern West Virginia. .DAY ONE...This afternoon and tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. 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. OHZ039>041-048>050-057>059-068-069-PAZ020-021-029-031-073-075- WVZ001>004-012-021-509-101715- Tuscarawas-Carroll-Columbiana-Coshocton-Harrison-Jefferson OH- Muskingum-Guernsey-Belmont-Noble-Monroe-Beaver-Allegheny-Washington- Greene-Westmoreland-Fayette-Hancock-Brooke-Ohio-Marshall-Wetzel- Marion-Monongalia- 112 PM EDT Thu Jul 9 2020 ...HEAT ADVISORY IN EFFECT UNTIL 8 PM EDT THIS EVENING... This Hazardous Weather Outlook is for east central Ohio, southwest Pennsylvania, western Pennsylvania, northern West Virginia and the northern panhandle of West Virginia. .DAY ONE...This afternoon and tonight. Please listen to NOAA Weather Radio or go to weather.gov on the Internet for more information about the following hazards. Heat Advisory. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. 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
422 PM EDT Thu Jul 9 2020
PAZ021-073-092045-
Westmoreland-Allegheny-
422 PM EDT Thu Jul 9 2020
...A STRONG THUNDERSTORM CAPABLE OF PRODUCING GUSTY WIND AND HEAVY
RAIN WILL AFFECT NORTHEASTERN ALLEGHENY AND NORTHWESTERN WESTMORELAND
COUNTIES...
At 421 PM EDT, a strong thunderstorm was located over Springdale, or
near Penn Hills. the storm is nearly stationary.
Wind gusts up to 45 mph are possible with this storm.
Locations impacted include...
Penn Hills... Plum...
Hampton Township... New Kensington...
Lower Burrell... Harrison Township...
O'hara Township... Oakmont...
Fox Chapel... Arnold...
Tarentum... Springdale...
This includes Pennsylvania Turnpike between mile markers 41 and 52.
Torrential rainfall also is occurring with this storm and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.
LAT...LON 4050 7971 4048 7986 4062 7994 4067 7977
4067 7974
TIME...MOT...LOC 2021Z 167DEG 3KT 4055 7981
SHALLENBERGERSpecial Weather Statement National Weather Service Pittsburgh PA 459 PM EDT Thu Jul 9 2020 PAZ021-092130- Allegheny- 459 PM EDT Thu Jul 9 2020 ...AN AREA OF STRONG THUNDERSTORMS CAPABLE OF PRODUCING GUSTY WIND AND HEAVY RAIN WILL AFFECT NORTHEASTERN ALLEGHENY COUNTY... At 458 PM EDT, strong thunderstorms were clustered over Shaler Township, or over Ross Township. the storm is nearly stationary. Wind gusts up to 45 mph are possible with this storm. Locations impacted include... Pittsburgh... Ross Township... McCandless Township... Franklin Park... Shaler Township... Hampton Township... Harrison Township... O'hara Township... Bellevue... Wexford... West View... Oakmont... This includes Pennsylvania Turnpike between mile markers 34 and 48. Torrential rainfall also is occurring with this storm and may cause localized flooding. Do not drive your vehicle through flooded roadways. LAT...LON 4065 7971 4045 7991 4050 8009 4066 8002 TIME...MOT...LOC 2058Z 200DEG 3KT 4053 7998 SHALLENBERGER
The Pittsburgh radar (KPBZ), 22 km away, was scanning. The volume nearest the first event began at 21:21 UTC.
11 thunderstorm wind. Local standard time, as filed.
The Department of Highways reported a large tree was found across the road on Route 8.
A local resident reported 2 large trees down in Franklin Park area.
A 911 Call Center reported several trees down in the vicinity of Cecil Township.
A local 911 Call Center reported trees and power lines down around the intersection of Bank Street and 2nd Street.
A local 911 Call Center reported several trees have fallen on Crucible Road and blocked River Road/Old Ferry Road.
A 911 Call Center reported a couple trees down across Home Run Road.
A 911 Call Center reported several trees down on SR88 north of SR188 intersection to the Washington County line.
A 911 Call Center reported trees and wires down oil 1700 Block East Maiden Street in South Strabane Township. Other trees reported down in the area as well.
A 911 Call Center reported multiple trees down on 800 Block East Wilmington Street.
A 911 Call Center reported trees down blocking the road at Main and Avella.
A local 911 Call Center reported a few trees down and blocking roads.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2020Every state in 2020This day in weather historyWarnings in Pennsylvania, July 2020
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: 903794, 903796, 903797, 903798, 903799, 903800, 903801, 903802, 903803, 903804, 903805.