Alert archive / Pennsylvania / Flash Flood Warnings in 2021

Flash Flood Warning 34, NWS Pittsburgh, PA

August 25, 2021Allegheny County, Washington County, Pennsylvania

NWS Pittsburgh, PA issued this flash flood warning at Aug 25, 2021, 6:05 PM EDT for Allegheny County, Washington County, Pennsylvania. It was in force for 46 min. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 25, 2021, 6:05 PM EDT (22:05 UTC)
Expired: Aug 25, 2021, 6:51 PM EDT
In force: 46 min
Issued by: NWS Pittsburgh, PA
Area: Storm-based polygon
Flood severity: None

Counties Allegheny County, PA, Washington County, PA

The radar

The Pittsburgh radar (KPBZ), 23 km from the middle of the area, began a volume at 22:08 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
Aug 25, 6:38 PM EDT	FLASH FLOOD	1 Wsw Hays, PA	FLOODED ROADWAY ON GREENGLEN DRIVE.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Pittsburgh, PA (KPIT), launched 12:00Z, 10.1 hours before the alert went out and 9 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 323 J/kg
Mixed-layer CIN: -55 J/kg
Mixed-layer LCL: 1166 m above ground
0-6 km bulk shear: 5 kt
0-1 km storm-relative helicity: -18 m²/s²
0-3 km storm-relative helicity: -18 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

584 
WGUS51 KPBZ 252205
FFWPBZ
PAC003-125-252330-
/O.NEW.KPBZ.FF.W.0034.210825T2205Z-210825T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Pittsburgh PA
605 PM EDT Wed Aug 25 2021

The National Weather Service in Pittsburgh has issued a

* Flash Flood Warning for...
  Central Allegheny County in southwestern Pennsylvania...
  Central Washington County in southwestern Pennsylvania...

* Until 730 PM EDT.

* At 605 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1.5 and 3 inches of 
  rain have fallen. Additional rainfall amounts of 1 to 2 inches are 
  possible in the warned area. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flash flooding of small creeks and streams, urban
           areas, highways, streets and underpasses as well as
           other poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  Pittsburgh, Penn Hills, Mount Lebanon, Bethel Park, McMurray, 
  McKeesport, Shaler Township, West Mifflin, North Side Pittsburgh, 
  Baldwin, Upper St. Clair, Scott Township, Wilkinsburg, Whitehall, 
  South Park Township, Robinson Township, Munhall, Jefferson Hills, 
  Brentwood and Swissvale.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

&&

LAT...LON 4048 8008 4051 7986 4029 7985 4029 8012

FLASH FLOOD...RADAR INDICATED

$$

2 follow-up statements

600 
WGUS71 KPBZ 252237
FFSPBZ

Flash Flood Statement
National Weather Service Pittsburgh PA
637 PM EDT Wed Aug 25 2021

PAC003-125-252330-
/O.CON.KPBZ.FF.W.0034.000000T0000Z-210825T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Allegheny PA-Washington PA-
637 PM EDT Wed Aug 25 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 730 PM EDT THIS 
EVENING FOR CENTRAL ALLEGHENY AND CENTRAL WASHINGTON COUNTIES...

At 637 PM EDT, local law enforcement reported flash flooding across 
the warned area. Between 1 and 3 inches of rain have fallen.

HAZARD...Flash flooding caused by heavy rain.

SOURCE...Law enforcement reported.

IMPACT...Flash flooding of small creeks and streams, urban areas,
         highways, streets and underpasses as well as other poor
         drainage and low-lying areas.

Some locations that will experience flash flooding include...
  Pittsburgh, Penn Hills, Mount Lebanon, Bethel Park, McMurray, 
  McKeesport, Shaler Township, West Mifflin, North Side Pittsburgh, 
  Baldwin, Upper St. Clair, Scott Township, Wilkinsburg, Whitehall, 
  South Park Township, Robinson Township, Munhall, Jefferson Hills, 
  Brentwood and Swissvale.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

&&

LAT...LON 4048 8008 4051 7986 4029 7985 4029 8012

FLASH FLOOD...OBSERVED

$$

979 
WGUS71 KPBZ 252251
FFSPBZ

Flash Flood Statement
National Weather Service Pittsburgh PA
651 PM EDT Wed Aug 25 2021

PAC003-125-252301-
/O.CAN.KPBZ.FF.W.0034.000000T0000Z-210825T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Allegheny PA-Washington PA-
651 PM EDT Wed Aug 25 2021

...FLASH FLOOD WARNING IS CANCELLED FOR CENTRAL ALLEGHENY AND 
CENTRAL WASHINGTON COUNTIES...

Flood waters have receded. The heavy rain has ended. Flooding is no 
longer expected to pose a threat. Please continue to heed remaining 
road closures.

LAT...LON 4048 8008 4051 7986 4029 7985 4029 8012

$$

The office that day

Everything else NWS Pittsburgh, PA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 25, 3:12 PM EDT	Special Weather Statement	PBZ	Mercer	33 min
Aug 25, 3:34 PM EDT	Areal Flood Advisory	PBZ	Mercer	116 min
Aug 25, 3:43 PM EDT	Special Weather Statement	PBZ	Allegheny	32 min
Aug 25, 4:12 PM EDT	Special Weather Statement	PBZ	Butler	18 min
Aug 25, 4:46 PM EDT	Special Weather Statement	PBZ	Beaver	14 min
Aug 25, 4:50 PM EDT	Areal Flood Advisory	PBZ	Allegheny, Butler	27 min
Aug 25, 5:17 PM EDT	Flash Flood Warning	PBZ	Allegheny, Butler	88 min
Aug 25, 5:20 PM EDT	Special Weather Statement	PBZ	Butler	10 min
Aug 25, 5:21 PM EDT	Flash Flood Warning	PBZ	Beaver	29 min
Aug 25, 5:25 PM EDT	Areal Flood Advisory	PBZ	Butler	27 min
Aug 25, 5:29 PM EDT	Areal Flood Advisory	PBZ	Allegheny, Washington	37 min
Aug 25, 5:35 PM EDT	Special Weather Statement	PBZ	Butler	25 min
Aug 25, 5:52 PM EDT	Flash Flood Warning	PBZ	Butler	74 min
Aug 25, 5:56 PM EDT	Flash Flood Warning	PBZ	Butler	89 min

Nearby

Flash Flood Warnings in Pennsylvania, 2021 Every flash flood warning in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.