Alert archive / Pennsylvania / Flash Flood Warnings in 2021

Flash Flood Warning 32, NWS Pittsburgh, PA

August 25, 2021Butler County, Pennsylvania

NWS Pittsburgh, PA issued this flash flood warning at Aug 25, 2021, 5:52 PM EDT for Butler County, Pennsylvania. It was in force for 74 min. 2 reports 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, 5:52 PM EDT (21:52 UTC)
Expired
Aug 25, 2021, 7:06 PM EDT
In force
74 min
Issued by
NWS Pittsburgh, PA
Area
Storm-based polygon
Flood severity
None

County Butler County, PA

The radar

The Pittsburgh radar (KPBZ), 40 km from the middle of the area, began a volume at 21:54 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

TimeReportWhereRemark
Aug 25, 6:05 PM EDTFLASH FLOODButler, PAFLOODING ON WEST BRADY STREET NEAR MILLER AVENUE
Aug 25, 6:30 PM EDTFLASH FLOOD1 Ene Oneida, PAROUTE 38 FLOODED NEAR ONEIDA VALLEY RESERVOIR.

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, 9.9 hours before the alert went out and 52 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-pSkew-T log-p diagram, Pittsburgh, PA at 12:00Z on 2021-08-25Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 323 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Pittsburgh, PA at 12:00Z on 2021-08-25The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -18 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
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.

110 
WGUS51 KPBZ 252152
FFWPBZ
PAC019-252330-
/O.NEW.KPBZ.FF.W.0032.210825T2152Z-210825T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Pittsburgh has issued a

* Flash Flood Warning for...
  West Central Butler County in west central Pennsylvania...

* Until 730 PM EDT.

* At 552 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2 and 3 inches of rain 
  have fallen. Additional rainfall amounts up to 1 inch 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...
  Butler, Homeacre-Lyndora, Shanor-Northvue, Meridian, Meadowood, 
  Oak Hills, Prospect, Connoquenessing, Portersville and Moraine 
  State Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4095 8016 4095 7982 4082 7991 4082 8016
      4083 8016 4084 8016 4085 8016 4087 8016
      4088 8016 4089 8016

FLASH FLOOD...RADAR INDICATED

$$
2 follow-up statements
834 
WGUS71 KPBZ 252159
FFSPBZ

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

PAC019-252330-
/O.CON.KPBZ.FF.W.0032.000000T0000Z-210825T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Butler PA-
559 PM EDT Wed Aug 25 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 730 PM EDT THIS 
EVENING FOR WEST CENTRAL BUTLER COUNTY...

At 559 PM EDT, local law enforcement reported flash flooding across 
the warned area. Between 2 and 3 inches of rain have fallen. 
Additional rainfall amounts up to 1 inch are possible in the warned 
area.

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...
  Butler, Homeacre-Lyndora, Shanor-Northvue, Meridian, Meadowood, 
  Oak Hills, Prospect, Connoquenessing, Portersville and Moraine 
  State Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4095 8016 4095 7982 4082 7991 4082 8016
      4083 8016 4084 8016 4085 8016 4087 8016
      4088 8016 4089 8016

FLASH FLOOD...OBSERVED

$$
425 
WGUS71 KPBZ 252306
FFSPBZ

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

PAC019-252316-
/O.CAN.KPBZ.FF.W.0032.000000T0000Z-210825T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Butler PA-
706 PM EDT Wed Aug 25 2021

...FLASH FLOOD WARNING IS CANCELLED FOR WEST CENTRAL BUTLER COUNTY...

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 4095 8016 4095 7982 4082 7991 4082 8016
      4083 8016 4084 8016 4085 8016 4087 8016
      4088 8016 4089 8016

$$

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 25, 3:12 PM EDTSpecial Weather StatementPBZMercer33 min
Aug 25, 3:34 PM EDTAreal Flood AdvisoryPBZMercer116 min
Aug 25, 3:43 PM EDTSpecial Weather StatementPBZAllegheny32 min
Aug 25, 4:12 PM EDTSpecial Weather StatementPBZButler18 min
Aug 25, 4:46 PM EDTSpecial Weather StatementPBZBeaver14 min
Aug 25, 4:50 PM EDTAreal Flood AdvisoryPBZAllegheny, Butler27 min
Aug 25, 5:17 PM EDTFlash Flood WarningPBZAllegheny, Butler88 min
Aug 25, 5:20 PM EDTSpecial Weather StatementPBZButler10 min
Aug 25, 5:21 PM EDTFlash Flood WarningPBZBeaver29 min
Aug 25, 5:25 PM EDTAreal Flood AdvisoryPBZButler27 min
Aug 25, 5:29 PM EDTAreal Flood AdvisoryPBZAllegheny, Washington37 min
Aug 25, 5:35 PM EDTSpecial Weather StatementPBZButler25 min
Aug 25, 5:56 PM EDTFlash Flood WarningPBZButler89 min
Aug 25, 6:05 PM EDTFlash Flood WarningPBZAllegheny, Washington46 min

Nearby

Flash Flood Warnings in Pennsylvania, 2021Every 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.