Alert archive / Pennsylvania / Flash Flood Warnings in 2021

Flash Flood Warning 20, NWS Pittsburgh, PA

August 7, 2021Allegheny County, Pennsylvania

NWS Pittsburgh, PA issued this flash flood warning at Aug 7, 2021, 6:02 PM EDT for Allegheny County, Pennsylvania. It was in force for 77 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Aug 7, 2021, 6:02 PM EDT (22:02 UTC)
Expired
Aug 7, 2021, 7:19 PM EDT
In force
77 min
Issued by
NWS Pittsburgh, PA
Area
Storm-based polygon
Flood severity
None

County Allegheny County, PA

The radar

The Pittsburgh radar (KPBZ), 39 km from the middle of the area, began a volume at 22:05 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.

The nearest sounding before it

Pittsburgh, PA (KPIT), launched 12:00Z, 10.0 hours before the alert went out and 31 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 2021-08-07Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 129 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 2021-08-07The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 5 square meters per square second.19395878Sfc1 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
129 J/kg
Mixed-layer CIN
-50 J/kg
Mixed-layer LCL
1226 m above ground
0-6 km bulk shear
24 kt
0-1 km storm-relative helicity
5 m²/s²
0-3 km storm-relative helicity
37 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.0

Open this sounding in Storm Lab

The text

As transmitted.

552 
WGUS51 KPBZ 072202
FFWPBZ
PAC003-080000-
/O.NEW.KPBZ.FF.W.0020.210807T2202Z-210808T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Pittsburgh PA
602 PM EDT Sat Aug 7 2021

The National Weather Service in Pittsburgh has issued a

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

* Until 800 PM EDT.

* At 602 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1.5 and 2.5 inches of 
  rain have fallen. 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...
  Plum.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4053 7979 4054 7973 4050 7971 4049 7978

FLASH FLOOD...RADAR INDICATED

$$
3 follow-up statements
051 
WGUS71 KPBZ 072213
FFSPBZ

Flash Flood Statement
National Weather Service Pittsburgh PA
613 PM EDT Sat Aug 7 2021

PAC003-080000-
/O.CON.KPBZ.FF.W.0020.000000T0000Z-210808T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Allegheny PA-
613 PM EDT Sat Aug 7 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 8 PM EDT THIS EVENING 
FOR EAST CENTRAL ALLEGHENY COUNTY...

At 613 PM EDT, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Between 1.5 and 2.5 inches of rain have 
fallen. 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...
  Plum.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4053 7979 4054 7973 4050 7971 4049 7978

FLASH FLOOD...RADAR INDICATED

$$
646 
WGUS71 KPBZ 072238
FFSPBZ

Flash Flood Statement
National Weather Service Pittsburgh PA
638 PM EDT Sat Aug 7 2021

PAC003-080000-
/O.CON.KPBZ.FF.W.0020.000000T0000Z-210808T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Allegheny PA-
638 PM EDT Sat Aug 7 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 8 PM EDT THIS EVENING 
FOR EAST CENTRAL ALLEGHENY COUNTY...

At 638 PM EDT, the public reported flooding across the warned area. 
Between 2 and 3 inches of rain have fallen.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Public 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...
  Plum.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 4053 7979 4054 7973 4050 7971 4049 7978

FLASH FLOOD...OBSERVED

$$
408 
WGUS71 KPBZ 072319
FFSPBZ

Flash Flood Statement
National Weather Service Pittsburgh PA
719 PM EDT Sat Aug 7 2021

PAC003-072329-
/O.CAN.KPBZ.FF.W.0020.000000T0000Z-210808T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Allegheny PA-
719 PM EDT Sat Aug 7 2021

...FLASH FLOOD WARNING IS CANCELLED FOR EAST CENTRAL ALLEGHENY 
COUNTY...

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

LAT...LON 4053 7979 4054 7973 4050 7971 4049 7978

$$

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 7, 4:53 PM EDTFlash Flood WarningPBZForest66 min
Aug 7, 5:34 PM EDTAreal Flood AdvisoryPBZAllegheny, Westmoreland31 min
Aug 7, 7:23 PM EDTSpecial Weather StatementPBZAllegheny22 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.