Alert archive / Utah / Flash Flood Warnings in 2021

Flash Flood Warning 91, NWS Salt Lake City, UT

August 12, 2021Washington County, Utah

NWS Salt Lake City, UT issued this flash flood warning at Aug 12, 2021, 6:26 PM MDT for Washington County, Utah. It was in force for 114 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 12, 2021, 6:26 PM MDT (00:26 UTC)
Expired: Aug 12, 2021, 8:20 PM MDT
In force: 114 min
Issued by: NWS Salt Lake City, UT
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Washington County, UT

The radar

The Cedar City radar (KICX), 64 km from the middle of the area, began a volume at 00:30 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

Flgstf/Belemont, AZ (KFGZ), launched 00:00Z, 0.4 hours before the alert went out and 226 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: 2 J/kg
Mixed-layer CIN: -99 J/kg
Mixed-layer LCL: 1844 m above ground
0-6 km bulk shear: 5 kt
0-1 km storm-relative helicity: -14 m²/s²
0-3 km storm-relative helicity: 46 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

582 
WGUS55 KSLC 130026
FFWSLC
UTC053-130330-
/O.NEW.KSLC.FF.W.0091.210813T0026Z-210813T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Salt Lake City UT
626 PM MDT Thu Aug 12 2021

The National Weather Service in Salt Lake City has issued a

* Flash Flood Warning for...
  Southeastern Washington County in southwestern Utah...

* Until 930 PM MDT.

* At 626 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 0.75 and 1 inch of rain 
  has fallen based on radar estimates. Dispatch noted washes 
  beginning to fill with water in the city. Flash flooding is 
  ongoing or expected to begin shortly.

  HAZARD...Life threatening flash flooding. Thunderstorms
           producing flash flooding.

  SOURCE...Radar.

  IMPACT...Life threatening flash flooding of creeks and streams,
           urban areas, highways, streets and underpasses.

* Some locations that will experience flash flooding include...
  Hildale.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Remain alert for flooding even in locations not receiving rain. Dry 
washes, streams, and rivers can become raging killer currents in a 
matter of minutes, even from distant rainfall.

&&

LAT...LON 3700 11310 3709 11294 3707 11290 3705 11290
      3700 11293 3700 11299 3700 11300

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

AD

1 follow-up statement

847 
WGUS75 KSLC 130220
FFSSLC

Flash Flood Statement
National Weather Service Salt Lake City UT
820 PM MDT Thu Aug 12 2021

UTC053-130230-
/O.CAN.KSLC.FF.W.0091.000000T0000Z-210813T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Washington UT-
820 PM MDT Thu Aug 12 2021

...FLASH FLOOD WARNING IS CANCELLED FOR SOUTHEASTERN WASHINGTON 
COUNTY...

Flood waters have receded per Hildale Dispatch. The heavy rain has 
ended. Flooding is no longer expected to pose a threat this evening.

LAT...LON 3700 11310 3709 11294 3707 11290 3705 11290
      3700 11293 3700 11299 3700 11300

$$

AD

The office that day

Everything else NWS Salt Lake City, UT issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 13, 4:20 PM MDT	Severe Thunderstorm Warning	SLC	Iron, Washington	25 min
Aug 13, 4:40 PM MDT	Severe Thunderstorm Warning	SLC	Washington	35 min
Aug 13, 5:14 PM MDT	Severe Thunderstorm Warning	SLC	Washington	16 min

Nearby

Flash Flood Warnings in Utah, 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.