Alert archive / Utah / Flash Flood Warnings in 2021

Flash Flood Warning 69, NWS Salt Lake City, UT

July 29, 2021Washington County, Utah

NWS Salt Lake City, UT issued this flash flood warning at Jul 29, 2021, 9:01 PM MDT for Washington County, Utah. It was in force for 3 hr. 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: Jul 29, 2021, 9:01 PM MDT (03:01 UTC)
Expired: Jul 30, 2021, 12:00 AM MDT
In force: 3 hr
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), 51 km from the middle of the area, began a volume at 03:05 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.

What was reported inside it

Time	Report	Where	Remark
Jul 29, 10:56 PM MDT	HEAVY RAIN 0	Toquerville, UT	WASHINGTON COUNTY DISPATCH REPORTS WATER OVER THE ROAD ON SR 17 NEAR TOQUERVILLE. WATER BRIEFLY DISRUPTED TRAFFIC FLOW. DEPTH OF WATER UNKNOWN AT TIME OF REPORT.

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

The nearest sounding before it

Las Vegas, NV (KVEF), launched 00:00Z, 3.0 hours before the alert went out and 225 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: 175 J/kg
Mixed-layer CIN: -39 J/kg
Mixed-layer LCL: 3675 m above ground
0-6 km bulk shear: 6 kt
0-1 km storm-relative helicity: -12 m²/s²
0-3 km storm-relative helicity: -6 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

435 
WGUS55 KSLC 300301
FFWSLC
UTC053-300600-
/O.NEW.KSLC.FF.W.0069.210730T0301Z-210730T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Salt Lake City UT
901 PM MDT Thu Jul 29 2021

The National Weather Service in Salt Lake City has issued a

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

* Until midnight MDT.

* At 901 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain along La Verkin Creek. Between 0.75 and 1.5 inches of 
  rain have fallen. Flash flooding is ongoing or expected to begin 
  shortly in La Verkin Creek down to where it meets the Virgin River.

  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...
  La Verkin Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

&&

LAT...LON 3720 11331 3736 11326 3736 11319 3718 11325

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

$$

MT

2 follow-up statements

796 
WGUS75 KSLC 300502
FFSSLC

Flash Flood Statement
National Weather Service Salt Lake City UT
1102 PM MDT Thu Jul 29 2021

UTC053-300600-
/O.CON.KSLC.FF.W.0069.000000T0000Z-210730T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Washington UT-
1102 PM MDT Thu Jul 29 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL MIDNIGHT MDT TONIGHT 
FOR CENTRAL WASHINGTON COUNTY...

At 1102 PM MDT, Doppler radar indicated thunderstorms producing 
heavy rain across the warned area. Between 1 and 2 inches of rain 
have fallen. Law enforcement has also reported water over a bridge 
along Sate Route 17 in Toquerville. 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...
  La Verkin Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

&&

LAT...LON 3720 11331 3736 11326 3736 11319 3718 11325

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

$$

LC

479 
WGUS75 KSLC 300557
FFSSLC

Flash Flood Statement
National Weather Service Salt Lake City UT
1157 PM MDT Thu Jul 29 2021

UTC053-300607-
/O.EXP.KSLC.FF.W.0069.000000T0000Z-210730T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Washington UT-
1157 PM MDT Thu Jul 29 2021

...FLASH FLOOD WARNING WILL EXPIRE AT MIDNIGHT MDT TONIGHT FOR 
CENTRAL WASHINGTON COUNTY...

The heavy rain has ended across central Washington County. 
Additional flooding is no longer expected. Runoff from earlier heavy 
rain is expected to decrease through late tonight. Please continue 
to heed any remaining road closures.

LAT...LON 3720 11331 3736 11326 3736 11319 3718 11325

$$

LC

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 29, 6:03 PM MDT	Flash Flood Warning Considerable damage threat	SLC	Garfield	117 min
Jul 29, 6:03 PM MDT	Special Weather Statement	SLC	Kane	27 min
Jul 29, 6:24 PM MDT	Special Weather Statement	SLC	Kane	36 min
Jul 29, 7:06 PM MDT	Special Weather Statement	SLC	Washington	24 min
Jul 29, 7:16 PM MDT	Special Weather Statement	SLC	Wayne	29 min
Jul 29, 7:23 PM MDT	Special Weather Statement	SLC	Wayne	37 min
Jul 29, 7:40 PM MDT	Flash Flood Warning Considerable damage threat	SLC	Kane	3 hr
Jul 29, 7:41 PM MDT	Severe Thunderstorm Warning	SLC	Garfield, Wayne	34 min
Jul 29, 7:46 PM MDT	Flash Flood Warning Considerable damage threat	SLC	Kane	3 hr
Jul 29, 7:52 PM MDT	Flash Flood Warning Considerable damage threat	SLC	Garfield, Wayne	113 min
Jul 29, 8:11 PM MDT	Special Weather Statement	SLC	Iron	19 min
Jul 29, 8:51 PM MDT	Special Weather Statement	SLC	Iron	39 min
Jul 29, 9:42 PM MDT	Special Weather Statement	SLC	Carbon	63 min
Jul 30, 3:38 AM MDT	Flash Flood Watch	SLC	Beaver, Garfield, Iron, Kane, Piute, Washington and 1 more	19 hr
Jul 30, 2:17 PM MDT	Flash Flood Warning Considerable damage threat	SLC	Washington	3 hr
Jul 30, 2:18 PM MDT	Special Weather Statement	SLC	Sevier	42 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.