Alert archive / Utah / Flash Flood Warnings in 2021

Flash Flood Warning 9, NWS Grand Junction, CO

July 13, 2021Grand County, Uintah County, Utah

NWS Grand Junction, CO issued this flash flood warning at Jul 13, 2021, 2:35 PM MDT for Grand County, Uintah 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 13, 2021, 2:35 PM MDT (20:35 UTC)
Expired: Jul 13, 2021, 5:45 PM MDT
In force: 3 hr
Issued by: NWS Grand Junction, CO
Area: Storm-based polygon
Flood severity: None

Counties Grand County, UT, Uintah County, UT

The radar

The Grand Junction radar (KGJX), 97 km from the middle of the area, began a volume at 20:38 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 13, 5:30 PM MDT	FLASH FLOOD	37 Nne Castle Valley, UT	NWS STORM SURVEY FOUND EVIDENCE OF A MAJOR FLASH FLOODING EVENT IN THE WESTWATER DRAINAGE VALLEY. WATER WAS ESTIMATED TO BE 6 TO UP TO 12 FEET DEEP BASED ON EROSION OF THE ARROYO WALLS. NUMEROUS INSTANCES OF DRY ARROYO CROSSINGS WASHED OUT WITH MAJOR TRANSPORT

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

The nearest sounding before it

Grand Junction, CO (KGJT), launched 12:00Z, 8.6 hours before the alert went out and 71 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: 27 J/kg
Mixed-layer CIN: -350 J/kg
Mixed-layer LCL: 3436 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 111 m²/s²
0-3 km storm-relative helicity: 184 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

321 
WGUS55 KGJT 132035
FFWGJT
UTC019-047-132345-
/O.NEW.KGJT.FF.W.0009.210713T2035Z-210713T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Grand Junction CO
235 PM MDT Tue Jul 13 2021

The National Weather Service in Grand Junction has issued a

* Flash Flood Warning for...
  Northeastern Grand County in east central Utah...
  South Central Uintah County in northeastern Utah...

* Until 545 PM MDT.

* At 235 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 2 inches of rain 
  have fallen. Additional rainfall amounts up to 0.5 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...
  Mainly rural areas of Northeastern Grand and South Central Uintah 
  Counties north of Interstate 70 in the Grand Flat desert.

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. 
Arroyos, streams, and rivers can become raging killer currents in a 
matter of minutes, even from distant rainfall.

&&

LAT...LON 3946 10941 3949 10936 3951 10928 3951 10922
      3947 10916 3942 10917 3936 10922 3930 10924
      3918 10918 3911 10914 3909 10916 3917 10921
      3924 10926 3926 10932 3929 10938 3934 10942
      3944 10944

FLASH FLOOD...RADAR INDICATED

$$

MAC

2 follow-up statements

859 
WGUS75 KGJT 132251
FFSGJT

Flash Flood Statement
National Weather Service Grand Junction CO
451 PM MDT Tue Jul 13 2021

UTC019-047-132345-
/O.CON.KGJT.FF.W.0009.000000T0000Z-210713T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Grand UT-Uintah UT-
451 PM MDT Tue Jul 13 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 545 PM MDT THIS 
AFTERNOON FOR NORTHEASTERN GRAND AND SOUTH CENTRAL UINTAH COUNTIES...

At 451 PM MDT, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Radar estimates between 1 and 2 inches 
of rain have fallen. Additional rainfall amounts up to 0.5 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...
  mainly rural areas of Northeastern Grand and South Central Uintah 
  Counties

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. 
Arroyos, streams, and rivers can become raging killer currents in a 
matter of minutes, even from distant rainfall.

&&

LAT...LON 3946 10941 3949 10936 3951 10928 3951 10922
      3947 10916 3942 10917 3936 10922 3930 10924
      3918 10918 3911 10914 3909 10916 3917 10921
      3924 10926 3926 10932 3929 10938 3934 10942
      3944 10944

FLASH FLOOD...RADAR INDICATED

$$

MDA

663 
WGUS75 KGJT 132340
FFSGJT

Flash Flood Statement
National Weather Service Grand Junction CO
540 PM MDT Tue Jul 13 2021

UTC019-047-132350-
/O.EXP.KGJT.FF.W.0009.000000T0000Z-210713T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Grand UT-Uintah UT-
540 PM MDT Tue Jul 13 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 545 PM MDT THIS AFTERNOON FOR 
NORTHEASTERN GRAND AND SOUTH CENTRAL UINTAH COUNTIES...

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

LAT...LON 3946 10941 3949 10936 3951 10928 3951 10922
      3947 10916 3942 10917 3936 10922 3930 10924
      3918 10918 3911 10914 3909 10916 3917 10921
      3924 10926 3926 10932 3929 10938 3934 10942
      3944 10944

$$

TGR

The office that day

Everything else NWS Grand Junction, CO issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 13, 4:47 PM MDT	Special Weather Statement	GJT	Grand	28 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.