Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 30, NWS Grand Junction, CO

July 24, 2021Mesa County, Montrose County, Colorado

NWS Grand Junction, CO issued this flash flood warning at Jul 24, 2021, 3:55 PM MDT for Mesa County, Montrose County, Colorado. 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 24, 2021, 3:55 PM MDT (21:55 UTC)
Expired
Jul 24, 2021, 6:51 PM MDT
In force
3 hr
Issued by
NWS Grand Junction, CO
Area
Storm-based polygon
Flood severity
None

Counties Mesa County, CO, Montrose County, CO

The radar

The Grand Junction radar (KGJX), 85 km from the middle of the area, began a volume at 21:59 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
Jul 24, 4:30 PM MDTFLASH FLOOD11 Nne Paradox, CONORMALLY DRY ARROYO ERUPTED INTO A RAGING WATERFALL. MUD AND DEBRIS FLOWED ON TO HIGHWAY 141. WATERFALL SHARED ON SOCIAL MEDIA.

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, 9.9 hours before the alert went out and 73 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, Grand Junction, CO at 12:00Z on 2021-07-24Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 19 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Grand Junction, CO at 12:00Z on 2021-07-24The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 40 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
19 J/kg
Mixed-layer CIN
-266 J/kg
Mixed-layer LCL
1844 m above ground
0-6 km bulk shear
5 kt
0-1 km storm-relative helicity
40 m²/s²
0-3 km storm-relative helicity
94 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

384 
WGUS55 KGJT 242155
FFWGJT
COC077-085-250100-
/O.NEW.KGJT.FF.W.0030.210724T2155Z-210725T0100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Grand Junction CO
355 PM MDT Sat Jul 24 2021

The National Weather Service in Grand Junction has issued a

* Flash Flood Warning for...
  Southwestern Mesa County in west central Colorado...
  Northwestern Montrose County in west central Colorado...

* Until 700 PM MDT.

* At 355 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. The expected rainfall rate is 1 
  to 2 inches in 1 hour. 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...
  Gateway.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3859 10906 3860 10906 3865 10906 3867 10906
      3871 10906 3873 10885 3848 10886 3850 10906

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...1-2 INCHES IN 1 HOUR

$$

KJS
1 follow-up statement
301 
WGUS75 KGJT 250051
FFSGJT

Flash Flood Statement
National Weather Service Grand Junction CO
651 PM MDT Sat Jul 24 2021

COC077-085-250101-
/O.CAN.KGJT.FF.W.0030.000000T0000Z-210725T0100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Mesa CO-Montrose CO-
651 PM MDT Sat Jul 24 2021

...FLASH FLOOD WARNING IS CANCELLED FOR SOUTHWESTERN MESA AND 
NORTHWESTERN MONTROSE COUNTIES...

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

A Flash Flood Watch remains in effect until 900 PM MDT for portions 
of Colorado and southeast Utah.

LAT...LON 3859 10906 3860 10906 3865 10906 3867 10906
      3871 10906 3873 10885 3848 10886 3850 10906

$$

NL

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 23, 6:04 PM MDTAreal Flood AdvisoryGJTRio Blanco116 min
Jul 23, 6:11 PM MDTAreal Flood AdvisoryGJTDelta2 hr
Jul 23, 6:17 PM MDTSpecial Weather StatementGJTDelta28 min
Jul 23, 6:37 PM MDTSpecial Weather StatementGJT38 min
Jul 23, 7:04 PM MDTAreal Flood AdvisoryGJTMesa, Montrose109 min
Jul 23, 7:14 PM MDTAreal Flood AdvisoryGJTGarfield, Mesa3 hr
Jul 23, 8:44 PM MDTAreal Flood AdvisoryGJTDolores, San Miguel2 hr
Jul 24, 3:51 AM MDTFlash Flood WatchGJTArchuleta, Delta, Dolores, Eagle, Garfield, Gunnison and 12 more17 hr
Jul 24, 11:57 AM MDTSpecial Weather StatementGJTGarfield48 min
Jul 24, 12:34 PM MDTAreal Flood AdvisoryGJTDelta, Gunnison, Mesa, Pitkin3 hr
Jul 24, 12:41 PM MDTSpecial Weather StatementGJTDelta49 min
Jul 24, 1:30 PM MDTSpecial Weather StatementGJTDelta30 min
Jul 24, 1:30 PM MDTSpecial Weather StatementGJTGarfield45 min
Jul 24, 1:32 PM MDTSpecial Weather StatementGJTOuray28 min
Jul 24, 1:36 PM MDTAreal Flood AdvisoryGJTGarfield, Mesa13 min
Jul 24, 1:46 PM MDTAreal Flood AdvisoryGJTSan Miguel3 hr
Jul 24, 1:49 PM MDTFlash Flood WarningGJTGarfield, Mesa3 hr
Jul 24, 2:09 PM MDTAreal Flood AdvisoryGJTSan Miguel55 min
Jul 24, 2:15 PM MDTSpecial Weather StatementGJTMontezuma30 min
Jul 24, 2:34 PM MDTAreal Flood AdvisoryGJTMontrose, San Miguel30 min
Jul 24, 2:45 PM MDTSpecial Weather StatementGJTMontezuma15 min
Jul 24, 3:03 PM MDTFlash Flood WarningGJTMontrose, San Miguel3 hr
Jul 24, 3:12 PM MDTFlash Flood Warning Considerable damage threatGJTGarfield, Mesa82 min
Jul 24, 3:27 PM MDTAreal Flood AdvisoryGJTMontezuma2 hr
Jul 24, 3:28 PM MDTFlash Flood Warning Considerable damage threatGJTEagle, Garfield69 min
Jul 24, 3:45 PM MDTAreal Flood AdvisoryGJTMontrose4 min
Jul 24, 3:47 PM MDTFlash Flood WarningGJTMontrose3 hr

Nearby

Flash Flood Warnings in Colorado, 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.