Alert archive / Colorado / Flash Flood Watches in 2021

Flash Flood Watch 19, NWS Grand Junction, CO

July 24, 202118 counties in Colorado; Grand County, San Juan County, Utah

NWS Grand Junction, CO issued this flash flood watch at Jul 24, 2021, 3:51 AM MDT for 18 counties in Colorado; Grand County, San Juan County, Utah. It took effect at Jul 24, 2021, 11:46 AM MDT. It was in force for 9 hr.

The area

The counties it named.

The facts

Issued
Jul 24, 2021, 3:51 AM MDT (09:51 UTC)
In effect from
Jul 24, 2021, 11:46 AM MDT
Expired
Jul 24, 2021, 9:00 PM MDT
In force
9 hr
Issued by
NWS Grand Junction, CO
Flood severity
None

Counties Archuleta County, CO, Delta County, CO, Dolores County, CO, Eagle County, CO, Garfield County, CO, Gunnison County, CO, Hinsdale County, CO, La Plata County, CO, Mesa County, CO, Moffat County, CO, Montezuma County, CO, Montrose County, CO, Ouray County, CO, Pitkin County, CO, Rio Blanco County, CO, Routt County, CO, San Juan County, CO, San Miguel County, CO, Grand County, UT, San Juan County, UT

The radar

The Grand Junction radar (KGJX), 54 km from the middle of the area, began a volume at 09:54 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

Grand Junction, CO (KGJT), launched 00:00Z, 9.9 hours before the alert went out and 74 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 00:00Z on 2021-07-24Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 917 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 00:00Z on 2021-07-24The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -20 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
917 J/kg
Mixed-layer CIN
-11 J/kg
Mixed-layer LCL
2718 m above ground
0-6 km bulk shear
7 kt
0-1 km storm-relative helicity
-20 m²/s²
0-3 km storm-relative helicity
120 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this flash flood watch went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Grand Junction, CO wrote its last area forecast discussion before this flash flood watch went out at Jul 23, 11:41 PM MDT, 4 hours 10 minutes earlier.

Area forecast discussion, Jul 23, 11:41 PM MDT, 4 hours 10 minutes before
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Hazardous weather outlook, Jul 23, 5:39 AM MDT, 22 hours 12 minutes before
Hazardous Weather Outlook
National Weather Service Grand Junction CO
539 AM MDT Fri Jul 23 2021

COZ001>014-017>023-UTZ022>025-027>029-241145-
Lower Yampa River Basin-Central Yampa River Basin-
Roan and Tavaputs Plateaus-Elkhead and Park Mountains-
Upper Yampa River Basin-Grand Valley-Debeque to Silt Corridor-
Central Colorado River Basin-Grand and Battlement Mesas-
Gore and Elk Mountains/Central Mountain Valleys-
Central Gunnison and Uncompahgre River Basin-
West Elk and Sawatch Mountains-Flat Tops-
Upper Gunnison River Valley-Uncompahgre Plateau and Dallas Divide-
Northwest San Juan Mountains-Southwest San Juan Mountains-
Paradox Valley/Lower Dolores River-
Four Corners/Upper Dolores River-Animas River Basin-
San Juan River Basin-Southeast Utah-Eastern Uinta Mountains-
Eastern Uinta Basin-Tavaputs Plateau-Arches/Grand Flat-
La Sal and Abajo Mountains-Canyonlands/Natural Bridges-
539 AM MDT Fri Jul 23 2021

This hazardous weather outlook is for eastern Utah and western
Colorado.

.DAY ONE...Today and Tonight

Deep monsoonal moisture will result in thunderstorm development
with the potential for heavy rainfall rates today.  Localized
flash flooding will be possible in response to heavy rains and
saturated soils.The recent burn scars will be especially
vulnerable with debris flows a likely impact. Gusty outflow winds
will accompany the strongest storms and possibly small hail.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Daily scattered to numerous showers and thunderstorms can be
expected through the weekend. Moderate to heavy rain and gusty
winds will be the primary threats with storms. Localized flash
flooding will be possible in response to heavy rains and
saturated soils. Unsettled weather is expected into the new work
week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected today or tonight, however
spotters are encouraged to relay rainfall amounts or any observed
flooding to the National Weather Service in Grand Junction.

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, 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
Jul 24, 3:55 PM MDTFlash Flood WarningGJTMesa, Montrose3 hr
Jul 23, 7:24 PM MDTAreal Flood AdvisoryGJTGrand, San Juan3 hr
Jul 24, 1:26 PM MDTAreal Flood AdvisoryGJTSan Juan3 hr
Jul 24, 3:35 PM MDTFlash Flood WarningGJTSan Juan3 hr
Jul 24, 3:42 PM MDTFlash Flood WarningGJTSan Juan2 hr

Nearby

Flash Flood Watches in Colorado, 2021Flash Flood Watches in Utah, 2021Every flash flood watch 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.