Alert archive / Colorado / Flash Flood Watches in 2021

Flash Flood Watch 33, NWS Grand Junction, CO

September 28, 20216 counties in Colorado

NWS Grand Junction, CO issued this flash flood watch at Sep 28, 2021, 12:06 PM MDT for 6 counties in Colorado. It was in force for 9 hr.

The area

The counties it named.

The facts

Issued
Sep 28, 2021, 12:06 PM MDT (18:06 UTC)
Expired
Sep 28, 2021, 9:00 PM MDT
In force
9 hr
Issued by
NWS Grand Junction, CO
Flood severity
None

Counties Eagle County, CO, Garfield County, CO, Moffat County, CO, Pitkin County, CO, Rio Blanco County, CO, Routt County, CO

The radar

The Grand Junction radar (KGJX), 114 km from the middle of the area, began a volume at 18:07 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 12:00Z, 6.1 hours before the alert went out and 124 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 2021-09-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 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 2021-09-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -27 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
2319 m above ground
0-6 km bulk shear
3 kt
0-1 km storm-relative helicity
-27 m²/s²
0-3 km storm-relative helicity
112 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

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 Sep 28, 11:48 AM MDT, 18 minutes earlier.

Area forecast discussion, Sep 28, 11:48 AM MDT, 18 minutes before
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Hazardous weather outlook, Sep 28, 4:36 AM MDT, 7 hours 30 minutes before
Hazardous Weather Outlook
National Weather Service Grand Junction CO
436 AM MDT Tue Sep 28 2021

COZ001>014-017>023-UTZ022>025-027>029-291045-
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-
436 AM MDT Tue Sep 28 2021

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

.DAY ONE...Today and Tonight

Showers and storms will spread northward today and become more
widespread this evening as another storm system pushes in from the
west. Storms will be capable of brief moderate rain and wind
gusts to 40 mph. The focus shifts across areas along and north of
I-70 for the best precipitation potential this evening into the
overnight hours.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Showers and storms will continue on Wednesday as a Pacific
disturbance tracks across the northern portion of the forecast
area. Temperatures will be much cooler with below normal
readings. Drier air pushes in from the west late in the week with
afternoon storms possible over the high terrain along the divide.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.

The office that day

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

IssuedProductOfficeCountiesLasted
Sep 28, 4:26 AM MDTDense Fog AdvisoryGJTLa Plata3 hr
Sep 28, 2:59 PM MDTAreal Flood AdvisoryGJTMesa89 min
Sep 28, 3:05 PM MDTAreal Flood AdvisoryGJTRio Blanco115 min
Sep 28, 4:03 PM MDTFlash Flood Warning Considerable damage threatGJTGarfield, Mesa97 min
Sep 28, 5:44 PM MDTSpecial Weather StatementGJTMesa31 min

Nearby

Flash Flood Watches in Colorado, 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.