Alert archive / Colorado / Flash Flood Watches in 2021

Flash Flood Watch 35, NWS Grand Junction, CO

September 29, 20216 counties in Colorado

NWS Grand Junction, CO issued this flash flood watch at Sep 29, 2021, 11:55 AM MDT for 6 counties in Colorado. It was in force for 11 hr.

The area

The counties it named.

The facts

Issued: Sep 29, 2021, 11:55 AM MDT (17:55 UTC)
Expired: Sep 29, 2021, 10:52 PM MDT
In force: 11 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 17:59 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.

The nearest sounding before it

Grand Junction, CO (KGJT), launched 12:00Z, 5.9 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-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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1010 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: -5 m²/s²
0-3 km storm-relative helicity: 88 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 Sep 29, 11:46 AM MDT, 9 minutes earlier.

Area forecast discussion, Sep 29, 11:46 AM MDT, 9 minutes before

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Hazardous weather outlook, Sep 29, 4:51 AM MDT, 7 hours 4 minutes before

Hazardous Weather Outlook
National Weather Service Grand Junction CO
451 AM MDT Wed Sep 29 2021

COZ001>014-017>023-UTZ022>025-027>029-301100-
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-
451 AM MDT Wed Sep 29 2021

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

.DAY ONE...Today and Tonight

Showers and storms will become more widespread today as a robust
Pacific disturbance approaches from the west and tracks across the
area late today. Storms will be capable of brief moderate to
heavy rain and wind gusts to 40 mph. The focus will be for areas
along and north of I-70 for the best precipitation potential.
Temperatures will be much cooler with highs about 15 degrees
below normal readings.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Scattered showers and storms will occur Thursday and Friday,
favoring the central and southern high terrain with drier air
pushing into the northwestern portion of the forecast area. Dry
and warmer conditions return for the weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.

In the hours before

Local storm report, Sep 29, 10:24 AM MDT, 1 hour 31 minutes before

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Local storm report, Sep 29, 10:32 AM MDT, 1 hour 23 minutes before

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Local storm report, Sep 29, 10:33 AM MDT, 1 hour 22 minutes before

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Local storm report, Sep 29, 10:54 AM MDT, 1 hour 1 minute before

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Local storm report, Sep 29, 10:55 AM MDT, 1 hour before

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Local storm report, Sep 29, 11:25 AM MDT, 30 minutes before

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The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 29, 12:07 AM MDT	Special Weather Statement	GJT		23 min
Sep 29, 12:32 AM MDT	Special Weather Statement	GJT	Mesa	28 min
Sep 29, 1:03 AM MDT	Special Weather Statement	GJT	Garfield	27 min
Sep 29, 5:58 AM MDT	Special Weather Statement	GJT		32 min
Sep 29, 8:10 AM MDT	Flash Flood Watch	GJT	Eagle, Garfield, Moffat, Pitkin, Rio Blanco, Routt	31 min
Sep 29, 8:41 AM MDT	Flash Flood Warning Considerable damage threat	GJT	Eagle, Garfield	3 hr
Sep 29, 12:24 PM MDT	Areal Flood Advisory	GJT	Mesa	4 hr
Sep 29, 1:14 PM MDT	Special Weather Statement	GJT		46 min

Nearby

Flash Flood Watches in Colorado, 2021 Every 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.