Alert archive / Colorado / Flash Flood Watches in 2021

Flash Flood Watch 17, NWS Grand Junction, CO

July 21, 202116 counties in Colorado

NWS Grand Junction, CO issued this flash flood watch at Jul 21, 2021, 1:44 PM MDT for 16 counties in Colorado. It took effect at Jul 22, 2021, 12:00 PM MDT. It was in force for 12 hr.

The area

The counties it named.

The facts

Issued: Jul 21, 2021, 1:44 PM MDT (19:44 UTC)
In effect from: Jul 22, 2021, 12:00 PM MDT
Expired: Jul 23, 2021, 12:00 AM MDT
In force: 12 hr
Issued by: NWS Grand Junction, CO
Flood severity: None

Counties Archuleta County, CO, Dolores County, CO, Eagle County, CO, Garfield County, CO, Gunnison County, CO, Hinsdale County, CO, La Plata 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

The radar

The Grand Junction radar (KGJX), 66 km from the middle of the area, began a volume at 19:48 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, 7.7 hours before the alert went out and 89 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: 6 J/kg
Mixed-layer CIN: -283 J/kg
Mixed-layer LCL: 2031 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 62 m²/s²
0-3 km storm-relative helicity: 90 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 21, 11:43 AM MDT, 2 hours 1 minute earlier.

Area forecast discussion, Jul 21, 11:43 AM MDT, 2 hours 1 minute before

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Hazardous weather outlook, Jul 21, 3:09 AM MDT, 10 hours 35 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
Jul 20, 7:53 PM MDT	Areal Flood Advisory	GJT	Montezuma	2 hr
Jul 20, 8:36 PM MDT	Flash Flood Warning Considerable damage threat	GJT	Eagle, Garfield	3 hr
Jul 21, 2:42 AM MDT	Flash Flood Watch	GJT	Archuleta, Dolores, Eagle, Garfield, Gunnison, Hinsdale and 10 more	21 hr
Jul 21, 3:18 PM MDT	Special Weather Statement	GJT	Archuleta	42 min
Jul 21, 3:22 PM MDT	Special Weather Statement	GJT	La Plata	38 min
Jul 21, 3:45 PM MDT	Special Weather Statement	GJT	La Plata	45 min
Jul 21, 4:30 PM MDT	Special Weather Statement	GJT	Montezuma	30 min
Jul 20, 7:36 PM MDT	Areal Flood Advisory	GJT	San Juan	114 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.