Alert archive / Colorado / Flash Flood Watches in 2021

Flash Flood Watch 29, NWS Grand Junction, CO

August 16, 20216 counties in Colorado

NWS Grand Junction, CO issued this flash flood watch at Aug 16, 2021, 5:44 PM MDT for 6 counties in Colorado. It was in force for 2 hr.

The area

The counties it named.

The facts

Issued: Aug 16, 2021, 5:44 PM MDT (23:44 UTC)
Expired: Aug 16, 2021, 8:00 PM MDT
In force: 2 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 23:43 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, 11.7 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: 25 J/kg
Mixed-layer CIN: -229 J/kg
Mixed-layer LCL: 2786 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: -1 m²/s²
0-3 km storm-relative helicity: 91 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 Aug 16, 5:44 PM MDT, 0 minutes earlier.

Area forecast discussion, Aug 16, 5:44 PM MDT, 0 minutes before

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Hazardous weather outlook, Aug 16, 4:02 AM MDT, 13 hours 42 minutes before

Hazardous Weather Outlook
National Weather Service Grand Junction CO
402 AM MDT Mon Aug 16 2021

COZ001>014-017>023-UTZ022>025-027>029-171015-
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-
402 AM MDT Mon Aug 16 2021

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

.DAY ONE...Today and Tonight

Thunderstorm development will occur again this afternoon and
evening mainly over the southern Colorado mountains. Some storms
will be capable of brief heavy rainfall rates and others capable
of producing gusty outflow winds in excess of 45 mph. Areas of smoke
will continue to affect air quality conditons.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Thunderstorm coverage will become more widespread by mid week as
a larger storm system moves through the region. The threat of
heavy rainfall rates or prolonged precipitation could impact burn
scars and lead to other runoff issues during this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today.

In the hours before

Special weather statement, Aug 16, 3:13 PM MDT, 2 hours 31 minutes before

Special Weather Statement
National Weather Service Grand Junction CO
313 PM MDT Mon Aug 16 2021

COZ019-021-162145-
Southwest San Juan Mountains CO-Four Corners/Upper Dolores River CO-
313 PM MDT Mon Aug 16 2021

...A strong thunderstorm will impact portions of north central
Montezuma County through 345 PM MDT...

At 313 PM MDT, Doppler radar was tracking a strong thunderstorm over
Dolores, or 37 miles west of Durango, moving west at 10 mph.

HAZARD...Winds in excess of 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Cortez, Dolores, Lebanon and Arriola.

This includes the following highways...
 U.S. Highway 491 in Colorado between mile markers 28 and 37.
 Colorado 145 between mile markers 1 and 14.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3748 10844 3742 10843 3736 10845 3736 10874
      3762 10860
TIME...MOT...LOC 2113Z 100DEG 9KT 3744 10851

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

ERW

Local storm report, Aug 16, 3:58 PM MDT, 1 hour 46 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
Aug 16, 3:13 PM MDT	Special Weather Statement	GJT	Montezuma	32 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.