Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 25, NWS Denver/Boulder, CO

July 5, 2021Grand County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Jul 5, 2021, 6:56 PM MDT for Grand County, Colorado. It was in force for 79 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Jul 5, 2021, 6:56 PM MDT (00:56 UTC)
Expired: Jul 5, 2021, 8:15 PM MDT
In force: 79 min
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Flood severity: None

County Grand County, CO

The radar

The Cheyenne radar (KCYS), 148 km from the middle of the area, began a volume at 00:58 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, 0.9 hours before the alert went out and 239 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: 173 J/kg
Mixed-layer CIN: -45 J/kg
Mixed-layer LCL: 3270 m above ground
0-6 km bulk shear: 6 kt
0-1 km storm-relative helicity: -18 m²/s²
0-3 km storm-relative helicity: 17 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

759 
WGUS55 KBOU 060056
FFWBOU
COC049-060215-
/O.NEW.KBOU.FF.W.0025.210706T0056Z-210706T0215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
656 PM MDT Mon Jul 5 2021

The National Weather Service in Denver has issued a

* Flash Flood Warning for...
  North Central Grand County in north central Colorado...

* Until 815 PM MDT.

* At 656 PM MDT, local law enforcement reported flash flooding 
  across the warned area. Between 1.5 and 2 inches of rain have 
  fallen. Flash flooding is already occurring.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Law enforcement reported.

  IMPACT...Flash flooding of small creeks and streams, gulches,
           roads, and poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  mainly rural areas of North Central Grand County

This includes the following streams and drainages...
  Buffalo Creek, Cabin Creek, East Fork Troublesome Creek, Middle 
  Fork Creek, Ethel Creek, Trout Creek, North Fork Cabin Creek, 
  Trail Creek, East Branch Willow Creek, Willow Creek, Wheatley 
  Creek and Corral Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

Continued Flash flooding of small creeks, streams, and ditches in 
the northwest portions of the East Troublesome burn area including 
areas along Highway 125. Rock slides or debris flows can also be 
expected across rural roads.

&&

LAT...LON 4033 10618 4033 10615 4033 10614 4034 10601
      4020 10602 4020 10624 4031 10622 4033 10620
      4033 10619

FLASH FLOOD...OBSERVED

$$

RPK

1 follow-up statement

449 
WGUS75 KBOU 060211
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
811 PM MDT Mon Jul 5 2021

COC049-060221-
/O.EXP.KBOU.FF.W.0025.000000T0000Z-210706T0215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Grand CO-
811 PM MDT Mon Jul 5 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 815 PM MDT THIS EVENING FOR 
NORTH CENTRAL GRAND COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

A Flash Flood Watch remains in effect until 1200 AM MDT for Portions 
of central and north central Colorado.

LAT...LON 4033 10618 4033 10615 4033 10614 4034 10601
      4020 10602 4020 10624 4031 10622 4033 10620
      4033 10619

$$

RPK

The office that day

Everything else NWS Denver/Boulder, CO issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 5, 6:58 PM MDT	Areal Flood Advisory	BOU	Arapahoe	92 min
Jul 5, 7:09 PM MDT	Special Weather Statement	BOU	Arapahoe	36 min
Jul 5, 7:36 PM MDT	Areal Flood Advisory	BOU	Adams, Arapahoe	84 min
Jul 5, 8:08 PM MDT	Special Weather Statement	BOU	Washington	37 min

Nearby

Flash Flood Warnings in Colorado, 2021 Every flash flood warning 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.