Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 29, NWS Denver/Boulder, CO

July 20, 2021Larimer County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Jul 20, 2021, 7:09 PM MDT for Larimer County, Colorado. It was in force for 81 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 20, 2021, 7:09 PM MDT (01:09 UTC)
Expired: Jul 20, 2021, 8:30 PM MDT
In force: 81 min
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Larimer County, CO

The radar

The Cheyenne radar (KCYS), 69 km from the middle of the area, began a volume at 01:11 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

Denver, CO (KDNR), launched 00:00Z, 1.2 hours before the alert went out and 200 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: 99 J/kg
Mixed-layer CIN: -49 J/kg
Mixed-layer LCL: 3076 m above ground
0-6 km bulk shear: 6 kt
0-1 km storm-relative helicity: -2 m²/s²
0-3 km storm-relative helicity: 36 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

892 
WGUS55 KBOU 210109
FFWBOU
COC069-210230-
/O.NEW.KBOU.FF.W.0029.210721T0109Z-210721T0230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
709 PM MDT Tue Jul 20 2021

The National Weather Service in Denver has issued a

* Flash Flood Warning for...
  Eastern Larimer County in north central Colorado...

* Until 830 PM MDT.

* At 709 PM MDT, local law enforcement reported flash flooding along 
  Highway 14 on the Poudre River.

  HAZARD...Life threatening flash flooding. Heavy rain produced
           flash flooding.

  SOURCE...Law enforcement reported.

  IMPACT...Life threatening flash flooding of creeks and streams,
           roads, and low lying areas.

* Some locations that will experience flash flooding include...
  Highway 14, Mishawaka and Poudre Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Move to higher ground now. Act quickly to protect your life.

&&

LAT...LON 4065 10519 4066 10524 4068 10525 4067 10543
      4067 10548 4069 10558 4071 10557 4070 10544
      4070 10523 4067 10522 4067 10520

FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Direnzo

1 follow-up statement

155 
WGUS75 KBOU 210226
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
826 PM MDT Tue Jul 20 2021

COC069-210236-
/O.EXP.KBOU.FF.W.0029.000000T0000Z-210721T0230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
826 PM MDT Tue Jul 20 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 830 PM MDT THIS EVENING FOR 
EASTERN LARIMER COUNTY...

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

LAT...LON 4065 10519 4066 10524 4068 10525 4067 10543
      4067 10548 4069 10558 4071 10557 4070 10544
      4070 10523 4067 10522 4067 10520

$$

Direnzo

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 20, 6:58 PM MDT	Flash Flood Warning Considerable damage threat	BOU	Larimer	92 min
Jul 21, 3:18 AM MDT	Flash Flood Watch	BOU	Boulder, Grand, Jackson, Larimer	17 hr
Jul 21, 1:30 PM MDT	Flash Flood Warning	BOU	Larimer	3 hr
Jul 21, 1:56 PM MDT	Areal Flood Advisory	BOU	Grand	3 hr
Jul 21, 2:31 PM MDT	Areal Flood Advisory	BOU	Park	119 min
Jul 21, 2:44 PM MDT	Special Weather Statement	BOU	Teller	46 min
Jul 21, 2:47 PM MDT	Flash Flood Warning	BOU	Larimer	103 min
Jul 21, 3:16 PM MDT	Flash Flood Warning	BOU	Grand, Larimer	3 hr
Jul 21, 3:22 PM MDT	Areal Flood Advisory	BOU	Park	69 min
Jul 21, 4:40 PM MDT	Areal Flood Advisory	BOU	Douglas	65 min
Jul 21, 5:06 PM MDT	Flash Flood Warning	BOU	Clear Creek	3 hr

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.