Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 19, NWS Denver/Boulder, CO

July 4, 2021Larimer County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Jul 4, 2021, 3:20 PM MDT for Larimer County, Colorado. It was in force for 85 min. 2 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Jul 4, 2021, 3:20 PM MDT (21:20 UTC)
Expired: Jul 4, 2021, 4:45 PM MDT
In force: 85 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), 92 km from the middle of the area, began a volume at 21:19 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.

What was reported inside it

Time	Report	Where	Remark
Jul 4, 3:29 PM MDT	FLASH FLOOD	1 Ene Glen Haven, CO	LARIMER COUNTY SHERIFFS OFFICE REPORTS FLASH FLOODING OCCURRING IN THE AREA.
Jul 4, 3:51 PM MDT	FLOOD	1 Sse Estes Park, CO	REPORT FROM MPING: RIVER/CREEK OVERFLOWING; CROPLAND/YARD/BASEMENT FLOODING.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Denver, CO (KDNR), launched 12:00Z, 9.3 hours before the alert went out and 197 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: 204 J/kg
Mixed-layer CIN: -314 J/kg
Mixed-layer LCL: 2162 m above ground
0-6 km bulk shear: 17 kt
0-1 km storm-relative helicity: 35 m²/s²
0-3 km storm-relative helicity: 80 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

916 
WGUS55 KBOU 042120
FFWBOU
COC069-042245-
/O.NEW.KBOU.FF.W.0019.210704T2120Z-210704T2245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
320 PM MDT Sun Jul 4 2021

The National Weather Service in Denver has issued a

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

* Until 445 PM MDT.

* At 320 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Flash flooding is already 
  occurring.

  HAZARD...Life threatening flash flooding. Thunderstorms
           producing flash flooding.

  SOURCE...Radar.

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

* Some locations that will experience flash flooding include...
  Estes Park, Glen Haven and Drake.

This includes the following additional locations...
	Crystal Mountain, The Retreat and Storm Mountain.

This includes the following streams and drainages...
  West Fork Little Thompson River, Big Thompson River, Pennock 
  Creek, Cow Creek, Sheep Creek, Miller Fork, Fall River, Solitude 
  Creek, Grouse Creek, Eld Creek, Black Creek, Glacier Creek, Fish 
  Creek, North Fork Big Thompson River, North Fork Little Thompson 
  River, Cedar Creek, Buckhorn Creek, Little Thompson River, 
  Cottonwood Creek and North Fork Fish Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

THIS IS A LIFE THREATENING SITUATION! Heavy Rainfall will cause 
extensive and severe flooding of creeks, streams, roads and culverts 
in the affected part of the Cameron Peak burn area. Rock slides or 
debris flows can also be expected across roads in the warning area.

&&

LAT...LON 4055 10534 4035 10530 4034 10552 4054 10555

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

RPK

2 follow-up statements

253 
WGUS75 KBOU 042155
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
355 PM MDT Sun Jul 4 2021

COC069-042245-
/O.CON.KBOU.FF.W.0019.000000T0000Z-210704T2245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
355 PM MDT Sun Jul 4 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 445 PM MDT THIS 
AFTERNOON FOR SOUTH CENTRAL LARIMER COUNTY...

At 355 PM MDT, Local law enforcement reports Flash flooding is 
occurring in and around the Glen Haven area.

HAZARD...Life threatening flash flooding. Thunderstorms producing
         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...
  Estes Park, Glen Haven and Drake.

This includes the following additional locations...
	Crystal Mountain, The Retreat and Storm Mountain.

This includes the following streams and drainages...
  West Fork Little Thompson River, Big Thompson River, Pennock 
  Creek, Cow Creek, Sheep Creek, Miller Fork, Fall River, Solitude 
  Creek, Grouse Creek, Eld Creek, Black Creek, Glacier Creek, Fish 
  Creek, North Fork Big Thompson River, North Fork Little Thompson 
  River, Cedar Creek, Buckhorn Creek, Little Thompson River, 
  Cottonwood Creek and North Fork Fish Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS IS A LIFE THREATENING SITUATION! Heavy Rainfall will cause 
extensive and severe flooding of creeks, streams, roads and culverts 
in the affected part of the Cameron Peak burn area. Rock slides or 
debris flows can also be expected across roads in the warning area.

&&

LAT...LON 4055 10534 4035 10530 4034 10552 4054 10555

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

$$

RPK

416 
WGUS75 KBOU 042237
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
437 PM MDT Sun Jul 4 2021

COC069-042247-
/O.EXP.KBOU.FF.W.0019.000000T0000Z-210704T2245Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
437 PM MDT Sun Jul 4 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 445 PM MDT THIS AFTERNOON FOR 
SOUTH CENTRAL 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 4055 10534 4035 10530 4034 10552 4054 10555

$$

RPK

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 3, 6:00 PM MDT	Flash Flood Warning	BOU	Logan	2 hr
Jul 3, 6:01 PM MDT	Areal Flood Advisory	BOU	Washington	89 min
Jul 3, 6:14 PM MDT	Special Weather Statement	BOU	Sedgwick	31 min
Jul 3, 7:26 PM MDT	Special Weather Statement	BOU	Lincoln	34 min
Jul 4, 10:34 AM MDT	Areal Flood Advisory	BOU	Larimer	86 min
Jul 4, 11:54 AM MDT	Areal Flood Advisory	BOU	Larimer	81 min
Jul 4, 12:10 PM MDT	Special Weather Statement	BOU	Larimer	50 min
Jul 4, 12:28 PM MDT	Areal Flood Advisory	BOU	Larimer	77 min
Jul 4, 12:37 PM MDT	Severe Thunderstorm Warning	BOU	Larimer	38 min
Jul 4, 1:51 PM MDT	Areal Flood Advisory	BOU	Larimer	75 min
Jul 4, 2:49 PM MDT	Special Weather Statement	BOU	Denver	26 min
Jul 4, 3:31 PM MDT	Areal Flood Advisory	BOU	Douglas	119 min
Jul 4, 3:56 PM MDT	Areal Flood Advisory	BOU	Elbert	53 min
Jul 4, 4:28 PM MDT	Special Weather Statement	BOU	Adams, Arapahoe	62 min
Jul 4, 4:43 PM MDT	Special Weather Statement	BOU	Elbert	62 min
Jul 4, 5:42 PM MDT	Special Weather Statement	BOU	Douglas	48 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.