Alert archive / Colorado / Flash Flood Warnings in 2021

Flash Flood Warning 5, NWS Denver/Boulder, CO

June 25, 2021Larimer County, Colorado

NWS Denver/Boulder, CO issued this flash flood warning at Jun 25, 2021, 2:04 PM MDT for Larimer County, Colorado. It was in force for 116 min. 1 report 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: Jun 25, 2021, 2:04 PM MDT (20:04 UTC)
Expired: Jun 25, 2021, 4:00 PM MDT
In force: 116 min
Issued by: NWS Denver/Boulder, CO
Area: Storm-based polygon
Flood severity: None

County Larimer County, CO

The radar

The Cheyenne radar (KCYS), 83 km from the middle of the area, began a volume at 20:06 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
Jun 25, 2:39 PM MDT	FLASH FLOOD	5 Wnw Masonville, CO	BUCKHORN ROAD SOUTH OF BIG BEAR ROAD CITIZEN REPORTED WATER RUNNING 5 TO 6 INCHES DEEP AND GROWING RAPIDLY.

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, 8.1 hours before the alert went out and 192 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: 50 J/kg
Mixed-layer CIN: -128 J/kg
Mixed-layer LCL: 1292 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: -9 m²/s²
0-3 km storm-relative helicity: 34 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

803 
WGUS55 KBOU 252004
FFWBOU
COC069-252200-
/O.NEW.KBOU.FF.W.0005.210625T2004Z-210625T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
204 PM MDT Fri Jun 25 2021

The National Weather Service in Denver has issued a

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

* Until 400 PM MDT.

* At 204 PM MDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the eastern portion of the Cameron Peak Burn 
  Area. Between 0.5 and 1 inch of rain has fallen. Additional 
  rainfall amounts up to 1 inch are possible in the warned area. 
  Flash flooding is ongoing or expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  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...
  Masonville and Horsetooth Mountain.

This includes the following additional locations...
Moondance Way, Stringtown Gulch, Big Bear, Lower Buckhorn on County 
Road 27 above Masonville and Storm Mountain.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Heavy Rainfall will cause minor flooding of creeks and streams, 
roads and roadside culverts in the affected part of the Cameron Peak 
burn area. The heavy rains could also trigger rock slides or debris 
flows.

&&

LAT...LON 4056 10538 4056 10519 4046 10518 4047 10540
      4050 10540

FLASH FLOOD...RADAR INDICATED

$$

Hanson

1 follow-up statement

361 
WGUS75 KBOU 252155
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
355 PM MDT Fri Jun 25 2021

COC069-252205-
/O.EXP.KBOU.FF.W.0005.000000T0000Z-210625T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
355 PM MDT Fri Jun 25 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 4 PM MDT THIS AFTERNOON FOR 
EAST CENTRAL LARIMER COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat, although hazards may remain from earlier flash flooding. 
Please heed  road closures.

LAT...LON 4056 10538 4056 10519 4046 10518 4047 10540
      4050 10540

$$

Hanson

The office that day

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

Issued	Product	Office	Counties	Lasted
Jun 24, 6:08 PM MDT	Severe Thunderstorm Warning	BOU	Lincoln	19 min
Jun 24, 6:19 PM MDT	Areal Flood Advisory	BOU	Larimer	86 min
Jun 24, 6:33 PM MDT	Special Weather Statement	BOU	Lincoln	42 min
Jun 24, 7:56 PM MDT	Special Weather Statement	BOU	Lincoln	49 min
Jun 25, 12:30 PM MDT	Special Weather Statement	BOU	Weld	45 min
Jun 25, 1:10 PM MDT	Special Weather Statement	BOU	Morgan	35 min
Jun 25, 1:25 PM MDT	Areal Flood Advisory	BOU	Larimer	70 min
Jun 25, 1:32 PM MDT	Areal Flood Advisory	BOU	Boulder	88 min
Jun 25, 1:52 PM MDT	Special Weather Statement	BOU	Logan	23 min
Jun 25, 1:59 PM MDT	Severe Thunderstorm Warning	BOU	Boulder, Jefferson	46 min
Jun 25, 2:16 PM MDT	Special Weather Statement	BOU	Douglas	44 min
Jun 25, 2:26 PM MDT	Special Weather Statement	BOU	Logan	49 min
Jun 25, 2:35 PM MDT	Special Weather Statement	BOU	Elbert	40 min
Jun 25, 2:50 PM MDT	Special Weather Statement	BOU	Broomfield	40 min
Jun 25, 2:57 PM MDT	Special Weather Statement	BOU	Weld	48 min
Jun 25, 3:10 PM MDT	Special Weather Statement	BOU	Phillips	50 min
Jun 25, 3:24 PM MDT	Special Weather Statement	BOU	Lincoln	51 min
Jun 25, 4:12 PM MDT	Areal Flood Advisory	BOU	Arapahoe	93 min
Jun 25, 4:42 PM MDT	Areal Flood Advisory	BOU	Arapahoe, Douglas	93 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.