Alert archive / Colorado / Flash Flood Warnings in 2021
Flash Flood Warning 76, NWS Denver/Boulder, CO
NWS Denver/Boulder, CO issued this flash flood warning at Aug 18, 2021, 3:14 PM MDT for Larimer County, Colorado. It was in force for 3 hr. No storm report in the archive falls inside the area while it was in force.
The area
The outline as issued.
The facts
- Issued
- Aug 18, 2021, 3:14 PM MDT (21:14 UTC)
- Expired
- Aug 18, 2021, 6:15 PM MDT
- In force
- 3 hr
- Issued by
- NWS Denver/Boulder, CO
- Area
- Storm-based polygon
- Flood severity
- None
County Larimer County, CO
The radar
The Cheyenne radar (KCYS), 87 km from the middle of the area, began a volume at 21:14 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 12:00Z, 9.2 hours before the alert went out and 215 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.
- Mixed-layer CAPE
- 1 J/kg
- Mixed-layer CIN
- -445 J/kg
- Mixed-layer LCL
- 2839 m above ground
- 0-6 km bulk shear
- 15 kt
- 0-1 km storm-relative helicity
- -49 m²/s²
- 0-3 km storm-relative helicity
- 63 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
781
WGUS55 KBOU 182114
FFWBOU
COC069-190015-
/O.NEW.KBOU.FF.W.0076.210818T2114Z-210819T0015Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
314 PM MDT Wed Aug 18 2021
The National Weather Service in Denver has issued a
* Flash Flood Warning for...
Central Larimer County in north central Colorado...
* Until 615 PM MDT.
* At 314 PM MDT, Doppler radar indicated thunderstorms producing
heavy rain across the warned area. Up to 0.5 inches of rain have
fallen. Additional rainfall amounts up to 0.5 inches 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...
Pennock Pass and Pingree Park.
This includes the following additional locations...
Box Prairie, Poudre Springs, Monument Gulch, Jacks Gulch, Upper
Pingree Park Road, Lower Pingree Park Road and Sky Ranch.
This includes the following streams and drainages...
Bennett Creek, Miller Fork, Little Beaver Creek, Cache La Poudre
River, Pennock Creek, Eld Creek, Pendergrass Creek, Buckhorn
Creek, South Fork Cache La Poudre River and Fall Creek.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Move to higher ground now. Act quickly to protect your life.
Heavy Rainfall will cause flash flooding of small creeks, streams,
and ditches in the affected part of the Cameron Peak burn area. Rock
slides or debris flows can also be expected across rural roads.
&&
LAT...LON 4066 10561 4068 10546 4052 10547 4052 10563
4067 10561
FLASH FLOOD...RADAR INDICATED
$$
RPK1 follow-up statement
339
WGUS75 KBOU 190010
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
610 PM MDT Wed Aug 18 2021
COC069-190020-
/O.EXP.KBOU.FF.W.0076.000000T0000Z-210819T0015Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
610 PM MDT Wed Aug 18 2021
...FLASH FLOOD WARNING WILL EXPIRE AT 615 PM MDT THIS EVENING FOR
CENTRAL LARIMER COUNTY...
The heavy rain has ended. Flooding is no longer expected to pose a
threat. Please continue to heed remaining road closures.
LAT...LON 4066 10561 4068 10546 4052 10547 4052 10563
4067 10561
$$
RPKThe office that day
Everything else NWS Denver/Boulder, CO issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 17, 6:31 PM MDT | Special Weather Statement | BOU | Arapahoe | 44 min |
| Aug 17, 6:35 PM MDT | Areal Flood Advisory | BOU | Jackson | 85 min |
| Aug 18, 3:01 PM MDT | Areal Flood Advisory | BOU | Larimer | 13 min |
| Aug 18, 4:54 PM MDT | Areal Flood Advisory | BOU | Larimer | 81 min |
Nearby
Flash Flood Warnings in Colorado, 2021Every 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.