Alert archive / Colorado / Flash Flood Warnings in 2021
Flash Flood Warning 75, NWS Denver/Boulder, CO
NWS Denver/Boulder, CO issued this flash flood warning at Aug 17, 2021, 4:41 PM MDT for Larimer County, Colorado. It was in force for 2 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 17, 2021, 4:41 PM MDT (22:41 UTC)
- Expired
- Aug 17, 2021, 6:55 PM MDT
- In force
- 2 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 22:41 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, 10.7 hours before the alert went out and 199 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 3046 m above ground
- 0-6 km bulk shear
- 6 kt
- 0-1 km storm-relative helicity
- -6 m²/s²
- 0-3 km storm-relative helicity
- 15 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
672
WGUS55 KBOU 172241
FFWBOU
COC069-180145-
/O.NEW.KBOU.FF.W.0075.210817T2241Z-210818T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
441 PM MDT Tue Aug 17 2021
The National Weather Service in Denver has issued a
* Flash Flood Warning for...
Central Larimer County in north central Colorado...
* Until 745 PM MDT.
* At 441 PM MDT, Doppler radar indicated thunderstorms producing
heavy rain across the warned area. Between 0.4 and 0.6 inches of
rain have fallen. Additional rainfall amounts of 0.5 to 1 inch are
possible in the warned area. Flash flooding is ongoing or expected
to begin shortly.
HAZARD...Flash flooding caused by thunderstorms in eastern
sections of the Cameron Peak burn area.
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...
mainly rural areas of Central Larimer County
This includes the following additional locations...
Upper Buckhorn along County Road 44H, Moondance Way, Stringtown
Gulch, Crystal Mountain, The Retreat and Storm Mountain.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Move to higher ground now. Act quickly to protect your life.
&&
LAT...LON 4051 10551 4059 10543 4056 10531 4054 10528
4045 10536 4047 10552
FLASH FLOOD...RADAR INDICATED
$$
TH2 follow-up statements
140
WGUS75 KBOU 180007
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
607 PM MDT Tue Aug 17 2021
COC069-180145-
/O.CON.KBOU.FF.W.0075.000000T0000Z-210818T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
607 PM MDT Tue Aug 17 2021
...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 745 PM MDT THIS
EVENING FOR CENTRAL LARIMER COUNTY...
At 607 PM MDT, Doppler radar indicated thunderstorms producing heavy
rain across the warned area. Between 0.5 and 1 inch of rain has
fallen in localized areas.
HAZARD...Flash flooding caused by thunderstorms.
SOURCE...Radar.
IMPACT...Flash flooding of small creeks and streams, gulches,
roads, and poor drainage and low-lying areas in eastern
sections of the Cameron Peak burn area.
Some locations that will experience flash flooding include...
mainly rural areas of Central Larimer County
This includes the following additional locations...
Upper Buckhorn along County Road 44H, Moondance Way, Stringtown
Gulch, Crystal Mountain, The Retreat and Storm Mountain.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
Heavy Rainfall could cause flooding of creeks, streams, roads and
culverts in eastern sections of the Cameron Peak burn area. Rock
slides or debris flows are also possible in the warning area.
&&
LAT...LON 4051 10551 4059 10543 4056 10531 4054 10528
4045 10536 4047 10552
FLASH FLOOD...RADAR INDICATED
$$
TH784
WGUS75 KBOU 180055
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
655 PM MDT Tue Aug 17 2021
COC069-180105-
/O.CAN.KBOU.FF.W.0075.000000T0000Z-210818T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
655 PM MDT Tue Aug 17 2021
...FLASH FLOOD WARNING IS CANCELLED FOR CENTRAL LARIMER COUNTY...
The heavy rain has ended. Flooding is no longer expected to pose a
threat.
LAT...LON 4051 10551 4059 10543 4056 10531 4054 10528
4045 10536 4047 10552
$$
THThe office that day
Everything else NWS Denver/Boulder, CO issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 17, 2:07 PM MDT | Areal Flood Advisory | BOU | Larimer | 53 min |
| Aug 17, 4:04 PM MDT | Areal Flood Advisory | BOU | Larimer | 86 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.