Alert archive / Colorado / Flash Flood Warnings in 2021
Flash Flood Warning 26, NWS Denver/Boulder, CO
NWS Denver/Boulder, CO issued this flash flood warning at Jul 20, 2021, 4:53 PM MDT for Larimer County, Colorado. It was in force for 82 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, 4:53 PM MDT (22:53 UTC)
- Expired
- Jul 20, 2021, 6:15 PM MDT
- In force
- 82 min
- Issued by
- NWS Denver/Boulder, CO
- Area
- Storm-based polygon
- Flood severity
- None
County Larimer County, CO
The radar
The Cheyenne radar (KCYS), 104 km from the middle of the area, began a volume at 22:56 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, 10.9 hours before the alert went out and 227 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
- 2720 m above ground
- 0-6 km bulk shear
- 17 kt
- 0-1 km storm-relative helicity
- -20 m²/s²
- 0-3 km storm-relative helicity
- 70 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
228
WGUS55 KBOU 202253
FFWBOU
COC069-210015-
/O.NEW.KBOU.FF.W.0026.210720T2253Z-210721T0015Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
453 PM MDT Tue Jul 20 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 453 PM MDT, Doppler radar indicated thunderstorms producing
heavy rain across the Cameron Peak burn area. Between 0.5 and 1
inch of rain has fallen. The expected rainfall rate is 1 to 2
inches in 1 hour. 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.
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...
Chambers Lake Campground.
This includes the following additional locations...
the Upper Poudre Canyon, Long Draw Road, Remote areas in the Cameron
Peak Wilderness and Hague Creek.
This includes the following streams and drainages...
May Creek, Joe Wright Creek, Sheep Creek, North Fork Joe Wright
Creek, Cache La Poudre River, Laramie River, La Poudre Pass Creek,
Mummy Pass Creek, South Fork Cache La Poudre River and Fall Creek.
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.
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 4047 10573 4050 10581 4054 10589 4066 10583
4068 10580 4064 10569 4052 10565 4048 10566
FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...1-2 INCHES IN 1 HOUR
$$
Direnzo1 follow-up statement
296
WGUS75 KBOU 202350
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
550 PM MDT Tue Jul 20 2021
COC069-210015-
/O.CON.KBOU.FF.W.0026.000000T0000Z-210721T0015Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
550 PM MDT Tue Jul 20 2021
...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 615 PM MDT THIS
EVENING FOR CENTRAL LARIMER COUNTY...
At 550 PM MDT, Doppler radar indicated thunderstorms producing heavy
rain across the Cameron Peak burn area. Between 1 and 1.5 inches of
rain have fallen. The expected rainfall rate is 0.5 to 1 inch in 1
hour. Additional rainfall amounts up to 0.5 inches are possible in
the warned area. Flash flooding is ongoing or expected to begin
shortly.
HAZARD...Flash flooding caused by thunderstorms.
SOURCE...Radar.
IMPACT...Flash flooding of small creeks and streams, gulches,
roads, and poor drainage and low-lying areas.
Some locations that will experience flash flooding include...
Chambers Lake Campground.
This includes the following additional locations...
The Upper Poudre Canyon, Long Draw Road, Remote areas in the Cameron
Peak Wilderness and Hague Creek.
This includes the following streams and drainages...
Joe Wright Creek, Sheep Creek, North Fork Joe Wright Creek, Cache
La Poudre River, Laramie River, La Poudre Pass Creek, Mummy Pass
Creek, South Fork Cache La Poudre River and Fall Creek.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
Move to higher ground now. Act quickly to protect your life.
Heavy Rainfall will cause flash flooding of small creeks, streams,
and ditches in the affected part of the Cameron Peak burn area. Rock
slides or debris flows can also be expected across rural roads.
&&
LAT...LON 4047 10573 4050 10581 4054 10589 4066 10583
4068 10580 4064 10569 4052 10565 4048 10566
FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...0.5-1 INCH IN 1 HOUR
$$
DirenzoThe office that day
Everything else NWS Denver/Boulder, CO issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 20, 3:27 PM MDT | Areal Flood Advisory | BOU | Grand | 78 min |
| Jul 20, 4:29 PM MDT | Areal Flood Advisory | BOU | Larimer | 91 min |
| Jul 20, 5:24 PM MDT | Flash Flood Warning | BOU | Larimer | 51 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.