Alert archive / Colorado / Flash Flood Warnings in 2021
Flash Flood Warning 51, NWS Denver/Boulder, CO
NWS Denver/Boulder, CO issued this flash flood warning at Jul 30, 2021, 4:30 PM MDT for Larimer County, Colorado. It was in force for 4 hr. 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 30, 2021, 4:30 PM MDT (22:30 UTC)
- Expired
- Jul 30, 2021, 8:32 PM MDT
- In force
- 4 hr
- Issued by
- NWS Denver/Boulder, CO
- Area
- Storm-based polygon
- Flood severity
- None
County Larimer County, CO
The radar
The Cheyenne radar (KCYS), 79 km from the middle of the area, began a volume at 22:31 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 30, 6:45 PM MDT | FLASH FLOOD | 4 Sse Buckhorn Mountain, CO | WASHOUTS OF ROADS AND DRIVEWAYS CROSSING BUCKHORN CREEK NORTH OF STRINGTOWN GULCH ROAD. |
| Jul 30, 7:15 PM MDT | FLOOD | 4 W Horsetooth Mountain, CO | BUCKHORN CREEK OUT OF ITS BANKS ALONG BUCKHORN RD. |
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, 10.5 hours before the alert went out and 195 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
- 2523 m above ground
- 0-6 km bulk shear
- 18 kt
- 0-1 km storm-relative helicity
- -18 m²/s²
- 0-3 km storm-relative helicity
- 2 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
038
WGUS55 KBOU 302230
FFWBOU
COC069-310130-
/O.NEW.KBOU.FF.W.0051.210730T2230Z-210731T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
430 PM MDT Fri Jul 30 2021
The National Weather Service in Denver has issued a
* Flash Flood Warning for...
East Central Larimer County in north central Colorado...
* Until 730 PM MDT.
* At 430 PM MDT, Doppler radar indicated thunderstorms producing
heavy rain across the warned area. Between 0.5 and 1 inch of rain
has fallen. Additional rainfall amounts of 1 to 2 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...
Stove Prairie, Glen Haven, Pennock Pass, Masonville and Horsetooth
Mountain.
This includes the following additional locations...
Box Prairie, Upper Buckhorn along County Road 44H, Moondance Way,
Stringtown Gulch, Big Bear, Lower Buckhorn on County Road 27 above
Masonville, Crystal Mountain, Monument Gulch, Lower Pingree Park
Road, The Retreat and Storm Mountain.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Move to higher ground now. Act quickly to protect your life.
&&
LAT...LON 4066 10543 4061 10533 4059 10525 4057 10522
4058 10517 4056 10517 4055 10516 4045 10520
4045 10531 4045 10546 4057 10553 4061 10553
4068 10553
FLASH FLOOD...RADAR INDICATED
$$
Bowen3 follow-up statements
556
WGUS75 KBOU 302326
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
526 PM MDT Fri Jul 30 2021
COC069-310130-
/O.CON.KBOU.FF.W.0051.000000T0000Z-210731T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
526 PM MDT Fri Jul 30 2021
...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 730 PM MDT THIS
EVENING FOR EAST CENTRAL LARIMER COUNTY...
At 526 PM MDT, Doppler radar indicated thunderstorms producing heavy
rain across the warned area. Between 1 and 1.5 inches of rain have
fallen. Additional rainfall amounts of 1 to 2 inches are possible in
the warned area. Flash flooding is already occurring.
HAZARD...Life threatening flash flooding. Thunderstorms producing
flash flooding.
SOURCE...Radar.
IMPACT...Life threatening flash flooding of creeks and streams,
roads, and low lying areas.
Some locations that will experience flash flooding include...
Stove Prairie, Glen Haven, Pennock Pass, Masonville and Horsetooth
Mountain.
This includes the following additional locations...
Box Prairie, Upper Buckhorn along County Road 44H, Moondance Way,
Stringtown Gulch, Big Bear, Lower Buckhorn on County Road 27 above
Masonville, Crystal Mountain, Monument Gulch, Lower Pingree Park
Road, The Retreat and Storm Mountain.
Millers Fork Road has been closed with debris flow and damage.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Move to higher ground now. Act quickly to protect your life.
THIS IS A LIFE THREATENING SITUATION! Heavy Rainfall will cause
extensive and severe flooding of creeks, streams, roads and culverts
in the affected part of the Cameron Peak burn area. Rock slides or
debris flows can also be expected across roads in the warning area.
&&
LAT...LON 4066 10543 4061 10533 4059 10525 4057 10522
4058 10517 4056 10517 4055 10516 4045 10520
4045 10531 4045 10546 4057 10553 4061 10553
4068 10553
FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
$$
Bowen348
WGUS55 KBOU 310117
FFWBOU
COC069-310300-
/O.EXT.KBOU.FF.W.0051.000000T0000Z-210731T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
717 PM MDT Fri Jul 30 2021
The National Weather Service in Denver has extended the
* Flash Flood Warning for...
East Central Larimer County in north central Colorado...
* Until 900 PM MDT.
* At 717 PM MDT, Doppler radar indicated thunderstorms producing
heavy rain across the warned area. Between 2 and 3 inches of rain
have fallen. Additional rainfall amounts of 0.5 to 1 inch are
possible in 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...
Stove Prairie, Glen Haven, Pennock Pass, Masonville and Horsetooth
Mountain.
This includes the following additional locations...
Box Prairie, Upper Buckhorn along County Road 44H, Moondance Way,
Stringtown Gulch, Big Bear, Lower Buckhorn on County Road 27 above
Masonville, Crystal Mountain, Monument Gulch, Lower Pingree Park
Road, The Retreat and Storm Mountain.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Move to higher ground now. Act quickly to protect your life.
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 4066 10543 4061 10533 4059 10525 4057 10522
4058 10517 4056 10517 4055 10516 4045 10520
4045 10531 4045 10546 4057 10553 4061 10553
4068 10553
FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
$$
Bowen917
WGUS75 KBOU 310232
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
832 PM MDT Fri Jul 30 2021
COC069-310242-
/O.CAN.KBOU.FF.W.0051.000000T0000Z-210731T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Larimer CO-
832 PM MDT Fri Jul 30 2021
...FLASH FLOOD WARNING IS CANCELLED FOR EAST CENTRAL LARIMER
COUNTY...
The heavy rain has ended. Flooded roads could still pose a threat.
Please continue to heed remaining road closures and never drive over
a flooded road.
A Flash Flood Watch remains in effect until 900 PM MDT Saturday for
Portions of central and north central Colorado.
A Flash Flood Watch remains in effect until 900 PM MDT Saturday for
Portions of central, north central, and northeast Colorado.
LAT...LON 4066 10543 4061 10533 4059 10525 4057 10522
4058 10517 4056 10517 4055 10516 4045 10520
4045 10531 4045 10546 4057 10553 4061 10553
4068 10553
$$
BowenThe office that day
Everything else NWS Denver/Boulder, CO issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 29, 6:37 PM MDT | Areal Flood Advisory | BOU | Grand | 83 min |
| Jul 29, 7:27 PM MDT | Areal Flood Advisory | BOU | Grand | 93 min |
| Jul 29, 7:50 PM MDT | Flash Flood Warning | BOU | Jackson, Larimer | 3 hr |
| Jul 29, 8:14 PM MDT | Flash Flood Warning | BOU | Grand | 112 min |
| Jul 29, 9:32 PM MDT | Special Weather Statement | BOU | Jackson | 28 min |
| Jul 29, 10:19 PM MDT | Areal Flood Advisory | BOU | Larimer | 86 min |
| Jul 30, 1:01 PM MDT | Flash Flood Warning | BOU | Larimer | 7 hr |
| Jul 30, 1:08 PM MDT | Areal Flood Advisory | BOU | Larimer | 6 min |
| Jul 30, 1:14 PM MDT | Flash Flood Warning | BOU | Larimer | 3 hr |
| Jul 30, 1:34 PM MDT | Flash Flood Warning | BOU | Larimer | 6 hr |
| Jul 30, 2:07 PM MDT | Flash Flood Warning | BOU | Larimer | 5 hr |
| Jul 30, 2:30 PM MDT | Flash Flood Warning | BOU | Clear Creek, Grand | 3 hr |
| Jul 30, 2:48 PM MDT | Areal Flood Advisory | BOU | Larimer | 87 min |
| Jul 30, 2:51 PM MDT | Flash Flood Warning | BOU | Grand | 4 hr |
| Jul 30, 3:02 PM MDT | Flash Flood Warning | BOU | Grand | 3 hr |
| Jul 30, 3:02 PM MDT | Special Weather Statement | BOU | Larimer | 43 min |
| Jul 30, 3:26 PM MDT | Severe Thunderstorm Warning | BOU | Larimer, Weld | 49 min |
| Jul 30, 3:45 PM MDT | Areal Flood Advisory | BOU | Grand | 2 hr |
| Jul 30, 3:59 PM MDT | Areal Flood Advisory | BOU | Larimer, Weld | 61 min |
| Jul 30, 4:11 PM MDT | Severe Thunderstorm Warning | BOU | Larimer, Weld | 49 min |
| Jul 30, 4:16 PM MDT | Flash Flood Warning | BOU | Grand | 3 hr |
| Jul 30, 4:28 PM MDT | Flash Flood Warning | BOU | Park | 3 hr |
| Jul 30, 5:36 PM MDT | Flash Flood Warning | BOU | Larimer | 3 hr |
| Jul 30, 5:37 PM MDT | Flash Flood Warning | BOU | Grand | 99 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.