Alert archive / Colorado / Flash Flood Warnings in 2021
Flash Flood Warning 61, NWS Denver/Boulder, CO
NWS Denver/Boulder, CO issued this flash flood warning at Jul 31, 2021, 3:37 PM MDT for Boulder 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
- Jul 31, 2021, 3:37 PM MDT (21:37 UTC)
- Expired
- Jul 31, 2021, 6:14 PM MDT
- In force
- 3 hr
- Issued by
- NWS Denver/Boulder, CO
- Area
- Storm-based polygon
- Flood severity
- None
County Boulder County, CO
The radar
The Denver radar (KFTG), 80 km from the middle of the area, began a volume at 21:40 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, 9.6 hours before the alert went out and 183 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
- 44 J/kg
- Mixed-layer CIN
- -277 J/kg
- Mixed-layer LCL
- 1127 m above ground
- 0-6 km bulk shear
- 13 kt
- 0-1 km storm-relative helicity
- -71 m²/s²
- 0-3 km storm-relative helicity
- -21 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
181
WGUS55 KBOU 312137
FFWBOU
COC013-010045-
/O.NEW.KBOU.FF.W.0061.210731T2137Z-210801T0045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
337 PM MDT Sat Jul 31 2021
The National Weather Service in Denver has issued a
* Flash Flood Warning for...
North Central Boulder County in northeastern Colorado...
* Until 645 PM MDT.
* At 337 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...
Jamestown.
This includes the following streams and drainages...
Little James Creek, South Saint Vrain Creek, North Saint Vrain
Creek, James Creek, Middle Saint Vrain Creek, Dry Creek and Left
Hand Creek.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Move to higher ground now. Act quickly to protect your life.
Heavy rainfall will cause flash flooding of creeks, streams, and
ditches in the Calwood burn area. Rock slides or debris flows can
also be expected. The main areas of concern are Heil Valley Ranch
and Lefthand Creek just above US 36.
&&
LAT...LON 4019 10539 4019 10523 4011 10527 4012 10541
4017 10540
FLASH FLOOD...RADAR INDICATED
$$
RPK3 follow-up statements
740
WGUS75 KBOU 312222
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
422 PM MDT Sat Jul 31 2021
COC013-010045-
/O.CON.KBOU.FF.W.0061.000000T0000Z-210801T0045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Boulder CO-
422 PM MDT Sat Jul 31 2021
...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 645 PM MDT THIS
EVENING FOR NORTH CENTRAL BOULDER COUNTY...
At 422 PM MDT, Emergency management reported flash flooding. People
from Geer Canyon to Left Hand Canyon Drive to Highway 36 should move
to higher ground now. Please avoid the area.
HAZARD...Life threatening flash flooding. Thunderstorms producing
flash flooding.
SOURCE...Emergency management reported.
IMPACT...Life threatening flash flooding of creeks and streams,
roads, and low lying areas.
Some locations that will experience flash flooding include...
Jamestown.
This includes the following streams and drainages...
Little James Creek, South Saint Vrain Creek, North Saint Vrain
Creek, James Creek, Middle Saint Vrain Creek, Dry Creek and Left
Hand Creek.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Move to higher ground now. Act quickly to protect your life.
Heavy rainfall will cause flash flooding of creeks, streams, and
ditches in the Calwood burn area. Rock slides or debris flows can
also be expected. The main areas of concern are Heil Valley Ranch
and Lefthand Creek just above US 36.
&&
LAT...LON 4019 10539 4019 10523 4011 10527 4012 10541
4017 10540
FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
$$
RPK421
WGUS75 KBOU 312342
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
542 PM MDT Sat Jul 31 2021
COC013-010045-
/O.CON.KBOU.FF.W.0061.000000T0000Z-210801T0045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Boulder CO-
542 PM MDT Sat Jul 31 2021
...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 645 PM MDT THIS
EVENING FOR NORTH CENTRAL BOULDER COUNTY...
At 542 PM MDT, Emergency management continued to report flash
flooding from Geer Canyon to Left Hand Canyon Drive to Highway 36.
People should move to higher ground now. Also please avoid the area.
HAZARD...Life threatening flash flooding. Heavy rain producing
flash flooding.
SOURCE...Emergency management reported.
IMPACT...Life threatening flash flooding of creeks and streams,
roads, and low lying areas.
Some locations that will experience flash flooding include...
Jamestown.
This includes the following streams and drainages...
Little James Creek, South Saint Vrain Creek, North Saint Vrain
Creek, James Creek, Middle Saint Vrain Creek, Dry Creek and Left
Hand Creek.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Move to higher ground now. Act quickly to protect your life.
Heavy rainfall will cause flash flooding of creeks, streams, and
ditches in the Calwood burn area. Rock slides or debris flows can
also be expected. The main areas of concern are Heil Valley Ranch
and Lefthand Creek just above US 36.
&&
LAT...LON 4019 10539 4019 10523 4011 10527 4012 10541
4017 10540
FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE
$$
RPK064
WGUS75 KBOU 010014
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
614 PM MDT Sat Jul 31 2021
COC013-010024-
/O.CAN.KBOU.FF.W.0061.000000T0000Z-210801T0045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Boulder CO-
614 PM MDT Sat Jul 31 2021
...FLASH FLOOD WARNING IS CANCELLED FOR NORTH CENTRAL BOULDER
COUNTY...
Flood waters have receded. The heavy rain has ended. Flooding is no
longer expected to pose a threat. Please continue to heed remaining
road closures.
A Flash Flood Watch remains in effect until 900 PM MDT for Portions
of central, north central, and northeast Colorado.
LAT...LON 4019 10539 4019 10523 4011 10527 4012 10541
4017 10540
$$
RPKThe office that day
Everything else NWS Denver/Boulder, CO issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 30, 6:01 PM MDT | Areal Flood Advisory | BOU | Boulder, Broomfield, Weld | 59 min |
| Jul 30, 6:08 PM MDT | Areal Flood Advisory | BOU | Adams, Denver | 82 min |
| Jul 30, 6:48 PM MDT | Areal Flood Advisory | BOU | Douglas, Elbert | 117 min |
| Jul 30, 7:13 PM MDT | Areal Flood Warning | BOU | Larimer | 3 hr |
| Jul 30, 7:35 PM MDT | Areal Flood Advisory | BOU | Boulder | 70 min |
| Jul 30, 7:52 PM MDT | Areal Flood Advisory | BOU | Boulder, Broomfield, Weld | 83 min |
| Jul 30, 7:53 PM MDT | Areal Flood Advisory | BOU | Larimer | 68 min |
| Jul 30, 8:19 PM MDT | Areal Flood Advisory | BOU | Douglas, Jefferson | 42 min |
| Jul 30, 9:34 PM MDT | Areal Flood Advisory | BOU | Adams, Boulder, Broomfield, Denver, Jefferson, Weld | 56 min |
| Jul 30, 9:35 PM MDT | Areal Flood Advisory | BOU | Clear Creek, Gilpin | 3 hr |
| Jul 30, 10:18 PM MDT | Flash Flood Warning | BOU | Boulder, Broomfield, Weld | 3 hr |
| Jul 30, 11:17 PM MDT | Special Weather Statement | BOU | Weld | 28 min |
| Jul 30, 11:24 PM MDT | Areal Flood Advisory | BOU | Weld | 81 min |
| Jul 30, 11:40 PM MDT | Areal Flood Advisory | BOU | Weld | 60 min |
| Jul 31, 1:12 AM MDT | Special Weather Statement | BOU | Logan | 33 min |
| Jul 31, 2:39 AM MDT | Special Weather Statement | BOU | Logan | 51 min |
| Jul 31, 3:20 AM MDT | Special Weather Statement | BOU | Phillips, Sedgwick | 40 min |
| Jul 31, 3:59 AM MDT | Areal Flood Advisory | BOU | Logan, Phillips, Sedgwick | 74 min |
| Jul 31, 11:49 AM MDT | Flash Flood Warning | BOU | Larimer | 2 hr |
| Jul 31, 12:27 PM MDT | Flash Flood Warning | BOU | Grand | 3 hr |
| Jul 31, 12:29 PM MDT | Areal Flood Advisory | BOU | Grand | 91 min |
| Jul 31, 12:32 PM MDT | Areal Flood Advisory | BOU | Grand | 88 min |
| Jul 31, 12:34 PM MDT | Areal Flood Advisory | BOU | Grand | 86 min |
| Jul 31, 12:39 PM MDT | Areal Flood Advisory | BOU | Park | 81 min |
| Jul 31, 12:42 PM MDT | Areal Flood Advisory | BOU | Park | 93 min |
| Jul 31, 1:05 PM MDT | Areal Flood Advisory | BOU | Larimer | 85 min |
| Jul 31, 1:33 PM MDT | Areal Flood Advisory | BOU | Grand | 87 min |
| Jul 31, 2:16 PM MDT | Flash Flood Warning | BOU | Larimer | 89 min |
| Jul 31, 2:43 PM MDT | Flash Flood Warning | BOU | Larimer | 92 min |
| Jul 31, 2:57 PM MDT | Areal Flood Advisory | BOU | Park | 93 min |
| Jul 31, 3:24 PM MDT | Flash Flood Warning | BOU | Larimer | 81 min |
| Jul 31, 3:29 PM MDT | Areal Flood Advisory | BOU | Boulder | 91 min |
| Jul 31, 3:33 PM MDT | Flash Flood Warning | BOU | Park | 3 hr |
| Jul 31, 3:51 PM MDT | Areal Flood Advisory | BOU | Boulder | 84 min |
| Jul 31, 4:31 PM MDT | Areal Flood Advisory | BOU | Park | 89 min |
| Jul 31, 4:42 PM MDT | Areal Flood Advisory | BOU | Park | 93 min |
| Jul 31, 4:52 PM MDT | Areal Flood Advisory | BOU | Park | 83 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.