Alert archive / Colorado / Flash Flood Warnings in 2021
Flash Flood Warning 56, NWS Denver/Boulder, CO
NWS Denver/Boulder, CO issued this flash flood warning at Jul 31, 2021, 12:27 PM MDT for Grand 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, 12:27 PM MDT (18:27 UTC)
- Expired
- Jul 31, 2021, 3:30 PM MDT
- In force
- 3 hr
- Issued by
- NWS Denver/Boulder, CO
- Area
- Storm-based polygon
- Flood severity
- None
County Grand County, CO
The radar
The Cheyenne radar (KCYS), 135 km from the middle of the area, began a volume at 18:29 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, 6.5 hours before the alert went out and 241 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.
426
WGUS55 KBOU 311827
FFWBOU
COC049-312130-
/O.NEW.KBOU.FF.W.0056.210731T1827Z-210731T2130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
1227 PM MDT Sat Jul 31 2021
The National Weather Service in Denver has issued a
* Flash Flood Warning for...
North Central Grand County in north central Colorado...
* Until 330 PM MDT.
* At 1227 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...
mainly rural areas of North Central Grand County
This includes the following streams and drainages...
Buffalo Creek, Trout Creek, Trail Creek, Colorado River, Willow
Creek, Gold Run, Illinois River and Soda 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 East Troublesome burn area. Rock slides or debris
flows can also be expected across rural roads.
&&
LAT...LON 4037 10604 4037 10601 4036 10601 4036 10599
4035 10597 4035 10596 4036 10595 4036 10591
4022 10587 4023 10608 4035 10609 4035 10608
FLASH FLOOD...RADAR INDICATED
$$
RPK2 follow-up statements
355
WGUS75 KBOU 311922
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
122 PM MDT Sat Jul 31 2021
COC049-312130-
/O.CON.KBOU.FF.W.0056.000000T0000Z-210731T2130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Grand CO-
122 PM MDT Sat Jul 31 2021
...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 330 PM MDT THIS
AFTERNOON FOR NORTH CENTRAL GRAND COUNTY...
At 122 PM MDT, Doppler radar indicated thunderstorms producing heavy
rain across the warned area. Between 0.5 and 1 inch of rain has
fallen. Additional rainfall amounts up to 0.5 inches are possible in
the warned area. Flash flooding is ongoing or expected to begin
shortly.
HAZARD...Flash flooding caused by thunderstorms.
SOURCE...Radar.
IMPACT...Flash flooding of small creeks and streams, gulches,
roads, and poor drainage and low-lying areas.
Some locations that will experience flash flooding include...
mainly rural areas of North Central Grand County
This includes the following streams and drainages...
Buffalo Creek, Trout Creek, Trail Creek, Colorado River, Willow
Creek, Gold Run, Illinois River and Soda Creek.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Move to higher ground now. Act quickly to protect your life.
Heavy Rainfall will cause flash flooding of small creeks, streams,
and ditches in the East Troublesome burn area. Rock slides or debris
flows can also be expected across rural roads.
&&
LAT...LON 4037 10604 4037 10601 4036 10601 4036 10599
4035 10597 4035 10596 4036 10595 4036 10591
4022 10587 4023 10608 4035 10609 4035 10608
FLASH FLOOD...RADAR INDICATED
$$
RPK204
WGUS75 KBOU 312130
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
330 PM MDT Sat Jul 31 2021
COC049-312140-
/O.EXP.KBOU.FF.W.0056.000000T0000Z-210731T2130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Grand CO-
330 PM MDT Sat Jul 31 2021
...FLASH FLOOD WARNING WILL EXPIRE AT 330 PM MDT THIS AFTERNOON FOR
NORTH CENTRAL GRAND 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 and north central Colorado.
LAT...LON 4037 10604 4037 10601 4036 10601 4036 10599
4035 10597 4035 10596 4036 10595 4036 10591
4022 10587 4023 10608 4035 10609 4035 10608
$$
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, 12:29 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, 3:37 PM MDT | Flash Flood Warning | BOU | Boulder | 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.