Alert archive / Colorado / Flash Flood Warnings in 2021
Flash Flood Warning 48, NWS Denver/Boulder, CO
NWS Denver/Boulder, CO issued this flash flood warning at Jul 30, 2021, 3:02 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 30, 2021, 3:02 PM MDT (21:02 UTC)
- Expired
- Jul 30, 2021, 6:00 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 Denver radar (KFTG), 126 km from the middle of the area, began a volume at 21:04 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
Grand Junction, CO (KGJT), launched 12:00Z, 9.0 hours before the alert went out and 226 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
- 28 J/kg
- Mixed-layer CIN
- -252 J/kg
- Mixed-layer LCL
- 1537 m above ground
- 0-6 km bulk shear
- 15 kt
- 0-1 km storm-relative helicity
- 16 m²/s²
- 0-3 km storm-relative helicity
- 101 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.0
The text
As transmitted.
610
WGUS55 KBOU 302102
FFWBOU
COC049-310000-
/O.NEW.KBOU.FF.W.0048.210730T2102Z-210731T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Denver CO
302 PM MDT Fri Jul 30 2021
The National Weather Service in Denver has issued a
* Flash Flood Warning for...
South Central Grand County in north central Colorado...
* Until 600 PM MDT.
* At 302 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 1.5 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...
mainly rural areas of South Central Grand County
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 Williams Fork burn area. Rock slides or debris
flows can also be expected across rural roads. Flooding is possible
downstream of the burn area along the Williams Fork.
&&
LAT...LON 3983 10596 3983 10599 3979 10602 3977 10603
3975 10605 3978 10606 3982 10607 3985 10610
3988 10608 3988 10605 3990 10602 3990 10598
3986 10596
FLASH FLOOD...RADAR INDICATED
$$
Bowen2 follow-up statements
855
WGUS75 KBOU 302159
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
359 PM MDT Fri Jul 30 2021
COC049-310000-
/O.CON.KBOU.FF.W.0048.000000T0000Z-210731T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Grand CO-
359 PM MDT Fri Jul 30 2021
...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 6 PM MDT THIS EVENING
FOR SOUTH CENTRAL GRAND COUNTY...
At 359 PM MDT, Doppler radar indicated thunderstorms continued
producing heavy rain in and south of southern half of the Williams
Fork burn scar. The storms are drifting slowly north. Between 1 and
1.5 inches of rain have fallen. Additional rainfall amounts of 0.5
to 1 inch are possible in the warned area. Flash flooding is ongoing
or expected to begin shortly.
HAZARD...Flash flooding caused by thunderstorms.
SOURCE...Radar.
IMPACT...Flash flooding of small creeks and streams, gulches,
roads, and poor drainage and low-lying areas.
Some locations that will experience flash flooding include...
mainly rural areas of South Central Grand County
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Move to higher ground now. Act quickly to protect your life.
Heavy Rainfall will cause flash flooding of small creeks, streams,
and ditches in the Williams Fork burn area. Rock slides or debris
flows can also be expected across rural roads. Flooding is possible
downstream of the burn area along the Williams Fork.
&&
LAT...LON 3983 10596 3983 10599 3979 10602 3977 10603
3975 10605 3978 10606 3982 10607 3985 10610
3988 10608 3988 10605 3990 10602 3990 10598
3986 10596
FLASH FLOOD...RADAR INDICATED
$$
TH914
WGUS75 KBOU 302350
FFSBOU
Flash Flood Statement
National Weather Service Denver CO
550 PM MDT Fri Jul 30 2021
COC049-310000-
/O.EXP.KBOU.FF.W.0048.000000T0000Z-210731T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Grand CO-
550 PM MDT Fri Jul 30 2021
...FLASH FLOOD WARNING WILL EXPIRE AT 6 PM MDT THIS EVENING FOR
SOUTH CENTRAL GRAND COUNTY...
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 Saturday for
Portions of central and north central Colorado.
LAT...LON 3983 10596 3983 10599 3979 10602 3977 10603
3975 10605 3978 10606 3982 10607 3985 10610
3988 10608 3988 10605 3990 10602 3990 10598
3986 10596
$$
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 | 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, 4:30 PM MDT | Flash Flood Warning | BOU | Larimer | 4 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.