Alert archive / Colorado / Flash Flood Watches in 2021
Flash Flood Watch 4, NWS Denver/Boulder, CO
NWS Denver/Boulder, CO issued this flash flood watch at Jul 22, 2021, 2:15 PM MDT for 9 counties in Colorado. It took effect at Jul 23, 2021, 11:00 AM MDT. It was in force for 9 hr.
The area
The counties it named.
The facts
- Issued
- Jul 22, 2021, 2:15 PM MDT (20:15 UTC)
- In effect from
- Jul 23, 2021, 11:00 AM MDT
- Expired
- Jul 23, 2021, 8:24 PM MDT
- In force
- 9 hr
- Issued by
- NWS Denver/Boulder, CO
- Flood severity
- None
Counties Boulder County, CO, Clear Creek County, CO, Gilpin County, CO, Grand County, CO, Jackson County, CO, Jefferson County, CO, Larimer County, CO, Park County, CO, Summit County, CO
The radar
The Denver radar (KFTG), 102 km from the middle of the area, began a volume at 20:15 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, 8.3 hours before the alert went out and 213 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
- 1 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 2242 m above ground
- 0-6 km bulk shear
- 0 kt
- 0-1 km storm-relative helicity
- -11 m²/s²
- 0-3 km storm-relative helicity
- 2 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
709 WGUS65 KBOU 222015 FFABOU URGENT - IMMEDIATE BROADCAST REQUESTED Flood Watch National Weather Service Denver CO 215 PM MDT Thu Jul 22 2021 .Thunderstorm activity will increase Friday with an elevated threat of flash flooding on the burn areas. COZ033>035-231100- /O.NEW.KBOU.FF.A.0004.210723T1800Z-210724T0300Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ South and East Jackson/Larimer/North and Northeast Grand/Northwest Boulder Counties Above 9000 Feet-South and Southeast Grand/West Central and Southwest Boulder/Gilpin/Clear Creek/Summit/North and West Park Counties Above 9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet- Including the cities of Glendevey, East Slopes Mosquito Range, Estes Park, Indian Peaks, Nederland, Eisenhower Tunnel, Rocky Mountain National Park, East Slopes Southern Gore Range, Mount Evans, Laramie and Medicine Bow Mountains, Red Feather Lakes, Cameron Pass, Breckenridge, Kenosha Mountains, Winter Park, Williams Fork Mountains, Willow Creek Pass, Rabbit Ears Range, and Berthoud Pass 215 PM MDT Thu Jul 22 2021 ...FLASH FLOOD WATCH IN EFFECT FROM FRIDAY AFTERNOON THROUGH FRIDAY EVENING... The National Weather Service in Denver has issued a * Flash Flood Watch for Portions of central and north central Colorado, including the following areas, in central Colorado, South and Southeast Grand/West Central and Southwest Boulder/Gilpin/Clear Creek/Summit/North and West Park Counties Above 9000 Feet. In north central Colorado, Larimer and Boulder Counties Between 6000 and 9000 Feet and South and East Jackson/Larimer/North and Northeast Grand/Northwest Boulder Counties Above 9000 Feet. * From Friday afternoon through Friday evening. * Slow moving thunderstorms capable of producing heavy rainfall, especially in the Cameron Peak, East Troublesome, CalWood and Williams Fork burn areas. * Excessive runoff from heavy rain may cause flash flooding of creeks and streams, roads and roadside culverts. The heavy rains could also trigger rock slides or debris flows PRECAUTIONARY/PREPAREDNESS ACTIONS... It is important to know where you are relative to streams, rivers, or creeks which can become killers in heavy rains. Campers and hikers should pay close attention to rapidly changing weather conditions and avoid streams or creeks if thunderstorms develop. && $$ Cooper
2 follow-up statements
783 WGUS65 KBOU 230700 FFABOU URGENT - IMMEDIATE BROADCAST REQUESTED Flood Watch National Weather Service Denver CO 100 AM MDT Fri Jul 23 2021 .Widespread slow moving thunderstorms are expected today with a threat of flash flooding in the burn areas. COZ032-240300- /O.EXB.KBOU.FF.A.0004.210723T1700Z-210724T0300Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ Grand and Summit Counties Below 9000 Feet- Including the cities of Hot Sulphur Springs, Kremmling, Dillon, Fraser, Grand Lake, and Granby 100 AM MDT Fri Jul 23 2021 ...FLASH FLOOD WATCH IN EFFECT FROM 11 AM MDT THIS MORNING THROUGH THIS EVENING... The National Weather Service in Denver has expanded the * Flash Flood Watch to include A portion of central Colorado, including the following area, Grand and Summit Counties Below 9000 Feet. * From 11 AM MDT this morning through this evening. * Slow moving thunderstorms capable of producing heavy rainfall, especially in the East Troublesome and Williams Fork burn areas. * Excessive runoff from heavy rain may cause flash flooding of creeks and streams, roads and roadside culverts. The heavy rains could also trigger rock slides or debris flows. PRECAUTIONARY/PREPAREDNESS ACTIONS... It is important to know where you are relative to streams, rivers, or creeks which can become killers in heavy rains. Campers and hikers should pay close attention to rapidly changing weather conditions and avoid streams or creeks if thunderstorms develop. You should monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued. && $$ COZ033>035-240300- /O.EXT.KBOU.FF.A.0004.210723T1700Z-210724T0300Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ South and East Jackson/Larimer/North and Northeast Grand/Northwest Boulder Counties Above 9000 Feet-South and Southeast Grand/West Central and Southwest Boulder/Gilpin/Clear Creek/Summit/North and West Park Counties Above 9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet- Including the cities of Glendevey, East Slopes Mosquito Range, Estes Park, Indian Peaks, Nederland, Eisenhower Tunnel, Rocky Mountain National Park, East Slopes Southern Gore Range, Mount Evans, Laramie and Medicine Bow Mountains, Red Feather Lakes, Cameron Pass, Breckenridge, Kenosha Mountains, Winter Park, Williams Fork Mountains, Willow Creek Pass, Rabbit Ears Range, and Berthoud Pass 100 AM MDT Fri Jul 23 2021 ...FLASH FLOOD WATCH NOW IN EFFECT FROM 11 AM MDT THIS MORNING THROUGH THIS EVENING... The Flash Flood Watch is now in effect for * Portions of central and north central Colorado, including the following areas, in central Colorado, South and Southeast Grand/West Central and Southwest Boulder/Gilpin/Clear Creek/Summit/North and West Park Counties Above 9000 Feet. In north central Colorado, Larimer and Boulder Counties Between 6000 and 9000 Feet and South and East Jackson/Larimer/North and Northeast Grand/Northwest Boulder Counties Above 9000 Feet. * From 11 AM MDT this morning through this evening. * Slow moving thunderstorms capable of producing heavy rainfall, especially in the Cameron Peak, East Troublesome, CalWood and Williams Fork burn areas. * Excessive runoff from heavy rain may cause flash flooding of creeks and streams, roads and roadside culverts. The heavy rains could also trigger rock slides or debris flows PRECAUTIONARY/PREPAREDNESS ACTIONS... It is important to know where you are relative to streams, rivers, or creeks which can become killers in heavy rains. Campers and hikers should pay close attention to rapidly changing weather conditions and avoid streams or creeks if thunderstorms develop. You should monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued. && $$ Danielson
822 WGUS65 KBOU 240224 FFABOU Flood Watch National Weather Service Denver CO 824 PM MDT Fri Jul 23 2021 COZ032>035-240330- /O.CAN.KBOU.FF.A.0004.000000T0000Z-210724T0300Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ Grand and Summit Counties Below 9000 Feet-South and East Jackson/Larimer/North and Northeast Grand/Northwest Boulder Counties Above 9000 Feet-South and Southeast Grand/West Central and Southwest Boulder/Gilpin/Clear Creek/Summit/North and West Park Counties Above 9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet- Including the cities of Winter Park, Rocky Mountain National Park, Laramie and Medicine Bow Mountains, Red Feather Lakes, Breckenridge, Williams Fork Mountains, Glendevey, Indian Peaks, Nederland, Eisenhower Tunnel, Kremmling, East Slopes Southern Gore Range, Mount Evans, Grand Lake, Cameron Pass, East Slopes Mosquito Range, Berthoud Pass, Granby, Kenosha Mountains, Estes Park, Willow Creek Pass, Hot Sulphur Springs, Dillon, Fraser, and Rabbit Ears Range 824 PM MDT Fri Jul 23 2021 ...FLASH FLOOD WATCH IS CANCELLED... The Flash Flood Watch for Portions of central and north central Colorado, including the following areas, in central Colorado, Grand and Summit Counties Below 9000 Feet and South and Southeast Grand/West Central and Southwest Boulder/Gilpin/Clear Creek/Summit/North and West Park Counties Above 9000 Feet. In north central Colorado, Larimer and Boulder Counties Between 6000 and 9000 Feet and South and East Jackson/Larimer/North and Northeast Grand/Northwest Boulder Counties Above 9000 Feet. has been cancelled. The Flood Watch is cancelled. Flooding is no longer expected to pose a threat. Please continue to heed remaining road closures. $$ Hiris
The office that day
Everything else NWS Denver/Boulder, CO issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 21, 6:01 PM MDT | Areal Flood Advisory | BOU | Douglas, Elbert | 89 min |
| Jul 21, 6:11 PM MDT | Flash Flood Warning | BOU | Grand | 3 hr |
| Jul 21, 6:19 PM MDT | Flash Flood Warning | BOU | Douglas | 3 hr |
| Jul 22, 11:15 AM MDT | Areal Flood Advisory | BOU | Larimer | 2 hr |
| Jul 22, 11:44 AM MDT | Areal Flood Advisory | BOU | Larimer | 2 hr |
| Jul 22, 12:04 PM MDT | Areal Flood Advisory | BOU | Larimer | 116 min |
| Jul 22, 2:14 PM MDT | Areal Flood Advisory | BOU | Grand | 22 min |
| Jul 22, 2:36 PM MDT | Flash Flood Warning | BOU | Grand | 5 hr |
| Jul 22, 3:13 PM MDT | Flash Flood Warning | BOU | Grand | 3 hr |
Nearby
Flash Flood Watches in Colorado, 2021Every flash flood watch 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.