Alert archive / Colorado / Flash Flood Watches in 2021
Flash Flood Watch 3, NWS Denver/Boulder, CO
NWS Denver/Boulder, CO issued this flash flood watch at Jul 21, 2021, 3:18 AM MDT for 4 counties in Colorado. It took effect at Jul 21, 2021, 12:00 PM MDT. It was in force for 8 hr.
The area
The counties it named.
The facts
- Issued
- Jul 21, 2021, 3:18 AM MDT (09:18 UTC)
- In effect from
- Jul 21, 2021, 12:00 PM MDT
- Expired
- Jul 21, 2021, 7:59 PM MDT
- In force
- 8 hr
- Issued by
- NWS Denver/Boulder, CO
- Flood severity
- None
Counties Boulder County, CO, Grand County, CO, Jackson County, CO, Larimer County, CO
The radar
The Cheyenne radar (KCYS), 121 km from the middle of the area, began a volume at 09:19 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 00:00Z, 9.3 hours before the alert went out and 227 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
- 99 J/kg
- Mixed-layer CIN
- -49 J/kg
- Mixed-layer LCL
- 3076 m above ground
- 0-6 km bulk shear
- 6 kt
- 0-1 km storm-relative helicity
- -2 m²/s²
- 0-3 km storm-relative helicity
- 36 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
874 WGUS65 KBOU 210918 FFABOU URGENT - IMMEDIATE BROADCAST REQUESTED Flood Watch National Weather Service Denver CO 318 AM MDT Wed Jul 21 2021 COZ033-035-211730- /O.NEW.KBOU.FF.A.0003.210721T1800Z-210722T0200Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ South and East Jackson/Larimer/North and Northeast Grand/Northwest Boulder Counties Above 9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet- Including the cities of Glendevey, Nederland, Rocky Mountain National Park, Laramie and Medicine Bow Mountains, Red Feather Lakes, Cameron Pass, Estes Park, Willow Creek Pass, and Rabbit Ears Range 318 AM MDT Wed Jul 21 2021 ...FLASH FLOOD WATCH IN EFFECT FROM NOON MDT TODAY THROUGH THIS EVENING... The National Weather Service in Denver has issued a * Flash Flood Watch for A portion of north central Colorado, including the following areas, 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 Noon MDT today through this evening. * Heavy rain possible in the Cameron Peak and East Troublesome Burn Scars. PRECAUTIONARY/PREPAREDNESS ACTIONS... 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, especially in the Cameron Peak and East Troublesome burn scars. 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. && $$ RPK
1 follow-up statement
832 WGUS65 KBOU 220159 FFABOU Flood Watch National Weather Service Denver CO 759 PM MDT Wed Jul 21 2021 COZ033-035-220300- /O.CAN.KBOU.FF.A.0003.000000T0000Z-210722T0200Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ South and East Jackson/Larimer/North and Northeast Grand/Northwest Boulder Counties Above 9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet- Including the cities of Glendevey, Nederland, Rocky Mountain National Park, Laramie and Medicine Bow Mountains, Red Feather Lakes, Cameron Pass, Estes Park, Willow Creek Pass, and Rabbit Ears Range 759 PM MDT Wed Jul 21 2021 ...FLASH FLOOD WATCH WILL EXPIIRE AT 8 PM MDT... The Flash Flood Watch for A portion of north central Colorado, including the following areas, Larimer and Boulder Counties Between 6000 and 9000 Feet and South and East Jackson/Larimer/North and Northeast Grand/Northwest Boulder Counties Above 9000 Feet. will expire at 8 PM MDT. The Flood Watch will expire at 8 PM MDT. Additional flooding is no longer expected to pose a threat. Please continue to heed remaining road closures. $$ Cooper
The office that day
Everything else NWS Denver/Boulder, CO issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 20, 6:58 PM MDT | Flash Flood Warning | BOU | Larimer | 92 min |
| Jul 20, 7:09 PM MDT | Flash Flood Warning | BOU | Larimer | 81 min |
| Jul 21, 1:30 PM MDT | Flash Flood Warning | BOU | Larimer | 3 hr |
| Jul 21, 1:56 PM MDT | Areal Flood Advisory | BOU | Grand | 3 hr |
| Jul 21, 2:31 PM MDT | Areal Flood Advisory | BOU | Park | 119 min |
| Jul 21, 2:44 PM MDT | Special Weather Statement | BOU | Teller | 46 min |
| Jul 21, 2:47 PM MDT | Flash Flood Warning | BOU | Larimer | 103 min |
| Jul 21, 3:16 PM MDT | Flash Flood Warning | BOU | Grand, Larimer | 3 hr |
| Jul 21, 3:22 PM MDT | Areal Flood Advisory | BOU | Park | 69 min |
| Jul 21, 4:40 PM MDT | Areal Flood Advisory | BOU | Douglas | 65 min |
| Jul 21, 5:06 PM MDT | Flash Flood Warning | BOU | Clear Creek | 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.