Alert archive / Colorado / Red Flag Warnings in 2025
Red Flag Warning 31, NWS Denver/Boulder, CO
NWS Denver/Boulder, CO issued this red flag warning at Dec 18, 2025, 2:44 PM MST for 13 counties in Colorado. It took effect at Dec 19, 2025, 5:00 AM MST. It was in force for 19 hr. No storm report in the archive falls inside the area while it was in force.
The area
The counties it named.
The facts
- Issued
- Dec 18, 2025, 2:44 PM MST (21:44 UTC)
- In effect from
- Dec 19, 2025, 5:00 AM MST
- Expired
- Dec 20, 2025, 12:00 AM MST
- In force
- 19 hr
- Issued by
- NWS Denver/Boulder, CO
Counties Adams County, CO, Arapahoe County, CO, Boulder County, CO, Broomfield County, CO, Clear Creek County, CO, Denver County, CO, Douglas County, CO, Elbert County, CO, Gilpin County, CO, Jefferson County, CO, Larimer County, CO, Park County, CO, Weld County, CO
The radar
The Denver radar (KFTG), 39 km from the middle of the area, began a volume at 21:50 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
Riverton, WY (KRIW), launched 12:00Z, 9.7 hours before the alert went out and 461 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 2446 m above ground
- 0-6 km bulk shear
- 107 kt
- 0-1 km storm-relative helicity
- -31 m²/s²
- 0-3 km storm-relative helicity
- 127 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
What forecasters said that day
The local office's own words before this red flag warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Denver/Boulder, CO wrote its last area forecast discussion before this red flag warning went out at Dec 18, 4:28 AM MST, 10 hours 16 minutes earlier.
Area forecast discussion, Dec 18, 4:28 AM MST, 10 hours 16 minutes before
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Local storm report, Dec 18, 9:08 AM MST, 5 hours 36 minutes before
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</html>The office that day
Everything else NWS Denver/Boulder, CO issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Dec 17, 6:57 PM MST | High Wind Warning | BOU | Larimer, Weld | 5 hr |
| Dec 18, 2:31 AM MST | Red Flag Warning | BOU | Logan, Morgan, Phillips, Sedgwick, Washington, Weld | 14 hr |
Nearby
Red Flag Warnings in Colorado, 2025Every red flag warning in 2025
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.