Much of the Front Range Foothills, South Park, Urban Corridor, and northeast CO plains were classified to be in severe to extreme drought (D2/D3) through the month of December. These conditions contributed significantly to the Marshall Wildfire, the costliest fire in Colorado history.
Every event with a place to put it; 16 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS BOU wrote it up.
Much of the Front Range Foothills, South Park, Urban Corridor, and northeast CO plains were classified to be in severe to extreme drought (D2/D3) through the month of December. These conditions contributed significantly to the Marshall Wildfire, the costliest fire in Colorado history. The Front Range experienced a very wet first half of the year, with well above normal precipitation and lush, tall grass growth. However, starting around July, a persistently dry weather pattern set up and held firm through the entire fall and early winter. Vegetation, while typically dry this time of year, was exceptionally dry as very little precipitation had fallen through the entire fall season. The ongoing drought conditions ensured larger fuels such as shrubs and trees were likewise critically dry. From the period of July 1st through December 29th, temperature and precipitation climate records showed Denver was the 2nd warmest, and by far the driest in recorded history (since 1872). Boulder was ranked 2nd warmest for precipitation, while 13th driest in recorded history.
The local office's own words before the first event, 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 the first event at Nov 30, 11:27 PM MST, 33 minutes earlier.
Area Forecast Discussion National Weather Service Denver/Boulder CO 1127 PM MST Tue Nov 30 2021 .UPDATE... Issued at 747 PM MST Tue Nov 30 2021 High clouds continue to push into our area. Current observations display warm temperatures steadily dropping across the mountains and eastern plains. Sky cover grids were updated to include the high cloud through early morning Wednesday. This shouldn't affect low temperatures tonight as areas east of the Rockies will drop to the mid 30s to lower 40s. Areas west of the Rockies can expect lows in the lower to mid 20s. && .SHORT TERM...(This evening through Wednesday) Issued at 240 PM MST Tue Nov 30 2021 High clouds continue to spread in from the north and they are pretty thick under the nose of the jet moving off of the Rockies this evening. These clouds will likely persist through the evening, then thin somewhat as the best lift moves east. There are still a lot of thinner high clouds behind the main area though, so we've continued to increase the cloud cover through the day tomorrow. The clouds should affect tonight's lows, so we've moderated them a little, especially in the colder areas. If there isn't some thinning of the clouds later tonight the lows will need to be raised some more. Likewise, highs on Wednesday may hinge on how thick the clouds are. The air mass would support near record highs in the lower 70s on the plains if it were sunny with a little breeze. We'll probably be just shy of the records and the current forecast looks alright. The passing of the jet max this evening brings a strengthened mid level inversion and a short lived increase in flow as low as 600-700 mb. This should produce a period of mountain wave enhancement over the Front Range. The current forecast handles this well although we could get a little more wind into the lower foothills where that tends to happen, i.e. down the hill to Rocky Flats and Boulder. .LONG TERM...(Wednesday night through Tuesday) Issued at 240 PM MST Tue Nov 30 2021 Strong persistent ridge will remain centered over the Great Basin through Saturday with weak flow aloft across Colorado. This will keep warm and dry conditions in place. Thursday looks very warm for December with highs in the lower to mid 70s over northeast Colorado. A few record highs could be reached. For Denver, the record high is 74F degrees. Airmass will continue to be very dry with only a few highs clouds expected. Will see a cool down for Friday when a weak cold front pushes through. Highs fall 10-15F, which is still about 15F above normal for this time of year. For northeast Colorado, this puts highs around 60 degrees. Mild temperatures continue Saturday. Flow aloft begins to increase as an upper level trough moves across the Northern Rockies. Could see winds increase later Saturday and Saturday night. Another weak cold front moves through for Sunday. This knocks temperatures down a little with highs in the 50s expected. The weather pattern for early to mid next week looks quite uncertain at this time. Models are in agreement with a system/upper level trough tracking southeast across the intermountain west. Little to no agreement on what this will look like yet, but this will be the first system in nearly two weeks that could bring precipitation to the area. Monday still looks mild and dry ahead of the storm system. Tuesday's weather will depend on the trough and it's timing. For now will have low PoPs in the forecast with slightly cooler temperatures. Can't rule out one more warm day Tuesday if this system ends up being a little slower. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1126 PM MST Tue Nov 30 2021 Expect VFR conditions to persist through the TAF period. Broken to scattered high cloudiness may persist as high level moisture streams in from the north, but the low to mid levels remain quite dry. Cross-sections indicate a persistent, weak mountain wave. Breezy westerly winds over the foothills are making it out to KBJC but shouldn't make it out to KDEN, where winds are coming around southeasterly and should be on their way to drainage for the night. There is little model consensus about winds tomorrow afternoon. The HRRR is indicating an anti-cyclonic flow on the northern plains in response to northwesterly flow over the Cheyenne Ridge, leading to easterly winds across the terminals, which is common in this flow pattern and seems most likely at this time - though winds may often practically be more light and variable. Winds should then come back around to drainage again in the evening. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && UPDATE...AD SHORT TERM...Gimmestad LONG TERM...Meier AVIATION...EJD
Hazardous Weather Outlook National Weather Service Denver/Boulder CO 1105 AM MST Tue Nov 30 2021 COZ030>051-011815- Jackson County Below 9000 Feet- West Jackson and West Grand Counties Above 9000 Feet- 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- Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear Creek/Northeast Park Counties Below 9000 Feet- Central and Southeast Park County- Larimer County Below 6000 Feet/Northwest Weld County- Boulder And Jefferson Counties Below 6000 Feet/West Broomfield County- North Douglas County Below 6000 Feet/Denver/West Adams and Arapahoe Counties/East Broomfield County- Elbert/Central and East Douglas Counties Above 6000 Feet- Northeast Weld County-Central and South Weld County-Morgan County- Central and East Adams and Arapahoe Counties- North and Northeast Elbert County Below 6000 Feet/North Lincoln County- Southeast Elbert County Below 6000 Feet/South Lincoln County- Logan County-Washington County-Sedgwick County-Phillips County- 1105 AM MST Tue Nov 30 2021 This hazardous weather outlook is for northeast and north central Colorado. .DAY ONE...This Afternoon and Tonight There will be a windy period tonight in the Front Range mountains and higher foothills, with widespread gusts up to around 45 mph and gusts up to 60 mph over the higher peaks. .DAYS TWO THROUGH SEVEN...Wednesday through Monday No hazardous weather is expected. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. Gimmestad/Meier
The national radar mosaic for the moment the first event began.
16 drought. Local standard time, as filed.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
Severe to extreme drought classification (D2/D3) through the month of December.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2021Every state in 2021This day in weather historyWarnings in Colorado, December 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 992727, 992728, 992729, 992730, 992731, 992732, 992733, 992734, 992735, 992736, 992737, 992738, 992739, 992740, 992741, 992742.