A winter storm produced the first significant snowfall in the northern mountains of Colorado, just in time for Christmas. 5 feet.
Every event with a place to put it; 6 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.
A winter storm produced the first significant snowfall in the northern mountains of Colorado, just in time for Christmas. Storm totals generally ranged from 1 to 2.5 feet. The heaviest snowfall occurred in mountains north of the I-70 corridor. Tragedy struck on Christmas Eve when a backcountry skier was buried in an avalanche near Cameron Pass.
Some of the more impressive 2-day storm totals from this event included: 29.9 inches near Mount Zirkel, 27.6 inches at Bear Lake and near Cameron Pass, 26.4 inches near Mt Audubon, 25.3 inches near Long's Peak, 24.2 inches near Trail Ridge, 24.1 inches near Gould, 21.8 inches near Arapahoe Peak and Spicer, 19.6 inches near Rabbit Ears Pass.
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 Dec 23, 10:52 AM MST, 3 hours 8 minutes earlier.
Area Forecast Discussion National Weather Service Denver/Boulder CO 1052 AM MST Thu Dec 23 2021 .UPDATE... Issued at 1030 AM MST Thu Dec 23 2021 The system bringing the mountain snow to Colorado is off to a good start this morning with webcams showing snow at many mountain passes. Snow is being reported in Middle and North Parks as well with Kremmling, Walden, and Grand Lake all seeing periods of snow showers. Water vapor imagery indicates that the plume of mid to high level moisture will continue to be over the northern mountains through the rest of the day without much change. Therefore, PoPs were increased slightly in the Middle and North Parks since snow has already been falling there and PoPs were quite low. With relatively warm temperatures along with it being daytime, there will not be much accumulation on the roads which should limit travel impacts today. By the late afternoon and early evening, moisture will deepen in the mountains and the coverage and intensity of the snow should increase. Overall, snowfall amounts look to be on track at the moment. Across the plains, temperatures have been very mild as expected. There are a few pockets of westerly winds making it onto the plains with gusts up to 30 mph. Fortunately, the westerly flow has actually increased the moisture at the surface which is unusual for our area. The dew point at KBJC went from 12 to 23 when the gusty westerly winds developed last hour. This is keeping the fire weather conditions limited despite the warm temperatures and gusty winds. && .SHORT TERM...(Today and tonight) Issued at 334 AM MST Thu Dec 23 2021 The transition to a persistent unsettled weather pattern will begin today. An impressive plume of moisture will get picked up ahead of a trough digging through the eastern Pacific, and then stream northeast right into Colorado. Integrated Vapor Transport (IVT) is quite impressive, reaching around 4 standardized anomalies into our forecast area toward midnight tonight, and upwards of 6-8 standardized anomalies into southwest Colorado! The ECMWF Extreme Forecast Index (EFI) and Shift of Tails (SOT) indicate a rather unusual event with significant impacts (at least in those areas favored by orographics in this extended storm). For the forecast details...Today, there is one plume of mainly mid/high level moisture spreading northeast into the state this morning, but the low levels are quite dry so quite a bit of virga/light precipitation expected through the majority of the day. Overall, we should see areas of light snow develop this morning, and then gradually become more widespread this afternoon and evening as the low levels saturate. Orographic flow is strongest for our northern tier of mountains, especially the Park Range where west/southwest flow aloft is still favorable. Meanwhile, Summit County will be most sheltered with relatively poor orographic lift in this flow pattern. Snow will become more widespread and heavier in the mountains late this evening and overnight as the deep and impressive moisture plume reaches the state and fully engulfs the high country. We'll likely see snowfall rates increase to 1-2" per hour late tonight in the Park Range, with lighter rates elsewhere due to upstream orographic sheltering. Nonetheless, most if not all of the mountain and high mountain valleys should see snow with hazardous/slow travel conditions, including the I-70 Corridor. Those conditions may worsen through Friday - see Long Term Discussion for reasons why. The Winter Storm Warning will continue for our northern mountain areas roughly along/north of a line from Rabbit Ears Pass to Rocky Mountain National Park, with an Advisory for North Park (banded snow late tonight through tomorrow) and for I-70 Summit County Corridor (less snow during first two thirds of event). The plains will remain mostly dry through tonight, although some spillover precipitation should push most of the northern foothills as the deepest moisture plume arrives. Perhaps a couple light rain showers or sprinkles on the adjacent plains overnight. Otherwise, today should feature quite mild temperatures across the plains, but some gusty winds. The stronger winds should occur in/near the Front Range Mountains and Foothills this morning, and then spread across adjacent I-25 Corridor through the afternoon as airmass destabilizes. We could see gusts around 50-60 mph in a few of the wind prone areas, while other locations along the Front Range see gusts of 30-45 mph. Overall, we've beefed up the wind forecast to account for the stronger flow aloft and some mixing. Fortunately, the mountain top stable layer is not well defined and should be slowly lifting to reduce mountain wave amplification, as there's 50+ knots near/just above mountain top. .LONG TERM...(Friday through Wednesday) Issued at 334 AM MST Thu Dec 23 2021 On Friday, a moist Pacific airmass will continue to flow into Colorado from the west-southwest as a strong quasi-zonal flow remains over the region. A potent upper level shortwave ejecting out of the Desert Southwest will move into the forecast area during the afternoon. This pattern will bring periods of moderate to heavy snow to the Northern Park and Gore Ranges, the Medicine Bow Range and Rocky Mountain National Park. This flow is not as favorable for areas to the south such as Summit County and the I-70 Corridor. However, plenty of QG lift associated with the shortwave combined with the potential for CSI banding with the 130KT+ upper jet should help increase the accumulation rates in these areas. At this time, it looks like the best chance for heavy snow may be from late afternoon into the early evening due to a more favorable orographic northwest flow and cold air advection during and shortly after the passage of the shortwave. In addition, wind gusts to 40 mph above timberline will likely cause blowing snow and reduced visibility resulting in hazardous travel. Therefore, the Winter Storm Warning and Advisory in effect through 5 am Saturday looks to be on track. Further east across the plains, the forecast is somewhat uncertain due to run to run model inconsistencies. Yesterday's solutions depicted dry weather due to downsloping flow. Many of the latest deterministic and ensemble members have considerably changed and are now showing a front moving across the northeastern Plains by Friday evening with some light QPF developing. This seems reasonable due to the location of the upper jet which could provide the potential for some banded precipitation. Temperatures look to be warm enough that any precipitation would mainly be in the form of light rain. On Saturday, the snow is expected to decrease in coverage and intensity as drier air moves in from the west. Another round of accumulating snow may return to the high country on Sunday as moisture and lift associated with another upper level shortwave moves across the state. Models are showing a powerful 165KT upper jet moving across the forecast during the afternoon. If this verifies, we could see some localized heavy snow bands developing over the high country with the possibility of some rain showers spilling onto the adjacent plains. For Monday through Wednesday, colder unsettled weather is expected as a longwave trough settles over the Western U.S. The mountains should continue to see periods of snow with mostly dry conditions on the plains. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) Issued at 1030 AM MST Thu Dec 23 2021 VFR conditions expected through the TAF period. West to northwest winds have pushed out to DEN late this morning and they should continue through the afternoon. Speeds should increase a bit somewhere around 19Z when the best mixing occurs and gusts could reach 25 knots. With moderate westerly winds, there is almost always a period where the winds are lighter or stronger than forecast so there is lower confidence than usual in the winds this afternoon. Drainage will be stronger than usual tonight. A cold front will move through late tonight/early tomorrow morning shifting winds to the north and then towards the east or northeast during the day tomorrow. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 2 PM this afternoon to 5 AM MST Saturday for COZ030-034. Winter Storm Warning from 2 PM this afternoon to 5 AM MST Saturday for COZ031-033. && UPDATE...Danielson SHORT TERM...Barjenbruch LONG TERM...Kalina AVIATION...Danielson
Hazardous Weather Outlook National Weather Service Denver/Boulder CO 1055 AM MST Thu Dec 23 2021 COZ030>051-241800- 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- 1055 AM MST Thu Dec 23 2021 ...HAZARDOUS TRAVEL AND SIGNIFICANT SNOW FOR THE MOUNTAINS... This hazardous weather outlook is for northeast and north central Colorado. .DAY ONE...Today and Tonight Snow has developed in the mountains today and it will become more widespread and heavier tonight. The heaviest snow is expected to arrive after midnight, and fall in the mountains roughly along and north of a line from Rabbit Ears Pass to Rocky Mountain National Park. Snowfall rates of 1 to 2 inches per hour will be possible there, and combined with gusty winds will create difficult travel conditions. Travel is not recommended overnight into Friday. Meanwhile, the I-70 Summit County corridor will see lighter snow through most of tonight, but even there some travel impacts can be expected with slick roads and slow travel speeds. Mostly dry conditions will prevail on the plains. Gusty winds will occur today in/near the foothills, with peak gusts of 30 to 50 mph, strongest in wind prone areas of the foothills. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Snow and blowing snow will continue to impact the mountains through Friday night with significant accumulations and difficult travel conditions expected in most areas. There could be some bands with locally heavy snow Friday into Friday evening. Locations north of Rabbit Ears Pass may see storm totals close to three feet, while other northern mountain areas see 12 to 24 inches, and the I-70 Mountain Corridor through Summit County seeing 6 to 14 inches by the time the storm winds down late Friday night. Some precipitation will be possible on the plains, especially in areas that are close to the foothills, but travel impacts are not expected. Christmas Day will see light snow showers in the mountains while the plains will be dry with mild temperatures. A series of low pressure systems on Sunday and Tuesday will bring more accumulating snow and hazardous travel to the mountains. The plains should remain mostly dry. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today or tonight. However, any snow accumulation reports from the mountains will be appreciated.
The national radar mosaic for the moment the first event began.
3 winter storm, 2 winter weather, 1 avalanche. Local standard time, as filed.
Storm totals included 29.9 inches near Mount Zirkel and 19.6 inches near Rabbit Ears Pass.
Storm totals included: 27.6 inches at Bear Lake and near Cameron Pass, 21.8 inches near Trail Ridge, 20.7 inches, 7 miles north-northwest of Kinikinik, 19.6 inches, 7 mile west of Four Corners, 15 inches, 5 miles west-southwest of Grand Lake, 15.0 inches, 8 miles west-northwest of Kremmling.
Six to twelve inches of snow fell across the North Park area of Jackson County.
Six to twelve inches of snow fell across the Middle Park area of Grand County and the valley locations of Summit County.
Storm totals included: 18.4 inches, 5 miles west-southwest of Winter Park, 17.2 inches near Loveland Pass, 17 inches just west of Silverthorne; 16 inches near Copper Mountain, 13 inches near Summit Ranch, and 12.6 inches near Berthoud Pass.
A backcountry skier was killed after being caught and fully buried in an avalanche. The avalanche occurred near Cameron Pass at 10,500 feet on the southeast portion of South Diamond Peak. The avalanche broke on a layer of snow 1 to 2 feet below the snow surface, and it was about 150 feet wide.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Avalanche, S & E Jackson / Larimer / N & Ne Grand / Nw Boulder Counties Above 9000 Feet | 2021-12-24 | 54 | Male | Outside/Open Areas | Direct |
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: 992513, 992514, 992515, 992518, 992519, 992535.