A storm system moved out of the Great Basin and into southwestern Colorado. Periods of moderate to heavy snow developed in and near the foothills of Boulder, Douglas and Jefferson counties including Denver and surrounding metro area.
Every event with a place to put it; 5 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 storm system moved out of the Great Basin and into southwestern Colorado. Periods of moderate to heavy snow developed in and near the foothills of Boulder, Douglas and Jefferson counties including Denver and surrounding metro area. The official measurement at Denver International Airport was 9.6 inches.
Storm totals included: 16.3 inches in Englewood; 15.5 inches near Cherry Hills Village; 14 inches near Highlands Ranch, 13 inches Littleton; 12.5 inches near Ken Caryl, 12 inches near Chatfield Reservoir and southeast Denver; 11 inches near Federal Heights, Thornton and Westminster; 10.5 inches in Arvada, 10 inches near Eldorado Springs, 9.5 inches near Lafayette and Louisville; 9 inches in southwest Boulder and near Foxfield and Strasburg; 8.5 inches near Broomfield; 7 inches near Wheat Ridge.
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 Feb 24, 3:39 PM MST, 1 hour 21 minutes earlier.
Area Forecast Discussion National Weather Service Denver/Boulder CO 339 PM MST Wed Feb 24 2021 .SHORT TERM...(This evening through Thursday) Issued at 300 PM MST Wed Feb 24 2021 Water vapor shows a trough moving across the intermountain west with QG ascent out ahead of it beginning to increase cloud cover over northern Colorado. At the surface, there is strong southeasterly flow across the eastern plains south of Boulder with northeasterly flow behind a weak cold front to the north of Boulder. This convergence and upslope component to the wind are starting to create snow showers over the norther foothills and I-25 corridor. Dew point depressions in the 20 to 30 degree range will initially keep much of the snow showers from reaching the surface but snow should become more widespread after 5pm. Still thinking the start time in Denver should be between 6 and 7 pm. There will be healthy upslope flow especially during this evening with this storm as surface gusts could reach 30 mph. Snow ratios should be best during the evening as well with soundings showing the isothermal layer close to the dendritic growth zone. Therefore, snowfall rates will be heaviest later this evening with rates up to an inch and a half per hour possible in the foothills and adjacent plains. During the overnight period, the upslope flow will weaken and the isothermal layer will be outside the dendritic growth zone. This means snowfall rates will decrease as the night progresses with rates closer to half an inch per hour. There will still be enough QG ascent aloft before the trough passes in the morning tomorrow for light snow showers to continue past sunrise. There is quite a bit of concern that the morning rush hour will be heavily impacted. With good snow rates overnight and snowfall continuing through the morning rush hour, there are likely to be many snow-covered roads. When all is said and done, snowfall along the urban corridor will be in the 4 to 8 inch range with higher amounts farther west. The highest snowfall totals will be in the foothills and adjacent plains where 5 to 10 inches are expected. There seems to be a growing potential for a couple places to reach a foot of snow where the best snow band lines up this evening along the convergence associated with the front. Our usual snowy spots towards the base of the foothills would be the most likely area to see a foot. The Winter Weather Advisories were kept the same after some consideration was given to upgrading to a Winter Storm Warning along the foothills and zone 39 which includes Boulder and Golden. Snowfall will end quickly during the mid morning tomorrow as subsidence moves over the area behind the passing shortwave trough. Skies will clear with below normal high temperatures. Gusty winds will develop across the eastern plains with gusts reaching up to 30 mph. .LONG TERM...(Thursday night through Wednesday) Issued at 237 PM MST Wed Feb 24 2021 By Thursday evening, the upper trough will be pushing out of the state with increasing subsidence. Cloud cover will break up during the late afternoon and evening Thursday. Temperatures will be cold overnight with fresh snow cover and clearing skies with lows in the teens across the plains and single digits in the high country. For Friday, flow were turn slightly zonal ahead of the next shortwave. There will be continued warming across the lower elevations with increasing downslope with a lee side surface low. Winds across the mountains will start to increase during the morning with the influence of a 100kt jet. Cross mountain flow seen on model cross-sections increases to almost 60kts by the afternoon. At this time there is a hint of a stable layer but just offset enough to keep the higher winds along the higher elevations and more typical gusty winds in the higher foothills and adjacent plains. Wind speeds across the plains could range from 20 to 40 mph with the higher values close to the Wyoming border. Also associated with the upper level feature some light mountain snow will be possible during the day on Friday across the higher elevations due to an increase in mid- level moisture and decent orographics. Amounts should remain on the lighter side with 1 to 4 inches possible. Snow accumulation chances will increase Friday night into Saturday with the next disturbance bringing additional moisture with a good shot of cold advection. Lapse rates will also increase into the evening and Saturday which will help with snowfall production. The trough then continues to dig into the desert southwest as an open wave Saturday night into Sunday. Model consistency at this point is extremely varied so confidence is low for the forecast after this point. However, we cannot rule out a slight chance of snow for the higher terrain due to the potential placement of the upper jet and trough. The lower elevations should remain mostly dry through the weekend with the overall downslope pattern still in place. Temperatures will also gradually rebound with highs on Saturday around seasonal normals and only slightly cooler for Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 300 PM MST Wed Feb 24 2021 Gusty southeasterly winds will continue until a cold front shifts winds more northeasterly around between 00-01Z. Behind this cold front, snow will begin roughly around 02Z with snowfall rates quickly increasing. There is a decent chance a band of snow will lower visibility to half a mile at DEN and lower ceilings to around 500 ft. Snow rates will decrease slightly around 06Z but will still be enough to reduce visibility to 1 mile. The snow begins to taper off Thursday morning with ceilings and visibility improving to VFR by midday. Strong southerly winds will develop tomorrow afternoon. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 8 AM MST Thursday for COZ035-036- 039>041. && SHORT TERM...Danielson LONG TERM...Bowen AVIATION...Danielson
Hazardous Weather Outlook National Weather Service Denver/Boulder CO 1115 AM MST Wed Feb 24 2021 COZ030>051-251815- 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- 1115 AM MST Wed Feb 24 2021 This hazardous weather outlook is for northeast and north central Colorado. .DAY ONE...This Afternoon and Tonight Snow is expected to develop in and near the northern foothills late this afternoon and then become more widespread across the area this evening. The more significant snow accumulations are expected to occur in and immediately adjacent to the foothills where several inches of snow are expected tonight and into tomorrow morning. We do see a fairly sharp drop-off of snow amounts to the east across the plains east of Denver International Airport. The main travel impacts will occur after the evening rush hour tonight but will heavily impact the morning commute Thursday morning. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Slick roads and some light snow are expected to linger along the Front Range and Palmer Divide into the Thursday morning commute. Additional snowfall amounts will be light, with an inch or less of snow over the Palmer Divide area and southern portions of Lincoln county. Snow will end from northwest to southeast across the area in the morning hours with clearing skies for the afternoon. Light snow is expected to redevelop in the mountains Friday, and continue off and on through the weekend. Strong, gusty winds can be expected over the mountains, foothills, and adjacent plains on Friday as well. Peak gusts greater than 60 mph, some blowing snow, and slick/slow travel conditions will occur over the higher mountain passes. The plains should see mostly dry conditions through early next week, although there may a couple spots that see some light snow, mainly Saturday night or early Sunday. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today or tonight.
The national radar mosaic for the moment the first event began.
3 winter weather, 2 winter storm. Local standard time, as filed.
Storm totals ranged from 8 to 16 inches.
Storm totals ranged from 6 to 12 inches.
Storm totals ranged from 3 to 6 inches.
Storm totals generally ranged from 3 to 8 inches, with locally higher amounts to around one foot.
Storm totals ranged from 3 to 8 inches.
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, February 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: 935190, 935191, 935192, 935193, 946261.