Bands of moderate to heavy snow showers coupled with strong winds produced poor visibilities and hazardous driving conditions in the mountains. Snow squalls impacts parts of the Interstate 70 corridor west of the Eisenhower Tunnel, as well as State Highway 40 west of Kremmeling.
Every event with a place to put it; 28 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.
Bands of moderate to heavy snow showers coupled with strong winds produced poor visibilities and hazardous driving conditions in the mountains. Snow squalls impacts parts of the Interstate 70 corridor west of the Eisenhower Tunnel, as well as State Highway 40 west of Kremmeling. Storm totals in the mountains and foothills ranged from 4 to 7 inches in most areas with up to 14 inches observed near Silverthorne. Along the urban corridor and northeast plains, strorm totals ranged from 3 to 6 inches west of Interstate 25, with amounts ranging from 1 to 5 inches elsewhere. Wind chill temperatures on the morning of the 23rd, ranged anywhere from -25F to -35F across the urban corridor and northeast plains. Several locations established new record low temperatures for the date including Denver. In Denver, record low temperatures of -7F and -11F were set on the 22nd and 23rd, with a record low maximum of 7 on the 23rd.
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 21, 11:05 PM MST, 55 minutes earlier.
Area Forecast Discussion National Weather Service Denver/Boulder CO 1105 PM MST Tue Feb 21 2023 .UPDATE... Issued at 913 PM MST Tue Feb 21 2023 Surface stations show that the incoming arctic cold front has pushed southward through Scottsbluff, NE towards the WY-CO border. At this rate, the front is a little quicker than anticipated and will reach the border within the next hour and Denver airport probably between 1:30 and 2:30 AM. This will bring the initial push of upslope and frontogenetical forcing to initiate snowfall across the region. Current radar shows snow developed in the northern mountains as anticipated. There are also a few showers that have developed ahead of the front (likely jet induced) by the WY border, but no reports of precipitation just yet. Water vapor imagery shows moisture pushing east into the region. Denver ACARS soundings show mid-level moisture trending upward, but still a good amount of dry air above and below to moisten to get snow hitting the ground. The frontal push should be the main initiator for this. Minor adjustments were made to the forecast in this update. The main one was decreasing snow chances slightly over the plains for tomorrow afternoon. Recent trends in the high-res models show a better likelihood for scattered coverage showers in that second round of snow in those areas. Overall this event is still shaping up for a messy AM and possibly PM commute tomorrow as well as chilly temperatures (especially Weds Night). && .SHORT TERM...(This evening through Wednesday) Issued at 329 PM MST Tue Feb 21 2023 Not too many changes to the forecast as the models have some variety in the minor details but are in fairly good agreement on the rest. The main changes to our forecast are backing off on the southward development of the showers in the early to middle part of the night. This will be trying to happen, but it looks like we were too ambitious with it. The other change is for more cooling Wednesday morning. The arctic front will probably come through most of our area by sunrise and it will suddenly be about 10 degrees and the temperature likely won't get warmer all day. There are two rounds to the snow, with a break in between them as a dry slot aloft moves over in the middle of the day. First, the incoming arctic air will be overrun and upslope will develop behind it for a good round of snow for several hours in the morning. There is some mid level deformation that is helping the showers begin along the northern border this evening, and this could help get steady precipitation going in Larimer county fairly early, but it would likely be rain through at least the middle of the night as it will still be pretty warm until the arctic front arrives. This scenario could produce a flash freeze event behind the front with the warm ground and especially where there is some rain ahead of the front. This is most likely for the I-25 corridor north of Denver before sunrise, but it could happen in Denver at rush hour. Snowfall amounts will be modulated by the dwell time of the snow band (longer duration in Larimer county) and by the expectation of continuing upslope outside of the main snow band (in and near the foothills). This is already covered pretty well in our forecast, so we haven't changed the snow totals much. The best mid/upper level forcing will come with the trough axis in the late afternoon and evening. There's a lot of cooling aloft which will produce deep instability, and also a lot of wind and wind shear in the unstable layer above the arctic air. This will likely produce elongated bands of showers that will race across the area. We though about introducing some isolated thunder to the mountains in the late afternoon/early evening. The amounts from this will be limited by the fast speed of the showers and the limited time (just a few hours) that we'll be in this regime. But the showers could produce substantial accumulations for a few spots. Overall, we're expecting most places to just get another inch or two out of this second round, with a bit more in the mountains, but there will likely be an upside surprise somewhere. .LONG TERM...(Wednesday night through Tuesday) Issued at 329 PM MST Tue Feb 21 2023 The axis of a strong shortwave trough will be in the process of moving through our CWA Wednesday evening before departing into Nebraska by around midnight. A few snow showers will be ongoing across the plains but they will come to an end quickly as the subsident flow aloft arrives. Most areas across the plains will see about a half inch of snow except for the far northeast corner which may see up to 2 inches. In the mountains, there will be healthy low level moisture and strong westerly, upslope flow that will keep snow going most of the night. That is why the warnings and advisories in the mountains continue for the majority of the night. The cold temperatures will be the primary concern Wednesday night and Thursday morning. A shallow arctic airmass will be in place across the plains as low temperatures will likely get below zero in most areas. Recent model data actually warmed low temperatures possibly due to low clouds sticking around for the majority of the night. The EC MOS data has a mean low temperature of -2 at DIA. We kept a forecast of -5 at DIA and a forecast of 0 in downtown Denver. Values will be between -5 to -10 across the farther northeast plains of Colorado. With winds staying in the 5-15 mph range, wind chills will reach as low as -25 for much of the eastern plains. A Wind Chill Advisory was issued for all lower elevation zones except for the Palmer Divide area. There was consideration for a Wind Chill Warning across the far northeast corner but it does not appear many areas will see wind chills below -25. The thinking is that (1) winds become calm and temperatures drop or (2) winds will stay stronger with warmer temperatures. Neither would allow for wind chills to drop much below -25. Southwesterly flow aloft will be over Colorado on Thursday with weak lee cyclogenesis over southeast Colorado. This will keep conditons pretty cold as a light easterly flow will persist throughout the day. Highs will stay in the teens across our forecast area. Dry air aloft will keep the plains dry but the mountains will see light snow showers. A trough will cutoff and stall over the west coast of California with ridging developing ahead of it over Colorado on Friday. There will be temperature and height increases aloft which will allow surface temperatures to warm up as well. A few very light snow showers will be possible in the mountains with very little impact to travel. The ridge over Colorado amplifies on Saturday and our entire forecast area should see dry conditions. High temperatures warm above normal with mostly sunny skies. The cutoff trough finally makes its move eastward on Sunday bringing snow to the mountains of Colorado. Light to moderate snow amounts are expected. There will be south-southwesterly surface winds over the plains so it will be quite mild and dry there. Zonal flow will develop over Colorado early next work week with a chance for snow continuing in the mountains and dry weather across the plains. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1051 PM MST Tue Feb 21 2023 Winds should shift northerly between 07-08Z for all sites. There is agreement with the previous shift for the timing of the front arriving between 09Z-11Z for all terminals. Accumulating snowfall will likely begin near 12Z along runways for KDEN and KBJC terminals along with a decrease in visibility for LIFR conditions Wednesday morning. It is possible for snowfall rates to decrease Wednesday afternoon where a period of "on-and- off" flurries will occur thus expecting an increase in visibility near IFR and ceilings improving to 1-2k ft. near 20-21Z. There is potential for another round of snow showers coming off the foothills to terminals near 01Z Wednesday night but for now, there is low confidence in this outcome thus will keep VCSH for now. Snow should subside by 06Z at all terminals keeping northerly flow. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning until 5 AM MST Thursday for COZ031. Winter Storm Warning until 5 AM MST Thursday for COZ033. Winter Weather Advisory until 6 AM MST Thursday for COZ034. Winter Storm Warning until 8 PM MST Wednesday for COZ035-038-039- 042. Winter Weather Advisory from 2 AM to 8 PM MST Wednesday for COZ036-040-041-043>045-048-050-051. Wind Chill Advisory from 8 PM Wednesday to 9 AM MST Thursday for COZ038-042>044-048>051. Wind Chill Advisory from midnight Wednesday night to 9 AM MST Thursday for COZ039-040-045-046. && UPDATE...Mensch SHORT TERM...Gimmestad LONG TERM...Danielson AVIATION...AD
Hazardous Weather Outlook National Weather Service Denver/Boulder CO 1122 AM MST Tue Feb 21 2023 COZ030>051-221830- 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- 1122 AM MST Tue Feb 21 2023 ...SNOW AND COLDER WEATHER MOVING IN... This hazardous weather outlook is for northeast and north central Colorado. .DAY ONE...Today and Tonight West winds at 20 to 40 mph will continue over the mountains and foothills this afternoon. Gusts up to 60 mph can be expected above timberline in the Front Range. Light snow showers will develop over the mountains this afternoon, then more widespread snow will develop late tonight. Snow will spread from the Wyoming border south to about Denver during the late night hours, with some accumulation and travel impact beginning along the northern I-25 corridor before morning. .DAYS TWO THROUGH SEVEN...Wednesday through Monday A winter storm will affect the area through Wednesday evening. Expect heavy snow in the northern mountains, the northern foothills, and northern I-25 corridor. Expect light to moderate snow across the plains. The Wednesday morning and evening commutes will be impacted especially farther north. Temperatures will drop below zero across the entire forecast area Thursday morning. Wind chills will be between -15 to -25 so it will be wise to limit time outdoors. Thursday into this weekend, temperatures will increase for all areas while the plains will dry out. The mountains will continue to see a daily chance of snow. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today or tonight. Any snowfall reports will be appreciated. Gimmestad/Danielson
The national radar mosaic for the moment the first event began.
14 winter weather, 12 extreme cold/wind chill, 2 winter storm. Local standard time, as filed.
Storm totals included: 6 inches near Berthoud, 5 inches at Horsetooth Reservoir and Loveland, with 4 inches in Fort Collins.
Storm totals included: 6.7 inches at the National Weather Service in Boulder, 6.2 inches in southwest Golden, 5.8 inches in Lyons, with 3 to 5 inches elsewhere.
Storm totals included 14 inches near Silver Plume, with 3 to 6 inches elsewhere. A snow squall during the early afternoon hours on the 22nd, impacting the I-70 corridor from around Silverthorne to Frisco. Another snow squall impacted State Highway 40, west to Kremmling due to blowing snow and poor visibility.
Storm totals ranged from 3 to 6 inches.
Storm totals ranged from 3 to 6 inches.
Storm totals ranged from 3 to 6 inches.
Storm totals ranged from 1 to 4 inches.
Storm totals ranged from 2 to 4 inches.
Storm totals ranged from 2 to 4 inches.
Storm totals ranged from 1 to 4 inches.
Storm totals ranged from 1 to 3 inches.
Storm totals ranged from 2 to 4 inches.
Storm totals ranged from 2 to 4 inches.
Storm totals ranged from 2 to 4 inches.
Storm totals ranged from 3 to 7 inches.
Storm totals ranged from 2 to 4 inches.
During the morning hours on the 23rd, wind chill temperatures ranged from -25F to -35F.
During the morning hours on the 23rd, wind chill temperatures ranged from -25F to -35F.
During the morning hours on the 23rd, wind chill temperatures ranged from -25F to -35F.
During the morning hours on the 23rd, wind chill temperatures ranged from -25F to -35F.
During the morning hours on the 23rd, wind chill temperatures ranged from -25F to -35F.
During the morning hours on the 23rd, wind chill temperatures ranged from -25F to -35F.
During the morning hours on the 23rd, wind chill temperatures ranged from -25F to -35F.
During the morning hours on the 23rd, wind chill temperatures ranged from -25F to -35F.
During the morning hours on the 23rd, wind chill temperatures ranged from -25F to -35F.
During the morning hours on the 23rd, wind chill temperatures ranged from -25F to -30F.
During the morning hours on the 23rd, wind chill temperatures ranged from -25F to -30F.
During the morning hours on the 23rd, wind chill temperatures ranged from -25F to -35F.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2023Every state in 2023This day in weather historyWarnings in Colorado, February 2023
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: 1082191, 1082192, 1082193, 1083406, 1083407, 1083411, 1082195, 1082196, 1082197, 1082198, 1082199, 1082200, 1082201, 1082202, 1082216, 1083416, 1082204, 1082205, 1082209, 1082210, 1082211, 1082212, 1082213, 1082214, 1082215, 1082206, 1082207, 1082208.