A progressive mid-level Pacific trough trekked across western Colorado and produced moderate snow over the northern mountains and some adjacent valleys. Heavier snow bands developed as a result of moderate instability which led to reduced visibility in blowing snow.
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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 GJT wrote it up.
A progressive mid-level Pacific trough trekked across western Colorado and produced moderate snow over the northern mountains and some adjacent valleys. Heavier snow bands developed as a result of moderate instability which led to reduced visibility in blowing snow.
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 Grand Junction, CO wrote its last area forecast discussion before the first event at Jan 4, 10:26 PM MST, 4 hours 34 minutes earlier.
Area Forecast Discussion National Weather Service Grand Junction CO 1026 PM MST Mon Jan 4 2021 .SHORT TERM...(Tonight through Tuesday night) Issued at 255 PM MST Mon Jan 4 2021 Mid and upper-level clouds have drifted eastward into eastern Utah and western Colorado this Monday afternoon. These clouds mark the arrival of our next minor winter weather event, set to move through the western slope tonight through Tuesday. Clouds will continue to thicken this evening and overnight as a shortwave trough dives through the northern Rockies. Light snow is expected to arrive in the mountains of northeast Utah after midnight and will spread east along the higher terrain of the US 40 corridor overnight through the predawn hours on Tuesday. A few trends have been noted with this event in recent mesoscale model runs. First, the opportunity for intense convective snow on the front end of this event appears notably lower. Forecast soundings do not show much instability (by winter standards) as the front passes, partly due to poor timing in the mid-morning hours, and partly due to weaker dynamics aloft. Mid-level frontogenesis fields as well as surface convergence are a bit lacking in comparison to some of the more notable frontally-forced snow squall events of late. The NAM remains more bullish for a brief mid-morning window for SNSQ parameter space in northern Colorado, however even the latest extended HRRR runs do not indicate much in the way of surface banding. Therefore, confidence is only low to moderate for intense snow squalls to materialize. The other trend is for a slightly more extended period of broad, light to moderate snowfall behind the front after it passes early Tuesday morning. Model QPF totals have increased by around 10% or so today, and snow totals in the current advisory for the Park Range are on the upper-end of advisory criteria. Consideration was given for an advisory for the Flat Tops as well, however will hold off until the evening to see if the upward model trends continue. The I-70 corridor from Vail to Vail Pass should also see around 3-5 inches of snow - not quite enough for winter highlights but certainly enough for some minor travel issues on Wednesday. The lower valleys from I-70 southward will not see much if anything from this event, with only a trace or less in Grand Junction, Montrose, and Gunnison. Flow will turn northwesterly on Tuesday afternoon with light snow coming to an end in the mountains overnight. Skies will clear quickly leading to a pretty cold night with lows running 5 to 10 degrees below average. .LONG TERM...(Wednesday through Monday) Issued at 255 PM MST Mon Jan 4 2021 By Wednesday morning, Tuesday's shortwave will have ejected eastward and will be in the process of closing off and digging into the central and southern Plains. In its wake, high pressure at the surface and aloft will build into the Great Basin and Four Corners. As a result, expect a return to quiet and tranquil weather under a mostly sunny sky. High temperatures will be within a few degrees either side of normal. The next shortwave trough we are watching lifts out of the Pacific Northwest and into the Intermountain West on Thursday. The 12Z deterministic runs of the GFS, CMC and NAM12 all keep this feature well to the north of the forecast area while only allowing for a few light snow showers across the far northern mountains. This solution is further supported by the 12Z GEFS. On the other hand, the 12Z ECMWF, EPS and GEPS all depict a stronger and deeper wave with more widespread precipitation farther south into the CWA. Given the model discrepancies at present, opted to continue with a blended solution for the time being. With that being said, even if the stronger/deeper solution came to fruition, not looking at much more than a minor event with sub-advisory snowfall amounts. Temperatures on Thursday will remain near normal. After that, much of the day on Friday is looking dry as shortwave ridging briefly returns. Quick on its heels, attention then turns to Friday night into Saturday when the potential for a more substantial storm comes into play. The deterministic runs of the ECMWF, GFS and CMC are all advertising a strong shortwave trough digging into the Great Basin and Four Corners region before closing off. While the means of their respective ensemble suites are smoothing out the details at this range, all are now hinting at a closed low solution. Still some time for details to become clearer, but its looking like Saturday will be active with potentially significant winter weather, especially in the higher elevations. Sunday likely sees improving conditions with just some lingering light snow showers in the mountains near the Continental Divide. Beyond that, another system is possible either Monday or Tuesday of next week. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1026 PM MST Mon Jan 4 2021 Mid and high level cloudiness spreading across E.Utah and W.Colorado ahead of the next system moving in early tomorrow. The biggest impacts appear to be over the ski country TAFs as the the lower valley terminals should stay VFR...though temporary ILS conditions are possible. KHDN to KEGE to KASE appear to be most under the gun with MVFR or below likely to occur by mid morning with KASE forecast to hit mins by 17Z. Improvement looks to arrive by mid afternoon as this systems translates to the Plains. Some post frontal winds could bring some gusts over 25 mph in some areas behind the system by 20Z. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Winter Weather Advisory until 5 PM MST Tuesday for COZ004. UT...None. && SHORT TERM...MAC LONG TERM...MDM AVIATION...TGJT
Hazardous Weather Outlook National Weather Service Grand Junction CO 503 AM MST Mon Jan 4 2021 COZ001>014-017>023-UTZ022>025-027>029-051400- Lower Yampa River Basin-Central Yampa River Basin- Roan and Tavaputs Plateaus-Elkhead and Park Mountains- Upper Yampa River Basin-Grand Valley-Debeque to Silt Corridor- Central Colorado River Basin-Grand and Battlement Mesas- Gore and Elk Mountains/Central Mountain Valleys- Central Gunnison and Uncompahgre River Basin- West Elk and Sawatch Mountains-Flat Tops- Upper Gunnison River Valley-Uncompahgre Plateau and Dallas Divide- Northwest San Juan Mountains-Southwest San Juan Mountains- Paradox Valley/Lower Dolores River- Four Corners/Upper Dolores River-Animas River Basin- San Juan River Basin-Southeast Utah-Eastern Uinta Mountains- Eastern Uinta Basin-Tavaputs Plateau-Arches/Grand Flat- La Sal and Abajo Mountains-Canyonlands/Natural Bridges- 503 AM MST Mon Jan 4 2021 This hazardous weather outlook is for eastern Utah and western Colorado. .DAY ONE...Today and Tonight Fog is possible across portions of northeast Utah and northwest Colorado this morning with improvement this afternoon. Light snow showers will develop over the northwest Colorado mountains overnight tonight. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Snow showers will continue, generally over the northern and central mountains, through Tuesday afternoon. Blowing snow could reduce visibility. The unsettled weather pattern looks to continue with disturbances moving into the region every few days bringing periodic light snow showers and increased clouds through the weekend. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
The national radar mosaic for the moment the first event began.
3 winter weather. Local standard time, as filed.
Generally 5 to 12 inches of snow fell across the area with up to 14 inches estimated at the Tower SNOTEL site. Winds gusted up to 47 mph at times.
Generally 2 to 6 inches of snow fell across the area. Winds gusted up to 33 mph at times which led to blowing snow and some hazardous travel conditions along Colorado Highway 40.
Generally 5 to 8 inches of snow fell across the area.
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, January 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: 927876, 927877, 927878.