A cold front and associated strong jet stream flow pushed through western Colorado and brought high elevation snow to some northern and central mountain areas of western Colorado.
Every event with a place to put it; 2 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 GJT wrote it up.
A cold front and associated strong jet stream flow pushed through western Colorado and brought high elevation snow to some northern and central mountain areas of western Colorado.
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 Sep 22, 10:35 PM MST, 4 hours 25 minutes earlier.
Area Forecast Discussion National Weather Service GRAND JUNCTION CO 1135 PM MDT Fri Sep 22 2017 .SHORT TERM...(Tonight through Saturday night) Issued at 222 PM MDT Fri Sep 22 2017 Gusty winds remain the main story this afternoon across the eastern Utah and western Colorado. The central Rockies are positioned on the eastern fringes of a deep trough centered over the northern Great Basin. The center of a 110 knot jet streak remains over the western slope, and afternoon mixing has allowed stronger wind gusts to descend once again today. Stronger wind gusts have been curtailed by considerable cloud cover, which has limited surface heating and resultant mixing to some extent. A diffuse frontal boundary is evident with in thermal fields around 700mb, and stretches from the central Wasatch range in Utah through the Uintas and into south-central Wyoming. Ahead of this boundary, numerous showers have developed in an environment characterized by 200-500 j/kg of SB CAPE and 30 knots of speed shear. Some isolated thunder has been noted north of the Tavaputs in northwest Colorado. A few weak thunderstorms will continue through early evening along with numerous quick-moving showers, before precipitation transitions to scattered showers overnight in the higher terrain as instability wanes. On Saturday, 700mb temperatures will drop by a few degrees as the mid-level frontal boundary moves east and fizzles over the central Rockies. Snow levels will descend to around 11-12 kft during the afternoon hours, and guidance has consistently indicated the potential for a few inches of snow above that elevation from Saturday afternoon through the evening and overnight. Lower elevations will experience another round of showers, which will be most common from the San Juans northward along the Divide, as well as in northwest Utah. Aloft, the western trough will cut off with an upper-level low remaining nearly stationary in central Utah. Southerly flow will favor the Uinta mountains for rain and higher elevation snowfall, with several inches possible on Saturday night through mid-day Sunday given proximity to the cold upper-level low and ample lift/moisture. .LONG TERM...(Sunday through Friday) Issued at 222 PM MDT Fri Sep 22 2017 Afternoon guidance is in good agreement showing the upper-level low shifting northeastward through the Uintas and into southern Wyoming on Sunday afternoon. Dry air will filter in south of Interstate 70, however one more day of unsettled weather is expected to the north before the low exits the Rockies. Sunday will feature the coolest weather during the forecast period as the upper low and trough axis pass over. Temperatures will run around 15 degrees below average. A consensus between MET and MAV MOS guidance was used for Sunday highs, and was adjusted downward based on 12z ECMWF ensemble guidance. If the ECMWF were to pan out, the Grand Valley may struggle to reach the 60 degree mark! Have not gone that low in this forecast package, however these notably low forecasts are worth noting for now. Lingering moisture along the Continental Divide and low heights will remain on Monday, enough that showers and an isolated rumble of thunder can not be completely ruled out of the forecast in the higher terrain. Elsewhere, a drying trend will set in. By Tuesday, our next weather disturbance will dive southward through the Great Basin. Forecast confidence decreases from Tuesday through the remainder of the week as major global models indicate another cut off upper-level low developing in the southwest. This low will keep things unsettled in the San Juans and Four Corner region. Overall, the trend of below average temperatures will continue into next week, although the airmass will not be quite as chilly as the fall preview in store for this weekend. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1135 PM MDT Fri Sep 22 2017 Spotty overnight showers will persist overnight though the threat of impacts to forecast terminals will be reduced. Meanwhile, ridgetop turbulence will persist over the next 24 hours. VFR conditions are most likely to continue throughout the forecast period, however some CIGS are likely to fall below ILS break points. Some riming or icing is possible as well with freezing temperatures lowering toward mountain top level overnight. Showers and thunderstorms increase on Saturday with a good chance for impacts at TAF sites including rain and strong outflow winds. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && SHORT TERM...MAC LONG TERM...MAC AVIATION...NL
Hazardous Weather Outlook National Weather Service GRAND JUNCTION CO 350 AM MDT Sat Sep 23 2017 COZ001>014-017>023-UTZ022>025-027>029-241000- 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- 350 AM MDT Sat Sep 23 2017 This hazardous weather outlook is for eastern Utah and western Colorado. .DAY ONE...Today and Tonight A passing cold front and strong jet stream overhead will produce scattered showers and thunderstorms across western Colorado today and this evening. Breezy conditions will continue through the period. .DAYS TWO THROUGH SEVEN...Sunday through Friday Expect a return to more unsettled weather as well as a significant cool down this weekend and next week as a cold front treks through the region which should lead to snow levels lowering in the mountains going into the weekend, especially further north. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
The national radar mosaic for the moment the first event began.
2 winter weather. Local standard time, as filed.
Generally 4 to 8 inches of snow was measured across the area.
Snowfall amounts of 6 to 9 inches were measured across the area above the 9000 foot level, including over 6 inches at the Grand Mesa Visitor's Center. Several vehicle accidents occurred on Colorado Highway 65 as a result of slick and snowpacked roads.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2017Every state in 2017This day in weather historyWarnings in Colorado, September 2017
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: 717950, 717949.