Freeze-thaw cycles after a period of significant rain and snowfall resulted in a debris flow onto Highway 40.
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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.
Freeze-thaw cycles after a period of significant rain and snowfall resulted in a debris flow onto Highway 40.
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 May 4, 12:58 AM MST, 9 hours 2 minutes earlier.
Area Forecast Discussion National Weather Service GRAND JUNCTION CO 158 AM MDT Thu May 4 2017 .SHORT TERM...(Today through Friday) Issued at 151 AM MDT Thu May 4 2017 A strong ridge will move over the area today and tonight with the ridgeline passing east of the area around sunset Friday. Winds aloft will remain from the NW through tonight and gradually weaken. As the ridgeline passes overhead Friday winds aloft will shift to to the southwest. The warming trend will continue through the period. .LONG TERM...(Friday night through Wednesday) Issued at 151 AM MDT Thu May 4 2017 Models were similar in driving the high pressure ridge farther east Friday night in response to a deepening, eastward propagating low pressure system moving ashore over the West Coast. The West Coast trough closes off on Saturday becoming centered over coastal southern California late in the day. Deep southerly flow develops ahead of the low drawing subtropical moisture from the Mexican plateau over the forecast area providing fuel for afternoon showers and thunderstorms. Expect moisture will initially arrive in the mid- levels of the atmosphere so it seems reasonable to expect relatively light precipitation. Higher elevations, especially in the southern and central Colorado mountains, will be favored areas for showers, though there is a slight chance that adjacent valleys could see some light rain reach the surface. Warm air advection will keep temperatures running well above normal which will, in turn, keep snow showers confined to areas above the timberline. Unsettled conditions are expected to impact the area through the remainder of the weekend and through midweek as the closed low slowly makes its way across the Desert Southwest. Sorting out the details appears a bit difficult at this point as GFS becomes the more progressive model taking the low center across northern Mexico Monday, then slowly northeastward across eastern Arizona to the Four Corners Tuesday, then over southwest Colorado Tuesday night into Wednesday. The ECMWF lags the GFS significantly and may be the better solution as model biases tend to move closed low pressure systems too quickly in most cases. In light of model differences, confidence in positioning and coverage of showers is low during the latter stages of the extended period. However, it does appear reasonable to forecast a trend toward cooler, more seasonable temperatures during the period as moisture continues to filter over the area fueling mainly afternoon/evening showers and thunderstorms which will limit solar insolation while providing diabatic cooling. && .AVIATION...(For the 12Z TAFS through 12Z Friday morning) Issued at 151 AM MDT Thu May 4 2017 VFR conditions will prevail across the area for the next 24 hours. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && SHORT TERM...CC LONG TERM...NL AVIATION...CC
Hazardous Weather Outlook National Weather Service GRAND JUNCTION CO 149 AM MDT Thu May 4 2017 COZ001>014-017>023-UTZ022>025-027>029-050800- 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- 149 AM MDT Thu May 4 2017 This hazardous weather outlook is for eastern Utah and western Colorado. .DAY ONE...Today and Tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Saturday through Tuesday: Breezy and slightly cooler with scattered afternoon and evening showers expected, mainly over the mountains. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
The national radar mosaic for the moment the first event began.
1 debris flow. Local standard time, as filed.
A debris flow consisting of dirt and boulders up to 20 feet in diameter came down onto Highway 40 and blocked the road for several hours.
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, May 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: 706462.