A persistent and unsettled northwesterly flow aloft brought yet another embedded upper level disturbance into the region that produced scattered to numerous showers and thunderstorms across western Colorado. Significant rainfall occurred with some storms and resulted in some flash flooding and mudslides.
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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 persistent and unsettled northwesterly flow aloft brought yet another embedded upper level disturbance into the region that produced scattered to numerous showers and thunderstorms across western Colorado. Significant rainfall occurred with some storms and resulted in some flash flooding and mudslides.
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 Aug 5, 1:47 PM MST, 1 hour 43 minutes earlier.
Area Forecast Discussion National Weather Service GRAND JUNCTION CO 247 PM MDT Sat Aug 5 2017 .SHORT TERM...(Tonight through Sunday night) Issued at 120 PM MDT Sat Aug 5 2017 A subtle 500mb shortwave trough continues to lift through the central Rockies this Saturday afternoon. Morning cloud cover from earlier precipitation has scattered out, and afternoon convection is initiating as expected over the higher terrain. The 12z GJT sounding sampled an atmosphere characterized by PWAT values of 1.01", 50-100 J/kg of CAPE (depending on your parcel choice), and 0-6km shear of 34 knots. CAM guidance was consistent throughout the morning in developing pockets of MUCAPE in the 750-1250 range. Combined with the sampled shear in the observed GJT morning sounding, parameter space would be conducive for a few stronger cells today, mixed in with the more run-of-the-mill daytime heating convection. The corridor with the best chances of seeing some isolated small hail and gusty winds this evening would be in the northern half of the CWA given stronger flow, and indeed that is where a few cells have already formed as of this discussion. Short term guidance keeps this area active through about 03z this evening, with the southern half of the CWA active until around 06z. The Sunday forecast appears more tranquil north of Interstate 70 as some drier air and light northwest flow works in. The focus for shower and thunderstorm development will shift to southeast Utah and southern Colorado as an elongated vort max heads northeastward out of Arizona and New Mexico. Short-term guidance focuses the best instability gradient south of a line from Moab to Ouray, and it is to the south of this corridor that we expect the greatest thunderstorm coverage for the second half of the weekend. PoPs have been adjusted upward in this forecast package to reflect these trends. .LONG TERM...(Monday through Saturday) Issued at 120 PM MDT Sat Aug 5 2017 The main player in the forecast for next week will be a weak subtropical jet that sets up over the southwestern CONUS, underneath a large ridge over the Pacific Northwest. The PACNW ridge will serve to block any major storm threats over the western CONUS during this timeframe. However, with faster southwest flow aloft remaining in place from southern California through Arizona, Utah, and Colorado, unsettled weather will continue over our region. As mentioned in previous discussions, PWAT values do not show any strong variation through the week, running just above 1 inch or so. Pinning down exactly which days will be most unsettled will likely come down to the timing of a few shortwave troughs skirting by to our east over the high plains, which would temporarily increase flow aloft and mid-level moisture values. The first one of these shortwaves looks to pass on Wednesday, with the second arriving perhaps on Friday. It is certainly possible that both of these systems will remain too far to our east to have any appreciable effect on thunderstorm chances, and forecast confidence is only moderate beyond Wednesday at this time. Regardless of exact precipitation trends, temperatures will run notably below average, especially early in the week. Confidence is high in the temperature forecast for the week ahead. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1126 AM MDT Sat Aug 5 2017 A few lingering showers persist over the San Juans but reported ceilings are hovering around 9K feet with light winds underneath. These showers will continue moving southeast but shouldn't pose any aviation threats. The usual convection will start firing shortly with another day of scattered showers and storms expected. The earlier rainfall may cause the convection to start a few hours later than usual but it is still expected. Like yesterday, some gusty winds and heavier downpours dropping visibilities briefly below 3 miles are possible. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && SHORT TERM...MAC LONG TERM...MAC AVIATION...TGR
Hazardous Weather Outlook National Weather Service GRAND JUNCTION CO 534 AM MDT Sat Aug 5 2017 COZ001>014-017>023-UTZ022>025-027>029-061200- 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- 534 AM MDT Sat Aug 5 2017 This hazardous weather outlook is for eastern Utah and western Colorado. .DAY ONE...Today and Tonight Scattered showers and thunderstorms are expected today and tonight across eastern Utah and western Colorado. Locally heavy rain, small hail and gusty winds to 40 mph are all possible with the strongest storms. .DAYS TWO THROUGH SEVEN...Sunday through Friday Isolated to scattered showers and thunderstorms are expected each day next week with gusty outflow winds, small hail and heavy rain possible. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected today or tonight, however spotters are encouraged to relay rainfall amounts or any observed flooding to the National Weather Service in Grand Junction.
Special Weather Statement National Weather Service Grand Junction CO 336 PM MDT SAT AUG 5 2017 COZ003-007-013-052215- Roan and Tavaputs Plateaus CO-Debeque to Silt Corridor CO- Flattops CO- 336 PM MDT SAT AUG 5 2017 ...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL GARFIELD COUNTY UNTIL 415 PM MDT... At 335 PM MDT, Doppler radar was tracking a strong thunderstorm 16 miles northwest of Rifle, or 34 miles northwest of Glenwood Springs, moving southeast at 10 mph. Dime size hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Rio Blanco. This includes Colorado 13 between mile markers 6 and 26. PRECAUTIONARY/PREPAREDNESS ACTIONS... Heavy rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 3969 10806 3985 10796 3978 10766 3954 10782 TIME...MOT...LOC 2135Z 297DEG 7KT 3974 10793 NL
Special Weather Statement
National Weather Service Grand Junction CO
347 PM MDT SAT AUG 5 2017
COZ002-003-013-052215-
Roan and Tavaputs Plateaus CO-Flattops CO-
Central Yampa River Basin CO-
347 PM MDT SAT AUG 5 2017
...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL RIO BLANCO COUNTY
UNTIL 415 PM MDT...
At 346 PM MDT, Doppler radar was tracking a strong thunderstorm 19
miles southwest of Meeker, or 43 miles northwest of Glenwood Springs,
moving northeast at 25 mph.
Nickel size hail and winds in excess of 40 mph will be possible with
this storm.
This storm will remain over mainly rural areas of south central Rio
Blanco County.
This includes Colorado 13 between mile markers 23 and 33.
This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
LAT...LON 3974 10810 3981 10816 3999 10792 3993 10784
3985 10780
TIME...MOT...LOC 2146Z 236DEG 24KT 3981 10808
CharnickSpecial Weather Statement National Weather Service Grand Junction CO 408 PM MDT SAT AUG 5 2017 COZ019>021-052300- Southwest San Juan Mountains CO- Paradox Valley/Lower Dolores River CO- Four Corners/Upper Dolores River CO- 408 PM MDT SAT AUG 5 2017 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN DOLORES AND WEST CENTRAL SAN MIGUEL COUNTIES UNTIL 500 PM MDT... At 408 PM MDT, Doppler radar was tracking a strong thunderstorm over Dove Creek, or 26 miles east of Monticello, moving north at 10 mph. Frequent cloud to ground lightning, dime sizehail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Dove Creek and Egnar. This includes the following highways... U.S. Highway 491 in Colorado between mile markers 53 and 66. Colorado 141 between mile markers 1 and 12. PRECAUTIONARY/PREPAREDNESS ACTIONS... Heavy rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 3767 10876 3769 10898 3795 10900 3792 10866 TIME...MOT...LOC 2208Z 186DEG 7KT 3776 10886 NL
Special Weather Statement National Weather Service Grand Junction CO 430 PM MDT SAT AUG 5 2017 COZ001-003-UTZ025-052315- Roan and Tavaputs Plateaus CO-Lower Yampa River Basin CO- Tavaputs Plateau UT- 430 PM MDT SAT AUG 5 2017 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN RIO BLANCO COUNTY UNTIL 515 PM MDT... At 429 PM MDT, Doppler radar was tracking a strong thunderstorm 28 miles southwest of Rangely, or 53 miles northwest of Grand Junction, moving southeast at 15 mph. Dime size hail and winds in excess of 40 mph will be possible with this storm. This storm will remain over mainly rural areas of southwestern Rio Blanco County. This includes Colorado 139 between mile markers 40 and 43. PRECAUTIONARY/PREPAREDNESS ACTIONS... Heavy rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 3973 10921 3985 10907 3965 10869 3965 10912 TIME...MOT...LOC 2229Z 307DEG 13KT 3975 10908 15
The Grand Junction radar (KGJX), 73 km away, was scanning. The volume nearest the first event began at 22:28 UTC.
2 debris flow, 1 flash flood, 1 heavy rain. Local standard time, as filed.
Colorado Highway 325 was closed in both directions in Rifle Gap between mile markers 6 and 8 due to a mudslide and flooding as a result of heavy rains. The Highway reopened 4 hours later.
After receiving 0.98 inches of heavy rain on August 4 and receiving another 1.20 inches throughout the whole day on August 5, flash flooding occurred. Rocks and other debris were washed across the pasture, into some trees, and also across the driveway due to the culverts running high. The debris and water flowing across the gravel driveway washed out a portion of the driveway. The siding on one of the outbuildings came off. Additionally, both the power and phone lines were out for a couple of hours. The Colorado Department of Transportation was out until 0200 on August 6 clearing the roads.
A mudslide occurred on County Road 5 near the intersection of Colorado Highway 13 as a result of heavy rains.
Flooding from Government Creek was reported to be impacting a residence near mile marker 8 along Colorado Highway 13 as a result of heavy rains.
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, August 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: 717934, 717941, 717936, 717938.