A midlevel shortwave trough trekked across the region. This feature tapped into residual moisture to produce scattered showers and thunderstorms.
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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 midlevel shortwave trough trekked across the region. This feature tapped into residual moisture to produce scattered showers and thunderstorms. The stronger storms produced gusty winds in excess of 58 mph across portions 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 Aug 6, 10:34 AM MST, 1 hour 23 minutes earlier.
Area Forecast Discussion National Weather Service Grand Junction CO 1134 AM MDT Fri Aug 6 2021 .SHORT TERM...(Today through Saturday) Issued at 446 AM MDT Fri Aug 6 2021 As mentioned in previous discussions a Pacific trough moving over the Great Basin early this morning has forced the mid-level high pressure ridge east of the area. Lift ahead of the approaching trough has resulted in scattered clouds above 20,000 ft ASL. Models remained consistent in moving the trough axis eastward over western Utah this afternoon. The pressure gradient increases as the cold front associated with this system moves to northeast Utah late this afternoon generating strong southwest winds across the forecast area. In addition, dynamic forcing coinciding with peak heating is expected to generate scattered high based showers and thunderstorms over the higher terrain. Given strength of the steering winds aloft, developing storms will be fast moving and the dry subcloud layer will limit the amount of rainfall which reaches the ground. Therefore, the threat of localized heavy rain producing excessive runoff or debris/mud flows is low. Meanwhile, the change in flow to the southwest will begin to erode smoke coverage across the region today. The trough axis moves to the Continental Divide late tonight and subsidence on the backside of this system combined with diurnal cooling is expected to bring an end to shower/thunderstorm activity this evening. Winds will decrease in the evening as mixing depth decreases with a shift in direction to the northwest with frontal passage. Subsidence continues Saturday as a shallow shortwave ridge develops in the wake of the trough which will yield an inversion aloft. Cooler temperatures, drying and the inversion are expected to inhibit moist convection Saturday, so quiet conditions are expected to prevail. Above normal temperatures persist today ahead of the approaching cold front. It's unlikely the front will reach northeast Utah before temperatures peak, so don't expect any significant changes in afternoon highs. However, clearing later tonight combined with cold air advection should yield cooler than normal morning lows and near, or a little below normal highs Saturday afternoon. .LONG TERM...(Saturday night through Thursday) Issued at 446 AM MDT Fri Aug 6 2021 Conditions could be a bit breezy across the north Sunday as another weak shortwave associated with an upper level trough moves across the Intermountain West and Northern Rockies. This trough stays north of us with dry conditions expected into early next week with above normal temperatures returning Sunday and beyond. Previous model runs were hinting at potential return of monsoonal moisture mid to late next week. However, latest model guidance and ensembles seem to favor a ridge of high pressure building back over the region or further west over the Great Basin, with moisture becoming suppressed to the south of the Four Corners, pooling in Arizona and New Mexico. This is likely due to the trough moving across the Intermountain West and Northern Rockies, helping suppress the high farther south and west. Regardless, the best potential for any convection may be across the southern mountains and up the southern/central Divide mid to late next week, as some moisture tries to sneak in under the high, but most areas look to remain dry. Low confidence in potential moisture return as there are still differences in placement of the high and subtle features that would trigger convection. Sticking with the ensembles which favor the ridge of high pressure maintaining its position over the Great Basin and drier conditions with isolated afternoon convection favoring high terrain along the divide. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 1130 AM MDT Fri Aug 6 2021 Strong, gusty winds are expected for all TAF sites this afternoon and into the evening hours as a disturbance swings through. Increasing clouds are also expected through the afternoon, along with some showers and thunderstorms for mountain TAF sites. The main threat with any storms that do form will be erratic, gusty outflow winds. Winds and clouds will decrease overnight. Tomorrow will see clear skies and winds following typical terrain driven patterns. VFR conditions will prevail for the next 24 hours. && .FIRE WEATHER... Issued at 446 AM MDT Fri Aug 6 2021 Conditions shift today with strong prefrontal winds developing across much of the region by midday. In combination with already drying low levels, critical conditions will be reached for areas with susceptible fuels. Therefore, Red Flag Warnings for the areas determined critical in coordination with fuel specialists will continue. Winds taper off by 8 PM MDT with a wind shift to the northwest occurring with frontal passage overnight. Through the weekend, localized fire weather conditions may recur each afternoon while high pressure remains suppressed to the south and a series of troughs pass north of the region. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Red Flag Warning until 8 PM MDT this evening for COZ200-202-203. UT...Red Flag Warning until 8 PM MDT this evening for UTZ490. && SHORT TERM...NL LONG TERM...MDA AVIATION...BGB FIRE WEATHER...TGJT
Hazardous Weather Outlook National Weather Service Grand Junction CO 453 AM MDT Fri Aug 6 2021 COZ001>014-017>023-UTZ022>025-027>029-071100- 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- 453 AM MDT Fri Aug 6 2021 This hazardous weather outlook is for eastern Utah and western Colorado. .DAY ONE...Today and Tonight Hot and dry conditions combine with strong southwest winds today leading to critical fire weather conditions across northwest and west-central Colorado and east-central Utah. A Red Flag Warning remains in effect for those areas from noon to 8 PM this evening. In addition, scattered showers and thunderstorms will develop this afternoon, though mainly over the mountains. Relatively fast moving, high based storms are unlikely to generate heavy rain, so the flash flood and mud/debris slide potential is low. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Precipitation chances remain low this weekend through the middle of next week. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1204 PM MDT FRI AUG 6 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1134 AM NON-TSTM WND GST DOUGLAS PASS 39.60N 108.81W
08/06/2021 M45 MPH GARFIELD CO MESONET
MESONET STATION CO098 139S034 DOUGLAS PASS.
&&
LTBThe Grand Junction radar (KGJX), 171 km away, was scanning. The volume nearest the first event began at 18:55 UTC.
6 thunderstorm wind. Local standard time, as filed.
A peak wind gust of 58 MPH was measured by the automated weather station at the Craig-Moffat County Airport.
A peak wind gust of 58 MPH was measured by the automated Mesonet weather station 1 mile north of Dowd.
A peak wind gust of 60 MPH was measured by the automated weather station at the Craig-Moffat County Airport.
A peak wind gust of 64 MPH was measured by the automated Mesonet weather station at Douglas Pass.
A peak wind gust of 66 MPH was measured by the automated weather station at the Craig-Moffat County Airport.
A peak wind gust of 58 MPH was measured by the automated weather station at the Meeker Coulter Field Airport.
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, August 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: 965551, 965552, 965555, 965554, 967179, 965556.