Ample monsoonal moisture was in place on the afternoon of August 10, along with some modest upper level support in the form of passing shortwaves and an upper level jet. This scenario supported widespread strong to severe convection across the region, resulting in severe wind gusts as well as heavy rain that led to multiple debris flows.
Every event with a place to put it. 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.
Ample monsoonal moisture was in place on the afternoon of August 10, along with some modest upper level support in the form of passing shortwaves and an upper level jet. This scenario supported widespread strong to severe convection across the region, resulting in severe wind gusts as well as heavy rain that led to multiple debris flows.
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 10, 4:53 PM MST, 37 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Grand Junction CO 553 PM MDT Sat Aug 10 2024 .KEY MESSAGES... - Showers and thunderstorms continue each afternoon and evening until further notice with gusty outflow winds, small hail, and frequent lightning possible. - Heavy rain rates with storms will bring an enhanced threat of flash flooding and debris flows through the weekend and into early next week. Saturated soils and steep terrain will be most susceptible to flooding. - Temperatures will remain near to several degrees below normal thanks to the abundance of clouds and showers. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 215 PM MDT Sat Aug 10 2024 Another active afternoon across the Western Slope as we continue to be under the influence of this current monsoonal surge. After this morning's showers in southeast Utah convection has re-fired area-wide, favoring the higher elevations of course. Similar to previous days, we've already seen some impressive rainfall rates of at least one inch/hour as well as small hail and plenty of lightning. The strongest storms thus far have largely been up north as a 60 to 70 kt jet drapes across northeast Utah and northwest Colorado. This jet is expected to remain fairly stationary through the short term as the associated shortwave trough pushes across Idaho and Montana. Even as the jet stays farther north, stronger storms can still be expected across the southern tier of the forecast area. SPC Mesoanalysis projects MUCAPE of 500 to 1000 J/kg attm with pockets of 1500 to almost 2000 J/kg present across southeast Utah. Additionally, PWATs continue to remain anomalously high with over an inch available region-wide and we've even got some decent shear of 25 to 30 kts attm. So, all that to say, storms today will be capable of producing gusty outflow winds to 40 kts, small hail, frequent lightning, and heavy rain. Grounds are well saturated out there with portions of the forecast area receiving more than three quarters of an inch to over an inch of rain in the last 24 hours. As a result, the potential for flash flooding is high for those saturated soils, vulnerable steep terrain, and anywhere we get training of storms. As we head into the evening hours, the base of the previously mentioned trough will drag through eastern Utah and western Colorado. This will provide sufficient forcing for nocturnal showers and storms with CAM guidance projecting a line pushing into east-central Utah around 09Z before progressing southeast into southwest Colorado through mid Sunday morning. We'll have to see if/how much these lingering showers de-stabilize things going into Sunday afternoon but, for now, it looks like there will be sufficient clearing to fuel another round of scattered convection. Aiding in re-development will be the passage of yet another embedded shortwave. There is a 30% chance for SBCAPE to exceed 1000 J/kg for portions of the forecast area, but a 30 to 50% chance to see 800 J/kg most elsewhere. Similar threats of gusty winds, heavy rain and small hail can be expected, as well as the continued threat for localized flash flooding. Once again we can expect nocturnal showers Sunday night, though it will be more isolated to scattered in nature as the daytime shortwave exits to the east. Outside of showers and storms, dry and cooler than normal weather will prevail through the short term. && .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 215 PM MDT Sat Aug 10 2024 By early Monday the stronger westerlies look to retreat northward in the wake of digging trough into the Plains and an upstream trough arriving to the PacNW coast. This subtle shift in the pattern to a more southerly flow into the 4 Corners squeezing the monsoonal plume into our CWA. Ensemble return intervals and M-Climate signatures are now a bit more relevant for anomalous moisture and this could be enough to bring a more widespread flooding threat. The above mentioned jet has been an important source for focusing larger scale ascent for organized storm formation. With it shifting northward this focus may wane but this could lead to slower storm motion and the ability for northward drifting storms to train. There is also a shearing low pressure system over the Baja region early in the week...of which some of the energy will be pulled northward across the 4 Corners region over the robust moisture plume. This pattern remains static through early Wednesday before the energy rotating through the upstream PacNW trough allows the westerlies to float southward. Model PWAT time series suggest a drying trend as this occurs. Will it totally flush out the monsoon moisture...unlikely...but hopefully enough to catch a break from a flooding threat before another surge arrives by Thursday. It looks like a busy end to the week as the remaining pieces of the shearing southern low is pulled northward by the western trough moving farther into the Intermountain West. Overall temperatures look to hover just below normal under the moisture plume then push back to near normal for the drier mid week period. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 541 PM MDT Sat Aug 10 2024 Eastern Utah and Northwest Colorado will continue to see scattered showers and thunderstorms this evening. An approaching wave will send some of this activity eastward through the overnight hours, favoring the I-70 corridor. Terminals will see periods of breakpoint ceilings and visibility, as well as gusty winds and small hail with these storms. A lull in storms and showers towards daybreak is likely, but daytime heating is expected to bring showers and thunderstorms right back to the terrain, especially those areas still saturated from the overnight activity. && .HYDROLOGY... Issued at 215 PM MDT Sat Aug 10 2024 Monsoonal moisture will keep showers and thunderstorms over the region through at least mid next week. Most of the higher terrain across the region, especially the southern and central mountains, will see potential rainfall rates in excess of 1-2" per hour through this period. This will lead to increasing threats for flash flooding and debris flows across the majority of the area. Stay weather aware over the coming days, especially if recreating outdoors and in locations prone to flash flooding and debris flows, and stay tuned for forecast updates, as well as any Watches, Warnings, and Advisories over the coming days. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...Flood Watch until 9 PM MDT this evening for UTZ027. && SHORT TERM... LONG TERM...15 AVIATION...TGJT HYDROLOGY...TGJT
Hazardous Weather Outlook National Weather Service Grand Junction CO 454 AM MDT Sat Aug 10 2024 COZ001>014-017>023-UTZ022>025-027>029-111100- 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- 454 AM MDT Sat Aug 10 2024 This Hazardous Weather Outlook is for northwest Colorado, southwest Colorado, west central Colorado, east central Utah, northeast Utah and southeast Utah. .DAY ONE...Today and tonight. Showers and thunderstorms continue today. Storms will be capable of producing gusty outflow winds, small hail, and brief bouts of heavy rainfall. Localized flash flooding and debris flows are possible, mainly along and south of the I-70 corridor today and tonight. .DAYS TWO THROUGH SEVEN...Sunday through Friday. Chances for daily showers and storms continue Sunday into next week. The potential for heavy rainfall is a threat through mid next week with localized flash flooding and debris flows possible across the region. .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
547 PM MDT Sat Aug 10 2024
COZ001>003-110015-
Roan and Tavaputs Plateaus CO-Lower Yampa River Basin CO-
Central Yampa River Basin CO-
547 PM MDT Sat Aug 10 2024
...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN RIO BLANCO COUNTY
THROUGH 615 PM MDT...
At 547 PM MDT, Doppler radar was tracking a strong thunderstorm 27
miles south of Rangely, or 42 miles north of Grand Junction, moving
east at 20 mph.
HAZARD...Wind gusts up to 50 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
This storm will remain over mainly rural areas of southwestern Rio
Blanco County.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential 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 3967 10872 3978 10871 3981 10842 3959 10847
TIME...MOT...LOC 2347Z 273DEG 17KT 3970 10865
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH
MSPreliminary Local Storm Report
National Weather Service Grand Junction CO
551 PM MDT Sat Aug 10 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0435 PM Tstm Wnd Gst 2 ESE Manila 40.98N 109.68W
08/10/2024 M45 MPH Daggett UT AWOS
AWOS station K40U 2 ESE Manila.
&&Special Weather Statement
National Weather Service Grand Junction CO
615 PM MDT Sat Aug 10 2024
COZ001>003-007-110045-
Roan and Tavaputs Plateaus CO-Debeque to Silt Corridor CO-
Lower Yampa River Basin CO-Central Yampa River Basin CO-
615 PM MDT Sat Aug 10 2024
...A STRONG THUNDERSTORM WILL IMPACT WEST CENTRAL GARFIELD COUNTY
THROUGH 645 PM MDT...
At 615 PM MDT, Doppler radar was tracking a strong thunderstorm 27
miles northwest of De Beque, or 39 miles north of Grand Junction,
moving east at 30 mph.
HAZARD...Wind gusts up to 50 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
This storm will remain over mainly rural areas of west central
Garfield County.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 3959 10863 3973 10861 3973 10826 3953 10827
TIME...MOT...LOC 0015Z 272DEG 28KT 3965 10850
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH
LTBSpecial Weather Statement
National Weather Service Grand Junction CO
623 PM MDT Sat Aug 10 2024
UTZ027-110100-
Arches/Grand Flat UT-
623 PM MDT Sat Aug 10 2024
...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN GRAND COUNTY
THROUGH 700 PM MDT...
At 623 PM MDT, Doppler radar was tracking a strong thunderstorm 18
miles northwest of Moab, moving east at 30 mph.
HAZARD...Wind gusts up to 50 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
Arches National Park.
This includes the following highways...
Interstate 70 in Utah between mile markers 192 and 200.
U.S. Highway 191 in Utah between mile markers 138 and 153.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 3865 10988 3883 10996 3900 10951 3874 10939
TIME...MOT...LOC 0023Z 250DEG 26KT 3878 10975
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH
KJSSpecial Weather Statement
National Weather Service Grand Junction CO
627 PM MDT Sat Aug 10 2024
COZ001-003-UTZ025-110100-
Roan and Tavaputs Plateaus CO-Lower Yampa River Basin CO-
Tavaputs Plateau UT-
627 PM MDT Sat Aug 10 2024
...A STRONG THUNDERSTORM WILL IMPACT WEST CENTRAL GARFIELD COUNTY
THROUGH 700 PM MDT...
At 626 PM MDT, Doppler radar was tracking a strong thunderstorm 34
miles south of Rangely, or 42 miles northwest of Grand Junction,
moving east at 20 mph.
HAZARD...Wind gusts up to 50 mph and nickel size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation and
outdoor objects is possible.
This storm will remain over mainly rural areas of west central
Garfield County.
This includes Colorado 139 between mile markers 29 and 40.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 3955 10906 3969 10902 3966 10877 3950 10881
TIME...MOT...LOC 0026Z 290DEG 16KT 3961 10899
MAX HAIL SIZE...0.88 IN
MAX WIND GUST...50 MPH
LTBSpecial Weather Statement
National Weather Service Grand Junction CO
628 PM MDT Sat Aug 10 2024
UTZ022-028-029-110100-
La Sal and Abajo Mountains UT-Southeast Utah UT-
Canyonlands/Natural Bridges UT-
628 PM MDT Sat Aug 10 2024
...A STRONG THUNDERSTORM WILL IMPACT EAST CENTRAL SAN JUAN COUNTY
THROUGH 700 PM MDT...
At 628 PM MDT, Doppler radar was tracking a strong thunderstorm 17
miles west of Monticello, moving east at 20 mph.
HAZARD...Wind gusts up to 50 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
This storm will remain over mainly rural areas of east central San
Juan County.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 3782 10982 3807 10969 3802 10935 3767 10951
TIME...MOT...LOC 0028Z 279DEG 19KT 3787 10965
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH
KJSThe Grand Junction radar (KGJX), 79 km away, was scanning. The volume nearest the first event began at 00:30 UTC.
2 debris flow, 1 thunderstorm wind. Local standard time, as filed.
Heavy rain from a thunderstorm resulted in mud and small rocks across Highway 139 near Douglas Pass.
Highway 82 closed due to a mudslide as a result of heavy rain near Cattle Creek. Road was closed around 1941 on August 10th and remained closed until the morning of August 11th. This occurred approximately 2 miles northwest of Cattle Creek.
Despite the saturated atmospheric profile, the strong to severe storms that developed on the afternoon of August 10 that were capable of producing severe winds. The peak gust with this storm was 59 mph, recorded twice at KDRO ASOS at the Durango-La Plata County Airport. This storm also produced heavy rain. No reports of damages or injuries were received.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2024Every state in 2024This day in weather historyWarnings in Colorado, August 2024
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: 1208158, 1208159, 1208130.