Abundant monsoon moisture remained across Western Colorado. This led to another round of showers and thunderstorms across much of the region.
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.
Abundant monsoon moisture remained across Western Colorado. This led to another round of showers and thunderstorms across much of the region. Storms were slow moving and produced heavy rain. As a result of the heavy rain, some flash flooding and debris flows occurred in both Garfield and Eagle counties. Additionally, some stronger storms produced large hail up to an estimated inch in diameter near Carbondale.
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 1, 4:42 AM MST, 4 hours 18 minutes earlier.
Area Forecast Discussion National Weather Service Grand Junction CO 542 AM MDT Tue Aug 1 2023 .SHORT TERM...(Today through Wednesday) Issued at 439 AM MDT Tue Aug 1 2023 As models had indicated over the past several runs, high pressure has settled over the southern Plains with southerly flow carrying subtropical moisture from the Gulf of Mexico and the Mexican Plateau over the forecast area. As a result, precipitable water values over eastern Utah and much of western Colorado ranged from an inch to around 1.2". This moisture surge fed numerous showers and thunderstorms on Monday with several reports of heavy rain with rates near one inch/hour. As of 10Z, an MCV over the eastern Tavaputs continued to generate showers and thunderstorms there, as well as over portions of the Grand Valley, eastern Uinta Basin and extreme northwest Colorado. A separate area of thunderstorm activity was moving across the northwest San Juans. It's likely that some of this activity will persist beyond sunrise. The pattern changes little today so the monsoonal moisture surge will continue over the region. This sets the stage for another round of widespread shower and thunderstorm activity with locally excessive rainfall likely. A weak short wave trough moving north- northeastward across western Utah may enhance thunderstorms along the northwestern edge of the forecast area and may give legs to nocturnal convection tonight. With ample moisture in place it won't take much to carry moist convection well into the night once again with northeast Utah and northwest Colorado favored. On Wednesday, the high over the southern Plains begins to expand west-southwestward across northern Mexico breaking off the moisture feed expectedfrom the south by shifting flow aloft to the southwest. In response, both GEFS and ECMWF ensembles indicated precipitable water levels will begin to decline with amounts ranging from 0.80 to 0.9" by the end of the day. Though this reduces the threat of excessive rainfall to some degree, it's still more than sufficient to generate another round of widespread shower and thunderstorm activity from late morning through the afternoon and into the evening. As expected, temperatures were cooler Monday and that trend continues today with highs dipping by 2 to 5 degrees for most locations with similar readings on Wednesday. Near normal lows are forecast tonight. .LONG TERM...(Wednesday night through Monday) Issued at 439 AM MDT Tue Aug 1 2023 With monsoonal moisture still advecting northeastward on Wednesday night, and an open wave still working through the Great Basin, expect shower and thunderstorm activity to linger into the overnight. Subsidence on the back side of the shortwave trough will work in for Thursday morning, bringing and end to the overnight convection and putting something of a limit on afternoon convection on Thursday. That said, plenty of deep subtropical moisture will still be in place over eastern Utah and western Colorado, meaning scattered showers and thunderstorms are still likely in the afternoon. In fact, the morning subsidence will allow for some extra sunshine and potentially pump up the available instability, meaning potentially stronger storms in the afternoon. While all this is going on in our neck of the woods, the subtropical high pressure will be starting to retrograde out of the Southern Plains and back into the Desert Southwest. By Friday morning, drier air will begin advecting into the Four Corners region. This forecaster doesn't quite buy how quickly models want to push much below normal PWAT values into eastern Utah and western Colorado, as models are notorious for trying to dry things out far too quickly during the monsoon season. That said, there will be drier air moving in all the same and it will lead to decreasing shower and storm coverage starting with the Four Corners region and working its way north through the weekend. Best coverage for showers and storms will remain north of the I-70 corridor, where moisture will hang on the longest, and where the influence of waves moving across the northern Rockies will be felt strongest. With such a blocky, highly amplified pattern, forecast confidence is low by early next week. Monday appears likely to see similar conditions as earlier in the weekend, but this has potential to change dramatically in the coming days as models get a better hold on the pattern for early next week. Overall, expect continued unsettled conditions, but with slightly drier conditions and lower storm coverage. Despite the return of the high pressure to the Desert Southwest, the unusual heat seen previously isn't forecast to make a comeback. Long term guidance is all in good agreement that temperatures will remain near normal through the period. This means highs in the low to mid 90s for the desert valleys, upper 70s to low 80s for the higher valleys, and 60s for the mountain towns. Low temperatures will likewise be within a few degrees of normal through the long term period. && .AVIATION...(For the 12Z TAFS through 12Z Wednesday morning) Issued at 542 AM MDT Tue Aug 1 2023 The ongoing surge of monsoon moisture and weak lift associated with a disturbance in the upper level flow sustained broad areas of showers and a few embedded thunderstorms early this morning. This activity was mainly over northwest Colorado and northeast Utah. Thunderstorms will again become widespread today, likely impacting most TAF sites during the afternoon and evening. VFR conditions will largely prevail, however brief MVFR visibility with stronger cells is likely at all TAF sites due to heavy rain this afternoon through the evening. Showers are likely to continue late tonight, but potential impacts on TAF sites is low. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && SHORT TERM...NL LONG TERM...BGB AVIATION...NL
Hazardous Weather Outlook National Weather Service Grand Junction CO 315 AM MDT Tue Aug 1 2023 COZ001>014-017>023-UTZ022>025-027>029-020915- 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- 315 AM MDT Tue Aug 1 2023 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 will increase in coverage and intensity again today as temperatures warm and the moist airmass destabilizes. Though decreasing in intensity, showers and thunderstorms are expected to persist through the night. The main threat from thunderstorms are localized excessive rainfall and lightning. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Widespread shower and thunderstorm activity will continue through midweek with concerns for localized flash flooding due to excessive rainfall peaking Wednesday and Thursday. Shower/thunderstorm activity will decrease beyond Thursday as drier air begins to filter into the region from the west. .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.
The Grand Junction radar (KGJX), 133 km away, was scanning. The volume nearest the first event began at 15:57 UTC.
1 debris flow, 1 hail, 1 flash flood. Local standard time, as filed.
A mudslide occurred up Sneve Gulch at Sylvan Lake as a result of heavy rain from thunderstorms.
Hail estimated to be an inch in diameter was reported on social media from Carbondale.
The Garfield County Sheriff's office reported flash flooding in portions of Carbondale as a result of heavy rain from thunderstorms.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2023Every state in 2023This day in weather historyWarnings in Colorado, August 2023
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: 1105498, 1105506, 1105497.