Monsoon moisture increased across the Four Corners region as a shortwave disturbance lifted overhead. This led to an uptick in shower and thunderstorm activity.
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The episode as NWS GJT wrote it up.
Monsoon moisture increased across the Four Corners region as a shortwave disturbance lifted overhead. This led to an uptick in shower and thunderstorm activity. Storms were slow moving and produced heavy rain which led to localized flash flooding in portions of San Juan County.
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 26, 1:47 PM MST, 1 hour 43 minutes earlier.
Area Forecast Discussion National Weather Service Grand Junction CO 247 PM MDT Fri Aug 26 2022 .SHORT TERM...(Tonight through Saturday night) Issued at 247 PM MDT Fri Aug 26 2022 Low stratus eroded quickly across eastern Utah and much of western Colorado this morning, allowing convection to flourish atop all exposed mountain ranges. In addition, current mesoanalysis places a shortwave trough straddling over the UT/CO border. The combination of diurnal heating and dynamic lift sliding across the region has expanded the areal coverage of storms today. In addition, this morning's sounding recorded 1.06 inches of precipitable water over KGJT, an indication of ample monsoonal moisture available to fuel convection. As a result, stronger cells have produced heavy rain rates, up to 1 inch per hour, and training storms have dropped persistent rainfall along terrain south of the I-70 corridor. Both of these environments are conducive to flooding over vulnerable areas. So, please heed any closures and monitor updated flooding headlines, especially if downstream/near steep terrain, impervious surfaces and/or recent burn scars. CAM guidance has shown consistent trends pushing storms along the trough's trajectory as the system slides southeast across the area. Then, subsidence in the wake of the trough will result in clearing conditions from northwest to the east- southeast. Therefore, do not anticipate much nocturnal convection tonight, as the trough is progged to move east of the Divide by midnight. Today's parting shortwave will be succeeded by a ridge building back over the CWA. Anticyclonic flow directly overhead will continue to pull monsoonal moisture across Arizona and New Mexico, though, the plume weakens to the north. Any remaining moisture will trickle into Utah and western Colorado, keeping PWATs at or just above normal. As a result, residual moisture will still be efficient enough to fuel another round of afternoon convection on Saturday. Storm coverage will be more isolated to scattered in nature, and driven by diurnal heating due to the lack of dynamic support aloft. Overall, expect a downturn in comparison to this afternoon, with storms diminishing after sunset. Temperatures trend upward on Saturday, under the influence of ridging. However, clearing conditions overnight do favor radiational cooling. Therefore, low temperatures remain steady, if not drop a few degrees, despite warm air advection. .LONG TERM...(Sunday through Friday) Issued at 247 PM MDT Fri Aug 26 2022 On Sunday, we will start to feel the influence of a shortwave tracking over the Northern Plains. It will shift flow to the west- northwest allowing for drier air to filter into the area. With a lack of forcing residual moisture may be enough to support convection over the higher terrain in the afternoon. There looks to be even less coverage of storms on Monday as that dry air settles into the area. Attention then turns to a weak shortwave moving over the Great Basin. It could account for some moisture return, but the models are not agreeing on where it may actually track. If moisture can increase with southerly flow ahead of the wave then we may see an uptick in convection. It will be moving into a ridge building overhead so some solutions take this wave up into the Northern Rockies. One thing that is more likely will be warmer than normal temperatures with the ridge building over our region. Daily afternoon storms may develop in the mountains most of next week, and highs will run 3 to 8 degrees above normal. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 1054 AM MDT Fri Aug 26 2022 Showers and storms will develop over the next few hours. Expect widespread storms over the mountains and isolated to scattered storm in the valleys. Expect possible heavy rain causing localized MVFR conditions, obscured peaks and gusty outflow winds associated with these storms. The showers and thunderstorms will end west to east through the late afternoon and evening with skies becoming partly cloudy overnight. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Flash Flood Watch until 9 PM MDT this evening for COZ008-010-013. UT...None. && SHORT TERM...ERW LONG TERM...KJS AVIATION...TGJT
Hazardous Weather Outlook National Weather Service Grand Junction CO 415 AM MDT Fri Aug 26 2022 COZ001>014-017>023-UTZ022>025-027>029-271015- 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- 415 AM MDT Fri Aug 26 2022 This hazardous weather outlook is for eastern Utah and western Colorado. .DAY ONE...Today and Tonight Expect widespread showers and thunderstorms over the higher terrain and isolated to scattered storms elsewhere today as the monsoonal surge continues for one more day. Heavy or persistent rainfall will be primary threat with slow moving storms to the south and possible training storms to the north. Look for stronger outflow winds likely across northern portions of eastern Utah and western Colorado. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Thunderstorm development Saturday will be mostly over the mountains of central and southern Colorado and along the Divide Sunday. Monday onward will have isolated thunderstorms only along the Divide with sunny warm conditions across the rest of Western Colorado and eastern Utah. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
Special Weather Statement
National Weather Service Grand Junction CO
340 PM MDT Fri Aug 26 2022
COZ006-017-262230-
Uncompahgre Plateau/Dallas Divide CO-Grand Valley CO-
340 PM MDT Fri Aug 26 2022
...A strong thunderstorm will impact portions of west central Mesa
County through 430 PM MDT...
At 340 PM MDT, Doppler radar was tracking a strong thunderstorm 7
miles southwest of Fruita, or 13 miles west of Grand Junction, moving
southeast at 15 mph.
HAZARD...Wind gusts up to 50 mph and penny size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Grand Junction.
This includes the following highways...
Interstate 70 in Colorado between mile markers 16 and 17.
U.S. Highway 50 in Colorado between mile markers 32 and 39.
Colorado 141 near mile marker 157.
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 3903 10895 3918 10881 3901 10845 3880 10867
TIME...MOT...LOC 2140Z 308DEG 12KT 3906 10881
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH
ERWThe Grand Junction radar (KGJX), 224 km away, was scanning. The volume nearest the first event began at 22:31 UTC.
1 flash flood. Local standard time, as filed.
Portions of the 9-mile scenic loop drive in Natural Bridges National Monument received flash flooding as a result of heavy rain from thunderstorms. The road was closed until debris was cleared the next day.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Utah in 2022Every state in 2022This day in weather historyWarnings in Utah, August 2022
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: 1041741.