Ample residual moisture lingered across west-central Colorado. This led to another round of diurnally-driven showers and thunderstorms, favoring the mountains along the Divide.
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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.
Ample residual moisture lingered across west-central Colorado. This led to another round of diurnally-driven showers and thunderstorms, favoring the mountains along the Divide. Some storms produced heavy rain. One such storm produced localized flooding in a portion of Eagle 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 27, 10:54 AM MST, 3 hours 6 minutes earlier.
Area Forecast Discussion National Weather Service Grand Junction CO 1154 AM MDT Sun Aug 27 2023 .SHORT TERM...(Today through Monday) Issued at 140 AM MDT Sun Aug 27 2023 A few isolated showers and storms are still holding on this morning over the northern and central Divide mountains. These should dissipate by daybreak. A quiet morning will give way to scattered showers and thunderstorms firing off the higher terrain. Ample moisture is expected to remain in the lower levels across western Colorado, so the threat of heavy rain and flash flooding continues. Across eastern Utah, drier surface air will gain a foothold, limiting storm coverage and moving the main threats more toward gusty outflow winds and lightning. Storm motions are expected to be slow thanks to high pressure nearly directly overhead, with storms remaining tied to the terrain at least to start with. As the afternoon progresses and the initial round of storms decay, showers and storms will begin to fire off their outflow boundaries. This makes predicting storm propagation difficult, so if recreating outdoors this afternoon and evening, keep a close eye on the sky and be sure to check for forecast updates or warnings and advisories. Storms will linger longest along the Divide once again tonight, before dissipating around midnight. By Monday, drier northwest flow will continue to erode the moist surface layer as the center of the high continues to drift to the west. The drier air will decrease afternoon storm coverage and limit the threat of heavy rains. Best coverage for Monday afternoon will be along the Divide once again, although a few showers and storms firing off the terrain further west is not out of the question. As far as temperatures are concerned, highs today will be near normal once again, with lows remaining near to a few degrees above normal. Temperatures begin to creep up starting tomorrow as conditions dry out and high pressure stays in charge. .LONG TERM...(Monday night through Saturday) Issued at 140 AM MDT Sun Aug 27 2023 Northwest flow will persist aloft across eastern Utah and western Colorado Monday night and continuing through Tuesday as the ridge remains centered over SoCal. This will result in drier and warmer conditions, though residual moisture may fuel isolated storms over the San Juan Mountains Tuesday afternoon. Flow will shift to the west Tuesday night through Wednesday as an upper level trough digs into the Pacific Northwest. This will de-amplify the ridge while also nudging its center slightly east over southern Arizona. As a result, dry weather will prevail across the Western Slope though continued pockets of near normal PWATs will likely fuel a high-based storm or two over the southern mountains. The main thing to monitor during the midweek period will be the potential for stronger winds as the jet rounding the upstream parent trough begins to tighten the gradient overhead. The drier air will see humidities drop back into the low to mid teens for many of the lower desert valleys as highs return to the mid to upper 90s. Therefore, localized areas of near critical fire conditions cannot be ruled out. Troughing will become more pronounced Thursday onwards as the first system lifts across the Dakotas while a second low drops south from the Gulf of Alaska. This will gradually shift flow aloft to the southwest across our forecast area, deflecting the high's center farther east across the Desert Southwest. Late Thursday but more-so Friday is when the high looks to arrive in the Southern Plains, also known as the more classic monsoon setup for us here on the Western Slope. Extended guidance has become better aligned for this late week period, keeping the high to our east while the low dominates the West Coast. This will usher in a notable push of subtropical moisture in the south/southwesterly flow with PWATs projected to climb back to well above normal by the week's end. Therefore, after a drier start to the long term period, a transition to a cooler, more unsettled pattern looks promising for its end. && .AVIATION...(For the 18Z TAFS through 18Z Monday afternoon) Issued at 1154 AM MDT Sun Aug 27 2023 Shower and thunderstorm development will increase through the afternoon as we use the remaining moisture before drier moves in for early next week. Storms will favor the terrain early on with a southerly drift and this means KRIL/KEGE/KDRO and the mountain TAF sites will be favored to see a storm pass nearby. Gusty winds will be the main threat and think flight conditions will stay above VFR...with a low probability of ILS conditions. Most activity will settle down by mid evening with less coverage expected on Monday with the Colorado High Country the favored location for storms. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && SHORT TERM...BGB LONG TERM...MMS AVIATION...15
Hazardous Weather Outlook National Weather Service Grand Junction CO 302 AM MDT Sun Aug 27 2023 COZ001>014-017>023-UTZ022>025-027>029-280915- 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- 302 AM MDT Sun Aug 27 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. Scattered showers and thunderstorms will fire off the terrain once again this afternoon, with a few storms capable of producing heavy rain and flash flooding. Other storm threats include gusty winds and frequent lightning. These showers and storms will taper off after sunset. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Drier air moving in from the northwest will day by day decrease shower and storm coverage, as well as severely limiting the heavy rain threat. A chance of storms will remain each afternoon through the week though, with gusty winds and lightning being the main threats. Monsoonal moisture returns for the weekend. .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.
Preliminary Local Storm Report
National Weather Service Grand Junction CO
1234 PM MDT Sun Aug 27 2023
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0900 AM Rain 3 SW Colona 38.24N 107.79W
08/27/2023 M1.35 inch Ouray CO Cocorahs
Cocorahs station CO-OR-15 Colona 3SW.
0630 AM Rain 3 E Milner 40.49N 106.96W
08/27/2023 M1.29 inch Routt CO Mesonet
Mesonet station FW5702 Steamboat Springs.
1215 PM Rain 2 ENE Rico 37.70N 108.00W
08/27/2023 M1.16 inch Dolores CO Mesonet
Mesonet station EW6434 Rico.
0700 AM Rain 3 NNW Ridgway 38.20N 107.77W
08/27/2023 M1.14 inch Ouray CO Cocorahs
Cocorahs station CO-OR-13 Ridgway 3.3NNW.
0700 AM Rain 1 SSW Durango 37.27N 107.87W
08/27/2023 M1.09 inch La Plata CO Cocorahs
Cocorahs station CO-LP-22 Durango 0.8SSW.
0630 AM Rain 2 ENE Rico 37.70N 108.00W
08/27/2023 M1.08 inch Dolores CO Mesonet
Mesonet station EW6434 Rico.
0700 AM Rain Rico 37.69N 108.03W
08/27/2023 M1.05 inch Dolores CO Cocorahs
Cocorahs station CO-DR-15 Rico 0.4 N.
0700 AM Rain 2 NNW Ridgway 38.19N 107.77W
08/27/2023 M1.02 inch Ouray CO Cocorahs
Cocorahs station CO-OR-27 Ridgway 2.4 NNW.
0457 AM Rain 1 ESE Durango 37.28N 107.85W
08/27/2023 M0.97 inch La Plata CO Cocorahs
Cocorahs station CO-LP-93 Durango.
0630 AM Rain 3 SSW Colona 38.24N 107.76W
08/27/2023 M0.96 inch Ouray CO Mesonet
Mesonet station UNRC2 2.8 S Colona.
0556 AM Rain 12 W Colona 38.31N 107.96W
08/27/2023 M0.76 inch Ouray CO Mesonet
Mesonet station TS894 Norwood Portable No.
1.
0542 AM Rain 4 E Egnar 37.91N 108.86W
08/27/2023 M0.73 inch San Miguel CO Mesonet
Mesonet station TS040 San Juan Portable.
0539 AM Rain 23 NE Fry Cyn 37.85N 109.84W
08/27/2023 M0.65 inch San Juan UT Mesonet
Mesonet station NLPU1 N Long Point, Fry Cyn
23NE.
0600 AM Rain 3 S Durango 37.25N 107.87W
08/27/2023 M0.62 inch La Plata CO Mesonet
Mesonet station DGOC2 2.6 S Durango (CBRFC).
0800 AM Rain 1 E Durango 37.29N 107.84W
08/27/2023 M0.59 inch La Plata CO Cocorahs
Cocorahs station CO-LP-124 1 E Durango.
0638 AM Rain 1 SW Durango 37.28N 107.88W
08/27/2023 M0.55 inch La Plata CO Mesonet
Mesonet station EW4277 Durango.
0700 AM Rain 1 NW Durango 37.30N 107.89W
08/27/2023 M0.55 inch La Plata CO Cocorahs
Cocorahs station CO-LP-111 Durango 1.4 NW.
0400 AM Rain 8 ESE Marble 39.02N 107.05W
08/27/2023 M0.50 inch Gunnison CO Mesonet
Mesonet station SOSC2 8.6 NW Mount Crested
Butte (SNOTEL).
&&Special Weather Statement
National Weather Service Grand Junction CO
153 PM MDT Sun Aug 27 2023
COZ003-007-272030-
Roan and Tavaputs Plateaus CO-Debeque to Silt Corridor CO-
153 PM MDT Sun Aug 27 2023
...A strong thunderstorm will impact portions of south central
Garfield County through 230 PM MDT...
At 153 PM MDT, Doppler radar was tracking a strong thunderstorm 19
miles northwest of Parachute, or 35 miles north of Grand Junction,
moving southeast at 15 mph.
HAZARD...Winds in excess of 40 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down small tree limbs and blow
around unsecured objects. Minor damage to outdoor objects
is possible.
This storm will remain over mainly rural areas of south central
Garfield County.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 3961 10843 3965 10837 3952 10821 3946 10836
TIME...MOT...LOC 1953Z 330DEG 12KT 3959 10837
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH
15Special Weather Statement
National Weather Service Grand Junction CO
223 PM MDT Sun Aug 27 2023
COZ003-007-013-272100-
Roan and Tavaputs Plateaus CO-Flat Tops CO-
Debeque to Silt Corridor CO-
223 PM MDT Sun Aug 27 2023
...A strong thunderstorm will impact portions of central Garfield
County through 300 PM MDT...
At 222 PM MDT, Doppler radar was tracking a strong thunderstorm 15
miles northwest of Rifle, or 35 miles west of Glenwood Springs,
moving southeast at 15 mph.
HAZARD...Winds in excess of 30 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
This storm will remain over mainly rural areas of central Garfield
County, including the following locations... Rio Blanco.
This includes Colorado 13 between mile markers 11 and 20.
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.
&&
LAT...LON 3969 10802 3976 10797 3972 10779 3959 10790
TIME...MOT...LOC 2022Z 305DEG 12KT 3970 10797
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...30 MPH
KJSThe national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Some standing water accumulated on a portion of I-70 as a result of heavy rain from thunderstorms. Radar estimated over an inch of rain fell in 40 minutes.
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: 1114207.