Monsoon moisture fueled scattered to numerous showers and thunderstorms across western Colorado. Even with the moisture, some of the stronger storms produced gusty winds in addition to heavy rain.
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.
Monsoon moisture fueled scattered to numerous showers and thunderstorms across western Colorado. Even with the moisture, some of the stronger storms produced gusty winds in addition to heavy rain. One storm in Delta County produced wind gusts estimated to be in excess of 58 mph which resulted in some damage near Eckert.
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 23, 4:40 PM MST, 20 minutes earlier.
Area Forecast Discussion National Weather Service Grand Junction CO 540 PM MDT Wed Aug 23 2023 .SHORT TERM...(Tonight through Thursday night) Issued at 338 PM MDT Wed Aug 23 2023 Morning cloud cover and lingering showers resulted in a bit later start to convection which began firing in earnest over the southern and central high terrain between 1 pm and 2 pm MDT. Most activity seems to be staying fairly anchored to the terrain with slow movement and storms collapsing as they drift off. Precipitable water (PWAT) on this morning's 12Z GJT sounding came in with 1.02 inches which keeps climbing higher each day as monsoonal moisture returns. One noticeable thing that wasn't present yesterday is the higher dew points and relative humidity as well as more saturation in the lower levels. This should result in more efficient heavy rain producers, especially Thursday and Friday as the remnants of post Tropical Storm Harold track across the region. The hi-res CAMs, especially the NAMNest which has had a pretty good track record with these surges, indicates convection blossoming this evening across southeast Utah and southwest Colorado as a leading shortwave tracks across the Four Corners. This wave moves through east-central Utah and west-central Colorado late this evening between 9 pm and midnight so nighttime convection looks like a good bet with frequent lightning, heavy rain and gusty winds along the leading edge of this line of storms. This convection continues with shower and isolated thunderstorm activity beyond midnight as decaying Tropical Storm Harold approaches the Four Corners by Thursday morning. Due to lingering shower activity as well as expected broken to overcast cloud cover into Thursday morning, this could inhibit stronger convection from developing Thursday afternoon or even put a delay on the start of more robust thunderstorm activity until late Thursday afternoon. The remnants of Tropical Storm Harold will move directly over eastern Utah into western Colorado from south to north Thursday afternoon and evening, resulting in more widespread showers and thunderstorms. As mentioned in previous discussions, PWAT anomalies are still on track to get a turbo boost with values approaching 200 to 250 percent of normal, meaning 1 to 1.4 inches of PWAT. The excessive cloud cover is a concern, but the dynamic forcing associated with this tropical system and robust shortwave may overcome this and still result in some areas seeing robust convection in areas that see some sun late Thursday afternoon into the evening. Overall, the potential for excessive rainfall with storms will increase Thursday, especially across southeast Utah and southwest Colorado, although the flooding threat may be more localized and not as widespread depending on how much cloud cover lingers through the afternoon. Also, expect more overnight convection Thursday night as Harold continues to track across northeast Utah and northwest Colorado with enough dynamic forcing to keep storms going through the night. Toyed with the notion of issuing a Flood Watch for this potential in coordination with surrounding offices of SLC, FGZ and ABQ, but elected to hold off and let the midnight shift have a closer look at this to see how the overnight convection evolves. Latest hi- res guidance has backed off a bit and delayed the onset of convection to later in the day Thursday with no real focus for which areas would see more robust convection as its fairly scattered to widespread. So, this will be something to monitor as the potential for heavy rain and resultant localized flooding does exists with storms Thursday. Temperatures through Thursday will trend below normal for highs and above normal for overnight lows given increase in clouds, showers and storms. .LONG TERM...(Friday through Wednesday) Issued at 338 PM MDT Wed Aug 23 2023 Rich monsoon moisture and remnants of Harold will keep an unsettled forecast in place for Friday afternoon. Afternoon showers and thunderstorms will once again bring flash flood concerns along with the usual host of problems like gusty winds, small hail, and lightning. The seemingly permanent ridge of high pressure set up over the Great Plains will once again flatten slightly thanks to a series of smaller disturbances tracking along the Canadian Border on Saturday. Models nudge the high center enough to dry things out some this weekend. However, there still looks like enough remnant moisture to recycle into some scattered shower activity on the terrain both Saturday and Sunday. Thanks to the previously mentioned Canadian Border activity, models shift the ridge axis westward on Monday and turn the tap off with a bout of northwest flow Monday afternoon. The West Slope will see quieter conditions Monday, but weak shortwaves over the Continental Divide will likely spark a shower or two Monday afternoon. Tuesday and Wednesday look like drier versions of Monday with the ridge axis holding up over the Great Basin. Another North Pacific low drops into the Pacific Northwest Tuesday. By Thursday, it drags a front across the Northern Rockies and breaks down the Great Basin ridge. Present solutions open the door for return of subtropical moisture and active weather to the West Slope Thursday afternoon. Afternoon temperatures will trend upward through the extended period, starting around seasonal averages on Friday, but pushing back 5-10 degrees over normals by next week thanks to the return of dry, cloud free skies. Overnight lows will trend warmer through the period thanks to overnight clouds early in the period and warmer temperatures under the ridge next week. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 535 PM MDT Wed Aug 23 2023 Scattered to broken skies will be the rule overnight with convection continuing through the evening hours and overnight as a weak wave moves through. Some embedded convection is also possible though most precip will be stratiform in nature. Do not anticipate dropping below VFR conditions but some brief MVFR is possible under the stronger cells. Tomorrow, the remnants of TS Harold will move across the area bringing scattered to broken skies, with some overcast thrown in down south, for most of the day. Expect some stronger showers and thunderstorms in the afternoon with the increased moisture. Forecast ceilings should hover between 8 to 10K feet but, again, that stronger convection may bring vis and cigs down very quickly. && .HYDROLOGY... Issued at 338 PM MDT Wed Aug 23 2023 Remnants from Tropical Storm Harold, currently situated over southwest New Mexico as of 20Z/Wed will begin to move over southeast Utah and southwest Colorado Thursday before spreading over the remainder of the region on Friday. ECMWF ensemble means indicated that this surge of moisture could raise precipitable water levels to between 1 and 1.4" across the forecast area by Thursday and Friday afternoon which equates to somewhere between 200 and 250% of normal. Though Harold will be much weakened by the time it arrives over the area, it should still supply enough dynamic forcing to generate widespread shower and thunderstorm activity. The threat of heavy rain rises significantly with this system as developing storms should be efficient rain producers and slow moving which may result in localized mud and debris flows and potential flash flooding. Locations at greatest risk are recent burn scars, areas of steep unstable terrain and those with poor drainage. WPC has much of our area under a marginal risk, with slight risk now expanded to include southeast Utah and southwest Colorado for Thursday. Cloud cover tonight into Thursday morning could inhibit stronger convection from developing early in the day, limiting the flash flood potential to localized and not as widespread. Therefore, opted not to issue a Flash Flood Watch at this time. While localized flash flooding is possible, the potential for more widespread flooding will have to be monitored with the latest guidance and trends. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && SHORT TERM...MDA LONG TERM...LTB AVIATION...TGR HYDROLOGY...TGJT
Hazardous Weather Outlook National Weather Service Grand Junction CO 258 AM MDT Wed Aug 23 2023 COZ001>014-017>023-UTZ022>025-027>029-240900- 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- 258 AM MDT Wed Aug 23 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. Increasing monsoonal moisture will once again lead to widespread shower and thunderstorm activity this afternoon. Chances for flash flooding over burn scars and other steep, flashy terrain will be on the increase. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. As the remnants of Tropical Storm Harold move into the Four Corners region, deep tropical moisture and better upper level dynamics will lead to widespread showers and thunderstorms capable of rain rates in excess of an inch per hour. The threat for flash flooding and debris or mudslides will be on the increase through the end of the week. Conditions dry out for the weekend, but chances for afternoon storms remain. .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
224 PM MDT Wed Aug 23 2023
COZ006-017-232100-
Uncompahgre Plateau/Dallas Divide CO-Grand Valley CO-
224 PM MDT Wed Aug 23 2023
...A strong thunderstorm will impact portions of west central Mesa
County through 300 PM MDT...
At 223 PM MDT, Doppler radar was tracking a strong thunderstorm 17
miles southwest of Fruita, or 20 miles southwest of Grand Junction,
moving north at 20 mph.
HAZARD...Winds in excess of 40 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 west central Mesa
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 3887 10887 3890 10896 3908 10894 3902 10873
TIME...MOT...LOC 2023Z 198DEG 16KT 3894 10890
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH
MillerThe Grand Junction radar (KGJX), 32 km away, was scanning. The volume nearest the first event began at 00:00 UTC.
1 thunderstorm wind. Local standard time, as filed.
Wind gusts estimated to be 70 mph downed power lines and knocked over some trees 1 mile west-southwest of Eckert.
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: 1113788.