High pressure began to retrograde to the west towards Arizona with drier air moving in from the north, keeping the subtropical moisture in place for areas south of Interstate 70. Enough moisture remained in addition to a shortwave moving through the flow to allow for a few strong storms still capable of moderate to heavy rainfall rates, that produced some localized flash flooding and mudslides…
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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.
High pressure began to retrograde to the west towards Arizona with drier air moving in from the north, keeping the subtropical moisture in place for areas south of Interstate 70. Enough moisture remained in addition to a shortwave moving through the flow to allow for a few strong storms still capable of moderate to heavy rainfall rates, that produced some localized flash flooding and mudslides in areas of steep terrain.
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 Jul 16, 10:25 AM MST, 2 hours 35 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Grand Junction CO 1125 AM MDT Tue Jul 16 2024 .KEY MESSAGES... - Temperatures are expected to remain a few degrees above normal with daily thunderstorm chances through the remainder of the week and into the weekend as moisture is recycled under the area of high pressure over the region. - Threats from thunderstorms will mainly be from gusty outflow winds though a few storms will be capable of producing smaller hail and moderate to heavy rainfall rates. Overall flooding threats remain low. - The combination of high based storms...gusty outflow winds and lightning will keep also keep a threat of new wildfire starts in the picture. && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 341 AM MDT Tue Jul 16 2024 The high pressure to the south that is dominating the weather pattern over eastern Utah and Western Colorado has shifted farther southeast over northern New Mexico over the last 12 hours. Models are in good agreement with the high retrograding to the west to the Arizona-New Mexico Border over the next 24 hours as a trough descends down over the Northern Plains. This will shift the monsoonal flow more to the south with most shower and thunderstorm activity along and south of the I-70 corridor while the northern areas will see more isolated convection than they had Monday with drier air starting to move in from the northeast. Pwats continue at about 0.80 inches across the region today, high enough to produce some localized heavy rain rates with some of the stronger thunderstorms, but again, the treats of flooding remains low. Expect the convection today to be triggered off orographics with little upper level support over the southern areas. There is some weak upper-level divergence across the northern areas that could trigger some surprise storms today over the northern areas, but guidance and the high resolution CAMS are playing it down with the dryer push of air. This is something to watch, so stay tuned to the forecast through the late morning. Look for the convection to initiate around noon over the higher terrain, increasing through the afternoon with max heating and tapering off going into the evening hours. Lingering showers and thunderstorms will continue over the higher terrain through the late evening, likely ending along the Divide sometime after midnight. Pwats Wednesday look to decrease a bit to about 0.60 inches across the region as the drier air continues to push in over eastern Utah and Western Colorado. This will push the convective activity more to the east along the divide through the early afternoon. As the high pressure along the Arizona-New Mexico Border moves to the north to the Four Corners area through Wedensday afternoon, the scattered showers and thunderstorms will shift south over the San Juan Mountains with isolated activity extending west to the Abajos and La Sals. Temperatures today will remain near normal to a little above normal under the ridge as the clouds will limit the diurnal heating with little change tomorrow. Though temperatures are near normal, mid July is the hottest time of the year for eastern Utah and Western Colorado with highs running around the century mark through the lower valleys. If you plan to be out in the hotter time of day, it's best to avoid strenuous activities and keep plenty of water on hand. Be aware that heat exhaustion can sneak up on you quickly. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Issued at 341 AM MDT Tue Jul 16 2024 According to strong model consensus, high pressure shifts slowly westward from the border of southwest Colorado to southeast Utah Thursday and Friday. Concurrently, a slug of moisture from the Mexican Plateau moves across Arizona and is carried northeastward across the area on Thursday. This will bring an uptick in shower/thunderstorm coverage Thursday afternoon/evening. The slow influx of moisture continues Friday with precipitable water levels rising to 120 to 150% of normal, or from 0.8 to 1" of moisture in the column. Consequently, coverage of moist convection increases further with increased chances of localized heavy rain. Though ECMWF and GFS ensembles disagreed on values, a drying trend begins this weekend as the high retrogrades to Great Basin. Flow from the north will bring drying and the region will experience a decrease of precipitable water with levels falling to 0.5 to 0.75" later this weekend and early next week. However, since drying occurs at mid- levels low level moisture will still be sufficient to generate scattered showers and thunderstorms each day from Saturday to Monday, especially across the south. However, with less moisture in the column the threat of excessive rainfall declines. Temperatures are expected to show little change, hovering near or a few degrees above normal throughout the long term period. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1123 AM MDT Tue Jul 16 2024 Thunderstorm activity is beginning to increase and will be isolated to scattered across the region this afternoon and evening. Limited coverage over most areas reduces confidence in impacts at most TAF sites where VCTS was used...with more confidence at KTEX...KVEL and KGUC looking at the latest radar and webcam trends. However most TAF sites have some probability of seeing gusty winds from nearby storms or from more organized outflow boundaries from farther storm complexes. Will amened TAF sites as these threats become more apparent from radar/satellite trends. Otherwise VFR should hold over the next 24 hours. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && SHORT TERM...DB LONG TERM...NL AVIATION...GJT
Hazardous Weather Outlook National Weather Service Grand Junction CO 345 AM MDT Tue Jul 16 2024 COZ001>014-017>023-UTZ022>025-027>029-170945- 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- 345 AM MDT Tue Jul 16 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. Expect showers and thunderstorms to redevelop over higher terrain from late morning to early afternoon today. The main threat from this activity is lightning, strong outflow winds and small hail. This activity will continue into the late evening. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. There is a chance for afternoon showers and thunderstorms in the mountains each day through the coming week. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
Special Weather Statement
National Weather Service Grand Junction CO
146 PM MDT Tue Jul 16 2024
COZ001-162015-
Lower Yampa River Basin CO-
146 PM MDT Tue Jul 16 2024
...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN MOFFAT COUNTY
THROUGH 215 PM MDT...
At 145 PM MDT, Doppler radar was tracking a strong thunderstorm 14
miles northeast of Dinosaur, or 35 miles east of Vernal, moving
southeast at 15 mph.
HAZARD...Wind gusts up to 40 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 Moffat
County.
This includes U.S. Highway 40 in Colorado between mile markers 17 and
21.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
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 4038 10898 4053 10887 4047 10847 4022 10870
TIME...MOT...LOC 1945Z 295DEG 14KT 4043 10887
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH
15The Grand Junction radar (KGJX), 169 km away, was scanning. The volume nearest the first event began at 19:58 UTC.
1 flash flood, 1 debris flow. Local standard time, as filed.
Heavy rainfall rates of 0.5 to 1 inch in less than an hour from a strong thunderstorm resulted in flash flooding in Hells Canyon through Dinosaur National Monument. An additional inch accumulation of pea sized hail also accompanied the heavy rain resulting in the flash flooding.
Heavy rainfall rates from a strong thunderstorm caused a mudslide to occur near Sawpit along Highway 145 between mile markers 76 and 80. This mudslide resulted in a closure of Highway 145 in both directions.
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, July 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: 1204524, 1204520.