Deep moisture from the remnants of post-tropical storm Ileana surged into the Four Corners region and through western Colorado ahead of a strong low pressure trough over northern California. This trough lifted through the area overnight into the afternoon of the 17th with strong to severe storms across southwest Colorado spreading north by the morning of the 17th.
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.
Deep moisture from the remnants of post-tropical storm Ileana surged into the Four Corners region and through western Colorado ahead of a strong low pressure trough over northern California. This trough lifted through the area overnight into the afternoon of the 17th with strong to severe storms across southwest Colorado spreading north by the morning of the 17th. A few storms generated wind gusts of 58 mph or greater with storm damage across La Plata county as well as debris flows across Montezuma 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 Sep 16, 10:50 AM MST, 1 hour 40 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Grand Junction CO 1150 AM MDT Mon Sep 16 2024 .KEY MESSAGES... - Widespread showers and storms are expected today and tomorrow as a system moves through the region. - Some storms may be capable of producing large hail, damaging winds and heavy rainfall. Therefore there is a chance for localized flooding. - Temperatures dip to near normal today in response to clouds and precipitation. A cold front moving through the region tomorrow is expected to bring cooler than normal readings for the latter part of the week. - Expect a break in the action Wednesday and Thursday before another system impacts the region Friday into the weekend. && .SHORT TERM /THROUGH TUESDAY/... Issued at 233 AM MDT Mon Sep 16 2024 Deep moisture from the remnants of post-tropical storm Ileana is beginning to advect into the forecast thanks to a strong low pressure currently located over northern California. The jet associated with that system is also spreading over the region. The combination of that along with the moisture advection has resulted in scattered convection, which will spread northward through the morning hours. The mositure is expected to increase even more later this morning so expect an increase in coverage of showers. As that precipitation moves to the northeast some clearing takes places in the Four Corners region. This surface heating coupled with steep lapse rates will result in CAPE upwards of 1000 j/kg. The shear provided from the California/Nevada low pressure in combination with this instability could support a round of more intense convection this afternoon. A few of these storms could become strong to severe and capable of producing large hail and damaging winds. Given the quality of the moisture heavy rainfall is also possible from strong cells and perhaps multiple rounds of storms. This means there is the potential for localized excessive rainfall, which could lead to debris/mud flows in our susceptible spots. The best location for these storms will be across the southwestern half of the forecast area. As the CAPE decreases after sunset the storm intensity should reduce. Although given the continued moisture advection isolated to scattered convection is possible tonight for a majority of the area. Highs today will be cooler than what we have seen the past week or so due to cooler midlevels, clouds and precip. Tomorrow the deep low pressure lifts northeastward and tracks over Idaho, northern Utah and Wyoming. The trailing cold front will pass through our area during the day. Forcing from the system increases and the front should provide lift as well. With the moisture in place we expect another round of widespread showers and storms ahead and along the front. The eastern two thirds of the area will be favored for showers and storms. Behind the front a dry slot pushes in from the southwest and modest subsidence so conditions should clear quickly from west to east. The main uncertainty tomorrow is how much instability will be present given pre- frontal clouds and precip. With shear in place any CAPE that can develop could result in a few strong storms capable of damaging winds. Most locations will clear out by sunset. The peaks could pick up some snow as freezing levels drop from convection and cold air advection. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Issued at 233 AM MDT Mon Sep 16 2024 Drier air sweeps in behind Tuesday's cold front, ushering in a much cooler air mass as overnight lows Tuesday night drop about 10 degrees from the previous night to around 5 to 10 degrees below normal. Rather crisp fall morning in store Wednesday with efficient radiational cooling under clearing skies. Highs on Wednesday will also be around 4 to 8 degrees or so below normal but a shade milder than Tuesday afternoon due to strengthening southwest flow ahead of another deep trough moving southward from the Pacific Northwest into the Great Basin. Models diverge in their solutions beyond Wednesday with not much agreement on the timing of this trough. The GFS is quicker with the trough moving across the area as an open wave Thursday night through Friday night, while the ECMWF is slower with this trough moving it across Friday night through Saturday night. The one thing models agree on though is this trough weakening significantly as it tracks eastward across the area...but the difference in timing is significant by about 24 hours difference. The blended guidance keeps scattered PoPs in the forecast Thursday night through Saturday afternoon, so essentially splits the difference which seems reasonable given the uncertainty. For what it's worth, the ECMWF is a bit more robust with this trough than the GFS but time will tell how much moisture comes with it and what this means for precipitation amounts. It is cool enough that we could be talking snow at the higher peaks with snow levels expected to be around 11kft at this moment in time with the passage of this open wave trough late in the week. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1150 AM MDT Mon Sep 16 2024 Scattered to widespread showers and storms are expected this afternoon and therefore kept VCTS going at most TAF sites well into the evening with showers becoming more isolated overnight. Periods of strong gusty winds and heavy rainfall are possible this afternoon/early evening. VFR to MVFR are expected with brief periods of IFR/ILS conditions possible with stronger storms. Showers pick up again Tuesday morning as a cold front associated with the current system moves eastward across the forecast area. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && SHORT TERM...KJS LONG TERM...MDA AVIATION...TGJT
Hazardous Weather Outlook National Weather Service Grand Junction CO 249 AM MDT Mon Sep 16 2024 COZ001>014-017>023-UTZ022>025-027>029-170900- 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- 249 AM MDT Mon Sep 16 2024 This hazardous weather outlook is for eastern Utah and western Colorado. .DAY ONE...Today and Tonight Scattered to widespread showers and storms are expected today and tonight. A few storms may be capable of producing large hail, damaging wind and heavy rainfall. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday A front moves through the area on Tuesday so expect another round of showers and storms. Conditions dry out and cool off Wednesday and Thursday before another system is possible Friday into the weekend. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
Preliminary Local Storm Report
National Weather Service Grand Junction CO
103 PM MDT Mon Sep 16 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1238 PM Tstm Wnd Gst Meeker 40.05N 107.88W
09/16/2024 M49 MPH Rio Blanco CO ASOS
ASOS station KEEO Meeker Airport.
&&
NLPreliminary Local Storm Report
National Weather Service Grand Junction CO
125 PM MDT Mon Sep 16 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0323 AM Tstm Wnd Gst 18 SE Massadona 40.02N 108.40W
09/16/2024 M46 MPH Rio Blanco CO Mesonet
Mesonet station PIRC2 Pinto, Massadona 18SE.
&&Preliminary Local Storm Report
National Weather Service Grand Junction CO
127 PM MDT Mon Sep 16 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1214 PM Non-Tstm Wnd Gst 1 W Douglas Pass 39.60N 108.82W
09/16/2024 M57 MPH Garfield CO Mesonet
Mesonet station CO098 139s034 Douglas Pass.
&&Preliminary Local Storm Report
National Weather Service Grand Junction CO
128 PM MDT Mon Sep 16 2024
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0155 PM Non-Tstm Wnd Gst 10 ESE Waunita Hot Spgs 38.48N 106.32W
09/15/2024 M52 MPH Gunnison CO AWOS
AWOS station KMYP Monarch Pass.
&&Special Weather Statement
National Weather Service Grand Junction CO
129 PM MDT Mon Sep 16 2024
COZ019>021-UTZ022-028-162000-
Southwest San Juan Mountains CO-
Paradox Valley/Lower Dolores River CO-
Four Corners/Upper Dolores River CO-La Sal and Abajo Mountains UT-
Southeast Utah UT-
129 PM MDT Mon Sep 16 2024
...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN DOLORES...WEST
CENTRAL SAN MIGUEL AND EAST CENTRAL SAN JUAN COUNTIES THROUGH 200 PM
MDT...
At 128 PM MDT, Doppler radar was tracking a strong thunderstorm near
Eastland, or 12 miles southeast of Monticello, moving northeast at
35 mph.
HAZARD...Wind gusts up to 50 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
Dove Creek, Eastland, Ucolo, and Egnar.
This includes the following highways...
U.S. Highway 491 in Colorado between mile markers 61 and 69.
U.S. Highway 491 in Utah between mile markers 3 and 17.
Colorado 141 between mile markers 1 and 12.
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 3756 10922 3763 10938 3809 10922 3785 10874
TIME...MOT...LOC 1928Z 213DEG 40KT 3772 10920
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH
LTBThe Grand Junction radar (KGJX), 79 km away, was scanning. The volume nearest the first event began at 19:30 UTC.
5 thunderstorm wind, 1 debris flow. Local standard time, as filed.
A thunderstorm wind gust of 59 mph was measured at a Mesonet station 1 mile west-southwest of Douglas Pass at 1256 MST.
Heavy Rainfall just east, northeast of Towaoc resulted in debris flows across Highline ditch/canal. Debris flow with mud and large boulders were noted near mile marker 29 on Highway 491 (between 21 Rd and B Rd).
A severe thunderstorm moved through 8 miles west of Ignacio and tracked to the northeast at 30 mph. Path and time was estimated based on the Severe Thunderstorm Warning issued. Thunderstorm wind damage occurred with downed trees, a bent electric pole and a twisted power pole. Property damage occurred in which an RV camper was smashed in half from the downed trees. Uncertain if this was tornado or straight line wind/downburst damage but leaning downburst winds.
A thunderstorm wind gust of 63 mph was measured at the Durango La Plata County Airport at 825 MST.
A thunderstorm wind gust of 59 mph was measured at the Meeker Coulter Field Airport at 823 MST.
Thunderstorm wind gust of 58 mph was measured at the Sunlight Mountain AWOS observation site at 1255 MST.
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, September 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: 1209228, 1209221, 1209258, 1209235, 1209240, 1209253.