Showers and thunderstorms moved across the Front Range Urban Corridor and eastern plains during the afternoon. Wind gusts to around 60 mph occurred with the first batch of showers (non-thunderstorm wind gusts) over the Denver Metro area.
Every event with a place to put it; 2 filed by county or forecast zone are drawn at its center, in a lighter ring. 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 BOU wrote it up.
Showers and thunderstorms moved across the Front Range Urban Corridor and eastern plains during the afternoon. Wind gusts to around 60 mph occurred with the first batch of showers (non-thunderstorm wind gusts) over the Denver Metro area. The showers intensified into thunderstorms as the raced northeastward onto the plains. Winds reached as high as 71 mph in the Sterling area and was accompanied by a wall of dust.
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 Denver/Boulder, CO wrote its last area forecast discussion before the first event at Sep 17, 10:43 AM MST, 2 hours 31 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Denver/Boulder CO 1143 AM MDT Tue Sep 17 2024 .KEY MESSAGES... - A line of thunderstorms with high and potentially damaging winds are likely this afternoon. Peak gusts from severe storms up to 60 mph likely in the mountains, 60-70 mph along the I-25 Corridor, and a few gusts of 70-80 mph possible over the eastern plains. - Cooler temperatures this weekend with good chances (30-60%) for rain and high mountain snow. && .UPDATE... Issued at 1046 AM MDT Tue Sep 17 2024 Forecast for a high impact weather day is coming together pretty much as anticipated. Satellite shows a fair amount of sunshine with warming temperatures across the Front Range and plains, while scattered thunderstorms had already developed on the West Slope of Colorado. There is excellent agreement in the short range convective allowing models (CAMs) showing storms organizing linearly over the mountains and then pushing east onto the I-25 Corridor 2-4 pm, and then moving quickly east across the plains 4-7 pm, and should be pretty much over by 8 pm. The one thing there's a little uncertainty with is the storms potentially having too much outflow along the Front Range in a low MLCAPE/high DCAPE environment. That could lead to new storm initiation east of original convection, and then organizing again more effectively east of the I-25 Corridor where damaging winds would be even more likely. Ingredients are all there for high winds with the storms, including DCAPE >1200 J/kg, strong mid level environmental flow (35-40 kts at 700 mb), and linear (QLCS-like) organization although MLCAPE a bit limited as discussed above. Thus, we think peak gusts from severe storms would be near 60 mph in the mountains, 60-70 mph along the I-25 Corridor, and potentially 70-80 mph over the plains east of I-25. Those would be the strongest, but almost all areas should see gusts of at least 40-55 mph. Winds will reach a given location well ahead of the showers and storms, so we're messaging safety for water recreationists. Also, scattered power outages can be expected in areas that see the strongest winds. Fire danger is also a threat with strong southwesterly winds and warm temperatures on the plains this afternoon, and the gust fronts along and ahead of storms. We are expected wetting rains with most storms in the mountains - hopeful we see that over the new Pearl fire or significant fire behavior possible there with the gusty winds associated with storms and/or post-frontal downslope winds. && .SHORT TERM /Through Tonight/... Issued at 352 AM MDT Tue Sep 17 2024 Water vapor satellite imagery showing a broad upper level low spinning over Nevada. Ahead of the low, lift is producing isolated showers over western Colorado already. The center of the low lifts into Wyoming by this evening, but as the trough axis races northeast across Colorado it will provide plenty of lift. By mid morning expect scattered thunderstorms across western Colorado. Daytime heating will destabilize the airmass ahead of the trough over central and eastern Colorado. Still good model agreement that a line of storms form by late morning over western/central Colorado. Mid level flow increases in the afternoon with 700 mb winds increasing to 35-40 kts by 21Z-00Z. Storm movement looks to be 35-40 knots as well and as mentioned in the last discussion a 20 knot forward outflow out of a storm moving 35 knots yields 55 knot winds. So it won't take much to produce strong winds today. Greatest instability will be over the eastern plains with SBCAPE of 500-1000 J/kg. The greater instability should produce more organized storm segments, leading to winds of 70 mph or locally stronger. The enhanced severe risk over the northeast plains looks on track. No big changes to the forecast for today. Will continue to highlight the strong wind threat from the thunderstorms this afternoon. For this evening and tonight, storms continue to race northeastward and exit the state by early to mid evening. Subsidence quickly moves in and brings mostly clear skies overnight. This may keep windy conditions going across the higher foothills and Front Range Mountains this evening. Expect a chilly night compared to recent nights due to the clear skies and dry airmass. Lows are expected to fall into the 40s overnight across northeast Colorado. The mountain valleys, likely fall below freezing with lows in the mid 20s to lower 30s. A little moisture hangs on overnight over the northeast plains where a little fog will be possible towards sunrise Wednesday morning. && .LONG TERM /Wednesday through Monday/... Issued at 352 AM MDT Tue Sep 17 2024 A few small changes were made this update to long-term forecast package. Strong subsidence values are displayed by QG fields along northeastern Colorado Wednesday. Strong southwesterly flow continues under high pressure creating mostly sunny skies and dry conditions. 700mb temperatures between 11-13C will lead to above normal temperatures Wednesday and Thursday. Additionally, low relative humidities are possible. Although wind gusts remain below 25 mph for the lower elevations, there is an increasing chance southwesterly winds could increase mid- afternoon given the upper level stationed in southeastern Wyoming especially for the foothills areas. This may lead to elevated fire weather conditions for the foothills briefly but mainly for Jackson and Larimer counties Wednesday afternoon. Additionally, Thursday similar conditions could occur with slightly stronger winds for the lower elevations leading to near critical conditions for the plains, Palmer Divide, and Lincoln county. There is good agreement for a weak shortwave increasing mid-level moisture starting Friday late afternoon. While MLCAPE values are low near 100 J/kg, isolated high based showers and storms with little rainfall are possible through late evening for both the mountains and plains. DCAPE values approach 1000-1300 J/kg therefore expect gusty winds associated with storms and showers. This forecast package included a decrease to PoPs Friday. Our next upper level trough pack a punch which could arrive this weekend. Majority of ensemble members are favoring precipitation arriving late Saturday morning first for the higher elevations. QPF fields range between 0.5-2 inches for the region. There is some uncertainty if this system hovers in the northeastern corner through Sunday afternoon. This resulted in NBM isolated PoPs for northeast Colorado through Sunday evening. ECMWF also keeps showers and storms lingering through Sunday evening. Either way, there is high confidence in cooler afternoon temperatures this weekend through early next week especially Saturday and Sunday. Saturday compared to Friday, temperatures are almost 10-15 degrees cooler for both the mountains and plains. Maybe even a chance for sweater weather? && .AVIATION /18Z TAFS through 18Z Wednesday/... Issued at 1143 AM MDT Tue Sep 17 2024 Main concern is for very strong winds of 40-55 kts at the airports with a line of thunderstorms this afternoon, as all ingredients support these strong gusts. A 10-15% chance of a 60kt gust. Most likely time for those will be between 21Z and 23Z. The strongest winds should occur along and just ahead of the showers and storms (and mainly from the SW/W). Winds will then turn more easterly or light/variable behind the showers and storms, eventually turning to fairly normal diurnal wind patterns from 06Z through Wednesday. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && UPDATE...Barjenbruch SHORT TERM...Meier LONG TERM...AD AVIATION...Barjenbruch
Hazardous Weather Outlook National Weather Service Denver/Boulder CO 1109 AM MDT Tue Sep 17 2024 COZ030>051-181715- Jackson County Below 9000 Feet- West Jackson and West Grand Counties Above 9000 Feet- Grand and Summit Counties Below 9000 Feet- South and East Jackson/Larimer/North and Northeast Grand/ Northwest Boulder Counties Above 9000 Feet- South and Southeast Grand/West Central and Southwest Boulder/ Gilpin/Clear Creek/Summit/North and West Park Counties Above 9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet- Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear Creek/Northeast Park Counties Below 9000 Feet- Central and Southeast Park County- Larimer County Below 6000 Feet/Northwest Weld County- Boulder And Jefferson Counties Below 6000 Feet/West Broomfield County- North Douglas County Below 6000 Feet/Denver/West Adams and Arapahoe Counties/East Broomfield County- Elbert/Central and East Douglas Counties Above 6000 Feet- Northeast Weld County-Central and South Weld County-Morgan County- Central and East Adams and Arapahoe Counties- North and Northeast Elbert County Below 6000 Feet/North Lincoln County- Southeast Elbert County Below 6000 Feet/South Lincoln County- Logan County-Washington County-Sedgwick County-Phillips County- 1109 AM MDT Tue Sep 17 2024 ...HIGH AND POTENTIALLY DAMAGING WINDS FROM SEVERE STORMS THIS AFTERNOON... This hazardous weather outlook is for northeast and north central Colorado. .DAY ONE...This Afternoon and Tonight A line of thunderstorms will race across the area this afternoon. As this line of thunderstorms moves through, wind gusts of 40 to 60 mph are expected. Isolated wind gusts of 70 to 80 mph will be possible with the stronger thunderstorms over the plains. The last of the storms will move out of the far northeast corner of Colorado by 7-8 mph. Impact will include significant danger to boaters and outdoor water enthusiasts, who should get off the water well before storms and gusty winds arrive. Scattered power outages are also possible. Breezy to windy conditions will likely linger over the higher foothills and Front Range Mountains through the evening, while other locations will see winds subside quickly behind the line of storms. Fire danger will be elevated due to very warm temperatures and gusty winds on the plains ahead of the front. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Dry conditions and above normal temperatures are expected both Wednesday and Thursday. This may lead to elevated fire weather conditions. By Friday, isolated to scattered chances for storms and showers return. The next storm system arriving this weekend will bring cooler unsettled weather to the region with rainfall on the plains and the potential for accumulating snow across the higher Front Range Mountains. .SPOTTER INFORMATION STATEMENT... Spotter are encouraged to provide any reports of severe wind gusts or wind damage this afternoon.
Special Weather Statement
National Weather Service Denver CO
150 PM MDT Tue Sep 17 2024
COZ034-036-039>041-172015-
Elbert/Central and East Douglas Counties Above 6000 Feet CO-
South and Southeast Grand/West Central and Southwest
Boulder/Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet CO-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield County
CO-
North Douglas County Below 6000 Feet/Denver/West Adams and Arapahoe
Counties/East Broomfield County CO-
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet CO-
150 PM MDT Tue Sep 17 2024
...GUSTY SHOWERS WILL IMPACT CENTRAL DOUGLAS...NORTHEASTERN PARK...
SOUTHEASTERN CLEAR CREEK AND JEFFERSON COUNTIES THROUGH 215 PM MDT...
At 150 PM MDT, Doppler radar was tracking gusty showers along a line
extending from 3 miles west of Pine Junction to 4 miles north of
Deckers, or along a line extending from 75 miles southwest of Greeley
to 31 miles southwest of Denver. Movement was northeast at 35 mph.
HAZARD...Wind gusts of 50 to 55 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Southwestern Lakewood, Highlands Ranch, Littleton, Evergreen,
Roxborough Park, Morrison, Idledale, Conifer, Pine Junction, Tiny
Town, Chatfield Reservoir, Kittredge, Buffalo Creek, Devil's Head,
Sedalia, Aspen Park, Cheesman Reservoir, Deckers, Bailey, and Floyd
Hill.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 3979 10537 3948 10485 3913 10522 3937 10560
TIME...MOT...LOC 1950Z 209DEG 31KT 3946 10545 3931 10522
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...55 MPH
HIRISSpecial Weather Statement
National Weather Service Denver CO
207 PM MDT Tue Sep 17 2024
COZ035-036-038>040-043-172030-
Central and South Weld County CO-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield County
CO-Larimer and Boulder Counties Between 6000 and 9000 Feet CO-
North Douglas County Below 6000 Feet/Denver/West Adams and Arapahoe
Counties/East Broomfield County CO-
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet CO-
Larimer County Below 6000 Feet/Northwest Weld County CO-
207 PM MDT Tue Sep 17 2024
...GUSTY SHOWERS WILL IMPACT SOUTHWESTERN WELD...BROOMFIELD...
SOUTHEASTERN LARIMER...NORTHERN JEFFERSON...NORTHWESTERN ADAMS AND
EASTERN BOULDER COUNTIES THROUGH 230 PM MDT...
At 206 PM MDT, Doppler radar was tracking gusty showers along a line
extending from near Cedar Cove to near Niwot to near White Ranch Open
Space, or along a line extending from 13 miles southwest of Fort
Collins to 74 miles west of Fort Morgan to 21 miles northwest of
Denver. Movement was northeast at 30 mph.
HAZARD...Wind gusts of 50 to 55 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Fort Collins, western Greeley, northern Thornton, northwestern
Arvada, Westminster, Boulder, Longmont, Loveland, Broomfield,
northwestern Northglenn, Lafayette, Windsor, Louisville, Erie,
Superior, Firestone, Johnstown, Frederick, Milliken, and Berthoud.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4029 10483 3993 10491 3978 10540 3988 10540
3988 10538 3989 10540 4040 10540 4073 10489
TIME...MOT...LOC 2006Z 235DEG 25KT 4040 10524 4010 10520 3985 10532
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...55 MPH
HIRISSpecial Weather Statement
National Weather Service Denver CO
211 PM MDT Tue Sep 17 2024
COZ036-039>041-172045-
Elbert/Central and East Douglas Counties Above 6000 Feet CO-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield County
CO-
North Douglas County Below 6000 Feet/Denver/West Adams and Arapahoe
Counties/East Broomfield County CO-
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet CO-
211 PM MDT Tue Sep 17 2024
...GUSTY SHOWERS WILL IMPACT NORTH CENTRAL DOUGLAS...WESTERN
ARAPAHOE...DENVER...NORTHERN JEFFERSON AND SOUTHWESTERN ADAMS
COUNTIES THROUGH 245 PM MDT...
At 210 PM MDT, Doppler radar was tracking gusty showers along a line
extending from near Bergen Park to 3 miles southeast of Morrison to
near Louviers, or along a line extending from 57 miles southwest of
Greeley to 13 miles southwest of Denver to 44 miles north of Colorado
Springs. Movement was north at 30 mph.
HAZARD...Wind gusts of 50 to 55 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Denver, southwestern Aurora, Lakewood, southwestern Thornton, Arvada,
Westminster, Centennial, southwestern Broomfield, Highlands Ranch,
southwestern Commerce City, northwestern Parker, Littleton,
southwestern Northglenn, Englewood, Wheat Ridge, Golden, Greenwood
Village, Evergreen, Federal Heights, and Lone Tree.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 3953 10517 3969 10543 3992 10533 3992 10523
3993 10524 3993 10528 3995 10527 3987 10493
3966 10469 3933 10501
TIME...MOT...LOC 2010Z 201DEG 26KT 3972 10533 3960 10514 3946 10503
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...55 MPH
HIRISThe Denver radar (KFTG), 58 km away, was scanning. The volume nearest the first event began at 21:55 UTC.
9 thunderstorm wind, 2 high wind. Local standard time, as filed.
Weather station CO007 Littleton C470/Wadsworth.
Weather station CO109 Rocky Flats Hwy 93 and 72.
Weather station CO066 Cedar Point.
Weather station CO035 I-76 Sterling.
Weather station TT562 North Sterling.
Weather station CO048 US 385 Holyoke.
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: 1203097, 1203098, 1203088, 1203089, 1203090, 1203091, 1203092, 1203093, 1203094, 1203095, 1203096.