Damaging Winds in Montana, July 24, 2024

Name: Damaging Winds in Montana, July 24, 2024
Start: 2024-07-24T19:19
End: 2024-07-24T20:57
Location: Montana

July 24, 2024 · NWS MSO · 4 events in 4 counties and zones

Hurricane force winds from a rare derecho brought widespread damage to west-central Montana. The Montana governor issued an executive order declaring a disaster in both Missoula and Mineral counties due to the extent of the damage and impact.

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: $4.0 million
Crop damage: None recorded
Events: 4

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.

What happened

The episode as NWS MSO wrote it up.

What forecasters said that day

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 Missoula, MT wrote its last area forecast discussion before the first event at Jul 24, 12:47 AM MST, 18 hours 32 minutes earlier.

Area forecast discussion, Jul 24, 12:47 AM MST, 18 hours 32 minutes before

Area Forecast Discussion
National Weather Service Missoula MT
147 AM MDT Wed Jul 24 2024

...ELEVATED FIRE WEATHER CONCERNS TODAY AND THURSDAY...

.DISCUSSION...Changes are coming today as the Northern Rockies
see more widespread coverage of thunderstorms. There may be just
enough instability for a few showers/storms this morning across
Lemhi County and Southwest Montana. But the main push of monsoon
moisture starts arriving early this afternoon and continues
through this evening with several episodes of thunderstorms. A
round of thunderstorms will kick off across southwest Montana and
west central Montana in the early to mid afternoon, bringing the
potential for outflow winds in excess of 50 mph and cloud to
ground lightning, meanwhile dry humidity and hot temperatures
persist. This combination will create critical fire weather
conditions, thus exacerbating ongoing wildfires and making it
extremely easy for new fires to start (whether they be lightning-
caused or human- caused.)

By this evening, another area of storms will initiate further to
the west over central Idaho and move into western Montana by
sunset. These storms will also bring the same threat as those
earlier in the day, but will encompass a much larger area of
coverage, potentially extending as far north as the Flathead
region of NW MT. A few storms will linger into early Thursday
morning.

As we reach midday Thursday, a stronger frontal feature will
support gusts of 30-35 mph across the majority of central Idaho
and western Montana. Humidity levels will improve slightly due to
cooler temperatures on Thursday, but strong winds will continue
to raise fire weather concerns. Breezy winds will persist into
Friday.

For those looking for relief from the hot temperatures, there is
good news as temperatures will trend cooler; returning to more
seasonable levels (highs in the 80s for valleys) Friday through
the middle of next week.

&&

.AVIATION...

Wildfire smoke will persist in causing intermittent reduced
visibility across the Northern Rockies due to numerous regional
smoke sources and several local fires. Visibility readings will
generally be at least 4SM to 6SM, except in areas close to local
wildfires.

Interest shifts to the increasing threat of thunderstorms. There
may be just enough instability for a few showers/storms this
morning across Lemhi County and Southwest Montana. But the main
push of monsoon moisture starts arriving early this afternoon and
continues through this evening with several episodes of thunderstorms.
There is a potential of strong outflow winds over 50 mph near any
thunderstorms.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Heat Advisory until midnight MDT Wednesday night for
     Flathead/Mission Valleys...Kootenai/Cabinet Region...Lower
     Clark Fork Region...Missoula/Bitterroot Valleys...
     Potomac/Seeley Lake Region...West Glacier Region.

     Red Flag Warning from noon to 9 PM MDT Wednesday for Flathead
     Reservation.

     Red Flag Warning from noon to 9 PM MDT Wednesday for Bitterroot.

     Red Flag Warning from noon to 9 PM MDT Wednesday for
     Deerlodge/West Beaverhead...East Beaverhead.

     Red Flag Warning from noon to 9 PM MDT Wednesday for East Lolo.

     Red Flag Warning from noon to 9 PM MDT Wednesday for West Lolo.

ID...Heat Advisory until 11 PM PDT Wednesday for Lower Hells
     Canyon/Salmon River Region...Northern Clearwater
     Mountains...Orofino/Grangeville Region...Southern
     Clearwater Mountains.

&&

In the hours before

Special weather statement, Jul 24, 4:42 PM MST, 2 hours 37 minutes before

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

The radar

The Missoula radar (KMSX), 63 km away, was scanning. The volume nearest the first event began at 02:19 UTC.

Open the radar archive at this moment

Event by event

4 thunderstorm wind. Local standard time, as filed.

Thunderstorm Wind, Missoula

When: July 24, 7:19 PM MST to 8:57 PM MST
Where: Missoula County, 6.06 mi SSW of Lolo Hot Spgs to 2.76 mi NNE of Seeley Lake Arpt
Measured: 70 kt (81 mph) measured gust
Property damage: $4.0 million
Reported by: Official NWS Observations
Coordinates: 46.651, -114.584

A state of emergency was declared by both the Missoula County Commission Chair and Missoula Mayor because of the unprecedented wind damage that occurred. The 80 to 100 mph winds brought thousands of trees down across the county. It wasn't just a quick gust, but rather high winds that lasted for a couple of minutes. This led to power and transmission poles breaking in half and triggering power outages that lasted for up to a week after, affecting close to 40,000 customers, many of which had to toss out spoiled food. One utility reported 80 power poles were broken across their service area with 42 of those knocked down or shattered along Mullan Road, located approximately 7 miles west of US-93. Many traffic lights did not work until two days after the event. The Missoula County 911 call center received over 600 calls with many people not getting through. The main repeater on Horseback Ridge, located southwest of Missoula, went down because of the wind and firefighters could only use line-of-sight radio communication throughout the night. Natural gas meters and natural gas lines were damaged. The DNRC gave a conservative estimate that 1,000 city trees were uprooted, splintered at the truck or suffered some other total failure. Their Missoula Campus lost 52 mature ponderosa pines, and over 25 tree species. Water conservation restrictions were put up in place because the Missoula Water was running on generators. Many parts of the city were shut down including parks and mainstem rivers due to downed power lines. Live power lines trapped many people traveling through the city, including two teenagers who sat in their car for over an hour until rescue personnel could reach them in the Lower Miller Creek area. Over a hundred homes had some sort of shingle or siding damage, and many could not get roofers to fix it until 2 months later. Portions of the Blackfoot River were closed due to downed power lines and damaged power poles and lines were also reported in the Clinton, Salmon Lake, Condon and Seeley Lake areas.

Thunderstorm Wind, Mineral

When: July 24, 7:19 PM MST to 7:57 PM MST
Where: Mineral County, 17.24 mi S of Rivulet to 3.42 mi NNE of Alberton
Measured: 56 kt (64 mph) estimated gust
Property damage: $5,000
Reported by: Fire Department/Rescue
Coordinates: 46.751, -114.736

Frenchtown Rural Fire District rpeorted a structure fire after a pine tree crashed onto a power line in Alberton, causing the lines to arc. The Mineral County Disaster and Emergency Services reported that its phone lines were down. The severe winds of the derecho clipped the southeastern third of Mineral County.

Thunderstorm Wind, Ravalli

When: July 24, 7:34 PM MST to 8:00 PM MST
Where: Ravalli County, 2.98 mi WNW of Stevensville to 1.84 mi E of Florence
Measured: 57 kt (66 mph) measured gust
Property damage: $25,000
Reported by: Mesonet
Coordinates: 46.511, -114.141

A weather station at the Stevensville Airport reported the gust to 66 mph originating out of the northwest. Multiple power line and pole issues were reported in the northern Ravalli County due to the winds. It appears that the Stevensville area was the furthest south extent of the derecho winds, while the Missoula area took a direct hit.

Thunderstorm Wind, Lake

When: July 24, 8:02 PM MST to 8:30 PM MST
Where: Lake County, 1.52 mi NNW of Arlee to 8.77 mi ENE of Post Creek
Measured: 65 kt (75 mph) estimated gust
Reported by: Public
Coordinates: 47.169, -114.096

A person from the public reported that there were dozens of trees down on forest service roads east and northeast of Arlee.

What these are

Thunderstorm Wind: Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Montana in 2024 Every state in 2024 This day in weather history Warnings in Montana, July 2024

Sources

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 2026-09-30. Each event’s entry at NCEI: 1204672, 1204741, 1204726, 1204745.