Hail and Damaging Wind in Montana, August 18, 2016

Name: Hail and Damaging Wind in Montana, August 18, 2016
Start: 2016-08-18T15:45
End: 2016-08-18T22:00
Location: Montana

August 18, 2016 · NWS MSO · 4 events in 3 counties and zones

A strong back-door cold front pushed south out of Canada and brought frequent wind gusts over 50 mph at times across portions of western Montana. It also triggered thunderstorms, one of which caused damage in the Missoula Valley.

Where it happened

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.

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: $7,000
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 Aug 18, 1:20 PM MST, 2 hours 25 minutes earlier.

Area forecast discussion, Aug 18, 1:20 PM MST, 2 hours 25 minutes before

Area Forecast Discussion
National Weather Service Missoula MT
220 PM MDT Thu Aug 18 2016

.DISCUSSION...High pressure continues to build east of the
Continental Divide setting up a surge of cold air to move across
western Montana this evening. Wind advisories have been issued
for several locations in northwest Montana due to the winds.

The most notable highlight is a High Wind Warning for Flathead
Lake and the surrounding area. Models indicate the strongest winds
will be this evening and will be strongest over the lake. Winds
30-40 mph with gusts near 50 mph are expected tonight. Considering
the warm lake water, cool air mass, strong winds, and long north-
south fetch across the lake, there is potential for waves over 5
feet on the southwestern shores of Flathead Lake tonight. With the
lake at full pool and the recreation season in full swing, the
area is at its most vulnerable for a high wind event, hence the
warning. Generally in Idaho winds will be much lighter and out of
the north, just bringing a bit of a cool down for central Idaho.

There is also a chance of thunderstorms this evening. Butte is
the most likely area to be affected by thunderstorms, but there is
also a slight chance a thunderstorm could also affect the Mission
valley.

Friday cool and stable conditions will cause skies to clear out
quickly for a nice, but cooler day with temperatures in the 70s in
western Montana and 80s in central Idaho.

A building high pressure ridge will lead to warm and dry weather
for the coming weekend with daytime highs returning to a few
degrees above normal by Sunday.

Beginning late Sunday into Monday, a low pressure trough will
settle into British Columbia and breakdown the high pressure
ridge. A cold front passage on Monday will lead to gusty westerly
winds with little, if any precipitation for the Northern Rockies.
It will also be cooler with temperatures at more seasonable levels
early next week.

&&

.AVIATION...A back-door cold front coming across the Continental
Divide will cause strong north and east winds at area terminals
KGPI and KMSO. Otherwise, expect isolated thunderstorms, mainly
along the Continental Divide with KBTM being the most likely to be
impacted around 00Z.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Wind Advisory until 6 AM MDT Friday Missoula/Bitterroot Valleys.

     High Wind Warning until 6 AM MDT Friday Flathead/Mission Valleys.

     Wind Advisory until 6 AM MDT Friday West Glacier Region.

     Wind Advisory until 6 AM MDT Friday Kootenai/Cabinet Region.

ID...&&

The radar

The Missoula radar (KMSX), 98 km away, was scanning. The volume nearest the first event began at 23:51 UTC.

Open the radar archive at this moment

Event by event

2 high wind, 1 thunderstorm wind, 1 hail. Local standard time, as filed.

High Wind, Flathead/Mission Valleys

When: August 18, 3:45 PM MST to 10:00 PM MST
Where: Flathead/Mission Valleys forecast zone
Measured: 50 kt (58 mph) estimated gust
Property damage: $1,000
Reported by: ASOS
Coordinates: 47.872, -114.424 (the zone’s center; the record gives no point)

Glacier Park International airport located north of Kalispell recorded winds sustained between 40 and 44 mph with gusts to 55 mph between 6:45 and 7:25 pm MDT. Wind gusts were estimated near 60 mph towards Bad Rock Canyon near Columbia Falls. A boat charter on Flathead Lake estimated 5 foot waves in Lakeside where his boat was docked. Several trees were knocked down in Kalispell with some power outages. The mid-lake buoy recorded a peak wind of 46 mph at 7:30 pm MDT.

Thunderstorm Wind, Missoula

When: August 18, 4:50 PM MST to 5:10 PM MST
Where: Missoula County, Missoula
Measured: 50 kt (58 mph) estimated gust
Property damage: $5,000
Reported by: Utility Company
Coordinates: 46.880, -114.000

Two transmission poles located in the South Hills area of Missoula were knocked out by the wind which caused a power outage. Multiple trees were pushed over by the wind including a 50 foot Ponderosa Pine tree that fell onto a home. A NWS employee reported that a Maple tree was snapped in half at the corner of Mount and Brooks Street.

Hail, Missoula

When: August 18, 4:50 PM MST to 5:10 PM MST
Where: Missoula County, Missoula
Measured: 1 in hail
Reported by: Public
Coordinates: 46.880, -114.000

A person from the public located in Missoula tweeted a photo of hail that appeared to be quarter size. There were multiple reports of nickel sized hail with some damage to gardens and vegetation. Intense rainfall was also produced by this storm, and the greater impact may have been street ponding.

High Wind, Kootenai/Cabinet Region

When: August 18, 6:45 PM MST to 8:30 PM MST
Where: Kootenai/Cabinet Region forecast zone
Measured: 50 kt (58 mph) estimated gust
Property damage: $1,000
Reported by: COOP Observer
Coordinates: 48.171, -114.863 (the zone’s center; the record gives no point)

A COOP located 2 miles northwest of Heron reported very strong ENE winds that uprooted several trees, caused metal roofing to be torn off a barn, and caused a power outage that lasted for 43 hours.

What these are

High Wind: Sustained non-thunderstorm winds of 40 mph or more for an hour, or gusts of 58 mph or more.
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.
Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.

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

The same day elsewhere

Every storm in Montana in 2016 Every state in 2016 This day in weather history Warnings in Montana, August 2016

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 2026-09-24. Each event’s entry at NCEI: 645843, 645844, 645845, 645846.