Hail and Damaging Wind in Montana, July 13 to 16, 2011

Name: Hail and Damaging Wind in Montana, July 13 to 16, 2011
Start: 2011-07-13T14:00
End: 2011-07-16T19:05
Location: Montana

July 13 to 16, 2011 · NWS MSO · 5 events in 3 counties and zones

Unstable and moist southwest flow aloft produced thunderstorms with hail over western Montana. This flow was caused by an upper level trough off the West Coast.

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: $1,000
Crop damage: $4,000
Events: 5

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.

Unstable and moist southwest flow aloft produced thunderstorms with hail over western Montana. This flow was caused by an upper level trough off the West Coast.

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 13, 1:43 PM MST, 17 minutes earlier.

Area forecast discussion, Jul 13, 1:43 PM MST, 17 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
243 PM MDT WED JUL 13 2011

.DISCUSSION...LOW PRESSURE OFF THE NORTHWEST COAST CONTINUES TO
SEND SHORT WAVES OF ENERGY THROUGH THE NORTHERN ROCKIES. THIS
UNSTABLE ATMOSPHERE HAS RESULTED IN THE DEVELOPMENT OF NUMEROUS
THUNDERSTORMS ACROSS MUCH OF THE SOUTHWEST MONTANA AND EAST
CENTRAL IDAHO THIS AFTERNOON. THUNDERSTORM ACTIVITY IS EXPECTED
THROUGH THE EVENING HOURS.

HEAVY DOWNPOURS OF RAIN IN A SHORT PERIOD OF TIME ARE POSSIBLE
WITH THUNDERSTORMS. THUS A FLASH FLOOD WATCH FOR HAS BEEN ISSUED
FOR THESE AREAS...WITH THE AREAS OF GREATEST IMPACT BEING THOSE
BURNED AREAS AND FLOOD PRONE BASINS INCLUDING NARROW HIGHWAY
CORRIDORS IN STEEP TERRAIN. A SEVERE THUNDERSTORM WATCH HAS ALSO BEEN
ISSUED THROUGH THIS EVENING AS HAIL UP TO AN INCH IN DIAMETER IS
POSSIBLE WITH THESE STORMS.

THE UPPER LEVEL LOW WILL SLOWLY MOVE NORTHEAST INTO ALBERTA CANADA
FRIDAY. ISOLATED CONVECTION IS POSSIBLE OVER SOUTHWEST MONTANA ALSO.
COOLER TEMPS ARE EXPECTED THURSDAY AND FRIDAY WITH HIGHS IN THE
MID 70S TO LOWER 80S.

SATURDAY AND SUNDAY...ANOTHER LOW PRESSURE SYSTEM WILL ENTER THE
NORTHWEST COAST PROVIDING SOUTHWEST FLOW ALOFT AND ONCE AGAIN
BRING PERIODIC SHORTWAVES OF ENERGY INTO THE NORTHERN ROCKIES. THE
RESULT WILL BE A CONTINUED THREAT OF AFTERNOON THUNDERSTORMS
ACROSS THE REGION.

MONDAY AND TUESDAY...STRONG HIGH PRESSURE OVER THE CENTRAL U.S.
WILL MOVE SLIGHTLY WESTWARD...ENOUGH TO INFLUENCE THE NORTHERN
ROCKIES BY PUSHING THE UPPER LEVEL LOW FAR ENOUGH NORTH TO KEEP
THE MAJORITY OF INSTABILITY AND CONVECTION IN CANADA. WARMER
TEMPERATURES ARE ANTICIPATED WITH HIGHS HOVERING AROUND 90 DEGREES
EXPECTED.

&&

.AVIATION...WIDESPREAD SHOWERS AND THUNDERSTORMS WILL CONTINUE
THROUGH LEMHI COUNTY AND SOUTHWEST MONTANA THIS
EVENING...EVENTUALLY EXPANDING WESTWARD THROUGH THE
BITTERROOT...MISSOULA AND FLATHEAD VALLEYS. A VERY MOIST
ATMOSPHERE AND LIGHT DIRECTIONALLY UNIFORM WINDS THROUGH THE MID
LEVELS WILL SUPPORT SLOW MOVING AND TRAINING STORMS THAT MAY PASS
OVER THE AIRFIELDS SEVERAL TIMES THROUGH THE EVENING. STORMS AND
ASSOCIATED CUMULONIMBUS WILL LINGER THROUGH AT LEAST 14/0400Z
BEFORE DISSIPATING. SKIES WILL SLOWLY CLEAR WITH LINGERING
SCATTERED CUMULUS OVERNIGHT AND LIGHT WINDS FOR THURSDAY MORNING
INTO MIDDAY.

&&

NOTE: FLOOD WATCHES...WARNINGS AND ADVISORIES WILL NOT BE LISTED BELOW.

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...NONE.
&&

SHORT TERM...RPN
LONG TERM....RPN
AVIATION...NOLTE

In the hours before

Local storm report, Jul 13, 11:15 AM MST, 2 hours 45 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
1215 PM MDT WED JUL 13 2011

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0245 PM     HAIL             1 NNW BROCK CREEK       46.61N 112.86W
07/12/2011  E1.00 INCH       POWELL             MT   PUBLIC

            QUARTER SIZE HAIL COVERED THE GROUND.

&&

KITSMILLER

The radar

The Missoula radar (KMSX), 99 km away, was scanning. The volume nearest the first event began at 20:58 UTC.

Open the radar archive at this moment

Event by event

4 hail, 1 thunderstorm wind. Local standard time, as filed.

Hail, Powell

When: July 13, 2:00 PM MST to 2:45 PM MST
Where: Powell County, 1 mi NNW of Brock Creek
Measured: 1 in hail
Reported by: Public
Coordinates: 46.613, -112.838

The public reported quarter sized hail that covered the ground.

Hail, Flathead

When: July 13, 6:30 PM MST to 7:00 PM MST
Where: Flathead County, 2 mi N of Bigfork
Measured: 0.88 in hail
Property damage: $1,000
Crop damage: $4,000
Reported by: Trained Spotter
Coordinates: 48.099, -114.070

Trained spotter estimated nickel sized hail, with damage to apples and cherries in an orchard. A truck five miles north of Bigfork received some dents in it's hood.

Hail, Silver Bow

When: July 14, 7:00 AM MST to 7:26 AM MST
Where: Silver Bow County, 8 mi S of Butte
Measured: 1 in hail
Reported by: Trained Spotter
Coordinates: 45.884, -112.530

A trained spotter reported quarter sized hail.

Thunderstorm Wind, Flathead

When: July 16, 6:40 PM MST to 6:50 PM MST
Where: Flathead County, 3 mi SE of Lakeside
Measured: 51 kt (59 mph) measured gust
Reported by: Mesonet
Coordinates: 47.989, -114.174

The Alert weather station on Angel Point of Flathead lake reported a gust to 59 mph.

Hail, Flathead

When: July 16, 6:54 PM MST to 7:05 PM MST
Where: Flathead County, 2 mi S of Olney
Measured: 1.5 in hail
Reported by: Trained Spotter
Coordinates: 48.521, -114.570

A trained spotter estimated 1.50 inch hail.

What these are

Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
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 2011 Every state in 2011 This day in weather history Warnings in Montana, July 2011

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: 331101, 331104, 331102, 331106, 331105.