Montana, 2002

Hail and Damaging Winds in Montana, August 4, 2002

August 4, 2002 · NWS MSO · 8 events in 2 counties and zones

Supercell thunderstorm formed over the Bitterroot Valley near Hamilton and moved north through the valley, impacting the communities of Stevensville to Florence. Extensive damage to property and crops was caused by large hail up to golf ball size, and strong winds in the Stevensville area.

Where it happened

Every event with a place to put it; 1 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

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The toll

Deaths
0
Injuries
0
Property damage
$2.0 million
Crop damage
$100,000
Events
8

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.

Supercell thunderstorm formed over the Bitterroot Valley near Hamilton and moved north through the valley, impacting the communities of Stevensville to Florence. Extensive damage to property and crops was caused by large hail up to golf ball size, and strong winds in the Stevensville area. Hail drifts up to 3 feet deep were reported along with flooding of one road from heavy rain with 3 inches in 30 minutes. State snowplows had to be called out to clear several miles of Highway 93 from Stevensville turnoff north towards Florence. Houses, garages, and farm outbuildings were damaged by falling trees, flying debris, hail and wind. The hail stripped trees bare, smashed windows, dented cars, bruised and cut horses as well as blew fruit off trees. Farmers reported bails of hay rolling 100 yards from the strong winds, with tons of unbailed hay blown away and lost. The storm weakened as it approached the Missoula Valley, but still caused large tree limbs to be broken off near the Linda Vista Golf Course, along with hail covering and damaging many yards in drifts of several inches deep.

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 4, 1:25 PM MST, 3 hours 48 minutes earlier.

Area forecast discussion, Aug 4, 1:25 PM MST, 3 hours 48 minutes before
WESTERN MONTANA AND NORTH CENTRAL IDAHO FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
225 PM MDT SUN AUG 4 2002

.SHORT TERM...UPDATES TO ZFP AND SFP IN STORE.

CURRENTLY...A COUPLE OF STORM LEFT IN THE WESTERN MONTANA CWA AFTER
SCATTERED GARDEN VARIETY THUNDERSTORMS FROM SALMON TO BUTTE...AND AN
IMPRESSIVE STORM THAT TRAVELED NORTH THROUGH THE BITTERROOT VALLEY.
THIS STORM PRODUCED WIDESPREAD SMALL AND LARGE HAIL...COVERING THE
GROUND IN MANY LOCATIONS FROM HAMILTON TO MISSOULA. SCATTERED SHOWERS
AND A FEW EMBEDDED RUMBLES OF THUNDER WERE DEVELOPING IN THE
KALISPELL AREA...AND MORE SCATTERED SHOWERS IN EASTERN OREGON/WA.
THESE SHOWERS ARE WELL AHEAD OF SLOW MOVING COOL FRONT/BATCH OF
DEEPER MOISTURE IN MID LEVEL (H7) TROUGH/CONVERGENT REGION. THIS
FEATURE WILL PRODUCE THE BEST PRECIP CHANCES FOR THE REMAINDER OF THE
NIGHT...MAINLY FROM MISSOULA NORTHWARD. THE SOUTHEAST CWA WILL SEE
ONLY SLIGHT CHANCES FOR SHOWERS/THUNDERSTORMS. THE STRONGEST
SHORTWAVE HAS SHIFTED EAST OF THE DIVIDE...AND ONLY WEAK DUSTURBANCES
WILL BE MOVING THROUGH THE FLOW...OVER TOP OF LOW LEVEL BOUNDARY THAT
WILL ONLY BE MAKING SLOW PROGRESS EASTWARD.

LOOK FOR SKIES TO BECOME CLOUDY ACROSS THE NW CWA WITH SCATTERED
SHOWERS DEVELOPING...AND POSSIBLY AN EMBEDDED THUNDERSTORM. WILL
HAVE TO BUMP MIN TEMPS UPWARD SEVERAL DEGREES FOR WESTERN MONTANA
TONIGHT DUE TO CLOUDS. NORTH CENTRALIDAHO TEMPS LOOK OK FOR FRONTAL
PASSAGE NEAR THAT AREA BY MORNING. WILL ALSO THROW IN SOME PATCHY
FOG FOR THE BITTERROOT VALLEY OVERNIGHT DUE TO VERY GOOD RAINS IN
MANY AREAS...ESPECIALLY ALONG THE EAST SIDE OF THE VALLEY. DICKSON

.LONG TERM...AVN AND MRF ARE SLOWER IN MOVING THE UPPER LEVEL TROUGH
OUT OF THE REGION. WILL KEEP A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS ON THURSDAY. BOTH MODELS FORM A CUT OFF LOW AS THE
TROUGH MOVES INTO CENTRAL MONTANA ON FRIDAY...WITH THE MRF HAVING THE
CENTER OF THE LOW FURTHER NORTH. THEN BY FRIDAY NIGHT THE MRF DROPS
THE LOW TO THE SOUTHEAST...PREFER THE AVN LOCATION OF THE LOW ON
FRIDAY...THEREFORE WILL HOLD ON TO A SLIGHT CHANCE OF SHOWERS IN THE
EASTERN ZONES FRIDAY...AND DRY WEST. FLAT RIDGE BUILDS INTO THE AREA
SATURDAY AND SUNDAY...FOR DRY CONDITION. KOLATA

.MSO...NONE.

...7-DAY SPOT TEMPS AND POPS...
LIB EBB 055/076 048/078 048/080 39433333
     UUUU 047/081 049/082 049/084 051/086 3911000000
FCA EBB 054/072 046/074 046/075 39433333
     UUUU 045/076 047/080 047/082 049/084 3911000000
POL EBB 056/073 051/075 050/076 39433333
     UUUU 049/077 051/081 051/083 053/087 3911000000
MSO BBB 056/075 047/076 048/076 39333333
     UUUU 047/079 049/082 049/084 051/088 3911000000
HMM BBB 055/074 049/075 046/077 39233333
     UUUU 045/078 047/081 047/083 049/087 3911000000
BTM BBB 049/073 043/074 044/076 39133322
     BBUU 044/076 046/079 046/081 048/080 3911100000
ORO BBB 056/075 053/078 054/080 39433333
     UUUU 054/083 058/085 058/087 060/096 3911000000
GRV BBB 052/071 048/073 049/076 39433333
     UUUU 049/079 053/080 053/082 055/088 3911000000
SMN BBB 054/077 045/076 046/079 39133322
     BUUU 046/080 048/081 048/083 050/087 3911000000

In the hours before

Special weather statement, Aug 4, 1:57 PM MST, 3 hours 16 minutes before
IDZ006-009-010-MTZ005>007-043-042130-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MISSOULA MT
256 PM MDT (156 PM PDT) SUN AUG 4 2002

...A SEVERE THUNDERSTORM WATCH IS NOT IN EFFECT FOR FLATHEAD...
POWELL...DEER LODGE AND SILVER BOW COUNTIES...

THE WATCH THAT WAS JUST ISSUED MISTAKENLY PUT THESE COUNTIES
IN THE WATCH. ALTHOUGH THUNDERSTORMS ARE EXPECTED...THEY ARE NOT
EXPECTED TO BE SEVERE. THEREFORE THERE IS NO SEVERE THUNDERSTORM
WATCH FOR THESE COUNTIES THIS EVENING.
Local storm report, Aug 4, 4:42 PM MST, 31 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
542 PM MDT SUN AUG 4 2002

TIME(MDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION......

0528 PM    4 SE HAMILTON             MT    1 INCH HAIL
08/04/02   RAVALLI                         REPORTED BY NWS SPOTTER

0531 PM    3 S HAMILTON              MT    1 INCH HAIL
08/04/02   RAVALLI                         REPORTED BY NWS SPOTTER

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

5 hail, 2 thunderstorm wind, 1 heavy rain. Local standard time, as filed.

Hail, Ravalli

When
August 4, 5:13 PM MST to 5:14 PM MST
Where
Ravalli County, Stevensville
Measured
1 in hail
Property damage
$2.0 million
Crop damage
$100,000
Reported by
TRAINED SPOTTER
Coordinates
46.500, -114.083

Heavy Rain, Ravalli

When
August 4, 5:15 PM MST to 5:45 PM MST
Where
Ravalli County, Stevensville
Reported by
GENERAL PUBLIC
Coordinates
46.082, -114.121 (the zone’s center; the record gives no point)

Hail, Ravalli

When
August 4, 5:15 PM MST
Where
Ravalli County, Stevensville
Measured
1.75 in hail
Reported by
BROADCAST MEDIA
Coordinates
46.500, -114.083

Thunderstorm Wind, Ravalli

When
August 4, 5:15 PM MST
Where
Ravalli County, 1 mi W of Stevensville
Measured
54 kt (62 mph)
Reported by
GENERAL PUBLIC
Coordinates
46.500, -114.100

Hail, Missoula

When
August 4, 5:32 PM MST
Where
Missoula County, 5 mi S of Lolo
Measured
0.75 in hail
Reported by
TRAINED SPOTTER
Coordinates
46.717, -114.117

Hail, Missoula

When
August 4, 5:52 PM MST
Where
Missoula County, Missoula
Measured
0.88 in hail
Reported by
TRAINED SPOTTER
Coordinates
46.883, -114.000

Thunderstorm Wind, Missoula

When
August 4, 5:52 PM MST
Where
Missoula County, Missoula
Measured
54 kt (62 mph)
Reported by
GENERAL PUBLIC
Coordinates
46.883, -114.000

Hail, Missoula

When
August 4, 5:56 PM MST
Where
Missoula County, Missoula
Measured
0.88 in hail
Reported by
TRAINED SPOTTER
Coordinates
46.883, -114.000

What these are

Hail
Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
Heavy Rain
Rainfall totals unusual for the place and season that did not produce a flood.
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

More

Every storm in Montana in 2002Every state in 2002This day in weather historyWarnings in Montana, August 2002

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: 5313834, 5313835, 5313836, 5313841, 5313837, 5313838, 5313839, 5313840.