Tornadoes and Hail in Montana, August 11, 2005

Name: Tornadoes and Hail in Montana, August 11, 2005
Start: 2005-08-11T19:27
End: 2005-08-11T20:43
Location: Montana

August 11, 2005 · NWS BYZ · 7 events in 2 counties and zones

5 hail, 2 tornado, as filed by the National Weather Service.

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: None recorded
Crop damage: None recorded
Events: 7

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 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 Billings, MT wrote its last area forecast discussion before the first event at Aug 11, 1:47 PM MST, 5 hours 40 minutes earlier.

Area forecast discussion, Aug 11, 1:47 PM MST, 5 hours 40 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
247 PM MDT THU AUG 11 2005

.SHORT TERM...VALID FOR FRI AND SAT...

WEATHER CHANGE ON TAP FOR THE REGION AS A STRONG NORTHERLY FLOW
ALOFT IS PROGGED TO DOMINATE SHORT TERM WEATHER FORECAST. FOR
TODAY...FLOW IS A BIT MORE DOWNSLOPISH THAN PREVIOUS DAYS BUT
ENOUGH LOW LEVEL MOISTURE LINGERS OVER THE REGION TO ALLOW
THUNDERSTORMS TO DEVELOP. CAPE IS NOT NEARLY AS HIGH AS PREVIOUS
DAYS BUT SHEAR IS A BIT BETTER SO SOME STORMS MAY PUT DOWN SOME
SMALL HAIL. COLD FRONT PROGGED TO MOVE INTO THE AREA SLOWER THAN
PREVIOUS FORECAST AND LOOKS TO BE AROUND 15Z FOR BILLINGS. STILL
DO NOT EXPECT MUCH WARMING TO OCCUR TOMORROW AND BEHIND THE FRONT
MUCH COOLER TEMPERATURES WITH UPSLOPE FLOW AND LOW CLOUDS WILL
MAKE IT FEEL VERY UNSUMMERLIKE. MOST INTERESTING PERIOD OF WEATEHR
WILL OCCUR LATE FRIDAY NIGHT THROUGH EARLY SATURDAY WHEN AN UPPER
LEVEL SHORTWAVE ROLLS ACROSS THE UPLSOPE LOW LEVEL AIRMASS AND
PROVIDES A DYNAMIC PERIOD OF LIFT. TEMPERATURES AT UPPER LEVEL
LOOK TO BE SUFFICIENT FOR SNOW AND WILL BE MENTIONING
ACCUMULATIONS FOR LOCATIONS ABOVE 7000 FEET. SATURDAY WILL BE AN
ANOTHER WELL BELOW NORMAL TEMPERATURE DAY BUT PRECIPITATION WILL
BE TAPERING OFF DURING THE DAY. BORSUM

.LONG TERM...VALID FOR SUN...MON...TUE...WED...THU...

FEW CHANGES TO THE GOING FORECAST. MAIN ADJUSTMENT WAS TO POPS.
DECREASED POPS SUNDAY AND SUNDAY NIGHT AS CONVERGENCE ALOFT SHOULD
PUT LARGE SUBSIDENCE AREA OVER SOUTHERN MONTANA. ANOTHER WAVE
ALOFT MOVES THROUGH ON MONDAY AFTERNOON FOR AN ADDITIONAL CHANCE
OF AFTERNOON AND EVENING SHOWERS. RIDGE ALOFT BUILDS INTO THE AREA
TUESDAY AND SOUTHWEST FLOW BECOMES ESTABLISHED THURSDAY. NEXT
SYSTEM DEVELOPS OVER PACIFIC NORTHWEST AND BEGINS TO SHED PIECES
OF ENERGY FURTHER TO THE EAST OVER MONTANA. STILL A LOT OF
UNCERTAINTY REGARDING STRENGTH AND TIMING OF NEXT SYSTEM SO LEFT
BROAD BRUSHED LOW POPS IN PLACE. TEMPERATURES SHOULD SLOWLY
INCREASE INTO THE MID TO UPPER 80S BY THURSDAY...WHICH IS NEAR
NORMAL FOR THIS TIME OF YEAR. CHAMBERS

&&

.AVIATION...

EXPECT VFR CONDITIONS THIS AFTERNOON INTO THIS EVENING WITH
ISOLATED SHOWERS AND THUNDERSTORMS MAINLY WEST OF AN MLS-4BQ LINE.
PRECIPITATION SHOULD DIMINISH AFTER MIDNIGHT. PATCHY MVFR TO IFR
CONDITIONS ARE EXPECTED TO DEVELOP AFTER 3 AM MDT WITH FOG
REDUCING VISIBILITIES TO AROUND 3 MILES AT TIMES. INCREASING
CLOUDINESS AND SHOWER ACTIVITY WILL DEVELOP BY MID MORNING FRIDAY. CHAMBERS

&&

.PRELIMINARY POINT TEMP/POPS...

    FRI     SAT     SUN     MON     TUE     WED     THU
-----------------------------------------------------------
BIL 055/063 045/062 046/076 055/080 056/082 058/085 056/083
    24/W    56/R    22/W    00/B    00/B    22/T    22/T
LVM 047/066 036/063 041/073 045/080 046/082 047/083 046/081
    24/W    56/R    22/W    02/T    21/B    22/T    22/T
HDN 054/066 043/063 045/079 053/083 057/085 058/087 057/085
    24/W    54/R    22/W    00/B    00/B    22/T    22/T
MLS 054/067 046/064 046/076 054/082 056/085 057/084 056/082
    23/W    42/R    12/W    00/U    00/B    02/T    22/T
4BQ 054/071 047/063 046/076 053/082 054/084 055/087 054/085
    24/W    53/R    22/W    02/T    01/B    22/T    22/T
BHK 052/067 043/061 046/074 052/078 053/080 054/083 053/081
    22/W    32/R    12/W    00/U    00/B    22/T    22/T
SHR 051/068 045/062 042/075 050/082 051/084 052/086 051/084
    34/W    56/R    20/B    02/T    22/T    22/T    22/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.

&&

WEATHER.GOV/BILLINGS

Hazardous weather outlook, Aug 10, 7:43 PM MST, 23 hours 44 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BILLINGS MT
843 PM MDT WED AUG 10 2005

MTZ028>042-056>058-063>068-WYZ098-099-120245-
SOUTHERN WHEATLAND-MUSSELSHELL-TREASURE-NORTHERN ROSEBUD-CUSTER-
FALLON-NORTHERN STILLWATER-YELLOWSTONE-POWDER RIVER-CARTER-
SOUTHERN BIG HORN-EASTERN CARBON-NORTHERN PARK-
NORTHERN SWEET GRASS-GOLDEN VALLEY-RED LODGE FOOTHILLS-
NORTHERN BIG HORN-SOUTHERN ROSEBUD-JUDITH GAP-PARADISE VALLEY-
LIVINGSTON AREA-BEARTOOTH FOOTHILLS-ABSAROKA/BEARTOOTH MOUNTAINS-
CRAZY MOUNTAINS-NORTHEAST BIG HORN MOUNTAINS-SHERIDAN FOOTHILLS-
843 PM MDT WED AUG 10 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
WYOMING...SOUTHEAST MONTANA...SOUTH CENTRAL MONTANA AND CENTRAL
MONTANA.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

NO HAZARDOUS WEATHER EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

The radar

The Billings radar (KBLX), 34 km away, was scanning. The volume nearest the first event began at 02:27 UTC.

Open the radar archive at this moment

Event by event

5 hail, 2 tornado. Local standard time, as filed.

Tornado, Stillwater

When: August 11, 7:27 PM MST to 7:45 PM MST
Where: Stillwater County, 6 mi W of Molt
Rating: F0
Path length: 7 mi
Path width: 50 yd
Reported by: TRAINED SPOTTER
Coordinates: 45.867, -109.050

Tornado, Yellowstone

When: August 11, 7:45 PM MST to 8:05 PM MST
Where: Yellowstone County, 12 mi SW of Acton
Rating: F0
Path length: 2 mi
Path width: 50 yd
Reported by: TRAINED SPOTTER
Coordinates: 45.817, -108.867

Thunderstorms began developing along an east to west oriented surface boundary southwest of Billings around 5:50 PM 11 August 2005 and remained anchored to the boundary through about 7:20 PM. A left moving supercell then began to move off the boundary and to the northeast. Over the next 45 minutes, the storm split numerous times as it moved northeast, but remained the dominate splitting cell. During this time, the storm either ignited or moved over a recently ignited fire by earlier convection. Around 8:27 PM, shortly after passing over the fire, a tornado was spotted by a motorcyclist traveling in the area. The cyclonic tornado likely developed along the storm's outflow and was not associated with the left moving supercell's mesocyclone. A pre-existing surface boundary possibly from convection to the north, was also in the vicinity. The F0 tornado moved northeast around 20 mph until 9:05 PM, when it lifted.Visually, the tornado was ominous looking, possibly because it picked up smoke. However, it appears the tornado's rotation was weak per video and lack of any evidence of the tornado in a storm survey conducted by a National Weather Service employee.

Hail, Yellowstone

When: August 11, 7:52 PM MST
Where: Yellowstone County, 9 mi SW of Acton
Measured: 1.75 in hail
Reported by: TRAINED SPOTTER
Coordinates: 45.833, -108.817

Hail, Stillwater

When: August 11, 8:10 PM MST
Where: Stillwater County, 1 mi W of Molt
Measured: 1.75 in hail
Reported by: TRAINED SPOTTER
Coordinates: 45.867, -108.950

Hail, Stillwater

When: August 11, 8:15 PM MST
Where: Stillwater County, Absarokee
Measured: 1.25 in hail
Reported by: TRAINED SPOTTER
Coordinates: 45.500, -109.433

Hail, Stillwater

When: August 11, 8:34 PM MST
Where: Stillwater County, 8 mi S of Columbus
Measured: 0.88 in hail
Reported by: TRAINED SPOTTER
Coordinates: 45.517, -109.250

Hail, Stillwater

When: August 11, 8:43 PM MST
Where: Stillwater County, 8 mi SSE of Columbus
Measured: 0.75 in hail
Reported by: TRAINED SPOTTER
Coordinates: 45.533, -109.183

What these are

Tornado: A violently rotating column of air in contact with the ground and extending from a thunderstorm, filed with its path, width and Fujita or Enhanced Fujita rating from the damage survey.
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 2005 Every state in 2005 This day in weather history The tornado archive for Montana, 2005 Warnings in Montana, August 2005

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: 5469308, 5469309, 5469306, 5469307, 5469305, 5469304, 5469303.