A cold front moving across western Montana combined with a steady stream of moisture from the Pacific set the stage for strong thunderstorms. Once the atmosphere became unstable due to day time heating severe thunderstorms developed over Glacier National Park.
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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.
The episode as NWS MSO wrote it up.
A cold front moving across western Montana combined with a steady stream of moisture from the Pacific set the stage for strong thunderstorms. Once the atmosphere became unstable due to day time heating severe thunderstorms developed over Glacier National Park.
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 7, 1:03 PM MST, 5 hours 27 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
203 PM MDT THU JUL 7 2011
.DISCUSSION...THUNDERSTORMS HAVE DEVELOPED ACROSS PARTS OF CENTRAL
IDAHO AND ARE MOVING NORTHEAST TOWARD SOUTHWEST/WEST CENTRAL
MONTANA. THUNDERSTORM DEVELOPMENT IS EXPECTED TO CONTINUE THROUGH
THE EVENING HOURS ACROSS THESE REGIONS. THE BIGGEST IMPACT WITH
THESE STORMS WILL START OUT WITH MAINLY GUSTY OUTFLOW WINDS. THE
LOWER ATMOSPHERE WILL BEGIN TO MOISTEN UP LATE THIS AFTERNOON AND
STORMS WILL TRANSITION TO MORE WET WITH BRIEF HEAVY RAIN POSSIBLE
WITH STORMS.
LATER THIS EVENING A COLD FRONT WILL BEGIN TO INFLUENCE THE
REGION. DYNAMIC SUPPORT WILL CONTINUE LATE THIS EVENING THROUGH
MUCH OF THE OVERNIGHT HOURS AS THE FRONT NEARS. THIS WILL RESULT
IN CONTINUED SCATTERED SHOWERS AND THUNDERSTORMS WITH AREAL
COVERAGE OF LIGHTNING GRADUALLY DECREASING BY FRIDAY MORNING.
FRIDAY...SHOWERS WILL END EARLY IN THE MORNING AS THE STRONG COLD
FRONT PUSHES THROUGH THE NORTHERN ROCKIES. THIS FRONT IS
ACCOMPANIED BY A STRONG JET STREAM ALOFT WITH TIGHT SURFACE
PRESSURE GRADIENTS. THIS WILL RESULT IN STRONG WESTERLY WINDS
THROUGHOUT THE DAY WITH GUSTS UP TO 40 MPH OR MORE IN AREAS. THE
STRONG WINDS WILL IMPACT FLATHEAD LAKE WITH INCREASING WAVE
HEIGHTS. MUCH COOLER TEMPERATURES ARE EXPECTED FRIDAY WITH HIGHS
15 DEGREES COOLER THAN THURSDAY.
SATURDAY THROUGH MONDAY...HIGH PRESSURE QUICKLY BUILDS OVER THE
REGION. DRY CONDITIONS WITH ABOVE NORMAL TEMPERATURES WILL RETURN.
HIGHS IN THE MID 80S TO NEAR 90S ARE EXPECTED.
TUESDAY AND WEDNESDAY...MODELS ARE SHOWING LOW PRESSURE OFF THE
WEST COAST DEVELOPING AND PUSHING THE MAIN UPPER RIDGE EAST. THIS
WILL RESULT IN MORE OF A SOUTHERLY FLOW AND POTENTIAL FOR
AFTERNOON/EVENING THUNDERSTORMS.
&&
.AVIATION...BUILDING CUMULONIMBUS AND THUNDERSTORMS ARE POSSIBLE
AT KBTM KMSO AND KSMN THROUGH THIS AFTERNOON AND GUSTY OUTFLOW WINDS
ARE POSSIBLE WITH PASSING STORMS. EXPECT MAINLY CLEAR SKIES AT
KGPI INTO THE LATE AFTERNOON BEFORE CLOUD COVER INCREASES. A COLD
FRONT WILL APPROACH THE REGION TONIGHT. THIS WILL RESULT IN A
POTENTIAL FOR SHOWERS AND ISOLATED THUNDERSTORMS AT ALL TERMINALS
AFTER 08/0400Z. THE STRONG FRONT WILL MOVE THROUGH THE NORTHERN
ROCKIES FRIDAY. ALL TERMINALS WILL EXPERIENCE STRONG WEST WINDS
AFTER 08/1200Z. GUSTS AROUND 35-40 KNOTS ARE POSSIBLE AT KMSO, KGPI
AND KBTM THROUGHOUT THE DAY.
&&
NOTE: FLOOD WATCHES...WARNINGS AND ADVISORIES WILL NOT BE LISTED BELOW.
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WIND ADVISORY FROM 6 AM TO 9 PM MDT FRIDAY BUTTE/BLACKFOOT
REGION...KOOTENAI/CABINET REGION...LOWER CLARK FORK
REGION...MISSOULA/BITTERROOT VALLEYS...POTOMAC/SEELEY LAKE
REGION...WEST GLACIER REGION.
WIND ADVISORY FROM 6 AM TO 9 PM MDT FRIDAY FLATHEAD/MISSION
VALLEYS.
ID...NONE.
&&
SHORT TERM...RPN
LONG TERM....KITSMILLER
AVIATION...RPNThe Missoula radar (KMSX), 166 km away, was scanning. The volume nearest the first event began at 01:30 UTC.
1 thunderstorm wind. Local standard time, as filed.
Wind gusts over 60 mph were estimated due to several trees 1 to 2 feet in diameter being knock down near Apgar. In addition a dozen trees approximately 1 foot in diameter were knocked down along Lake McDonald.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2011Every state in 2011This day in weather historyWarnings in Montana, July 2011
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: 329268.