A severe thunderstorm passing over Lost Trail Pass produced up to one inch hail, impacting travel over Highway 93.
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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 severe thunderstorm passing over Lost Trail Pass produced up to one inch hail, impacting travel over Highway 93.
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 13, 1:55 PM MST, 6 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MISSOULA MT 255 PM MDT THU AUG 13 2009 ...COOL AND WET WEEKEND EXPECTED WITH SNOW POSSIBLE ABOVE 8000 FEET ALONG THE CONTINENTAL DIVIDE... .DISCUSSION...PRETTY ACTIVE AND COMPLEX WEATHER PATTERN THE NEXT 48 HOURS. CURRENTLY A BAND OF RAIN EXTENDS FROM WEST CENTRAL IDAHO THROUGH WEST CENTRAL MONTANA UP TO THE GLACIER NP REGION. BEHIND THIS BAND SHOWERS AND THUNDERSTORMS ARE DEVELOPING IN NORTHEAST IDAHO AND THE PANHANDLE OF IDAHO AND WILL ENTER FAR NORTHWEST MONTANA LATE THIS AFTERNOON AND EVENING. AHEAD OF THE BAND OF RAIN SCATTERED THUNDERSTORMS ARE DEVELOPING IN SOUTHWEST MONTANA. SOME OF THESE STORMS MAY PRODUCE SOME BRIEF HEAVY RAIN LOCAL GUSTY WINDS. ALL OF THIS ACTIVITY IS EXPECTED TO DIMINISH LATE TONIGHT. A STRONG LOW PRESSURE SYSTEM FOR THIS TIME OF YEAR WILL MOVE INTO WASHINGTON FRIDAY AND ACROSS NORTHWEST MONTANA DURING FRIDAY NIGHT AND SATURDAY. THIS IS A COLD SYSTEM FOR THIS TIME OF YEAR AND CONTAINS ABUNDANT MOISTURE. THE MAJORITY OF PRECIPITATION WILL FALL AHEAD OF THE LOW ON THROUGH FRIDAY AFTERNOON AND EVENING. EXACT PLACEMENT OF THE LOW IS UNCERTAIN AT THIS TIME...BUT CURRENTLY THE MOST AMOUNTS OF RAIN...UP TO AN INCH...ARE POSSIBLE ALONG THE CONTINENTAL DIVIDE. VALLEY LOCATIONS IN WEST CENTRAL MONTANA COULD SEE UP TO A HALF INCH OF RAIN. SATURDAY NIGHT...THE LOW MOVES OVER THE REGION AND USHERS IN MUCH COOLER AIR. SNOW LEVELS ARE EXPECTED TO FALL TO NEAR 7000 FEET. WRAP AROUND MOISTURE FROM THIS LOW IS EXPECTED TO PERSIST ALONG THE CONTINENTAL DIVIDE...ESPECIALLY GLACIER NATIONAL PARK. SNOW ACCUMULATIONS ABOVE 8000 FEET UP TO AN INCH ARE POSSIBLE. WHERE AND HOW MUCH WILL DEPEND ON THE TRACK OF THE LOW AND TIMING OF THE COLDEST AIR. STAY TUNED FOR FURTHER UPDATES. SUNDAY...UNSTABLE AIR AND MOISTURE IN PLACE BEHIND THE LOW WILL PRODUCE AFTERNOON SHOWERS ACROSS THE REGION. THE UPPER LEVEL LOW WILL GRADUALLY SHIFT EASTWARD SATURDAY NIGHT AND SUNDAY...BRINGING A SLOW DECREASE IN PRECIPITATION FROM WEST TO EAST. SUNDAY AFTERNOON WILL LIKELY STILL BE SHOWERY...ESPECIALLY ALONG THE CONTINENTAL DIVIDE. WITH CONTINUED CLOUD COVER AND A COOL AIRMASS OVERHEAD...TEMPERATURES ARE EXPECTED TO REMAIN BELOW NORMAL. FORECAST MODELS HANG ON TO A COOL NORTH TO NORTHWESTERLY FLOW FOR MONDAY THROUGH WEDNESDAY WITH A RIDGE OF HIGH PRESSURE BEGINNING TO BUILD OFF THE WEST COAST. THIS WILL ALLOW TEMPERATURES TO REMAIN NEAR NORMAL FOR THIS TIME OF YEAR. THERE IS SOME DISCREPANCY ON HOW MUCH MOISTURE AND ENERGY WILL BE ABLE TO PROPAGATE THROUGH THE FLOW...SO KEPT THE CHANCE OF PRECIPITATION NEAR CLIMATOLOGY UNTIL BETTER CONSISTENCY IS REACHED. THE RIDGE OF HIGH PRESSURE IS EXPECTED TO MOVE OVER THE NORTHERN ROCKIES LATE NEXT WEEK...BRINGING A DRYING AND WARMING TREND TO THE AREA. && .AVIATION...A BROAD LINE OF SHOWERS WILL SLOWLY WORK ITS WAS ACROSS THE REGION THIS AFTERNOON AND EVENING RESULTING IN PERIODS OF LIGHT RAINFALL AT KGPI AND KMSO THROUGH THIS EVENING. ISOLATED THUNDERSTORMS WILL ALSO BE POSSIBLE AT KGPI THROUGH THIS EVENING. TO THE SOUTH...THUNDERSTORMS HAVE BEGUN TO DEVELOP OVER THE BITTERROOT AND SAPPHIRE MOUNTAINS. ADDITIONAL STORMS ARE EXPECTED TO DEVELOP THROUGH THE REST OF TODAY AND LIKELY IMPACT KMSN AND KBTM. VARIABLE...GUSTY WINDS WILL LIKELY BE THE PRIMARY THREAT WITH THESE THUNDERSTORMS. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...NONE. ID...NONE. && SHORT TERM...RPN LONG TERM....PALLISTER AVIATION...DICKERSON
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE MISSOULA MT 240 PM MDT THU AUG 13 2009 MTZ002-141200- WEST GLACIER REGION- 240 PM MDT THU AUG 13 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST MONTANA. .DAY ONE...THIS AFTERNOON AND TONIGHT RAIN SHOWERS WILL PERSIST THROUGH THE EVENING HOURS...HOWEVER WIDESPREAD HAZARDOUS WEATHER IS NOT ANTICIPATED AT THIS TIME. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY A COLD LOW PRESSURE SYSTEM FOR THIS TIME OF YEAR WILL MOVE THROUGH FRIDAY AND SATURDAY. SNOW IS POSSIBLE AS SNOW LEVELS ARE EXPECTED TO LOWER TO AROUND 7500 FEET FRIDAY NIGHT AND 7000 FEET SATURDAY. THERE IS A POSSIBILITY THAT AN INCH SNOW COULD FALL AT HIGHER ELEVATIONS ABOVE 8000 FEET FRIDAY NIGHT AND SATURDAY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. MTZ043-141200- POTOMAC/SEELEY LAKE REGION- 240 PM MDT THU AUG 13 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WEST CENTRAL MONTANA. .DAY ONE...THIS AFTERNOON AND TONIGHT SCATTERED SHOWERS ARE EXPECTED THROUGH 9 PM...HOWEVER WIDESPREAD HAZARDOUS WEATHER IS NOT ANTICIPATED THROUGH THE EVENING. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY A COLD LOW PRESSURE SYSTEM FOR THIS TIME OF YEAR WILL MOVE THROUGH FRIDAY AND SATURDAY. SNOW IS POSSIBLE AS SNOW LEVELS ARE EXPECTED TO LOWER TO AROUND 8000 FEET FRIDAY NIGHT AND 7500 FEET SATURDAY. THERE IS A POSSIBILITY THAT AN INCH SNOW COULD FALL AT HIGHER ELEVATIONS ABOVE 8000 FEET FRIDAY NIGHT AND SATURDAY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. MTZ001-004-140300- KOOTENAI/CABINET REGION-LOWER CLARK FORK REGION- 240 PM MDT THU AUG 13 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST MONTANA AND WEST CENTRAL MONTANA. .DAY ONE...THIS AFTERNOON AND TONIGHT THUNDERSTORMS WHICH HAVE FORMED THIS AFTERNOON IN THE IDAHO PANHANDLE AND NORTHEAST WASHINGTON WILL MOVE INTO NORTHWEST MONTANA LATE THIS AFTERNOON THROUGH THE EVENING. THESE STORMS WILL BE CAPABLE OF PRODUCING DEADLY LIGHTNING...VERY HEAVY RAINFALL AND GUSTY WINDS. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY AM UNSEASONABLE COLD UPPER LEVEL SYSTEM WILL MOVE INTO THE REGION THIS WEEKEND. HOWEVER WIDESPREAD HAZARDOUS WEATHER APPEAR UNLIKELY AT THIS TIME. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. IDZ009-010-MTZ006-007-140300- WESTERN LEMHI COUNTY-EASTERN LEMHI COUNTY- BITTERROOT/SAPPHIRE MOUNTAINS-BUTTE/BLACKFOOT REGION- 240 PM MDT THU AUG 13 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL IDAHO AND WEST CENTRAL MONTANA. .DAY ONE...THIS AFTERNOON AND TONIGHT STRONG THUNDERSTORMS HAVE BEGUN TO DEVELOP OVER THE BITTERROOT AND SAPPHIRE MOUNTAINS THIS AFTERNOON. THESE STORMS WILL MOVE TO THE NORTHEAST AT AROUND 30 MPH AND BE CAPABLE OF PRODUCING GUSTY WINDS TO 50 MPH...HAIL UP TO 1 INCH IN DIAMETER AND BRIEF HEAVY RAINFALL. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY A COLD LOW PRESSURE SYSTEM FOR THIS TIME OF YEAR WILL MOVE THROUGH FRIDAY AND SATURDAY. SNOW IS POSSIBLE AS SNOW LEVELS ARE EXPECTED TO LOWER TO AROUND 8000 FEET FRIDAY NIGHT AND 7500 FEET SATURDAY. THERE IS A POSSIBILITY THAT AN INCH SNOW COULD FALL AT HIGHER ELEVATIONS ABOVE 8000 FEET FRIDAY NIGHT AND SATURDAY. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MISSOULA MT
248 PM MDT THU AUG 13 2009
IDZ009-010-MTZ005-006-132130-
EASTERN LEMHI COUNTY-WESTERN LEMHI COUNTY-
BITTERROOT/SAPPHIRE MOUNTAINS-MISSOULA/BITTERROOT VALLEYS-
248 PM MDT THU AUG 13 2009
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN RAVALLI...SOUTHWESTERN
GRANITE AND NORTHERN LEMHI COUNTIES UNTIL 330 PM MDT...
AT 242 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 14 MILES WEST OF GIBBONSVILLE...OR 33 MILES
NORTHWEST OF SALMON...MOVING NORTHEAST AT 35 MPH.
HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 50 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN AND FREQUENT
DANGEROUS LIGHTNING.
LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...LOST TRAIL PASS AND
SULA.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
IF THREATENING WEATHER APPROACHES YOUR AREA...GO INDOORS AND STAY
AWAY FROM WINDOWS. IF YOU ARE CAUGHT OUTSIDE...MOVE TO A WELL
PROTECTED AREA.
&&
LAT...LON 4582 11364 4582 11373 4573 11381 4575 11388
4569 11388 4566 11392 4562 11390 4547 11432
4562 11445 4574 11435 4611 11383 4585 11358
TIME...MOT...LOC 2047Z 237DEG 31KT 4563 11415
DICKERSONSPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MISSOULA MT
254 PM MDT THU AUG 13 2009
MTZ006-007-132145-
BITTERROOT/SAPPHIRE MOUNTAINS-BUTTE/BLACKFOOT REGION-
254 PM MDT THU AUG 13 2009
...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL POWELL AND NORTHEASTERN
GRANITE COUNTIES UNTIL 345 PM MDT...
AT 251 PM MDT...STORM SPOTTERS REPORTED A STRONG THUNDERSTORM NEAR
PHILIPSBURG...OR 20 MILES SOUTH OF DRUMMOND...MOVING NORTHEAST AT 35
MPH.
HAIL UP TO ONE-HALF INCH IN DIAMETER IS EXPECTED WITH THIS STORM.
LOCATIONS NEAR THE PATH OF THIS STORM
INCLUDE...DRUMMOND...GARRISON...MAXVILLE...PRINCETON...HALL...JENS...
GOLDCREEK...BROCK CREEK...HELMVILLE...AVON...FINN...ELLISTON AND
BLOSSBURG.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
IF THREATENING WEATHER APPROACHES YOUR AREA...GO INDOORS AND STAY
AWAY FROM WINDOWS. IF YOU ARE CAUGHT OUTSIDE...MOVE TO A WELL
PROTECTED AREA.
&&
LAT...LON 4626 11326 4640 11338 4712 11282 4709 11278
4684 11278 4684 11255 4670 11252 4670 11242
4666 11240 4666 11233 4662 11228 4659 11229
TIME...MOT...LOC 2053Z 234DEG 31KT 4640 11325
KITSMILLERThe Missoula radar (KMSX), 149 km away, was scanning. The volume nearest the first event began at 20:59 UTC.
1 hail. Local standard time, as filed.
A motorist traveling over Lost Trail Pass observed nickel and quarter sized hail while traveling over the Montana side of the pass.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2009Every state in 2009This day in weather historyWarnings in Montana, August 2009
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: 192917.