Evening thunderstorms blew down trees in Hamilton and Missoula with 200 to 300 lightning strikes on the Bitterroot National Forest.
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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.
Evening thunderstorms blew down trees in Hamilton and Missoula with 200 to 300 lightning strikes on the Bitterroot National Forest.
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 30, 7:24 PM MST, 1 hour 36 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MISSOULA MT 824 PM MDT SUN AUG 30 2009 .UPDATE...HAVE UPDATED CHANCE FOR PRECIPITATION...AMOUNT OF PRECIPITATION AND LOCATION OF HEAVIEST PRECIPITATION IN THE FORECAST FOR TONIGHT AND TOMORROW MORNING. && .DISCUSSION...THE STRONG UPPER LEVEL LOW IS CURRENTLY SPINNING NEAR BOISE/IDAHO AND SLOWLY DRIFTING TO THE EAST. A BROAD AREA OF INSTABILITY AND LIFT ASSOCIATED WITH THIS LOW HAS ROTATED OVER CENTRAL IDAHO THIS EVENING...SPREADING SHOWERS AND THUNDERSTORMS ACROSS MUCH OF NORTH CENTRAL IDAHO AND WEST CENTRAL MONTANA. GUSTY WINDS TO ALMOST 50 MPH...UP TO 1/2 INCH HAIL AND VERY HEAVY RAINFALL HAVE BEEN ASSOCIATED WITH THE STRONGER STORMS. THE STRONGEST STORMS ARE CURRENTLY LOCATED IN A SEMI-CIRCLE SPANNING FROM GEORGETOWN LAKE NORTHWEST TO MISSOULA AND THEN WEST NORTHWEST OVER THE NORTHERN CLEARWATER MOUNTAINS TO NEAR ELK RIVER, IDAHO. THIS IS ALONG THE LEADING EDGE OF THE INSTABILITY AXIS AND THUS PROVIDING ABUNDANT LIGHTNING AND VERY STRONG WINDS AS THE STORMS MOVE GENERALLY NORTH. FORECAST MODELS AND OBSERVATIONAL TRENDS FROM SATELLITE IMAGERY SUGGEST THAT THE UPPER LOW WILL SLOWLY TREK EAST WITH A SLIGHT MOTION POSSIBLY TO THE NORTH OVER NIGHT AND FINALLY BEING POSITIONED OVER CUSTER COUNTY, IDAHO BY 12Z MONDAY MORNING. GIVEN THIS MOTION WOULD ANTICIPATE PRECIPITATION TO CONTINUE THROUGH THE NIGHT TO THE NORTH OF THE LOW OVER MUCH OF NORTHERN IDAHO AND CLEARWATER COUNTIES. RECENTLY EXPANDING AND COOLING CLOUD TOPS OVER THESE AREAS INDICATE THAT A BROAD AREA OF LIGHT TO MODERATE SHOWERS WITH EMBEDDED THUNDERSTORMS MAY BE DEVELOPING. FARTHER SOUTH OVER SOUTHERN LEMHI COUNTY ANOTHER WAVE OF INSTABILITY APPEARS TO BE AGGRESSIVELY DEVELOPING GIVEN THE COOLING CLOUD TOPS AND INCREASE IN LIGHTNING ACTIVITY. THESE SHOWERS AND THUNDERSTORMS WILL FOLLOW A SIMILAR TRACK OVER THE NEXT 6 HOURS...MOVING IN A NORTH AND THEN NORTHWEST MOTION AROUND THE UPPER LOW. THE MAIN DIFFERENCE IS THAT THIS WAVE OF DEVELOPMENT IS SETTING UP FARTHER TO THE EAST AND THUS WOULD EXPECT THE GENERAL MOTION TO EVENTUALLY IMPACT THE BIG HOLE...DILLON...WISDOM AREAS BEFORE MOVING NORTH INTO POSSIBLY THE BUTTE AREA LATER TONIGHT OR VERY EARLY MONDAY MORNING. THE FORECAST HAS BEEN UPDATED TO TAKE BOTH OF THESE CONVECTIVE WAVES INTO CONSIDERATION. AS WELL HAVE DECIDED TO CANCEL THE FLASH FLOOD WATCH WHICH WAS IN EFFECT FOR IDAHO COUNTY. AT THIS TIME DO NOT ANTICIPATE SEEING FLASH FLOODING OVER ANY OF THE FLOOD PRONE AREAS...INCLUDING BURN AREAS THROUGH THE NIGHT. HOWEVER GIVEN THAT CONVECTIVE PRECIPITATION WILL CONTINUE OVER LEMHI COUNTY THIS EVENING AND OVERNIGHT HAVE MAINTAINED THE PREVIOUSLY ISSUED WATCH. && .AVIATION...A CUTOFF LOW PRESSURE SYSTEM WILL MOVE THROUGH SOUTH CENTRAL IDAHO EXPANDING SHOWERS AND THUNDERSTORMS ALONG ITS EASTERN EDGE THROUGH SOUTHWEST MONTANA. AREAS SOUTH OF A LINE FROM KMLP TO KHLN WILL HAVE THE BEST CHANCES OF SEEING SHOWER ACTIVITY OVERNIGHT. GUSTY WINDS...VISIBILITY REDUCTIONS AND LOWERED CEILINGS...AT TIMES OBSCURING MOUNTAINS AND PASSES...WILL BE POSSIBLE UNDER THE HEAVIEST SHOWERS. AS THE LOW CONTINUES MOVING TO THE EAST...CLOUDS AND RAIN SHOWERS WILL LINGER THROUGH MONDAY. && .PREV DISCUSSION... /ISSUED 620 PM MDT SUN AUG 30 2009/ DISCUSSION...THE UPPER LEVEL LOW PRESSURE SYSTEM CONTINUES TO MAKE ITS WAY THROUGH CENTRAL IDAHO TODAY AND IS STILL EXPECTED TO BRING HEAVY RAINS TO CENTRAL IDAHO AND SOUTHWEST MONTANA THIS EVENING THROUGH MONDAY AND INTO MONDAY NIGHT. AS THERE IS AN INCREASED AMOUNT OF INSTABILITY ASSOCIATED WITH THIS SYSTEM...THUNDERSTORMS HAVE ALREADY BEGUN TO FORM THROUGHOUT CENTRAL IDAHO THIS AFTERNOON. THUNDERSTORMS WILL CONTINUE THIS AFTERNOON AND EVENING ACROSS LEMHI COUNTY IN IDAHO...CENTRAL IDAHO INCLUDING THE CLEARWATER MOUNTAINS...AND THEN SPREAD INTO SOUTHWEST MONTANA AS THE AFTERNOON WEARS ON. THE MAIN THREAT EXPECTED FROM THESE STORMS WILL BE HEAVY RAINFALL ALTHOUGH SMALL HAIL AND GUSTY WINDS ARE ALSO POSSIBLE IN STRONGER CELLS THAT DEVELOP. HEAVY RAINFALL WILL BECOME WIDESPREAD BY TONIGHT THROUGHOUT CENTRAL IDAHO AS WELL AS SOUTHWEST MONTANA. THE MAIN AREAS EXPECTED TO BE AFFECTED CONTINUE TO BE CENTRAL IDAHO AND LEMHI COUNTY IN IDAHO THROUGH TOMORROW MORNING...AND THEN GRADUALLY SHIFT EASTWARD AND SPREAD ACROSS SOUTHWEST MONTANA INCLUDING THE BUTTE/BLACKFOOT REGION. RAINFALL VALUES OF OVER AN INCH HAVE ALREADY BEEN RECORDED BY SOME LOCATIONS IN THESE AREAS WITH ADDITIONAL AMOUNTS EXPECTED OVERNIGHT. A FLASH FLOOD WATCH HAS THEREFORE BEEN ISSUED, HIGHLIGHTING FLOOD PRONE AREAS IN CENTRAL IDAHO THROUGH TOMORROW MORNING. PLEASE REFER TO THE WATCH(ES) FOR ADDITIONAL FLOOD INFORMATION AND STAY TUNED TO CHANGES IN THE FORECAST AS THIS POTENT WEATHER SYSTEM CONTINUES ON ITS PATH. TUESDAY...THE UPPER CLOSED LOW MOVES INTO EASTERN MONTANA. INSTABILITY AND MOISTURE BEHIND THIS LOW IS EXPECTED TO PRODUCE MOUNTAIN SHOWERS ACROSS MUCH OF WESTERN MONTANA. INSTABILITY WILL REMAIN OVER THE REGION AS THE UPPER LOW EXITS WELL INTO EASTERN MONTANA. WEDNESDAY...ALL MODELS SHOW A RIDGE OF HIGH PRESSURE BRIEFLY NOSING ITS WAY INTO THE NORTHERN ROCKIES. WARM TEMPERATURES ABOUT 10-15 DEGREES ABOVE NORMAL ARE ANTICIPATED UNDER THIS RIDGE. THURSDAY THROUGH SUNDAY...MODELS ARE INDICATING A RETURN TO A PROGRESSIVE PATTERN WITH MORE FREQUENT WEATHER DISTURBANCES MOVING THROUGH THE REGION. THERE ARE SOME DIFFERENCES THOUGH WITH THE PLACEMENT AND TIMING OF VARIOUS SYSTEMS ANTICIPATED. THE GFS SOLUTION IS MOST AGGRESSIVE DEVELOPING A LONG WAVE TROF ACROSS WESTERN U.S. BY THURSDAY AND FRIDAY WHILE OTHER MODELS HOLD OFF ON THIS SOLUTION UNTIL THE WEEKEND GIVEN THIS UNCERTAINTY CLIMATOLOGY FOR PRECIP CHANCES WILL CONTINUE TO BE USED AFTER THURSDAY. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...NONE. ID...NONE. && SHORT TERM...DICKERSON LONG TERM....ALLEGRETTO AVIATION...LOEFFELBEIN
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE MISSOULA MT 240 PM MDT SUN AUG 30 2009 MTZ005>007-311200- MISSOULA/BITTERROOT VALLEYS-BITTERROOT/SAPPHIRE MOUNTAINS- BUTTE/BLACKFOOT REGION- 240 PM MDT SUN AUG 30 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WEST CENTRAL MONTANA. .DAY ONE...THIS AFTERNOON AND TONIGHT A LOW PRESSURE SYSTEM WILL LIKELY BRING NUMEROUS SHOWERS AND SCATTERED THUNDERSTORMS TO NORTH CENTRAL IDAHO THROUGH SOUTHWEST MONTANA THIS AFTERNOON AND OVERNIGHT. THIS REGION HAS THE POTENTIAL OF RECEIVING SIGNIFICANT PRECIPITATION OVER THE NEXT 24 HOURS. SOME THUNDERSTORMS COULD BECOME STRONG ENOUGH TO PRODUCE SMALL HAIL AND GUSTY WINDS THIS AFTERNOON AND EVENING. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. IDZ006-311200- SOUTHERN CLEARWATER MOUNTAINS- 140 PM PDT SUN AUG 30 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL IDAHO. FOR THE LATEST INFORMATION ON WATCHES...WARNINGS AND ADVISORIES...GO TO WEATHER.GOV/MISSOULA. .DAY ONE...THIS AFTERNOON AND TONIGHT A LOW PRESSURE SYSTEM WILL LIKELY BRING NUMEROUS SHOWERS AND SCATTERED THUNDERSTORMS TO NORTH CENTRAL IDAHO THROUGH SOUTHWEST MONTANA THIS AFTERNOON AND OVERNIGHT. THIS REGION HAS THE POTENTIAL OF RECEIVING SIGNIFICANT PRECIPITATION OVER THE NEXT 24 HOURS. SOME THUNDERSTORMS COULD BECOME STRONG ENOUGH TO PRODUCE SMALL HAIL AND GUSTY WINDS THIS AFTERNOON AND EVENING. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .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
612 PM MDT SUN AUG 30 2009
IDZ006-MTZ004>006-310100-
SOUTHERN CLEARWATER MOUNTAINS-
BITTERROOT/SAPPHIRE MOUNTAINS-LOWER CLARK FORK
REGION-MISSOULA/BITTERROOT VALLEYS-
612 PM MDT SUN AUG 30 2009
...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN RAVALLI...SOUTHERN
MISSOULA AND NORTHEASTERN IDAHO COUNTIES UNTIL 700 PM MDT/600 PM
PDT/...
AT 610 PM MDT...STORM SPOTTERS REPORTED A STRONG THUNDERSTORM NEAR
STEVENSVILLE...OR 15 MILES NORTH OF HAMILTON...MOVING NORTH AT 20
MPH.
HAIL UP TO ONE-HALF INCH IN DIAMETER AND WIND GUSTS UP TO 40 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN AND FREQUENT
DANGEROUS LIGHTNING.
LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...STEVENSVILLE...
FLORENCE AND LOLO.
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 11434 4669 11451 4683 11396 4656 11383
4651 11385 4650 11387 4646 11385 4642 11386
4639 11381 4634 11379
TIME...MOT...LOC 0012Z 162DEG 19KT 4647 11410
DICKERSONSPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE MISSOULA MT 714 PM MDT SUN AUG 30 2009 MTZ004>006-043-310200- BITTERROOT/SAPPHIRE MOUNTAINS-LOWER CLARK FORK REGION-MISSOULA/BITTERROOT VALLEYS-POTOMAC/SEELEY LAKE REGION- 714 PM MDT SUN AUG 30 2009 ...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL MISSOULA COUNTY UNTIL 800 PM MDT... AT 711 PM MDT...STORM SPOTTERS REPORTED A STRONG THUNDERSTORM NEAR LOLO...OR 7 MILES SOUTHWEST OF MISSOULA...MOVING NORTH AT 15 MPH. SPOTTERS HAVE REPORTED STRONG WINDS IN THE MILLER CREEK AREA OF MISSOULA. WIND GUSTS UP TO 40 MPH ARE EXPECTED WITH THIS STORM. LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...MISSOULA...EAST MISSOULA...AND FRENCHTOWN. LAT...LON 4705 11432 4698 11393 4675 11394 4675 11430 TIME...MOT...LOC 0112Z 182DEG 12KT 4679 11407
The Missoula radar (KMSX), 18 km away, was scanning. The volume nearest the first event began at 03:58 UTC.
1 thunderstorm wind. Local standard time, as filed.
Thunderstorms that moved from the Bitterroot Valley northward to the Missoula Valley, blew down two rotten cottonwood trees in Hamilton, and three trees in the city of Missoula.
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: 215647.