Severe thunderstorm developed over Beaverhead County producing strong outflow winds.
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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 TFX wrote it up.
Severe thunderstorm developed over Beaverhead County producing strong outflow winds.
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 Great Falls, MT wrote its last area forecast discussion before the first event at Jul 20, 10:40 AM MST, 3 hours 5 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 1140 AM MDT FRI JUL 20 2012 .UPDATE...ACTIVE WEATHER CONTINUES TO BE EXPECTED TODAY AS AN UPPER LEVEL WAVE OVER THE PACIFIC NORTHWEST SWINGS ACROSS THE NORTHERN ROCKIES. THIS FEATURE WILL INTERACT WITH AN UNSEASONABLY MOIST AND UNSTABLE AIRMASS TO PRODUCE SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS OVER MY NORTHWEST ZONES THIS AFTERNOON AND EVENING. GOING FORECAST FOR POTENTIAL SEVERE WEATHER APPEARS TO BE ON TRACK. HAVE MADE UPDATES FOR THE MORNING PERIOD INCREASE SKY COVER AND THE CHANCE OF PRECIPITATION ACROSS MY EASTERN ZONES. HAVE ALSO LOWERED MAX TEMPERATURES ACROSS THE NORTH WHERE CLOUD COVER IS EXPECTED TO PERSIST THROUGH MUCH OF THE DAY. FINALLY...HAVE LOWERED SKY COVERAGE TO PARTLY CLOUDY FOR MUCH OF THE SOUTHERN HALF OF THE CWA THIS AFTERNOON. WATER VAPOR IMAGERY SHOWS A GOOD PUNCH OF DRY AIR PUSHING INTO THIS AREA. WILL NOT REDUCE POPS IN THE SOUTH SINCE THE PARTIAL CLEARING WILL ALLOW THE AIRMASS TO DESTABILIZE WITH SCATTERED THUNDERSTORMS DEVELOPING IN THE SOUTHWEST THIS AFTERNOON THEN MOVING INTO CENTRAL MONTANA DURING THE EVENING. WILL ALSO UPDATE THE HWO PRODUCT IN ORDER TO EMPHASIZE THAT MANY OF THESE STORMS COULD PRODUCE VERY HEAVY RAIN IN SHORT AND INTENSE BURSTS THAT COULD POSSIBLY LEAD TO LOCALIZED FLOODING. MPJ && .AVIATION... UPDATED 1740Z. VFR CONDITIONS EXPECTED TODAY WITH WIDESPREAD MID-LEVEL CEILINGS OVER CENTRAL/SOUTHWEST MT. UPPER LEVEL TROF CURRENTLY IN NORTHERN OREGON WILL MOVE TO NORTHWEST MT BY THIS EVE. INCREASING INSTABILITY AND VEERING WINDS FROM THE APPROACHING TROF WILL LEAD TO DEVELOPMENT OF SCATTERED STRONG-TO-SEVERE THUNDERSTORMS THIS AFTN/EVE... ESPECIALLY ALONG LINE FROM KCTB TO KHVR. STORM ACTIVITY WILL ALSO EXTEND SOUTH TO KGTF/KHLN/KLWT BUT HAVE LESSER CHANCE OF SEVERE CONDITIONS THERE. BRIEF MVFR CONDITIONS FROM HEAVY RAINFALL AND STRONG SHIFTING OUTFLOW WINDS POSSIBLE NEAR ANY STORM CELLS. SKY COVER WILL DIMINISH OVER AERODROMES AFTER 06Z. BRITTON && .PREV DISCUSSION... /ISSUED 550 AM MDT FRI JUL 20 2012/ TODAY THROUGH SUNDAY...A RATHER ACTIVE WEATHER DAY IS EXPECTED OVER NORTH CENTRAL MONTANA TODAY...WHILE QUIETER AND WARM/HOT TEMPERATURES RESIDE OVER THE REGION THROUGH THE WEEKEND. WITH AN UPPER LEVEL RIDGE OF HIGH PRESSURE OVER THE PANHANDLE OF TEXAS THIS MORNING...UPPER LEVEL MOISTURE IS MOVING NORTHWARD THROUGH THE ROCKIES. THE AIRMASS IS A BIT DRIER THEN IT HAS BEEN FOR AREAS SOUTH OF GREAT FALLS...WITH DEW POINTS CURRENTLY IN THE 30S AND 40S...WHILE DEW POINTS ARE AROUND 60 UP NEAR THE US/CANADIAN BORDER. THUS AS THE SHOWER ACTIVITY MOVES NORTHWARD THIS MORNING FROM IDAHO AND THROUGH SOUTHWEST MONTANA...EXPECT THE PRECIP TO BECOME HEAVIER...ESPECIALLY NORTH OF GREAT FALLS. THE AIRMASS BECOMES QUITE UNSTABLE BETWEEN CUT BANK AND HAVRE AROUND 3 PM TODAY...AND THIS AREA IS THE BEST LOCATION TO SEE SEVERE WEATHER...THUS A SLIGHT RISK OF SEVERE THUNDERSTORMS HAS BEEN ISSUED BY SPC FOR THIS REGION. DAMAGING WINDS/LARGE HAIL/HEAVY RAIN/FREQUENT LIGHTNING CAN BE EXPECTED FROM ANY SEVERE STORM TODAY. AFTERNOON HIGHS TODAY WILL CLIMB INTO THE UPPER 80S/MID 90S. FOR TONIGHT...EXPECT THE STORMS TO GRADUALLY END FROM SOUTH TO NORTH. ON SATURDAY AND SUNDAY...EXPECT THE AIRMASS TO CONTINUE TO GRADUALLY DRY OUT...WHILE AFTERNOON TEMPERATURES REMAIN ABOUT 5 TO 10 DEGREES ABOVE NORMAL. THERE WILL BE A SMALL CHANCE FOR THUNDERSTORMS DURING THE AFTERNOON/EVENING HOURS OVER THE WEEKEND...BUT MOST OF THE THUNDERSTORM ACTIVITY WILL BE CONFINED TO THE MOUNTAIN AREAS OF SOUTHWEST MONTANA. BRUSDA SUNDAY NIGHT THROUGH FRIDAY...LONG-RANGE FORECAST MODELS MAINTAINING GOOD CONSISTENCY AND AGREEMENT ON EXPECTED CONDITIONS FOR THE WEEK AHEAD. PERIOD BEGINS WITH BROAD UPPER LEVEL RIDGE DRIFTING INTO ERN MT ON SUN EVE...ALLOWING MONSOONAL MOISTURE TO GENERATE SCATTERED SHOWERS AND THUNDERSTORMS SUN NIGHT MAINLY OVER SOUTHWEST MT. SOUTHWEST FLOW ALOFT OVER OUR REGION STRENGTHENS ON MONDAY IN RESPONSE TO A VIGOROUS PACIFIC LOW PRESSURE SYSTEM MAKING ITS WAY ALONG THE US/CAN BORDER. A SURFACE COLD FRONT FROM THIS SYSTEM SHOULD CROSS THE CONTINENTAL DIVIDE MONDAY EVE WHERE IT WILL TAP INTO THE MONSOONAL MOISTURE TO BRING ANOTHER ROUND OF THUNDERSTORMS...WITH MODELS SHOWING WIDER COVERAGE OF STORMS PARTICULARLY OVER THE CENTRAL MT COUNTIES. MODELS HAVE ALSO SLIGHTLY INCREASED PRECIPITABLE WATER VALUES...THOUGH SURFACE DEW POINTS ARE SOMEWHAT DRY...SO A MIX OF DRY/WET STORMS SEEMS LIKELY. THE COLD FRONT WILL BE WELL DOWNSTREAM BY TUES MORNING AS THE LOW PRESSURE CENTER LIFTS INTO SRN ALBERTA. WESTERLY FLOW AND A RETURN TO DRY CONDITIONS DEVELOP BEHIND THE FRONT ALONG WITH SOME BREEZY TO LOCALLY GUSTY WINDS ON TUES...LIKELY INCREASING WILDLAND FIRE DANGER OVER PORTIONS OF CENTRAL/SOUTHWEST MT. THE UPPER LEVEL RIDGE GRADUALLY REBUILDS OVER THE NRN ROCKIES THRU MIDWEEK AND THE NEXT PUSH OF MONSOONAL MOISTURE BEGINS TO ARRIVE THURS WITH SCATTERED THUNDERSTORMS POSSIBLE THURS AND FRI EVENING. HIGH TEMPERATURES REMAIN ABOUT 5-8 DEGREES ABOVE NORMAL ON MON BUT THE COLD FRONT PASSAGE WILL DROP BACK HIGHS INTO THE LOW-MID 80S FOR TUES/WED. TEMPS THEN REBOUND UPWARD A FEW DEGREES EACH DAY FOR THE LATTER HALF OF THE WEEK...REACHING THE UPPER 80S TO LOW 90S BY FRIDAY. WARANAUSKAS && .PRELIMINARY POINT TEMPS/POPS... GTF 92 59 91 58 / 30 30 10 10 CTB 82 54 87 51 / 50 40 10 10 HLN 93 58 92 58 / 30 30 10 10 BZN 93 51 93 50 / 20 10 10 10 WEY 82 41 82 41 / 30 20 20 10 DLN 90 52 89 52 / 30 10 10 10 HVR 89 60 92 56 / 30 30 10 10 LWT 88 56 88 55 / 30 20 10 10 && .TFX WATCHES/WARNINGS/ADVISORIES... NONE. && WEATHER.GOV/GREATFALLS
HAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE GREAT FALLS MT 1040 AM MDT FRI JUL 20 2012 MTZ009>013-044>051-211200- NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL-CASCADE- CHOUTEAU-TOOLE-LIBERTY-EASTERN PONDERA-BLAINE- SOUTHERN ROCKY MOUNTAIN FRONT-EASTERN TETON-JUDITH BASIN-FERGUS- 1040 AM MDT FRI JUL 20 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL MONTANA AND NORTH CENTRAL MONTANA. .DAY ONE...TODAY AND TONIGHT SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS NORTH CENTRAL MONTANA TODAY. SOME STORMS COULD BE SEVERE...WITH DAMAGING WINDS...LARGE HAIL...FREQUENT LIGHTNING...AND HEAVY RAINFALL. VERY HEAVY RAIN IN SHORT AND INTENSE BURSTS COULD LEAD TO LOCALIZED FLOODING. THE BEST TIME FRAME FOR SEVERE WEATHER TO OCCUR WILL BE FROM NOON UNTIL 9 PM TODAY. BE PREPARED FOR POSSIBLE SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING. ANY SPOTTER REPORTS OF SEVERE WEATHER WOULD GREATLY BE APPRECIATED. MTZ008-014-015-052>055-211200- BEAVERHEAD-CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON-JEFFERSON- BROADWATER-MEAGHER-GALLATIN- 1040 AM MDT FRI JUL 20 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST MONTANA. .DAY ONE...TODAY AND TONIGHT THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
The Missoula radar (KMSX), 165 km away, was scanning. The volume nearest the first event began at 20:46 UTC.
1 thunderstorm wind. Local standard time, as filed.
Outflow winds produced a wind gust of 52KT (60MPH) as reported 5 miles E of Wisdom.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2012Every state in 2012This day in weather historyWarnings in Montana, July 2012
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: 398257.