Several waves moved around a slow moving upper level trough situated over the Pacific Northwest and initiated thunderstorms over southwest Montana.
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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.
Several waves moved around a slow moving upper level trough situated over the Pacific Northwest and initiated thunderstorms over southwest Montana.
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 Jun 12, 2:44 AM MST, 10 hours 56 minutes earlier.
Area Forecast Discussion National Weather Service Missoula MT 344 AM MDT Wed Jun 12 2013 .DISCUSSION...A low pressure system continues to sit along the British Columbia coast this morning and will pump waves of moisture and energy into western Montana and north central Idaho today. The first wave will affect northwest Montana this morning with light to moderate showers and isolated thunderstorms. A second wave is expected early this afternoon and evening and will combine with upper level jet support to produce a good chance of thunderstorms. Some of these thunderstorms could become strong this afternoon and evening, mainly across southwest Montana and southern Lemhi County. The main threats will again be for heavy rain, small hail, and gusty winds. In addition to thunderstorms, gusty winds can be expected this afternoon across Lemhi County into southwest Montana. Thunderstorms will linger into the overnight hours across southwest Montana, a few of which could remain strong. A strong cold front will approach the region from the west during the day Thursday. A lot of moisture and energy will accompany the front that will once again present a threat of more strong storms. The front will impact central Idaho and northwest Montana earlier in the day and track eastward through west-central and southwest Montana in the afternoon and evening. The atmosphere doesn't look to be overly unstable, however with a strong jet streak, enough upper-level dynamics could support some gusty winds from storms that do develop. The strongest storms should be along the front and possibly in southwest Montana and Lemhi county in Idaho just ahead of the front. A cooler airmass will move over the region behind the front that will drop snow levels down to 6000-8000ft by Friday morning. Models depict a band of precipitation developing over southwest Montana and Lemhi county Friday morning, that could bring down colder temperatures and possibly support snow developing over Lost Trail pass and the highest elevations of the southern Bitterroot. It isn't out of the question for Lost Trail Pass to pick up a dusting to one half inch of snow by sunrise Friday. Warm and dry conditions are expected for the weekend as high pressure builds back over the region. However, precipitation chances will increase early next week as the ridge of high pressure begins to push eastward. Forecast models are hinting at a return to a cooler/more moist pattern by mid week as an upper level trough (possibly a closed low) moves into the region. && .AVIATION...A low pressure system will pump waves of moisture into western Montana and north central Idaho today. This will increase mid level cloud cover across the region and may obscure some of the higher terrain. The first such wave will produce mainly showers with a few isolated thunderstorms across northwest Montana. A second, stronger wave will move into southwest Montana and Lemhi County in Idaho this afternoon. This wave will produce a good chance of thunderstorms, mainly affecting airfields KBTM and KSMN between 12/2100z and 13/0200z. Thunderstorms this afternoon will be capable of very heavy rain, small hail and gusty winds. In addition to thunder, winds will become gusty this afternoon as a surface boundary moves through the region, especially for southwest Montana and Lemhi County. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && Follow us on Facebook and Twitter! https://www.facebook.com/US.NationalWeatherService.Missoula.gov https://www.twitter.com/NWSMissoula
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MISSOULA MT
211 PM MDT WED JUN 12 2013
MTZ007-122100-
BUTTE/BLACKFOOT REGION-
211 PM MDT WED JUN 12 2013
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN POWELL...
NORTHWESTERN SILVER BOW AND EASTERN DEER LODGE COUNTIES UNTIL 300 PM
MDT...
AT 205 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 10 MILES SOUTHWEST OF GREGSON HOT SPRINGS...OR 12
MILES SOUTH OF ANACONDA. THIS STORM WAS NEARLY STATIONARY.
HAIL UP TO ONE-HALF INCH IN DIAMETER 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...GREGSON HOT
SPRINGS...SILVER BOW...WARM SPRINGS...CRACKERVILLE...OPPORTUNITY...
RAMSAY AND NISSLER.
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 4584 11292 4599 11308 4637 11254 4634 11249
4631 11255 4627 11254 4622 11258 4619 11256
4619 11251 4618 11250 4613 11251 4608 11246
TIME...MOT...LOC 2011Z 180DEG 0KT 4596 11298The Missoula radar (KMSX), 144 km away, was scanning. The volume nearest the first event began at 20:38 UTC.
3 hail. Local standard time, as filed.
The first severe thunderstorm developed over the Beaverhead National Forest south of Anaconda before 2pm MDT and tracked northeast over Gregson Hot Springs producing up to one inch hail.
A person from the public reported hail to the estimated size of ping pongs that caused damage to the roof to their house and extensive damage to their camper. The hail lasted for approximately 10 minutes.
The hail began at 11:45 pm MDT and lasted for 10 minutes. The estimated quarter-size hail fell in the last two minutes of the event.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2013Every state in 2013This day in weather historyWarnings in Montana, June 2013
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: 458846, 458855, 458857.