An active week of severe weather unfolded across the Northern Rockies from August 18th through the 21st. Subtle waves lifting through a southwesterly flow aloft just west of an upper level ridge combined with ample surface heating and shear to result in multiple rounds of severe weather, most notably on August 19th when a line of strong thunderstorms lifted northward across the plains and…
Every event with a place to put it. Tap one for its entry below.
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.
An active week of severe weather unfolded across the Northern Rockies from August 18th through the 21st. Subtle waves lifting through a southwesterly flow aloft just west of an upper level ridge combined with ample surface heating and shear to result in multiple rounds of severe weather, most notably on August 19th when a line of strong thunderstorms lifted northward across the plains and adjacent areas.
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 Aug 18, 4:36 PM MST, 2 hours 23 minutes earlier.
Area Forecast Discussion National Weather Service Great Falls MT 536 PM MDT Sun Aug 18 2024 ...Aviation Section Updated... .SYNOPSIS... Moist, southwest flow aloft will bring showers and thunderstorms to the Northern Rockies through the first half of the upcoming work week, with a few thunderstorms this afternoon and evening and then again on Monday potentially being strong to severe. Main threat from any severe storm today will be damaging winds, with hail and damaging winds being the threats on Monday. High temperatures will once again warm well above normal on Monday, with most locations reaching the mid-80s to mid-90s. && .DISCUSSION... Rest of today through Tuesday...primary forecast concerns throughout the period will be thunderstorms, some of which could become strong to severe late this afternoon through the evening hours tonight and then again on Monday, and above normal temperatures. H500 ridge axis will remain just east of the Northern Rockies and over the Northern High Plains through the period, with subtle shortwaves lifting northeast and over Southwest through North Central Montana within the overall moist, southwest flow aloft. Strong surface heating this afternoon and then again on Monday, will produce high temperatures well above normal and in the mid-80s to mid-90s on both days, which combined with sufficient moisture and shear will help to support isolated to scattered thunderstorms during the afternoon and evening hours (today and Monday). Terrain based cumulus has already developed early this afternoon over the mountains of Northern Idaho and Southwest Montana, with showers and thunderstorms expected to develop over the next 1-2 hours over these same areas. These showers and thunderstorms will then lift northeast and over the remainder of Southwest through North Central Montana through the late afternoon and evening hours tonight before gradually exiting most of the CWA around midnight tonight. A few showers and thunderstorms may linger beyond midnight tonight along the Hi-Line in North Central Montana and along the Idaho/Wyoming borders, but overall coverage will decrease beyond the aforementioned midnight hour. Given the marginally sheared environment through the evening hours tonight the primary concern with any of the stronger thunderstorms will be gusty and erratic winds and potentially a few damaging wind gusts. By Monday slightly stronger shear and instability will support a better (5% to 15%) chances for hail, potentially large, along with the continued threat for damaging winds. Given these risks for hail and/or damaging winds the Storm Prediction Center (SPC) continues to maintain a Marginal Risk for severe thunderstorms across most if not all of Southwest through North Central Montana today and on Monday. Shower and thunderstorm development on Monday is expected to be slightly further north and over Southwest and into portions of Central Montana during the early afternoon hours, with this activity then lifting northeast and across the remainder of the CWA through the evening hours. Wednesday through next Sunday...ensemble clusters predominately favor broad troughing over the Pacific Northwest, Great Basin, and Northern Rockies for much of the period; with the leading mode of uncertainty being the exact position and/or timing of the H500 trough as it slowly digs southeast from the Eastern Pacific over the Pacific Northwest and Great Basin before lifting northeast over the Northern Rockies. The position and/or timing of the aforementioned trough will ultimately impact when and how long "cooler" temperatures arrive and persist across the Northern Rockies, in addition to precipitation chances. Latest deterministic NBM guidance supports high temperatures falling near to below normal for the days on Wednesday and Thursday in wake of a series of weak surface cold fronts, warming back above normal on Friday as a warm front lifts northeast amongst increasing southerly flow aloft ahead of the main trough axis moving overhead, and falling back near to normal over the upcoming weekend as the trough shifts east of the Northern Rockies. Daily chances (15% to 30%) for precipitation will also exist across portions of the Northern Rockies throughout the period, mainly along and near the cold fronts on Wednesday and Thursday, over the higher terrain and lifting warm front on Friday, and across all areas over the weekend. - Moldan && .AVIATION... 19/00Z TAF Period The primary concern this TAF period will be for showers and thunderstorms progressing northeastward across the region overnight. Gusty winds will be the main concern with these thunderstorms, but some small hail will be possible early this evening. Another round of showers and thunderstorms will develop Monday afternoon, once again moving from southwest to northeast. -AM Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 55 93 55 89 / 50 20 40 10 CTB 54 89 54 84 / 40 20 40 10 HLN 56 93 53 92 / 60 50 40 20 BZN 54 91 49 91 / 10 40 20 20 WYS 44 79 40 80 / 30 50 30 10 DLN 52 86 48 85 / 10 30 10 10 HVR 63 96 60 93 / 50 20 50 10 LWT 57 91 53 90 / 20 30 40 20 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && http://www.weather.gov/greatfalls
Special Weather Statement National Weather Service Great Falls MT 714 PM MDT Sun Aug 18 2024 MTZ302-303-308-190145- Southern High Plains MT- Eastern Glacier, Western Toole, and Central Pondera MT- Northern High Plains MT- 714 PM MDT Sun Aug 18 2024 ...A STRONG THUNDERSTORM WILL IMPACT CENTRAL PONDERA...SOUTHEASTERN GLACIER AND NORTH CENTRAL TETON COUNTIES THROUGH 745 PM MDT... At 714 PM MDT, Doppler radar was tracking a strong thunderstorm 16 miles southwest of Valier, or 25 miles west of Conrad, moving north at 25 mph. HAZARD...Penny size hail. SOURCE...Radar indicated. IMPACT...Minor hail damage to vegetation is possible. Locations impacted include... Dupuyer. PRECAUTIONARY/PREPAREDNESS ACTIONS... If outdoors, consider seeking shelter inside a building. && LAT...LON 4803 11238 4806 11265 4842 11264 4839 11223 TIME...MOT...LOC 0114Z 188DEG 23KT 4813 11250 MAX HAIL SIZE...0.75 IN MAX WIND GUST...<30 MPH Ludwig
Special Weather Statement National Weather Service Great Falls MT 716 PM MDT Sun Aug 18 2024 MTZ308-309-190200- Eastern Pondera and Eastern Teton MT-Southern High Plains MT- 716 PM MDT Sun Aug 18 2024 ...A STRONG THUNDERSTORM WILL IMPACT CENTRAL LEWIS AND CLARK AND SOUTH CENTRAL TETON COUNTIES THROUGH 800 PM MDT... At 716 PM MDT, Doppler radar was tracking a strong thunderstorm 9 miles west of Fairfield, or 14 miles south of Choteau, moving north at 10 mph. HAZARD...Nickel size hail. SOURCE...Radar indicated. IMPACT...Minor hail damage to vegetation is possible. Locations impacted include... Choteau. PRECAUTIONARY/PREPAREDNESS ACTIONS... If outdoors, consider seeking shelter inside a building. Torrential rainfall is also occurring with this storm and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 4750 11208 4755 11234 4783 11230 4776 11192 TIME...MOT...LOC 0116Z 194DEG 8KT 4760 11219 MAX HAIL SIZE...0.88 IN MAX WIND GUST...<30 MPH Ludwig
Special Weather Statement
National Weather Service Great Falls MT
724 PM MDT Sun Aug 18 2024
MTZ312-190215-
Cascade County below 5000ft MT-
724 PM MDT Sun Aug 18 2024
...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN CHOUTEAU AND NORTH
CENTRAL CASCADE COUNTIES THROUGH 815 PM MDT...
At 724 PM MDT, Doppler radar was tracking a strong thunderstorm 9
miles west of Belt, or 10 miles southeast of Great Falls, moving
north at 15 mph.
HAZARD...Wind gusts up to 40 mph and penny size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
Great Falls, Black Eagle, Malmstrom Afb, and Tracy.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4760 11105 4757 11101 4757 11097 4741 11104
4740 11119 4760 11134 4761 11105
TIME...MOT...LOC 0124Z 175DEG 12KT 4742 11112
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH
AMSpecial Weather Statement
National Weather Service Great Falls MT
728 PM MDT Sun Aug 18 2024
MTZ313-317-190200-
Judith Basin County and Judith Gap MT-
Little Belt and Highwood Mountains MT-
728 PM MDT Sun Aug 18 2024
...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN JUDITH BASIN COUNTY
THROUGH 800 PM MDT...
At 728 PM MDT, Doppler radar was tracking a strong thunderstorm over
Geyser, or 14 miles northwest of Stanford, moving north at 15 mph.
HAZARD...Wind gusts up to 40 mph and nickel size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
Geyser.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4719 11038 4720 11056 4741 11062 4741 11027
TIME...MOT...LOC 0128Z 189DEG 14KT 4725 11050
MAX HAIL SIZE...0.88 IN
MAX WIND GUST...40 MPH
AMSpecial Weather Statement
National Weather Service Great Falls MT
746 PM MDT Sun Aug 18 2024
MTZ307-308-312-315-316-320-190215-
Southern Rocky Mountain Front MT-Cascade County below 5000ft MT-
Big Belt, Bridger and Castle Mountains MT-Southern High Plains MT-
Upper Blackfoot and MacDonald Pass MT-Gates of the Mountains MT-
746 PM MDT Sun Aug 18 2024
...STRONG THUNDERSTORMS WILL IMPACT CENTRAL LEWIS AND CLARK...SOUTH
CENTRAL TETON AND SOUTHWESTERN CASCADE COUNTIES THROUGH 815 PM MDT...
At 746 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 16 miles south of Augusta to 6 miles south of
Wolf Creek. Movement was northeast at 30 mph.
HAZARD...Wind gusts of 50 to 55 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
Wolf Creek, Bowmans Corner, Tower Rock State Park, Bean Lake, and
Craig.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
&&
LAT...LON 4761 11219 4703 11165 4680 11212 4726 11255
TIME...MOT...LOC 0146Z 224DEG 24KT 4725 11243 4691 11211
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...55 MPH
LudwigSpecial Weather Statement
National Weather Service Great Falls MT
753 PM MDT Sun Aug 18 2024
MTZ310-190245-
Western and Central Chouteau County MT-
753 PM MDT Sun Aug 18 2024
...A STRONG THUNDERSTORM WILL IMPACT WEST CENTRAL CHOUTEAU COUNTY
THROUGH 845 PM MDT...
At 753 PM MDT, Doppler radar was tracking a strong thunderstorm 13
miles south of The Knees, or 23 miles north of Great Falls, moving
north at 20 mph.
HAZARD...Wind gusts of 50 to 55 mph and nickel size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
The Knees.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4779 11107 4779 11137 4809 11140 4810 11098
TIME...MOT...LOC 0153Z 180DEG 19KT 4783 11121
MAX HAIL SIZE...0.88 IN
MAX WIND GUST...55 MPH
AMThe Great Falls radar (KTFX), 51 km away, was scanning. The volume nearest the first event began at 01:58 UTC.
20 thunderstorm wind, 8 hail. Local standard time, as filed.
Public reports quarter sized hail. Gusty winds were also observed, which blew around items at the residence.
Public weather station reported a severe caliber gust. Location was estimated.
Public report of large hail in northern Beaverhead county. Photo received via email showing the large hail.
Public report of quarter sized hail 2 ENE of Manhattan. Wheat fields were damaged by the hail. Time and location was estimated.
Public weather station measured a severe caliber gust.
The DOT sensor at Spokane Creek MTSPK measured a 58 mph gust along US-287 at mile marker 55.7.
COOP observer reports quarter sized hail fell for about ten minutes.
ASOS station KGTF Great Falls Airport measured a sever caliber gust.
Public weather station measured a severe caliber gust.
Public weather station measured a severe caliber gust.
Mesonet station GW1987 Ethridge 3 SE measured a severe caliber gust.
MT DOT sensor MTDEN East of Denton measured a sever caliber gust.
A trained spotter in Lewistown reported a severe caliber gust.
A spotter traveling northbound on US-87 noted two snapped power poles near mile marker 31. Power outages were confirmed in the area.
Mesonet station GW3478 TCTIBER measured a severe caliber gust.
Mesonet station GW3862 Loma 18 NW measured a sever caliber gust.
RAWS sensor JPKM8 Judith Peak measured a severe caliber gust. Given RAWS reports once per hour, time of gust was estimated using radar.
Mesonet station MTWST Sweetgrass DOT sensor measured a sever caliber gust.
Mesonst station GW3530 Rudyard 11 S measured a severe caliber gust.
Public Wunderground sensor KMTCHEST53 measured a severe caliber gust.
ASOS station KHVR Haver Airport measured a severe caliber gust.
Trained spotter reported half dollar sized hail while traveling through Sheridan. Time estimated using radar.
A trained spotter reported hail between 1 and 2 inches in diameter which shattered/splattered upon impact.
Trained spotter reports hail up to the size of a quarter.
An Ambient weather sensor in Bozeman measured a severe caliber gust.
The DOT sensor at Bozeman Pass MTBZH measured a severe caliber gust.
AWOS sensor K1CM Charlie near Geyser measured a 60 mph gust.
Trained spotter reported hail up to the size of quarters.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2024Every state in 2024This day in weather historyWarnings in Montana, August 2024
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: 1200362, 1200364, 1200365, 1200366, 1200367, 1200368, 1200369, 1200370, 1200371, 1200372, 1200373, 1200374, 1200375, 1200376, 1200377, 1200378, 1200379, 1200380, 1200381, 1200382, 1200383, 1200385, 1200386, 1200388, 1200389, 1200390, 1200391, 1200392.