Strong daytime heating and an unstable atmosphere combined with an approaching low pressure system to produce and sustain a few severe thunderstorms which spread downburst winds across portions of northeast Montana during the late and overnight hours.
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 GGW wrote it up.
Strong daytime heating and an unstable atmosphere combined with an approaching low pressure system to produce and sustain a few severe thunderstorms which spread downburst winds across portions of northeast Montana during the late and overnight hours.
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 Glasgow, MT wrote its last area forecast discussion before the first event at Aug 17, 7:44 PM MST, 3 hours 45 minutes earlier.
Area Forecast Discussion National Weather Service Glasgow MT 844 PM MDT Tue Aug 17 2021 .DISCUSSION... Going forecast needed some tweaking as winds increased from Fort Peck on NW this evening giving rise to Fire Weather Concerns. Extended the Red Flag Warning through 3 am to cover the time until these winds diminish. Cancelled the Heat Advisory and left Lake Wind Advisory in place. Scattered showers/isolated thunderstorms are moving northeast across mainly the NW third of the CWA tonight. But the big thing this evening are the winds. They cranked up as surface high pressure over Alberta has been pressing into the area. Winds should begin to shift east and diminishing somewhat later tonight as a surface low moves from SE Montana into the Dakotas. TFJ Previous Discussion... Hot and dry conditions will continue for the next few hours before a cold front moves through the area. Strong north winds are expected with this cold front and these winds will continue through the overnight hours. A Lake Wind Advisory remains in effect for Fort Peck Lake through Wednesday. In addition to the winds, a few showers and thunderstorms are expected to develop this evening into tonight across Northeast Montana. There will not be much in the way of accumulating precipitation with these showers and storms, but they may produce strong wind gusts to near 60 mph at times, particularly between 5 PM and midnight. Behind the cold front the smoke will largely clear and much cooler temperatures are expected for the remainder of the week. There will also be better chances for showers and thunderstorms throughout the week, most notably Thursday into Friday. Another trough over the weekend could bring more chances for showers. -Mottice && .AVIATION... FLIGHT CAT: MVFR-VFR. DISCUSSION: Strong NE winds near and to the NW of Fort Peck Lake this evening will continue till about Midnight then gradually diminish. Scattered showers moving northeast will affect KGGW this evneing but KOLF, KSDY and KGDV should remain dry tonight. LLWS: Low level wind shear is possible at times till Wednesday morning. && .GLASGOW WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 3 AM MDT Wednesday for MTZ122-136-137. Lake Wind Advisory until 6 PM MDT Wednesday For Fort Peck Lake for Central and Southeast Phillips...Central and Southern Valley...Garfield...McCone...Petroleum. && weather.gov/glasgow
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GLASGOW MT
1107 PM MDT TUE AUG 17 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1100 PM NON-TSTM WND GST FLAXVILLE 48.80N 105.17W
08/17/2021 M60 MPH DANIELS MT TRAINED SPOTTER
WINDS HAVE BEEN GUSTING TO 60 MPH FOR THE
LAST 45 MINUTES.
&&PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GLASGOW MT
1115 PM MDT TUE AUG 17 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1044 PM NON-TSTM WND GST 14 NNW HELL CREEK REC A 47.80N 107.02W
08/17/2021 M58 MPH VALLEY MT MESONET
MESONET STATION KIGM8 KING COULEE.
&&PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GLASGOW MT
1117 PM MDT TUE AUG 17 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1041 PM NON-TSTM WND GST 15 S ZORTMAN 47.70N 108.48W
08/17/2021 M51 MPH PHILLIPS MT MESONET
MESONET STATION MCDM8 MANNING CORRAL
DOGTOWN.
1032 PM NON-TSTM WND GST 1 ESE ZORTMAN 47.91N 108.50W
08/17/2021 M50 MPH PHILLIPS MT MESONET
MESONET STATION ALDM8 ZORTMAN 1E.
&&Special Weather Statement
National Weather Service Glasgow MT
1156 PM MDT Tue Aug 17 2021
MTZ016-017-022-023-180730-
Garfield MT-Central and Southeast Phillips MT-McCone MT-
Central and Southern Valley MT-
1156 PM MDT Tue Aug 17 2021
...Strong winds along a boundary will impact portions of
northeastern Phillips, northeastern Garfield, southwestern Valley
and northwestern McCone Counties through 130 AM MDT...
At 1155 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Saco to 26 miles west of The Pines Rec
Area to 8 miles northeast of Brusett. Movement was east at 25 mph.
HAZARD...Wind gusts of 50 to 55 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. The strongest winds may occur away from
rain and lightning.
Locations impacted include...
Glasgow, Nashua, Fort Peck, The Pines Rec Area, Tampico, Hinsdale,
Duck Creek Rec Area, Fort Peck Marina, Hell Creek Rec Area, St.
Marie, Vandalia, Park Grove, The Bentonite Plant, Haxby and Whatley.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
If on or near Fort Peck Lake, get out of the water and move indoors
or inside a vehicle.
&&
LAT...LON 4854 10639 4795 10632 4743 10638 4746 10724
4797 10720 4851 10727
TIME...MOT...LOC 0555Z 271DEG 20KT 4845 10722 4798 10716 4754 10719
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...55 MPH
NWS GlasgowSpecial Weather Statement
National Weather Service Glasgow MT
1200 AM MDT Wed Aug 18 2021
MTZ018-180615-
Daniels MT-
1200 AM MDT Wed Aug 18 2021
...A strong thunderstorm will impact portions of northwestern Daniels
County through 1215 AM MDT...
At 1200 AM MDT, Doppler radar was tracking a strong thunderstorm 7
miles northeast of Richland, or 22 miles east of Opheim, moving
northeast at 40 mph.
HAZARD...Wind gusts of 50 to 55 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
This storm will remain over mainly rural areas of northwestern
Daniels County.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4900 10561 4877 10586 4885 10609 4900 10601
TIME...MOT...LOC 0600Z 208DEG 33KT 4889 10592
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...55 MPH
NWS GlasgowPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GLASGOW MT
1207 AM MDT WED AUG 18 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1102 PM NON-TSTM WND GST 2 WNW JORDAN 47.33N 106.95W
08/17/2021 M56 MPH GARFIELD MT ASOS
ASOS STATION KJDN JORDAN.
&&The Glasgow radar (KGGW), 2 km away, was scanning. The volume nearest the first event began at 06:30 UTC.
2 thunderstorm wind. Local standard time, as filed.
A 61mph wind gust was measured at the Glasgow Airport ASOS site.
A 58mph wind gust was measured at the Wolf Point Airport ASOS site.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2021Every state in 2021This day in weather historyWarnings in Montana, August 2021
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: 978014, 978015.