An upper-level ridge of hot temperatures and a lee surface trough brought scattered, mainly-dry thunderstorms to the area, some of which produced severe downburst winds and stronger gusts as it moved eastward across northeast Montana. As this gust front approached the Montana/North Dakota border, it met more unstable air, and strengthened into a line of severe thunderstorms.
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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 GGW wrote it up.
An upper-level ridge of hot temperatures and a lee surface trough brought scattered, mainly-dry thunderstorms to the area, some of which produced severe downburst winds and stronger gusts as it moved eastward across northeast Montana. As this gust front approached the Montana/North Dakota border, it met more unstable air, and strengthened into a line of severe thunderstorms.
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 Jul 10, 11:44 AM MST, 2 hours 26 minutes earlier.
Area Forecast Discussion National Weather Service Glasgow MT 1244 PM MDT Mon Jul 10 2017 .SHORT TERM...for northeast Montana...today through Wed... Synoptic setup: A large area of hot high pressure resides over the southwestern quarter of the CONUS. A ridge spur runs north of this through eastern Wyoming and Montana. A weak trough runs down the coastline from British Columbia to northern Oregon. Zonal to southwest flow resides between thes two features over western and central Montana where a jet streak is evident on water vapor. This afternoon through this evening: Near the surface a lee side mountain trough has set up over eastern Montana and is low pressure center over southern Saskatchewan. This low is being driven by the jet aloft and kicking the aloft ridge into the Dakotas. This in turn is destabilizing the atmosphere to the west where showers and thunderstorms have already developed. A couple showers and thunderstorms developed across northeastern zones but should be out of the area by roughly 130PM. The next batch are anticipated to arrive around 4 to 6 PM along the southwestern zones. As showers and thunderstorms exit the mountains for this warm dry sector... downburst winds are expected to form which may become damaging at times across Petroleum and Garfield counties. Tuesday: Showers are expected to taper down and travel across mostly southern zones through the early morning hours leaving a few showers across eastern zones. Some new isolated showers activity may drop down on a weak backdoor front during the afternoon hours. GAH .LONG TERM...Wed night through Mon... Shortwave trough moves to the east Tuesday Night. A slight chance of showers could linger into the evening. Although the ridge rebounds on Wednesday, a weak wave in the afternoon and evening could bring a slight chance of thunderstorms to parts of the region. Meanwhile, somewhat cooler temperatures will linger. The heat returns on Thursday as the ridge continues to build back into Montana and widespread highs in the 90s return. The ridge becomes stronger on Friday and remains in place on Saturday with hot and dry weather. Highs will be near 100 in many areas. Models differ Sunday and Monday. GFS keeps strong ridge in place while the ECMWF brings a shortwave trough across the Canadian Prairies that flattens the ridge and bring a weak cold front. Will maintain a hot and dry forecast for now. Forrester && .AVIATION... FLIGHT CAT: VFR. SYNOPSIS: There will be mid and high level clouds and thunderstorms ahead of a front that will move through Northeast Montana this afternoon and evening. SVR THUNDERSTORMS: Scattered thunderstorms this afternoon and tonight have the potential for downburst winds that could briefly exceed 50 kts along with hail. HIGH DENSITY ALTITUDE: With temperatures in the upper 90s today in some places takeoffs may need longer distance. WIND: South to west at 10 to 15 kts this afternoon... becoming west around 10 kts tonight... veering to the northwest at 10 to 15 kts Tuesday. GAH && .GLASGOW WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 11 PM MDT this evening for MTZ134>137. && weather.gov/glasgow
Hazardous Weather Outlook National Weather Service Glasgow MT 335 AM MDT Mon Jul 10 2017 MTZ016>027-059>062-110800- Central and Southeast Phillips-Central and Southern Valley- Daniels-Sheridan-Western Roosevelt-Petroleum-Garfield-McCone- Richland-Dawson-Prairie-Wibaux-Northern Phillips- Southwest Phillips-Northern Valley-Eastern Roosevelt- 335 AM MDT Mon Jul 10 2017 This Hazardous Weather Outlook is for portions of northeast Montana. .DAY ONE...Today and Tonight A Red Flag Warning is in effect from Noon until 11 PM today due to the combination of low relative humidity, gusty winds, and lightning from dry thunderstorms for zones 134, 135, 136, and 137. Isolated to scattered thunderstorms are expected this afternoon and evening. A few storms could be severe with large hail and damaging winds. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Hot temperatures with highs in the 90s to near 100 return on Thursday and will continue through the weekend. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to standard operating procedures.
Special Weather Statement
National Weather Service Glasgow MT
127 PM MDT MON JUL 10 2017
MTZ021-060-102045-
Petroleum MT-Southwest Phillips MT-
127 PM MDT MON JUL 10 2017
...SPECIAL WEATHER STATEMENT...
At 116 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 27 miles east of Geraldine to 9 miles southeast
of Winifred to 13 miles southwest of Grass Range. Movement was
northeast at 25 mph.
West southwest winds 15 to 25 mph with gust in excess of 30 mph will
be possible with these storms. Wind speeds tend to increase after
the passage of the initial wind shift from the gust front and
typically continue an hour or 2 after the gust front.
Locations impacted include...
Zortman, Landusky, Tiegen and Fred Robinson Bridge between 2 to 245
pm MDT.
.
LAT...LON 4792 10889 4792 10863 4798 10861 4786 10840
4717 10819 4701 10861 4710 10861 4710 10874
4727 10872 4727 10859 4730 10859 4731 10834
4739 10831 4756 10831 4758 10842 4762 10844
4760 10848 4764 10876 4768 10878 4773 10889
TIME...MOT...LOC 1916Z 233DEG 22KT 4774 10971 4748 10921 4693 10905
tcSpecial Weather Statement
National Weather Service Glasgow MT
148 PM MDT MON JUL 10 2017
MTZ021-102030-
Petroleum MT-
148 PM MDT MON JUL 10 2017
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN PETROLEUM COUNTY
UNTIL 230 PM MDT...
At 146 PM MDT, Doppler radar was tracking a strong thunderstorm 8
miles northwest of Flatwillow, or 9 miles southwest of Winnett,
moving east at 15 mph.
Thunderstorm wind gusts in excess of 45 mph will be possible with
this storm. Blowing dust will be possible as well.
Locations impacted include...
Flatwillow and Tiegen.
LAT...LON 4684 10861 4707 10861 4712 10843 4680 10829
4679 10859
TIME...MOT...LOC 1946Z 253DEG 15KT 4692 10852
TCSpecial Weather Statement
National Weather Service Glasgow MT
238 PM MDT MON JUL 10 2017
MTZ021-022-102145-
Petroleum MT-Garfield MT-
238 PM MDT MON JUL 10 2017
...SIGNIFICANT WEATHER ADVISORY FOR PETROLEUM AND SOUTHWESTERN
GARFIELD COUNTIES UNTIL 345 PM MDT...
At 237 PM MDT, Doppler radar was tracking strong thunderstorms 8
miles northwest of Flatwillow, or 12 miles southwest of Winnett,
moving east at 20 mph.
Nickel size hail and wind gusts up to 50 mph will be possible with
this storm.
Locations impacted include...
Winnett, Flatwillow, Petrolia Lake, Cat Creek, Tiegen and Valentine.
LAT...LON 4727 10872 4727 10859 4731 10858 4731 10834
4732 10831 4737 10832 4741 10818 4685 10787
4685 10789 4684 10786 4680 10785 4679 10784
4678 10785 4676 10783 4675 10863 4684 10863
4684 10861 4710 10861 4710 10874
TIME...MOT...LOC 2037Z 247DEG 19KT 4690 10855
AEHThe Billings radar (KBLX), 109 km away, was scanning. The volume nearest the first event began at 21:07 UTC.
13 thunderstorm wind, 2 hail. Local standard time, as filed.
A trained spotter reported penny sized hail in addition to heavy rainfall and wind gusts up to approximately 50 mph.
The Dry Blood Creek RAWS site reported a wind gust of 63 mph.
The Malta South US-191 DOT site measured a 59 mph wind gust.
The South Sawmill Creek RAWS site measured a 68 mph wind gust.
A 60 mph wind gust was measured at the Jordan ASOS site.
The King Coulee RAWS site measured a 66 mph wind gust.
A trained spotter reported sustained winds of approximately 40 mph with gusts to approximately 60 mph. Blowing dust was reducing visibility to less than 1/2 mile with the stronger gusts.
The South Sawmill RAWS site measured a 58 mph wind gust.
A NWS employee reported 3/4 inch diameter tree branches down due to thunderstorm outflow winds. Time is estimated based on radar.
A 59 mph wind gust was measured at the Glasgow International Airport ASOS site.
A Mesonet station in West Glasgow measured sustained winds of 56 mph, with a wind gust of 70 mph.
A 65 mph wind gust was measured at the King Coulee RAWS site.
Thunderstorm winds uprooted a tree in the yard of a home in Glendive. The report was received via social media. Based on the photograph, the tree appeared to be approximately 18 inches in diameter at the base with a relatively shallow root system. The estimated wind speed is 60 mph.
A motorist reported quarter size hail on Montana Highway 7 approximately 10 miles south of Wibaux. The report was received via social media.
A motorist reported wind gusts of approximately 60 mph on Montana Highway 7 approximately 10 miles south of Wibaux. The report was received via social media.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2017Every state in 2017This day in weather historyWarnings in Montana, July 2017
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: 699730, 699731, 699732, 699735, 699736, 699737, 699741, 699939, 699739, 699740, 699940, 699738, 700195, 699733, 699734.