With a weakly unstable atmosphere, strong thunderstorms from the higher terrain of central and southern Montana eventually developed into a few isolated severe thunderstorms and pushed strong to severe wind gusts into portions of northeast 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 GGW wrote it up.
With a weakly unstable atmosphere, strong thunderstorms from the higher terrain of central and southern Montana eventually developed into a few isolated severe thunderstorms and pushed strong to severe wind gusts into portions of northeast 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 Glasgow, MT wrote its last area forecast discussion before the first event at May 30, 5:32 PM MST, 1 hour 43 minutes earlier.
Area Forecast Discussion...UPDATED National Weather Service Glasgow MT 632 PM MDT Wed May 30 2018 .DISCUSSION... Early Evening Update: Main update was to edit pops/wx grids based on radar trends. So far, T-storms have produced only small hail and non-severe wind gusts. Additional storms can be seen upstream on the radar and satellite imagery. So there remains the possibility of a strong storm or two later tonight. SCT Afternoon Update: Most changes in the forecast were to PoP/QPF for tonight and tomorrow. Confidence continues to increase in severe weather potential across the region especially tomorrow, thus mentions of Large Hail, Damaging Winds and Heavy Rain are included in the weather grids beginning this afternoon. No mentions of tornadoes yet in the forecast, but early analysis of ingredients tomorrow afternoon in especially the Yellowstone River Valley leads to the thinking of not being able to rule out chances for at least a brief spin-up. Otherwise, the forecast was relatively untouched so as to focus on tonight/tomorrow. Bigelbach PREVIOUS DISCUSSION: Synoptic Setup: Hot high pressure has built itself up over the Four Corners with a slug of hot air rapidly moving along a ridge from Southern Idaho into southeastern Montana. A large trough sets over the coast of British Columbia and then turns off shore of the Pacific northwest and California as it goes south. Between these two airmasses is a southwest to zonal flow with a strong jet and pacific moisture running from northern California through the Pacific Northwest and into northern Montana and the Canadian Prairie Provinces. Today: The ridge to the south will build further into the southeast Montana keeping conditions partly cloudy and dry. A surface trough will help to develop afternoon showers over the central Montana mountains. Tonight: The ridge will slowly eject into the Dakotas as southwest flow brings a series of increasingly strong mid to upper level jets through the region. the first one will help to detach the afternoon mountain showers and float them over our western zones in the evening hours and spread light rain into the area. Thursday and Thursday night: Hot high pressure in the southeast and increasingly strong jets ladened with mid-level moisture passing overhead will act to increase showers activity into afternoon thunderstorms while tightening a surface temperatures gradient into a cold front across northern zones in the afternoon. CAPE is expected to rise from about 500 to 2000 J/kg in the warm sector but may be rather skinny. Bulk shear however will be high leading to a large hail threat with any thunderstorms that do develop in the afternoon and evening. As the front moves through the whole CWA thunderstorms should transition back to less severe rain showers near midnight. Friday through Sunday night: Some remnant rain showers will be possible Friday but these periods kick of a warming and drying trend from here onward. The weekend itself looks to contain dry excellent weather in the 70s. Monday onward: The ridge is expected to break down in these periods with showers and thunderstorms again, but no individual mode in the model ensembles seems preferred yet. Confidence here onward is below average. GAH && .AVIATION... Expected Flight Category: VFR Synopsis: A cold front will move through the region tonight, bringing chances for showers and thunderstorms mainly to the western sites (GGW, OLF) tonight. Another round of stronger thunderstorms will be likely Thursday, affecting all of the sites in the afternoon and evening. Ceilings should remain VFR, though in the strongest showers and thunderstorms, it is possible some reductions to high MVFR may be possible. Impacts to operations likely underneath thunderstorms due to the potential for damaging hail and gusty and erratic winds. Winds: Expect mainly southeast to southwest winds today under around 10 kts for GGW and OLF, and northwest winds under 10 kts for SDY and GDV, with all sites gradually turning to the northeast overnight while generally increasing in speed up to 10-15 kts before Thursday afternoon. Bigelbach/sct && .GLASGOW WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch from Thursday afternoon through late Thursday night for Southwest Phillips. && weather.gov/glasgow
Special Weather Statement National Weather Service Glasgow MT 219 PM MDT WED MAY 30 2018 MTZ016-017-059-061-302115- Central and Southeast Phillips MT-Northern Valley MT- Northern Phillips MT-Central and Southern Valley MT- 219 PM MDT WED MAY 30 2018 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN PHILLIPS AND NORTHERN VALLEY COUNTIES UNTIL 315 PM MDT... At 218 PM MDT, Doppler radar was tracking a strong thunderstorm 8 miles northeast of Hinsdale, or 27 miles northwest of Glasgow, moving northeast at 40 mph. Dime size hail and winds in excess of 30 mph will be possible with this storm. Locations impacted include... Opheim, Hinsdale, St. Marie, Port Of Opheim, Tampico, Vandalia, Thoeny, Frenchman Reservoir, Baylor and Larslan. LAT...LON 4900 10636 4850 10608 4825 10704 4900 10745 TIME...MOT...LOC 2018Z 239DEG 35KT 4851 10701 AEH
Special Weather Statement National Weather Service Glasgow MT 239 PM MDT WED MAY 30 2018 MTZ017-302145- Central and Southern Valley MT- 239 PM MDT WED MAY 30 2018 ...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL VALLEY COUNTY UNTIL 345 PM MDT... At 238 PM MDT, Doppler radar was tracking a strong thunderstorm near Tampico, or 8 miles west of Glasgow, moving east at 35 mph. Dime size hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Glasgow, Nashua, Tampico, St. Marie and Whatley. LAT...LON 4796 10690 4826 10704 4856 10609 4822 10589 TIME...MOT...LOC 2038Z 247DEG 29KT 4822 10682 AEH
Special Weather Statement
National Weather Service Glasgow MT
337 PM MDT WED MAY 30 2018
MTZ021-302245-
Petroleum MT-
337 PM MDT WED MAY 30 2018
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN PETROLEUM COUNTY
UNTIL 445 PM MDT...
At 337 PM MDT, Doppler radar was tracking a strong thunderstorm 9
miles northwest of Flatwillow, or 13 miles southwest of Winnett,
moving east at 10 mph.
Nickel size hail and wind gusts up to 50 mph will be possible with
this storm.
Locations impacted include...
Flatwillow and Tiegen.
LAT...LON 4684 10863 4684 10861 4709 10861 4716 10848
4676 10818 4675 10863
TIME...MOT...LOC 2137Z 254DEG 9KT 4689 10859
AEHSpecial Weather Statement National Weather Service Glasgow MT 348 PM MDT WED MAY 30 2018 MTZ017-022-023-302245- Garfield MT-McCone MT-Central and Southern Valley MT- 348 PM MDT WED MAY 30 2018 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN GARFIELD... SOUTHEASTERN VALLEY AND NORTHWESTERN MCCONE COUNTIES UNTIL 445 PM MDT... At 347 PM MDT, Doppler radar was tracking a strong thunderstorm near Nashua, or 17 miles southeast of Glasgow, moving east at 25 mph. Half inch hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Nashua, Fort Peck, Fort Peck Marina, Duck Creek Rec Area, Frazer and Park Grove. PRECAUTIONARY/PREPAREDNESS ACTIONS... If on or near Fort Peck Lake, get out of the water and move indoors or inside a vehicle. Remember, lightning can strike out to 10 miles from the parent thunderstorm. If you can hear thunder, you are close enough to be struck by lightning. Move to safe shelter now! Do not be caught on the water in a thunderstorm. && LAT...LON 4792 10662 4822 10644 4821 10585 4780 10597 TIME...MOT...LOC 2147Z 285DEG 21KT 4806 10633 AEH
Special Weather Statement
National Weather Service Glasgow MT
739 PM MDT WED MAY 30 2018
MTZ021-022-310245-
Petroleum MT-Garfield MT-
739 PM MDT WED MAY 30 2018
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN PETROLEUM AND
SOUTHWESTERN GARFIELD COUNTIES UNTIL 845 PM MDT...
At 737 PM MDT, Doppler radar was tracking a strong thunderstorm over
Mosby, or 23 miles east of Winnett, moving northeast at 40 mph.
Nickel size hail and winds in excess of 40 mph will be possible with
this storm.
Locations impacted include...
Sand Springs, Mosby, Edwards, Brusett, Steve Fork and Cat Creek.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 4724 10831 4750 10717 4686 10692 4685 10789
4682 10785 4680 10784 4680 10785 4679 10784
4678 10785 4676 10783 4676 10791
TIME...MOT...LOC 0137Z 244DEG 37KT 4698 10785
AEHThe Glasgow radar (KGGW), 149 km away, was scanning. The volume nearest the first event began at 02:13 UTC.
5 thunderstorm wind. Local standard time, as filed.
Public estimated wind gusts up to 60 mph and nickel size hail.
ASOS site at the Jordan Airport measured a 62 mph wind gust.
NWS employee estimated 60 mph wind gusts.
ASOS site at the Glasgow airport measured a 59 mph wind gust.
Public reported a tree fell on an unoccupied car.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2018Every state in 2018This day in weather historyWarnings in Montana, May 2018
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: 757942, 757943, 757944, 757945, 757946.