A large area of thunderstorms moved up into our area from southeastern Montana. Although the far southern area was under a Severe Thunderstorm Watch, no severe storms occurred over our region.
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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.
A large area of thunderstorms moved up into our area from southeastern Montana. Although the far southern area was under a Severe Thunderstorm Watch, no severe storms occurred over our region. However the storms that did make it up into our area produced heavy rains which led to some flash flooding.
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 27, 1:11 AM MST, 4 hours 49 minutes earlier.
Area Forecast Discussion National Weather Service Glasgow MT 211 AM MDT Sat May 27 2023 .DISCUSSION... *** KGGW Radar Out Till Tuesday May 30th *** Upper low/trough over the Pacific NW will split today with one part moving east into western Montana and the other part digging south into California. Moist southerly flow aloft will continue today across eastern Montana. One shortwave moving north early this morning is currently bringing an area of showers and thunderstorms north across the forecast area. That wave will move north this morning taking the showers and thunderstorms with it. Unstable and moist atmosphere will combine with another wave moving north across eastern Montana this afternoon and evening to bring more showers and thunderstorms, some with heavy rain to the region. Will extend the flood watch to midnight tonight (06Z Sunday). The upper trough moves into eastern Montana late tonight reducing the moist flow and instability somewhat which will lessen the thunderstorm chances after midnight tonight. On Sunday, the upper trough moves through the area turning the southerly flow aloft to the SW and then, more westerly Sunday Night. While showers and thunderstorms will be possible mainly in the afternoon with an unstable atmosphere, the deep moisture will be to the east which will limit the chances for heavy rain. Zonal flow aloft on Monday and Tuesday will bring mainly dry mornings but there will be enough afternoon and evening instability for chances of showers and thunderstorms. An upper trough moves into the Pacific coast on Wednesday with a ridge to the east which will turn the flow aloft to a southerly direction over Montana bringing back the deep moisture and chances for heavy rain. This pattern is expected to continue into next weekend. && .AVIATION... FLIGHT CAT RANGE: VFR - MVFR - IFR DISCUSSION: One area of showers and thunderstorms will lift north this morning. Then, there will be chances for more showers and thunderstorms today and tonight with the best chances this afternoon and evening. There will be a mix and VFR, MVFR, and IFR CIGS this morning with a mix and low and mid level clouds. The low clouds move to the north by afternoon with some breaks in the mid level clouds expected this afternoon. A mix of MVFR and IFR conditions are possible in storms. Mainly mid level clouds are expected tonight while there is a chance some low clouds could develop late tonight. WIND: East to NE 5 to 15 knots early, veering to the SE this afternoon and becoming variable 5 to 10 knots tonight with mainly west winds at KGGW and south winds at KGDV and KSDY. Gusty and erratic winds are possible near passing thunderstorms and any outflow boundaries. && .GLASGOW WATCHES/WARNINGS/ADVISORIES... Flood Watch through this evening for Central and Southeast Phillips...Central and Southern Valley...Daniels...Dawson... Eastern Roosevelt...Garfield...McCone...Northern Phillips... Northern Valley...Petroleum...Prairie...Richland...Sheridan... Southwest Phillips...Western Roosevelt...Wibaux. && weather.gov/glasgow
The national radar mosaic for the moment the first event began.
1 flash flood. Local standard time, as filed.
A CoCoRaHS observer reported 8 to 10 inches of water over Highway 16 at 2 miles south of Savage. They also reported 2 County Road bridges washed out in the same area.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2023Every state in 2023This day in weather historyWarnings in Montana, May 2023
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: 1093542.