Above normal snowpack combined with a warmer than normal May contributed to flooding across western Montana.
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 MSO wrote it up.
Above normal snowpack combined with a warmer than normal May contributed to flooding across western 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 Missoula, MT wrote its last area forecast discussion before the first event at May 17, 1:34 PM MST, 6 hours 41 minutes earlier.
Area Forecast Discussion National Weather Service Missoula MT 234 PM MDT Thu May 17 2018 .DISCUSSION...Satellite and radar trends reveal a general upper level trough over the Northern Rockies this afternoon. Earlier, slow moving moderate rain showers brought close to an inch of rain to the Dixon, Montana area. A few thunderstorms have been building and dissipating over Silver Bow County bringing lightning and periods of moderate rainfall there this afternoon. Also of note, rising pressure towards Cut Bank has resulted in a north to east pressure gradient along the Continental Divide; and as of this discussion, Kalispell has started to feel a northeast breeze while the Helmville area started to experience an east wind a few hours ago. More showers and a few thunderstorms are expected through late this evening across the area. Impacts from the heavier downpours will be reduced visibility, potential lightning and ponding of water. One change to this forecast package was to reduce the chance for precipitation over the Flathead Valley this evening as northeast winds will inhibit shower activity. Also north to east winds will increase into the overnight with some locations gusting near 30 mph including Columbia Falls, Flathead Lake, and along the Divide. The western U.S. will remain influenced by low pressure during Friday and this weekend. Below average temperatures, easterly winds, and rain showers are all expected on Friday. The main concentration for rain is most likely to occur along the Divide and in north-central Idaho, but most places will see at least a light shower by Friday evening. Temperatures return to closer to average on Saturday with rain showers and a few thunderstorms. High temperatures return to above average on Sunday which will continue for most if not all of next week. Above normal moisture, daytime heating, and weak disturbances during Sunday and next week will cause daily shower and thunderstorm chances. && .AVIATION...Scattered showers with a few thunderstorms are anticipated over the next 24 hours. It appears that BTM will see the best chance for thunderstorms while a few terrain-driven storms could get close to MSO and SMN through 18/0300z. Periods of lower visibility and ceilings will occur with stronger showers. Northeast winds gusting near 25 knots will develop especially at GPI tonight and locations along the Continental Divide will experience breezy easterly winds through 18/2100Z. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...For flood warning details please visit weather.gov/missoula ID...None. &&
The national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
The Bitterroot River near Missoula reached flood stage and caused flooding in low-lying areas and contributed to high groundwater near the Linda Vista and lower Miller creek areas.
The Clark Fork River again reached flood stage and caused flooding of the access road to the sewage lagoons outside of Plains.
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: 753985, 753973.