Warmer than normal temperatures causes rapid snow melt and leads to a prolonged period of flooding on the Salmon River. The Salmon river continued to rise into the month of June where the greatest impacts occurred.
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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 MSO wrote it up.
Warmer than normal temperatures causes rapid snow melt and leads to a prolonged period of flooding on the Salmon River. The Salmon river continued to rise into the month of June where the greatest impacts occurred. Only minor flooding was observed during the month of May. See the month of June for more detailed information.
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 31, 2:37 AM MST, 4 hours 53 minutes earlier.
Area Forecast Discussion National Weather Service Missoula MT 337 AM MDT Wed May 31 2017 .DISCUSSION...Another very warm day will occur over the Northern Rockies today but changes are coming as the recent high pressure shifts east and is replaced by southwesterly flow. An embedded disturbance in this flow will set off scattered showers and thunderstorms during the afternoon and evening hours. Conditions are favorable for a few strong thunderstorms capable of damaging winds and hail by late in the afternoon. Areas of showers and isolated thunderstorms will continue tonight through Thursday with a cold front passage. Noticeably cooler temperatures will occur on Thursday behind the cold front with highs nearly 20 degrees cooler compared to Wednesday for west central Montana. Cool and unsettled weather will continue on Friday. Brief warm and dry conditions return by Saturday and daytime temperatures will reach well above normal. This drier high pressure will be short-lived, however. The upper level flow will transition to southwesterly from an approaching low pressure system, and moisture will feed into the area beginning Sunday afternoon. Showers and thunderstorms will become more widespread by Sunday evening into Monday, with a rapid temperature cool-down by Monday. This closed low will stall over the northwestern U.S., keeping moisture over the Northern Rockies through at least Tuesday. Emphasis of precipitation will be over western Montana locations. This persistent shower pattern and increased snow melt will promote concerns for rising river/stream levels through this period. && .AVIATION...High and mid level moisture will increase through the day ahead of a disturbance that will initiate the ridge break down. Scattered showers and thunderstorms are expected to develop mid to late afternoon and push northward across the region. All terminal sites stand a chance of thunderstorms but KMSO and KGPI have the higher potential, generally after 31/2200z. Initially, the lower levels of the atmosphere will be quite dry so showers and storms will be capable of strong and gusty winds, along with hail. Areas of showers and isolated thunderstorms will continue tonight into Thursday ahead and along a cold front. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. &&
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
The USGS river gauge Salmon River at Salmon reported minor flooding on May 31st. The river continued to rise and reached moderate flood stage in the first half of June. See June storm data report for more information.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2017Every state in 2017This day in weather historyWarnings in Idaho, May 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: 698258.