Anomalous atmospheric moisture with slow moving thunderstorms triggered a few debris flows in Lemhi County.
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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.
Anomalous atmospheric moisture with slow moving thunderstorms triggered a few debris flows in Lemhi County.
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 Jun 6, 12:26 PM MST, 1 hour 34 minutes earlier.
Area Forecast Discussion National Weather Service Missoula MT 126 PM MDT Tue Jun 6 2023 .DISCUSSION...A well-formed closed low pressure circulation over central California is continuing to send moisture north into the Northern Rockies. This feature is part of a much larger puzzle that includes a high amplitude ridge over the central U.S. and another low spinning over the East Coast. The California low will remain in place over the next few days with the help of the other atmospheric features over the U.S., sending smaller scale disturbances north and eastward towards Idaho and Montana. In the short term... this afternoon and Wednesday... clear skies in the morning with some deep instability and available moisture will be capable of fueling afternoon showers and thunderstorms throughout north-central Idaho and southwest Montana. Lack of strong steering winds and appreciable shear will result in storms producing mostly heavy rain and small hail, with little in the way of damaging hail or strong outflow winds. An increase in moisture on Wednesday will allow afternoon storm activity to spread further north. A more significant rain event will begin on Thursday. A mid levels low will setup over northwest Wyoming, pushing additional Gulf moisture into the Northern Rockies from the east. Precipitable water amounts will jump to about 200-250 percent of normal. Lift will be provided by the mid levels circulation and enhanced by terrain. The heaviest rainfall will be along and south of I-90 over western Montana and into north-central Idaho. Areas north of I-90 along the Continental Divide will also see periods of heavy rain on Thursday. The mid levels circulation will migrate to the northwest on Friday, bringing the focus of heavier precipitation north and west. Expect chances for heavy rain to increase across all of northwest Montana north of I-90, as well as Clearwater and Idaho Counties. Visitors to Glacier Park should be prepared for wet weather Thursday afternoon through Saturday morning. && .AVIATION...Scattered showers and a few thunderstorms will be in the vicinity of KBTM and KSMN through 07/0300z. Brief heavy rain may occur with storms. A lesser chance of showers or a thunderstorm will be in the vicinity of KMSO. Skies will clear overnight and Wednesday morning with another potential for scattered showers and thunderstorms redevelop in the vicinity of all terminals. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. &&
The Missoula radar (KMSX), 199 km away, was scanning. The volume nearest the first event began at 20:59 UTC.
1 flash flood, 1 debris flow. Local standard time, as filed.
The Beartrack Mine reported significant runoff on several of the nearby drainages, and the flood waters including soot from the 2022 Moose Creek wildfire overflowed several structures with no significant damage.
A dispatcher reported flooding with mud and rocks across the north bound lane of US-93 near Twelve Mile County Road. The location was near milepost 292.9 north of Elk Bend.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2023Every state in 2023This day in weather historyWarnings in Idaho, June 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: 1094974, 1101166.