A few warm days and nights to increase snowmelt, followed by a rain event that had several hours of rain over the Salmon River Basin culminated in high flows the evening of May 6th. 75 .
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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.
A few warm days and nights to increase snowmelt, followed by a rain event that had several hours of rain over the Salmon River Basin culminated in high flows the evening of May 6th. Twelve hour precipitation at the Salmon RAWS was recorded at 0.82 , with values up stream in the basin ranging from around 0.15 to 0.75 . There was widespread light rain with some very wet, fast moving showers and thunderstorms embedded. Also, the Pahsimeroi River upstream along the county border registered a record discharge into the Salmon River, but this was largely thought to be backflow from the Salmon itself as the Pahsimeroi gage is near the mouth.
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 7, 1:56 PM MST, 59 minutes earlier.
Area Forecast Discussion National Weather Service Missoula MT 256 PM MDT Sun May 7 2017 .DISCUSSION....Persistent clouds and light rain showers will limit heating today, keeping temperatures well below seasonal averages, which are already into the 60s for highs. Current satellite imagery shows clearing to the west over eastern Washington, and this drier air mass will slowly work its way east over the Northern Rockies this evening and overnight. The forecast stays relatively dry for the first half of the week, with a ridge of high pressure building. Temperatures quickly make their way back into the 70s by mid-week. Both Wednesday and Thursday look warm and "early summer"-like. This pattern will continue to promote high elevation snowmelt, so those using area rivers and streams for recreation should proceed with caution, as flows will be cold and swift. (For more detailed info, please see the Hydrologic Discussion below) The main weather change this week comes on Thursday evening as showers and thunderstorms move in from the west. A low pressure system migrates east and then is forecast to stall off the coast of Washington. Temperatures cool to at-or-below seasonal normals by Friday into the weekend, with periods of showers through the weekend. && .AVIATION...Mid-level ceilings and rain will come to an end for most sites this evening as drier air moves in from the west. Expect rain showers to taper off by sunset for all locations. Overnight winds will be light with partly clear skies. Sites in northwest Montana, including KGPI have a chance for patchy fog in the morning due to today's (Sunday's) rain, but currently models favor a low stratus deck instead. This seems reasonable given upstream observations and current cloud coverage. && .HYDROLOGY...Warm temperatures during the middle of the upcoming week will again begin to accelerate snow melt in the terrain. Given the above average snowpack (many basins 110 to 120% of normal), many rivers are expected to rise to near bankfull by late in the week. A few sites that look like they could continue to deal with flood or near-flood river levels are: the Salmon River near Salmon, ID; the Yaak River near Troy, MT; and the Flathead River near Columbia Falls. Those with property along the river should keep an eye on water levels and the forecast for the next several weeks as snowmelt has begun in earnest. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. &&
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
1237 PM MDT SUN MAY 7 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0142 PM HAIL 7 ENE SULA 45.88N 113.85W
05/06/2017 E1.00 INCH RAVALLI MT PUBLIC
MOSTLY NICKEL-SIZED HAILSTONES, WITH A FEW
GETTING TO QUARTER-SIZED. PERSON LOOKED
OUTSIDE AFTERWARD, BUT DIDN'T FIND ANY
SIGNIFICANT DAMAGE. WINDS WERE STRONG WITH
STORM, ESTIMATED 40 TO 50 MPH. LOTS OF
LIGHTNING OVERHEAD.
&&
LVPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
1240 PM MDT SUN MAY 7 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0145 PM HAIL 9 ENE SULA 45.89N 113.83W
05/06/2017 E0.88 INCH RAVALLI MT PUBLIC
PUBLIC REPORTED MANY NICKEL-SIZED HAILSTONES
WITH HAIL COVERING THE GROUND. RESIDENT
HASN'T CHECKED FOR DAMAGE YET, BUT WINDS
WERE GUSTY. LIGHTNING WAS REPORTED.
&&
LVPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
123 PM MDT SUN MAY 7 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0230 PM HAIL 8 WSW GEORGETOWN 46.14N 113.39W
05/06/2017 E1.00 INCH GRANITE MT PUBLIC
RESIDENT REPORTED GROUND COVERED WHITE WITH
QUARTER-SIZED HAIL. A FEW STRIKES OF
LIGHTNING ACCOMPANIED THE STORM.
&&
LVThe national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Local emergency manager reported flooding at the Oregon Bar campground 7 miles north of Salmon. Also an NWS employee reported minor flooding in the Elk Bend area, where water was flowing over yards and into outbuildings.
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: 698158.