Moist and warm southwest flow combined with unusually cold sub-surface temperatures to produce freezing rain across low elevation valleys in central Idaho. The freezing rain caused widespread travel impacts, and caused all schools in the district to close.
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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.
Moist and warm southwest flow combined with unusually cold sub-surface temperatures to produce freezing rain across low elevation valleys in central Idaho. The freezing rain caused widespread travel impacts, and caused all schools in the district to close.
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 Jan 17, 1:52 PM PST, 8 hours 8 minutes earlier.
Area Forecast Discussion
National Weather Service Missoula MT
252 PM MST Tue Jan 17 2017
...Periods of Freezing Rain for Portions of the Northern
Rockies...
.DISCUSSION...A very weak disturbance will continue to move
through northwest Montana potentially causing some light snow and
potentially some light freezing drizzle. The cold pools continue
to plague several of the valleys across the Northern Rockies, for
example the Bitterroot valley temperatures are in the teens while
a couple thousand feet up the mountains temperatures are warming
well into the 30s this afternoon. A significant plume of moisture
will continue to move towards the Northern Rockies. This plume
will have a north south trajectory so the heaviest precipitation
appears to be over Idaho and steadily diminishing through western
Montana. Winter storm warnings have been issued for Clearwater
county up into northwest Montana for later tonight through
Wednesday. This area will have a combination of snow, then
freezing rain and finally all rain by Wednesday afternoon. Even
though the precipitation will be rain, sub surface temperatures
remain well below freezing so after sunset tomorrow roadways could
refreeze. Another concern is the weight loading of snow due to the
rain which will put extra strain on structures. Winter weather
advisories have been issued for west central and the remainder of
northwest Montana for this event. Precipitation will be lighter
but the potential of freezing rain is a high probability. Most
valley locations should finally mix out the cold pools with the
exception of Missoula and Salmon valleys.
Thursday precipitation potential continues ahead of an approaching
colder air mass and front. Snow levels of 4000 feet in northwest
Montana to 5000 feet in west central and southwest Montana and
central Idaho are expected. As a result valley locations can
expect precip in the form of rain Thursday with relatively light
amounts less than .05".
Cooler air makes its way into the region Thursday evening.
Fortunately it won't be the kind of extreme cold we have received
over the last few weeks. Temperatures will be at or slightly below
normal with generally highs in the upper 20s to lower 30s and
lows in the teens through Monday next week. Expect scattered snow
showers Friday and Saturday with some light accumulations in the
mountains.
SUNDAY a weather system makes its way into the region from the
south. Unlike our system today temperatures should be low enough
for precipitation to remain all snow. Right on its heels models
are showing a moderate to strong cold front to impact the region
with some windy conditions, colder temperatures and continued
mountain snow and perhaps a return of some snow bands through
Tuesday. Confidence is pretty good for a weather system and cold
front early next week HOWEVER there isn't a lot of confidence on
details such as snow banding, snow amounts or wind potential.
The middle to end of next week models are in fair agreement
showing a return of a pretty strong ridge over the west. If it
came to fruition we could see a return of inversions and colder
valleys.
&&
.AVIATION...Low stratus and some fog continue in the Flathead and
Mission valleys producing some limited visibility down to 6 miles
and haze and some mountain obscurations. Some mid to higher level
clouds are entering the northern Rockies. A weather system with
warmer air aloft will enter the region this evening. It is
expected to impact KGPI after 18/0200z and and KMSO after
18/0900z with a mixture of snow, rain and/or freezing rain. There
is some uncertainty of how much precipitation is expected. The
main focus of heavier precipitation is along the Idaho/Montana
border. Current thoughts are up to .10" of liquid precip at KGPI
and .05" at KMSO but 50-100 miles could make a big difference.
Temperatures will warm up enough Wednesday afternoon for terminals
to receive a mix of light snow and rain. KBTM and KSMN will
remain mostly dry overnight.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT... Winter Weather Advisory from 11 PM this evening to 11 PM
MST Wednesday Missoula/Bitterroot Valleys...Potomac/Seeley Lake
Region...West Glacier Region.
Winter Storm Warning from 11 PM this evening to 11 PM MST
Wednesday Lower Clark Fork Region.
Winter Weather Advisory from 11 PM this evening to 11 PM MST
Wednesday Flathead/Mission Valleys.
Winter Storm Warning until 11 PM MST Wednesday Kootenai/Cabinet
Region.
ID...Winter Storm Warning from 10 PM this evening to 10 PM PST
Wednesday Northern Clearwater Mountains...
Orofino/Grangeville Region.
Winter Weather Advisory from 10 PM this evening to 10 PM PST
Wednesday Southern Clearwater Mountains.
&&The national radar mosaic for the moment the first event began.
1 winter storm. Local standard time, as filed.
The Emergency Manager of Clearwater County reported secondary roads were like an ice skating rink due to freezing rain. Due to the icy roads, all schools in the district were closed.
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, January 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: 674651.