A system digging south out of Canada accompanied by a strong upper level jet produced strong bands of precipitation across portions of north central Idaho.
Every event with a place to put it; 3 filed by county or forecast zone are drawn at its center, in a lighter ring. 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.
A system digging south out of Canada accompanied by a strong upper level jet produced strong bands of precipitation across portions of north central Idaho.
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 Dec 16, 2:32 AM PST, 2 hours 13 minutes earlier.
Area Forecast Discussion
National Weather Service Missoula MT
332 AM MST WED DEC 16 2015
...Valley and mountain snow impacting travel today...
...Potential freezing rain Thursday night into Friday...
.DISCUSSION...Snow has been falling through the night across most
of northwest and west central Montana, as well as north central
Idaho. Bursts of heavier snow have brought early accumulations,
with snow expected to continue and intensify through the morning.
The heaviest snow is still expected to occur across west central
Montana between daybreak and mid-to-late morning, and will impact
travel for the morning commute. The I-90 corridor and the Missoula
and Bitterroot valleys are still on tap to see the most
enhancement and greatest snow production, with difficult travel
likely at times.
Snow will shift further south through the afternoon, impacting the
rest of central Idaho and southwest Montana, bringing additional
snowfall accumulations and travel impacts. Overall, widespread
amounts of 2 to 5 inches for valleys are likely, with greater
amounts over mountain passes. Lingering snow showers behind the
initial push of precip will occur through the day, so while the
most impactful snowfall has passed...another inch or two of snow
could occur through this evening.
It should be noted that there is also a chance for lake effect
snow to happen around Flathead Lake through Thursday. The current
pattern supports the potential for snow to occur, with local
accumulations potentially affecting communities in the immediate
vicinity of the lake.
A warm front will begin to impact north central Idaho by Thursday
afternoon with a gradually increase in light snowfall. Snow will
transition to rain Thursday evening for the valleys as warmer air
aloft moves overhead. Light freezing rain will be possible late
Thursday night for the lowest valleys, which may lead to localized
slippery road conditions.
Across western Montana, this same warm front will bring areas of
snow Thursday night. Warm air aloft will transition the snow to
rain for lower elevations on Friday morning. Remnant cold air in
the valleys may results in pockets of freezing rain from roughly
Superior to Hot Springs and Missoula to Hamilton, making the
Friday morning commute potentially difficult with very slick
roads. For the rest of northwest Montana and area mountain passes,
precipitation will remain primarily as snow.
A cold front will drop southward across the region Friday
afternoon through Saturday morning, resulting in light snow
accumulations in the valleys with several additional inches of
snow for mountain passes. An unstable atmosphere and a weak
passing disturbance will bring periods of snow showers Saturday,
but once again, accumulations will remain light.
An active westerly flow will result in occasional snowfall and
seasonably cold temperatures for the Northern Rockies all of next
week. Although forecast models agree on the active pattern, there
is considerable disagreement on the timing of significant weather
producing features. Disruptions to holiday travel are very
possible, so please stay tuned for the latest forecast updates.
&&
.AVIATION...Snow, moderate to heavy at times, has begun to impact
KGPI and KMSO this morning and will continue through the day. The
greatest threat to aviation will be dramatic reductions in
visibility due to bursts of heavier snowfall, particularly at KMSO
between 16/1200Z and 16/1800Z. Low ceilings will also become
problematic at times. After 16/1800Z, KBTM and KSMN will begin to
see their vsby/ceil drop as snow spreads further south, impacting
operations through this evening. Lingering snow will continue to
fall at all terminals through roughly 17/0400Z, with the chance
for patchy freezing fog and/or low stratus to develop thereafter.
Few impacts are expected from fog/stratus, as confidence in its
development is low at this time.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 11 PM MST this evening
Bitterroot/Sapphire Mountains...Butte/Blackfoot Region...
Missoula/Bitterroot Valleys.
Winter Weather Advisory until 3 PM MST this afternoon Lower
Clark Fork Region...Potomac/Seeley Lake Region.
Winter Weather Advisory until noon MST today Flathead/Mission
Valleys...Kootenai/Cabinet Region...West Glacier Region.
ID...Winter Weather Advisory until 10 PM PST this evening Lower Hells
Canyon/Salmon River Region...Northern Clearwater
Mountains...Orofino/Grangeville Region...Southern
Clearwater Mountains.
&&The national radar mosaic for the moment the first event began.
3 heavy snow. Local standard time, as filed.
A spotter located in Weippe reported 5.5 inches of heavy snow and web cams at Greer Grade on Highway 11 revealed very low visibility and intense snow.
A person from the public located northeast of Glenwood off of Road 100 in Idaho County reported an estimated 8 to 10 inches of snow.
A spotter located 3 miles northeast of Orofino reported 7.5 inches of snow that fell in 5 hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2015Every state in 2015This day in weather historyWarnings in Idaho, December 2015
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: 612882, 612886, 612887.