An upper level wave dropped out of British Columbia, embedded in northwesterly flow and brought periods of blowing snow and snow especially in the Camas Prairie. A plume of moisture with tropical origins interacted with this wave to provide higher snowfall amounts as compared with other northwest waves.
Every event with a place to put it; 5 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.
An upper level wave dropped out of British Columbia, embedded in northwesterly flow and brought periods of blowing snow and snow especially in the Camas Prairie. A plume of moisture with tropical origins interacted with this wave to provide higher snowfall amounts as compared with other northwest waves.
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 20, 7:54 AM PST, 6 minutes earlier.
Area Forecast Discussion
National Weather Service Missoula MT
854 AM MST Fri Dec 20 2013
.UPDATE...Added winter weather advisories for the remainder of
western Montana.
&&
.DISCUSSION...Upstream weather stations and webcams in British
Columbia are showing the effects of the very moist weather system
poised to strike central Idaho and to a lesser degree western
Montana today. Forecast soundings combined with information
derived from CIPS analogs show that some places across Clearwater
and Idaho Counties could see very intense snowfall rates
approaching 2 inches per hour. This will exacerbate road conditions
to the point that some vehicles may have trouble traveling through
unplowed locations. New NAM forecast soundings continue to point
to strong southerly winds from the Camas Prairie southwards to
Grangeville which will create blowing and drifting snow in those
sections. In the January 5, 2009 event, which has some similarities
to later today, some of the county roads in those areas closed
down due to drifting snow. By this evening, some of these roads
could become impassable due to the heavy falling snow and blowing
snow, reducing visiblities down to zero at times with snow drifts
forming.
&&
.AVIATION...Moisture in the northwesterly flow aloft is beginning
to move into Idaho and western Montana early this morning. Light
snow is beginning to fall in northwest Montana and will increase
throughout the region today. Mountains will be obscured by clouds
and snow today, tonight, and most of Saturday. Visibilities and low
ceilings will become common by the afternoon through north central
Idaho and western Montana. The current storm system is expected to
produce heavy snow through north central Idaho at all elevations,
and places like Grangeville will also have wind. Winds and snow
will cause treacherous conditions into Saturday morning in the
vicinity of Grangeville and at higher elevations. The moisture
feed will weaken by midday Saturday, so snow will decrease.
The upcoming weekend will have high chances for light snow, on and
off lowed visibilities and ceilings, and continued obscurations in the
terrain.
&&
.PREV DISCUSSION... /ISSUED 354 AM MST Fri Dec 20 2013/
..HEAVY SNOW THIS EVENING THROUGH SATURDAY MORNING FOR CENTRAL
IDAHO...
DISCUSSION...The next snow producing weather system is starting
to move into Idaho and western Montana. Light snow has begun to
fall this morning in NW Montana with heavier snow to develop this
afternoon. There is a chance that we will see widespread light
snow by the morning commute, but this should not pose much of an
impact. North central Idaho is still on track to accumulate the
highest amounts of snow during this event that will peak tonight.
The potential still exists for wind to increase overnight in
Grangeville and the Camas Prairie so very low visibilities with
blowing and drifting snow could make for a dangerous situation if
traveling late this evening and tonight. The rest of north central
Idaho will accumulate widespread snow amounts of 10 to 15 inches
or more by Saturday morning. So travel will be slow going at best.
Western Montana will also have snow this afternoon through tonight
but with less impacts, though travel will be slowed at times
through Saturday morning. Snow will taper off through Saturday as
we lose our moisture feed.
Additional light snow will return for Saturday night and likely
continue through Tuesday morning. There may be little if any
break in mountain snowfall during this time frame so mountain
passes have a good chance to remain snow covered. Meanwhile
the valleys will continue to see periods of light snow but with
lesser travel impacts expected. A better defined weather feature
will slide across the region late Monday into Tuesday resulting in
perhaps some better chances for accumulating snowfall in the
valleys. However this system is quick moving and by Christmas Eve
drier air will already be moving into the region, limiting light
snow chances to far NW Montana/Glacier Park region overnight.
For Christmas Day some locations in NW Montana and along the
Divide may see some light snowfall while Idaho locations remain
largely dry. Quite cold conditions are expected to develop across
SW and west central Montana due to recent snowfall and a clearing
sky overnight. The rest of the week will be rather tranquil as
high pressure moves in overhead and helps establish some valley
inversions. However this is short lived as long range models
return the Northern Rockies to a potentially more active NW flow
aloft by next weekend.
AVIATION...Moisture in the northwesterly flow aloft is beginning
to move into Idaho and western Montana early this morning. Light
snow is beginning to fall in northwest Montana and will increase
throughout the region today. Mountains will be obscured by clouds
and snow today, tonight, and most of Saturday. Visibilities and low
ceilings will become common by the afternoon through north central
Idaho and western Montana. The current storm system is expected to
produce heavy snow through north central Idaho at all elevations,
and places like Grangeville will also have wind. Winds and snow
will cause treacherous conditions into Saturday morning in the
vicinity of Grangeville and at higher elevations. The moisture
feed will weaken by midday Saturday, so snow will decrease.
The upcoming weekend will have high chances for light snow, on and
off lowed visibilities and ceilings, and continued obscurations in the
terrain.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY until 11 AM MST Saturday Butte/Blackfoot
Region.
WINTER WEATHER ADVISORY until 11 AM MST Saturday
Bitterroot/Sapphire Mountains.
WINTER WEATHER ADVISORY until 11 AM MST Saturday
Missoula/Bitterroot Valleys.
WINTER WEATHER ADVISORY until 11 AM MST Saturday Lower Clark
Fork Region.
WINTER WEATHER ADVISORY until 11 AM MST Saturday
Flathead/Mission Valleys...Kootenai/Cabinet Region.
WINTER WEATHER ADVISORY until 11 AM MST Saturday West Glacier
Region.
WINTER WEATHER ADVISORY until 11 AM MST Saturday Potomac/Seeley
Lake Region.
ID...WINTER WEATHER ADVISORY until 11 AM MST Saturday Eastern Lemhi
County...Western Lemhi County.
WINTER WEATHER ADVISORY until 10 AM PST Saturday Lower Hells
Canyon/Salmon River Region.
WINTER STORM WARNING until 10 AM PST Saturday
Orofino/Grangeville Region.
WINTER STORM WARNING until 10 AM PST Saturday Northern
Clearwater Mountains...Southern Clearwater Mountains.
&&
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https://www.twitter.com/NWSMissoulaThe national radar mosaic for the moment the first event began.
3 winter weather, 1 winter storm, 1 heavy snow. Local standard time, as filed.
The COOP observer located in Pierce, measured 5.0 of total snowfall with 0.62 of liquid equivalent during the storm. Other snowfall amounts include: 6 Elk Butte SNOTEL and 4 Shanghi Summit SNOTEL.
The Idaho County highway reported white-out conditions from Whitebird Grade to Grangeville and from Grangeville to Cottonwood due to blowing snow and snow. They also reported that they received over 30 automobile accident calls. Southerly winds between 20 to 25 mph developed around 2:45 pm PST across the Camas Prairie, as observed by an ITD road sensor located 3.8 miles south-southeast of Cottonwood. The sensors at the Grangeville Idaho County Airport, reported southerly winds sustained between 25-30 mph with gusts to 41 mph between 6:24 pm and 9:44 pm PST. Weather spotters reported 2 per hour snowfall rates in Woodland and in Kamiah around 3:55 pm PST. Other snowfall amounts: 6.5 E Kooskia, 6 1 mi. ENE Woodland, and 4.5 3 mi. NE Orofino.
The ITD road sensor at Whitebird Hill on US-95 reported 0.25 of precipitation which could equate to around 3 of snowfall. It reported visibilities below one-half mile at times between 1:46 and 11:16 pm PST, and web-cams indicated blowing snow and snow. The winds were southerly between 10 and 20 mph during the event.
A trained spotter in Elk City measured 8.5 of snow that mainly fell during the afternoon and evening on Dec. 20. The Lowell ASOS reported around 0.10 of precipitation each hour from 4 to 8 pm PST which could equate to over 1 per hour snowfall rates, and temperatures ranged between 29-30 deg. F during the event. It recorded a total precipitation amount of 0.69 which could be converted to around 8 of snowfall. Other snowfall amounts: 12.4 Dixie COOP, 9 Mountain Meadows SNOTEL, and 8 2 miles north of Elk City.
A trained spotter located 1 mile east-southeast of Salmon estimated 5.5 of snowfall. The Saddle Mountain SNOTEL recorded 4 of snowfall with 0.50 of snow water equivalent during the storm.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2013Every state in 2013This day in weather historyWarnings in Idaho, December 2013
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: 496949, 496926, 496952, 496938, 496953.