Drifting snow on US 95 from Whitebird Hill to Cottonwood led to a road closure during December 30th morning commute.
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The episode as NWS MSO wrote it up.
Drifting snow on US 95 from Whitebird Hill to Cottonwood led to a road closure during December 30th morning commute.
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 30, 3:00 AM PST, 3 hours earlier.
Area Forecast Discussion
National Weather Service Missoula MT
400 AM MST Thu Dec 30 2021
.DISCUSSION...A low pressure system is currently making its way
into the Northern Rockies which will causing widespread snow.
North central Idaho is still anticipated to receive the brunt of
the storm. Clearwater and Idaho counties should expected to
receive between 4 to 7 inches over the next 24 hours, heavier
amounts in the higher terrain. The models are indicating that
gusty southerly winds could develop over the Grangeville area
later this morning into the afternoon. This wind will decrease
snow amounts on the Camas Prairie, but gusts up to 35 mph could
create localized blowing snow. The remainder of the Northern
Rockies should expected 1 to 3 inches of new snow accumulation
during the passage of this system today through tonight.
This evening another surge of arctic air appears to flow over the
Continental Divide causing gusty easterly winds from Marias Pass
to Kalispell along HWY 2 and evening from Rogers Pass to Bonner
along HWY 200 tonight. These gusty winds will create very cold
wind chill readings during the overnight hours into Friday
morning.
The upper level flow will remain northerly over the Northern
Rockies on Friday which is conducive to lingering light snow
showers with cold air remain entrenched in the valleys. A ridge
of high pressure is expected to develop over the region this
weekend. This ridge will cause a decrease in precipitation, but
uncertainty lies on how much warming will the valleys experience.
The models continue to trend towards a very active weather period
for the Northern Rockies next week.
&&
.AVIATION...A disturbance will continue to move through the
Northern Rockies for the next 24 hours bring widespread snow. KGPI
and KMSO is currently experience snow and should experience a
break around 30/17z. A second round of snow is expected this
evening for KGPI and KMSO. KBTM appears to have vicinity snow
showers throughout the event. While KSMN appears to be impacted by
snow between 30/13z to 30/21z. Clearwater and Idaho counties of
Idaho will have the biggest impacted from the snow over the next
24 hours. As for wind concerns, strong westerly winds will
continue to impact the Glacier National Park region this morning
then diminish. The Grangeville Idaho area should have gusty
southerly winds develop late this morning through the afternoon.
Finally another surge of easterly winds expected this evening
along the Continental Divide, potentially impacting KGPI by
31/03z.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT... Winter Weather Advisory until 11 AM MST Friday Lower Clark Fork
Region.
ID...Winter Weather Advisory until 10 AM PST Friday Lower Hells
Canyon/Salmon River Region.
Winter Weather Advisory until 10 AM PST Friday
Orofino/Grangeville Region.
Winter Weather Advisory until 10 AM PST Friday Southern
Clearwater Mountains.
Winter Weather Advisory until 10 AM PST Friday Northern
Clearwater Mountains.
&&The national radar mosaic for the moment the first event began.
1 winter storm. Local standard time, as filed.
The Idaho Department of Transportation closed US 95 from Whitebird Hill to Cottonwood due to drifting snow and poor visibility. The closure went through the morning commute, lifting around 1000 am.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2021Every state in 2021This day in weather historyWarnings in Idaho, December 2021
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: 997612.