Wind Chill Watch 1, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
332 AM MST Fri Mar 1 2019

...BLOWING AND DRIFTING SNOW FOLLOWED BY EXTREMELY COLD WIND
CHILLS ALONG THE CONTINENTAL DIVIDE THROUGH SATURDAY...

.DISCUSSION...The forecast remains on track for the next arctic
front to arrive in western Montana today. It will move into the
state from Canada near Glacier Park and slide down the front
range. This is a very strong, very cold high pressure system which
has prompted us to issue warnings for our zones along the
Continental Divide. This system will unfold in 5 steps in
northwest Montana:

1) Deep, fresh snow already on the ground from recent systems.
2) 2-4 inches of new, powdery snow in northwest Montana.
3) Strong east winds 20-30 mph.
4) Blowing and drifting snow causing whiteout conditions at times.
5) Very cold temperatures causing very cold wind chills.
6) Very, very cold temperatures Monday, Tuesday, and Wednesday mornings.

The rest of western Montana will see around half an inch of new
snow with strong winds and very cold temperatures at least 20
degrees below average for the next few days. While this is
certainly extreme conditions, especially for this time of year, it
is not unprecedented. Looking back through the records for more
than a century there have been several occurrences of systems this
cold in late February and early March. So it is likely we will
see some daily records set, but unlikely that we will break the
record lows for the entire month of March.

Central Idaho will also be much colder than average, but is not
expected to receive much if any snow from this system.

Models agree well also on another system bringing snow to the
region Wednesday night into Thursday. At a time of year we might
expect some rain though, the temperatures remain cold enough that
Montana should experience all snow, whereas in central Idaho
there will be some rain mixed in.

&&

.AVIATION...Clear skies last night has allowed for the development
of patchy freezing fog throughout the Northern Rockies. This fog
will dissipate by mid to late morning and potentially impact KMSO
and KBTM. A subtle feature is dropping out of Alberta Canada this
morning causing light snow over KGPI. A secondary system swings
through the region from the west later today causing scattered
showers over the remainder of the region. The biggest concern will
be the strong arctic airmass that will blast through the region
from the north and east. KGPI will be first impacted as wind gusts
over 30 mph and enhanced snow is expected around 01/15z. The
arctic will push into KMSO and KBTM around 02/00z. Blowing and
drifting snow will also be an issue as this arctic impacts the
region.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning from 10 AM this morning to noon MST
     Saturday Butte/Blackfoot Region...Potomac/Seeley Lake
     Region.

     Winter Storm Watch from noon MST today through Saturday morning
     Bitterroot/Sapphire Mountains.

     Winter Storm Watch from this evening through Saturday morning
     Missoula/Bitterroot Valleys.

     Winter Storm Watch from this evening through Saturday morning
     Lower Clark Fork Region.

     Winter Storm Warning from 10 AM this morning to noon MST
     Saturday Flathead/Mission Valleys.

     Winter Storm Warning from 6 AM this morning to noon MST Saturday
     West Glacier Region.

ID...None.
&&

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