High Wind in Idaho, November 13, 2020

Area Forecast Discussion
National Weather Service Missoula MT
340 AM MST Fri Nov 13 2020

.DISCUSSION...Radar and observations upstream have shown light
precipitation in the form of rain or snow in eastern Washington
early this morning. Also gusty winds have been reported from
central Idaho to southwest Montana. Expect precipitation to spread
eastward with time this morning. There were no big changes to the
forecast today in terms of the snow chances. We continue to have
low confidence that freezing rain will occur, especially tonight
when the upper levels will have cooled down behind the cold front
and it will be unstable, supporting more snow showers with gusty
winds more than anything else.

Forecast soundings continue to show strong south winds developing
between Whitebird Hill and the Camas Prairie, Idaho this morning.
Colder air in the vicinity of Grangeville in the upper 20s and
the easterly orientation of the wind gradient is currently
limiting the winds at this time, but they are expected to ramp up
by later this morning, potentially gusting near 50 mph. This could
cause drifting and blowing snow and the advisory is still warranted.

After a cold front moves through tonight, persistent snow showers
will continue through Saturday bringing periodic low visibility
and gusty winds

On Sunday another trough, not as moist as today's system, will
move through the region. It will mainly bring more mountain snow
with some valley accumulation. With the flow aloft more zonal and
surface low pressure moving off to the east, expect more gusty
winds on Sunday with temperatures near seasonal readings.

An upper level ridge builds on Monday and Tuesday with
temperatures moderating into the 40s and 50s. While a warm front
will bring rain and snow to portions of central Idaho and
northwest Montana on Monday, Tuesday may be mostly dry especially
over western Montana. Snow levels will be on the rise: to 5000
feet Monday and to 7000 feet on Tuesday. The remainder of next
week continues to be unsettled with a series of systems that bring
showers to the area.

&&

.AVIATION...Moderate to heavy snowfall is expected in the higher
terrain of central Idaho into western Montana today. Strong
southerly winds are expected in these areas, especially in the
wind prone locations like the Camas Prairie in Idaho, and portions
of southwest Montana. Low level wind shear is a concern in
valleys, but should stay near or below 40 knots. Ceilings are
forecast to lower as showers increase during Friday. A cold front
passage Friday tonight, between 14/0300Z and 14/0600Z will bring
lower snow levels, snow showers and gusty winds through Saturday.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Lake Wind Advisory from 11 AM this morning to 5 PM MST Saturday
     for Flathead Lake in the Flathead/Mission Valleys.

     Winter Weather Advisory until 2 PM MST Saturday West Glacier
     Region.

     Winter Weather Advisory until 10 AM MST Saturday
     Kootenai/Cabinet Region.

     Winter Weather Advisory until 10 AM MST Saturday
     Bitterroot/Sapphire Mountains.

     Winter Weather Advisory until 10 AM MST Saturday Lower Clark
     Fork Region.

ID...Winter Weather Advisory until 9 AM PST Saturday Northern
     Clearwater Mountains...Southern Clearwater Mountains.

     Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Saturday Eastern Lemhi County...Western Lemhi County.

     Winter Weather Advisory until 9 AM PST Saturday ABOVE 3000 FEET
     for the Lower Hells Canyon/Salmon River Region.

     Winter Weather Advisory until 9 AM PST Saturday
     Orofino/Grangeville Region.

&&