Snow Squall Warning 5, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
228 PM MST Sun Feb 16 2020

.DISCUSSION...Considerable snow showers are ongoing with the
potential of a few snow bands through late this evening under
unstable northwest flow. Travelers watch for sudden reductions in
visibility, slick roads, and variable road conditions. Additional
snow showers will occur late tonight into Monday morning. Snow
amounts will highly variable from a dusting to several inches. The
main focus for the snow showers will be north-central Idaho into
west-central and southwest Montana. A secondary band of heavy snow
is possible on US 2 east of Kalispell as well. Allow a little
extra time if you will be traveling, impacts will last into the
Monday morning commute.

Scattered snow showers will continue Monday afternoon into Tuesday
morning but impacts will become much more localized.

A ridge remains in the forecast starting Wednesday. Today models
have trended weaker than yesterday by having several shortwaves
moving over the ridge. This will have little impact on the
forecast due to the air mass being very dry. With the dry air mass
and stable conditions and at least a few inches of snow on the
ground in the region's valleys, radiative cooling at night will
lead to strong valley inversions. The potential for air stagnation
remains, especially in the Seeley Lake area and around Missoula.

Models still agree pretty well, though they have all at the same
time slowed down the front for next weekend with it moving through
the northern Rockies on Sunday now.

&&

.AVIATION...Unstable northwest flow has lead to snow showers which
will continue across the region over the next 24 hours. A few
heavy snow bands may develop through this evening as well but
determining exact locations will be a struggle. Sudden reductions
in visibility and lowered ceilings will accompany showers with VFR
conditions outside of showers. Any gusty winds that develop behind
the afternoon cold front will quickly diminish after sunset.

&&

.AIR STAGNATION...A ridge will build over the region Wednesday.
Very quickly short waves start cutting it down, but it takes a
while and in the meantime a very dry air mass remains over the
northern Rockies. The very dry air mass in combination with at
least a few inches of snow in many of the valleys will cause very
strong radiative cooling resulting in cold temperatures and strong
valley inversions. The coldest, most stable morning is expected to
be Thursday morning at this time. With cloud cover moving in ahead
of a cold front for Sunday, it will be difficult to mix out the
valley inversions until the front arrives which currently looks
like Sunday.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory from 7 PM this evening to 11 AM MST
     Monday Missoula/Bitterroot Valleys.

     Winter Weather Advisory until 11 AM MST Monday Lower Clark Fork
     Region.

     Winter Weather Advisory until 11 AM MST Monday West Glacier
     Region.

     Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Monday Bitterroot/Sapphire Mountains.

     Winter Weather Advisory until 11 AM MST Monday Potomac/Seeley
     Lake Region.

     Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Monday Butte/Blackfoot Region.

ID...Winter Weather Advisory until 10 AM PST Monday Northern
     Clearwater Mountains.

     Winter Weather Advisory until 10 AM PST Monday Southern
     Clearwater Mountains.

&&