Winter Weather Advisory 50, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
332 AM MST Thu Nov 11 2021

.DISCUSSION...Northwest flow featuring a warm, moist airmass is
encroaching on the Pacific Northwest this morning. This system
will bring precipitation to north-central Idaho and much of
western Montana by sunrise, and southwest Montana by later this
morning. While temperatures tonight suggest precipitation will
start out as snow, cross sections show moisture to be concentrated
lower in the atmosphere, in a layer that is warmer than the
temperatures conducive to snow formation. The result will be a
good chance for freezing rain. Areas of concern for freezing rain
this morning will be Highway 12 from about Lowell, ID east to the
Lolo Pass summit, the Camas Prairie, Lookout Pass, Lost Trail
Pass, and Highway 93 through the Bitterroot Valley. As surface
temperatures warm throughout the day, precipitation will
transition to rain. The exception will be northwest Montana, where
snow levels will stay low enough to produce snow into Friday
morning. Moisture could remain shallow enough to produce freezing
rain again on Friday morning where surface temperatures are able
to drop below freezing on Friday night. The Mission Valley,
Flathead Valley, Highway 2 corridor, and possibly the Bitterroot
Valley will be the most likely locations for a light glaze.

Another shot of moisture will arrive Friday under mostly westerly
flow aloft. By this time, temperatures will be warm enough for
the prevailing precipitation type to be rain, even at higher
elevations. Saturday will bring a short break in widespread
precipitation. Daytime high temperatures will begin to creep up
through the weekend, reaching the upper 50s to low 60s in some
valleys by Monday. That’s not to say that we dry out. Sunday
will bring another round of rainy weather.

&&

.AVIATION...Water vapor and IR satellite imagery are showing
cooling cloud tops moving in from the west this morning. Snow
will arrive at KMSO by about 11/1600Z. Expect ceiling and
visibility at KMSO to remain lowered until about 11/1800Z due to
mist and snow. Some showers will also be possible at KGPI. This
round of precipitation will cause terrain to be obscured across
the Clearwater and Bitterroot ranges of central Idaho and western
Montana for much of the day today. After a short break this
afternoon from about 11/2200Z to about 12/0400Z, precipitation
will resume tonight in the form of a rain- snow mix and a chance
for freezing rain at both KMSO and KGPI.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&