Winter Storm Watch 4, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
404 AM MST Tue Feb 4 2020

.DISCUSSION...
A winter storm is still on track to impact the Northern Rockies
starting later tonight. In the meantime, a chance of light
precipitation remains in southwest Montana and central Idaho, as
moisture leftover from our last weather system lingers today.
Current satellite imagery shows Pacific moisture streaming into
British Columbia. This plume will reach the Northern Rockies
tonight and begin to impact travel by early Wednesday morning, so
be prepared for potentially slippery roads on the morning commute.
Cold temperatures will keep precipitation as snow throughout the
day on Wednesday. By Thursday morning, a warm front will make its
way into the region, raising snow levels gradually to above 4000
feet. During this transition to valley rain, freezing rain will
also be a strong possibility as warmer air overruns the cold air
in the valleys. Thursday morning will also see an increase in
winds as an upper level jet streak positions itself over northwest
Montana. These winds will result in blowing snow, especially in
the higher terrain. Precipitation continues through the end of the
week, with a break in the Pacific moisture plume by Friday
afternoon.

Model agreement is improving on another round of unsettled weather
arriving Saturday as a trough of low pressure moves into the
Northern Rockies from the northwest. This system will bring more
moisture and cold air for the rest of the weekend.

&&

.AVIATION...

A persistent area of elevated light snow will exist across north
central Idaho and western Montana air space through 04/1800Z.
Ceilings at KMSO, KGPI, and surrounding area may fluctuate at
times, with occasional high terrain obscurations also present.
Snow may be observed at times, however no visibility reductions
are anticipated. After 05/0000Z, low clouds will quickly move over
Northern Rockies air space from the northwest. Terrain
obscurations will become common thereafter, as a significant plume
of moisture moves into the region. Wind over high terrain will
gust as high as 40 knots, while wind at terminals will likely be
much weaker. Snow may significantly impact ceiling and visibility
at times for KGPI, KMSO, and KSMN beginning at 05/0600Z and
continuing through at least Thursday.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Watch from this evening through Wednesday evening
     Bitterroot/Sapphire Mountains.

     Winter Storm Watch from late Wednesday night through late
     Thursday night Potomac/Seeley Lake Region.

     Winter Storm Watch from late Wednesday night through late
     Thursday night Butte/Blackfoot Region.

ID...Winter Storm Watch from this evening through Wednesday afternoon
     Northern Clearwater Mountains.

     Winter Storm Watch from this evening through Wednesday afternoon
     Southern Clearwater Mountains.

     Winter Storm Watch from this evening through Wednesday afternoon
     Lower Hells Canyon/Salmon River Region.

     Winter Storm Watch from this evening through Wednesday afternoon
     Orofino/Grangeville Region.

&&