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206
FXUS65 KMSO 232155
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
253 PM MST SUN NOV 23 2014

...Light snow accumulations through much of north central Idaho
and western Montana through Monday morning...

...POTENTIAL HEAVY SNOW EVENT IN THE MOUNTAINS AND THROUGH
NORTHWEST MONTANA MONDAY NIGHT INTO WEDNESDAY...

.DISCUSSION...

Snow is beginning to expand throughout northern Idaho and
northwest Montana this afternoon as a shortwave trough approaches
the region. There is a high chance for most people to have light
snow accumulations by Monday morning as the trough continues to
trek through north central Idaho and western Montana. Widespread
slick roadways are possible overnight so winter weather advisories
are in effect.

POTENTIAL HEAVY SNOW:

A brief break in snow is possible Monday afternoon before the
next, potentially heavy snow producing, weather system arrives.
The next weather system is going to have a lot of moisture and
there is moderate to high confidence of the storm to develop but
snow levels are in question with much lower confidence. This
weather system will be warm front dominated so snow levels will
rise. The questions are, how quickly this transition will occur,
and will valley locations be able to see snow accumulations before
the rise? As of now there is fair agreement that precipitation
will start as snow Monday night and transition to rain at lower
elevations through Tuesday. High snow levels, above many mountain
passes, are possible late Tuesday into Wednesday. The valleys of
northwest Montana are of particular focus since snow levels will
be slower to rise leaving a higher chance for snow accumulations.
At this time only moderate snow accumulations are being forecast
in the northwest Montana valleys, but heavy snow is forecast for
high elevations. Travel impacts are becoming likely due to snow
Tuesday into Wednesday.

Precipitation may linger in northwest Montana into Thursday but
timing issues leave this uncertain.

There are indications that the moist flow will return for the
weekend as colder air moves in from the east. Snow will again be
possible through the weekend but confidence is low due to high
changeability in the extended model guidance.


&&

.AVIATION...Widespread snow will develop this evening with
localized snow bands forecast for the overnight. Low ceilings and
reduced visibilities can be expected throughout north central
Idaho and western Montana including all TAF sites through much of
tonight. Widespread light accumulations are expected through
Monday morning. Snow coverage will decrease early Monday morning
with lowest chances anticipated through the afternoon. Ceilings
improvements are also expected by Monday afternoon.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY from 6 PM this evening to 8 AM MST
     Monday Butte/Blackfoot Region.

     WINTER WEATHER ADVISORY until 8 AM MST Monday
     Bitterroot/Sapphire Mountains.

     WINTER WEATHER ADVISORY until 8 AM MST Monday
     Missoula/Bitterroot Valleys.

     WINTER WEATHER ADVISORY until 8 AM MST Monday Lower Clark Fork
     Region.

     WINTER WEATHER ADVISORY until 8 AM MST Monday Flathead/Mission
     Valleys...Kootenai/Cabinet Region.

     WINTER WEATHER ADVISORY until 8 AM MST Monday Potomac/Seeley
     Lake Region...West Glacier Region.

     WINTER STORM WATCH from Monday evening through Wednesday morning
     West Glacier Region.

     WINTER STORM WATCH from Monday evening through Tuesday evening
     Potomac/Seeley Lake Region.

ID...WINTER WEATHER ADVISORY from 6 PM this evening to 8 AM MST
     Monday Eastern Lemhi County...Western Lemhi County.

     WINTER WEATHER ADVISORY until 7 AM PST Monday Southern
     Clearwater Mountains.

     WINTER WEATHER ADVISORY until 7 AM PST Monday Northern
     Clearwater Mountains.

&&

$$





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