Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 251106
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
405 AM MST TUE NOV 25 2014

...Difficult travel over mountain passes through Wednesday...

...Much colder and snowy by Saturday...

.DISCUSSION...The first phase in a rather complicated weather
system is well underway this morning. Fairly widespread
precipitation overnight has brought light snow accumulations to
many valley locations in north central Idaho and western Montana,
especially across northwest Montana. Moderate to even heavy
snowfall has fallen across the mountain passes. Travel this
morning may be slow going.

The bulk of precipitation will briefly shift southward today,
giving northwest Montana a short lived break, or at least
significant decrease in intensity, from snowfall. However,
moderate to heavy precipitation is anticipated to continue and
even intensify across north- central Idaho and southwest/west-
central Montana through this morning. Meanwhile, snow levels will
be on the increase which makes precipitation type, particularly in
the valley locations, difficult to anticipate. Moderate to heavy
snow will continue generally for elevations above 4000 feet,
including passes such as Lolo, Lookout, Lost Trail, Homestake and
MacDonald Pass. In the valleys, precipitation is expected to
transition from light snow, to a rain/snow mix, to rain by
afternoon. Overall, sloppy conditions should be expected with very
changeable road conditions over short distances.

This evening and tonight, the band of moderate to heavy
precipitation is expected to shift northward towards northwest
Montana. At the same time, forecast models show a lowering of snow
levels, so another period of accumulating snow is expected for
both mountains and valleys across northwest Montana, generally
along and north of the Interstate 90 corridor, including the
Flathead, Mission and Missoula valleys.

By mid-day Wednesday, precipitation will mainly be occurring
across northwest Montana. Snow levels will continue to rise above
most all valley locations and at this point, travel impacts due to
snow should mainly be isolated to mountain passes.

Thanksgiving looks to be a showery day, especially across
northwest Montana. Temperatures will be relatively warm for this
time of year with many valley locations expected to reach the mid
40s. Travel impacts should be fairly low due to continued high
snow levels.

A significant change is expected to begin Friday night in to
Saturday. Forecast models continue to bring an arctic cold front
south out of Canada. This cold front is expected to interact with
a moist flow aloft and could produce some significant travel
impacts due to snow. Initially snow will mainly impact mountain
passes Friday evening, but snow levels will lower to valley
locations Saturday, which could create more widespread travel
impacts. In addition to snow, much colder temperatures are
expected, with low temperatures possibly reaching back down below
zero by Sunday, especially in western Montana. Thankfully,
forecast models continue to show this cold period being relatively
short lived.


&&

.AVIATION...Snow and rain are still in the forecast for all TAF
sites today. Model profiles suggest that KGPI should see a brief
lull in snowfall from late this morning until this evening, when
snow will return in force. KMSO and KBTM are forecast to hold onto
precipitation chances all day, with exact precipitation type being
a tricky call, as we will flirt with the freezing mark. That being
said, better chances for snow occur late this afternoon into the
overnight when temperatures cool. Surface winds will decrease with
time as winds aloft relax, but terrain obscurations and low
ceilings will continue with today`s wave of moisture.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY until 11 PM MST this evening
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region.

     WINTER WEATHER ADVISORY from 3 PM this afternoon to 11 PM MST
     this evening Missoula/Bitterroot Valleys.

     WINTER WEATHER ADVISORY until 5 AM MST Wednesday
     Flathead/Mission Valleys...Kootenai/Cabinet Region...Lower
     Clark Fork Region.

     WINTER STORM WARNING until 11 PM MST Wednesday West Glacier
     Region.

     WINTER STORM WARNING until 11 AM MST Wednesday Potomac/Seeley
     Lake Region.

ID...WINTER WEATHER ADVISORY until 11 PM MST this evening for Lost
     Trail Pass in the Eastern Lemhi County.

     WINTER WEATHER ADVISORY until 10 PM PST this evening ABOVE 4000
     FEET for the Northern Clearwater Mountains...Southern
     Clearwater Mountains.

     WIND ADVISORY until 7 AM PST this morning for the Camas
     Prairie...Grangeville and Highway 95 in the Lower Hells
     Canyon/Salmon River Region...Orofino/Grangeville Region.

     WINTER WEATHER ADVISORY until 11 PM MST this evening ABOVE 5000
     FEET for the Western Lemhi County.

     WINTER WEATHER ADVISORY until 7 AM PST this morning ABOVE 3500
     FEET for the Lower Hells Canyon/Salmon River Region...
     Orofino/Grangeville Region.

&&

$$




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