Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 222156
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
256 PM MST Wed Nov 22 2017

...Strong Cold Front Thanksgiving Evening...

.DISCUSSION...For rest of this afternoon and evening, rain showers
will continue to decrease and a brief break in precipitation is
expected across most valleys. This break will be short-lived as
the next weather system begin to move in late tonight.

Thanksgiving Day will be warm, windy and wet across the Northern
Rockies. Areas that see the greatest rain will likely not see as
much wind compared to areas that are drier. The greatest
precipitation will be across northwest Montana and Clearwater
county of Idaho where steady periods of rain will be increasing
throughout the day. Rainfall rates could become heavy at times
especially over the higher terrain where rain amounts of 1 to 1.5
inches is possible over 24 hours. Although the rain could be heavy
at times, flooding is not expected due to the high elevation snow
helping to absorb the moisture. Winds will become breezy across
central Idaho and northwest Montana but confidence is low for
damaging winds. The main area of concern for possibly some
damaging winds will be the Flathead and Mission valleys. As of
now, it is looking like there could be pockets of damaging wind
gusts during the afternoon and evening.

For west-central Montana and southwest Montana, Thanksgiving
morning will be fairly dry with just a few rain showers possible.
The main concern for this area will be the gusty and potentially
damaging winds. Winds will begin to pick up mid day and will
become gusty by the afternoon. Latest model runs have trended
slightly slower with the frontal passage and now the strongest
winds will likely be slightly later (after sunset). Wind gusts of
40-45 mph is looking likely with scattered areas of 50 to 60 mph
winds Thursday evening with the frontal passage. Also as the
front moves through, rain will change to moderate to heavy snow at
Lolo and Lost Trail passes Thursday night. The snow will not last
long, but a short period (2-4 hours) of heavy snow will be
possible.

A weak ridge of high pressure will persist Saturday into mid day Sunday,
but clouds and isolated very light precipitation should continue
to shift across the northern Rockies. Temperatures will be 5 to 10
degrees above normal.

The next significant weather system is due Sunday night into
Monday. This weather system should bring a cooler air mass to the
region with falling snow levels. Although the showers may change
to snow by Monday morning in many areas...the main impact of the
snow should be to the mountain passes and road stretches on either
side of mountain passes from the Camas Prairie eastward across
western Montana. In addition, by the time the rain changes to snow
or a mix of rain and snow early Monday in the valleys, the
precipitation should become more scattered and light.

&&

.AVIATION...Precipitation will taper off and mixing will increase
at low elevations, so improvements with higher ceilings and
visibility are expected into the evening and night from
Grangeville eastward across southwest Montana and Lemhi County.
Farther north, enough moisture will continue to shift across
northwest Montana to support scattered light showers and local
terrain obscurations into Thursday.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...High Wind Watch from Thursday afternoon through late Thursday
     night Bitterroot/Sapphire Mountains...Butte/Blackfoot
     Region...Flathead/Mission Valleys...Missoula/Bitterroot
     Valleys...Potomac/Seeley Lake Region...West Glacier Region.

ID...None.
&&

$$


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