Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 162053

Area Forecast Discussion
National Weather Service Missoula MT
253 PM MDT Mon Oct 16 2017

...Windy conditions on Tuesday Afternoon...

.DISCUSSION...A amplitude ridge will continue to cause fair
conditions across the Northern Rockies this afternoon and overnight.
Temperatures today should be near to slightly above normal for
this time of year.

Upper levels winds will be steadily strengthen throughout the
night and into Tuesday, as a mid level jet develops over the
Northern Rockies. A cold front will be swinging through the region
Tuesday afternoon and evening allowing some of these strong winds
to mix down to the surface producing wind gusts of 30 to 45 mph
across western Montana with the higher terrain receiving gusts in
excess of 50 mph. Idaho will experience gusty winds in the higher
terrain, but the location of the mid level jet is not conducive to
strong winds mixing down to the surface. These strong winds will
cause some tree damage, difficult driving conditions and large
waves on area lakes. The latest runs of the models have decreased
the amount of moisture associated with this cold front. The higher
terrain across northwest Montana appears to receive the most
significant amount, while the valleys experience downsloping

A second disturbance is expected to move through the Northern
Rockies on Wednesday. The winds aloft do not appear to be as
strong as Tuesday, so impacts from winds should be minimal. Once
again the moisture associated with this feature has decreased with
the best chance of precipitation being across northwest Montana.
Temperatures on Wednesday appear to be slightly below normal.

A trough of low pressure digs along the Pacific coast on Thursday
causing the upper level flow pattern to become southwesterly. This
flow will usher in a very warm air mass. Temperatures for Thursday
should be around 10 degrees above normal, as most valley locations
will be in the 60s and 70s.

A strong cold front swings through the Northern Rockies on Friday.
Ahead of this front the Riggins and Camas Prairie area could
experience gusty southerly winds. The front will create widespread
precipitation with gusty westerly winds behind the front. Snow
levels will start off fairly high, then drop dramatically behind
the front. The timing of precipitation with the lowering of the
snow levels will be the determining factor on when and where snow
impacts will occur across the Northern Rockies.

The models are still hinting at a cooler period through the
weekend. A very moist westerly flow appears to develop over the
region Saturday night into Sunday which could cause significant
precipitation to areas along the Montana/Idaho border.


.AVIATION...Fair flying conditions are being observed through much
of Idaho and western Montana today. The exception is along the
divide where gusty winds continue. West winds are also increasing
at mountain- top level and are still expected to reach 40-60 kts
during Tuesday. Model guidance are showing a southerly surface
pressure gradient over the region tonight so north-south oriented
valleys may see some wind overnight tonight. Flathead Lake and the
Mission Valley is most likely to see wind overnight. A cold front
will approach from the west on Tuesday and winds are forecast to
increase ahead of the front and become very gusty with its passage
during Tuesday afternoon and evening. Wind advisories have been
issued for much of western Montana with 30-40 kts winds to be
common on Tuesday with gusts 40-50 kts possible.


MT...Wind Advisory from 3 PM Tuesday to midnight MDT Tuesday night
     Butte/Blackfoot Region...Lower Clark Fork Region...
     Missoula/Bitterroot Valleys...Potomac/Seeley Lake Region.

     Wind Advisory from noon to 9 PM MDT Tuesday Flathead/Mission
     Valleys...Kootenai/Cabinet Region...West Glacier Region.


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