Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 262125

Area Forecast Discussion
National Weather Service Missoula MT
225 PM MST THU NOV 26 2015


Temperatures will stay pretty cold through at least early next
week. Average high temperatures in the valleys this time of year
are in the mid 30s. The majority of the region will be at least
10 degrees cooler than normal for this time of year. The Butte
region will be the coldest. Temperatures of near 20 below zero
are possible tonight with overnight lows below zero through
Sunday morning.

The cold air across the area will continue to be trapped in the
lower valleys, aka cold pools. There is no major synoptic pattern
that would suggest these cold pools will scour or mix out through
early to mid next week. In addition to cold pools, valley fog is
likely to form creating impacts of low visibility and black ice in
the morning hours. The Mission Valley may even form a persistent
low stratus layer by this weekend that lasts the entire day and

Some valleys impacted most by cold pools or valley fog include:

The Missoula and Bitterroot valleys
Lower valleys of Northwest Montana
The Seeley/Swan Valleys
Lower valleys of Central Idaho  (Elk City)
Lemhi county.

As far as precipitation chances:

Dry conditions will prevail through the middle of next week as high
pressure remains across the region. The only exceptions to the
dry weather will be an outside chance of lake-effect snow forming
on the south end of Flathead Lake tonight into Friday morning.
Sudden changes in road conditions will be possible, if lake-effect
snow does develop. Also, a weather system will pass well south of
the area late in the weekend which may lead to a few light snow
showers across Lemhi County into southwest Montana.

By late next week, forecast models agree a gradual breakdown of
the high pressure ridge under a strengthening southwest flow. This
may open up the door to a variety of wintry weather, while also
mixing out some of the stagnant valley cold pools.


.AVIATION...Little impact to aviation is expected for this
afternoon with mainly clear skies. Tonight we do expect patchy
freezing fog or stratus clouds to develop at KGPI, KMSO and KBTM.
Lower ceilings and reduced visibilities are possible for Friday
morning especially at KGPI, where they have the greatest chance
of freezing fog or stratus development.


.AIR STAGNATION...Models are coming into more agreement through
mid next week for generally stable conditions and inversions
creating stagnant air which could create air quality issues.



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