Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 302132

Area Forecast Discussion
National Weather Service Missoula MT
232 PM MST MON NOV 30 2015

.DISCUSSION...Low stratus, patchy fog, and occasional flurries
will persist across the valleys of northwest Montana through at
least tomorrow, and probably into Wednesday. The Missoula/Seeley
Lake valleys, and the Orofino/Grangeville area of Idaho, will
have stratus/fog redevelop during the overnight hours and early
morning hours. The clouds are expected to decrease throughout the
day tomorrow. Temperatures will be very similar to the past
several days.

A weak disturbance is still anticipated to make its way into
portions of the Northern Rockies late Wednesday into Wednesday
night. The models are still struggling with the fine details of
this disturbance, but light precipitation should be expected
across north central Idaho into northwest Montana. The timing of
the feature, plus the amount of warming at the ridge tops, will
determine the precipitation type that ends up falling across
valley locations. The most probable scenario is widespread light
snow across north central Idaho and northwest Montana. Freezing
rain is a possibility if the precipitation moves in during the
afternoon/early evening hours. Valley inversion are not
anticipated to break up, so most valleys will remain well below

The next weather system looks to arrive on Friday, and could bring
snowfall back to our mountains and mountain passes. For those
traveling, Lookout Pass and Lolo Pass could see the most
precipitation from this system. Mountain ranges spanning across
northwest Montana and central Idaho will benefit overall from this
particular system`s snowfall, however strong upper level winds
could make for inclement backcountry travel. Depending on how
snow levels shake out, lower mountain passes (ie: near or below
5000 feet) may see a period of mixed precip before changing to

As a brief return to high pressure takes us through the remainder
of the weekend, next week could be pretty interesting. Fairly
strong westerly flow could bring about measurable snowfall amounts
to the mountains. That being said, there are still major
differences between forecast models. Given the impact to valleys
and travel as well as backcountry conditions, we`ll keep an eye on
this developing scenario.


.AVIATION...Strong cold pools will persist over the region through
tomorrow. As a result, the stratus deck over northwestern Montana
will stick around for at least another day. Aviation sites, such
as KGPI, will continue to see low ceilings of around 1000 feet.
Site KBTM will see vicinity fog, which could briefly drift over
the terminal at times this morning, greatly reducing the
visibility. KMSO will see a brief reduction of visibility tomorrow
morning around sunrise due to freezing fog, that will lift and
diminish late morning into the early afternoon. All aviation
sites that see the low stratus deck will also have periods of
occasional light snow flurries/showers.


.HYDROLOGY...Due to persistent frigid temperatures, ice has begun
to form along area rivers and creeks from Idaho and across western
Montana. Observations have been reported of river ice beginning
to back up in localized areas, though no flooding is being
reported. With continued cold temperatures expected through the
middle of this week, ice may continue to grow even further and may
contribute to very minor localized flooding.


.AIR STAGNATION...Continued stable conditions with little
atmospheric mixing has caused persistent valley inversions across
the region. This has contributed to a degradation of air quality
across portions of west central Montana. Air quality may be slow
to improve given that stable conditions are expected through at
least the middle of this week.



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