Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 172152
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
252 PM MST Tue Jan 17 2017

...Periods of Freezing Rain for Portions of the Northern
Rockies...

.DISCUSSION...A very weak disturbance will continue to move
through northwest Montana potentially causing some light snow and
potentially some light freezing drizzle. The cold pools continue
to plague several of the valleys across the Northern Rockies, for
example the Bitterroot valley temperatures are in the teens while
a couple thousand feet up the mountains temperatures are warming
well into the 30s this afternoon. A significant plume of moisture
will continue to move towards the Northern Rockies. This plume
will have a north south trajectory so the heaviest precipitation
appears to be over Idaho and steadily diminishing through western
Montana. Winter storm warnings have been issued for Clearwater
county up into northwest Montana for later tonight through
Wednesday. This area will have a combination of snow, then
freezing rain and finally all rain by Wednesday afternoon. Even
though the precipitation will be rain, sub surface temperatures
remain well below freezing so after sunset tomorrow roadways could
refreeze. Another concern is the weight loading of snow due to the
rain which will put extra strain on structures. Winter weather
advisories have been issued for west central and the remainder of
northwest Montana for this event. Precipitation will be lighter
but the potential of freezing rain is a high probability. Most
valley locations should finally mix out the cold pools with the
exception of Missoula and Salmon valleys.

Thursday precipitation potential continues ahead of an approaching
colder air mass and front. Snow levels of 4000 feet in northwest
Montana to 5000 feet in west central and southwest Montana and
central Idaho are expected. As a result valley locations can
expect precip in the form of rain Thursday with relatively light
amounts less than .05".

Cooler air makes its way into the region Thursday evening.
Fortunately it won`t be the kind of extreme cold we have received
over the last few weeks. Temperatures will be at or slightly below
normal with generally highs in the upper 20s to lower 30s and
lows in the teens through Monday next week. Expect scattered snow
showers Friday and Saturday with some light accumulations in the
mountains.

SUNDAY a weather system makes its way into the region from the
south. Unlike our system today temperatures should be low enough
for precipitation to remain all snow. Right on its heels models
are showing a moderate to strong cold front to impact the region
with some windy conditions, colder temperatures and continued
mountain snow and perhaps a return of some snow bands through
Tuesday. Confidence is pretty good for a weather system and cold
front early next week HOWEVER there isn`t a lot of confidence on
details such as snow banding, snow amounts or wind potential.

The middle to end of next week models are in fair agreement
showing a return of a pretty strong ridge over the west. If it
came to fruition we could see a return of inversions and colder
valleys.








&&

.AVIATION...Low stratus and some fog continue in the Flathead and
Mission valleys producing some limited visibility down to 6 miles
and haze and some mountain obscurations. Some mid to higher level
clouds are entering the northern Rockies. A weather system with
warmer air aloft will enter the region this evening. It is
expected to impact KGPI after 18/0200z and and KMSO after
18/0900z with a mixture of snow, rain and/or freezing rain. There
is some uncertainty of how much precipitation is expected. The
main focus of heavier precipitation is along the Idaho/Montana
border. Current thoughts are up to .10" of liquid precip at KGPI
and .05" at KMSO but 50-100 miles could make a big difference.
Temperatures will warm up enough Wednesday afternoon for terminals
to receive a mix of light snow and rain. KBTM and KSMN will
remain mostly dry overnight.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT... Winter Weather Advisory from 11 PM this evening to 11 PM
      MST Wednesday Missoula/Bitterroot Valleys...Potomac/Seeley Lake
      Region...West Glacier Region.

     Winter Storm Warning from 11 PM this evening to 11 PM MST
     Wednesday Lower Clark Fork Region.

     Winter Weather Advisory from 11 PM this evening to 11 PM MST
     Wednesday Flathead/Mission Valleys.

     Winter Storm Warning until 11 PM MST Wednesday Kootenai/Cabinet
     Region.

ID...Winter Storm Warning from 10 PM this evening to 10 PM PST
     Wednesday Northern Clearwater Mountains...
     Orofino/Grangeville Region.

     Winter Weather Advisory from 10 PM this evening to 10 PM PST
     Wednesday Southern Clearwater Mountains.

&&

$$



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