Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 212205
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
305 PM MST Tue Feb 21 2017

.DISCUSSION...

A mix of low elevation rain and high elevation snow showers will
continue to exist over much of the Northern Rockies at times
through Wednesday evening. Mountain passes will also continue to
experience intermittent snow covered roadways. Temperatures will
once again cool to near freezing in area valleys tonight, creating
slick patches on area roadways. The lower elevations of the I-90
corridor west of Missoula will likely be impacted the most from a
mix of snow-cover, black ice, and deep slush at times.

Relatively cold air will begin to take hold on the Northern
Rockies on Wednesday night and continue to be present through at
least the weekend. Beneath a trough of cold air of air aloft, snow
showers will develop periodically throughout this time. There are
no other large scale features to promote the snow showers;
however, the daytime heating contribution (convective) will be
significant. Bouts of hazardous winter driving conditions, most
concentrated during the overnight and morning hours, will be
possible.

Models are having a difficult time characterizing the airmass
over the Inland Pacific Northwest after the weekend, with some
runs of the GFS suggesting an arctic to bring very cold air well
west of the Continental Divide. Any way you slice it, temperatures
will continue to be noticeably below the seasonal average.
Sometime early next week, we could see a return to "shovel-able"
snow in the valleys. Unlike early January cold, late February
arctic airmasses tend to be shorter duration. In summary, winter
just doesn`t seem to want to quit!

&&

.AVIATION...Occasional snow showers will continue for KGPI this
afternoon and evening, with little to no accumulation is expected
until after 22/0400z, as ground and near surface temperatures
remain above freezing. Other TAF sites will see vicinity showers,
but models indicate the coverage of scattered showers to slowly
decrease throughout the night. KBTM and KSMN remain windy until
the the early morning hours, with gusts in the 20 to 30 kt range
through 22/0800z, after which time the pressure gradient aloft
weakens, and gusts should diminish. KMSO and KGPI could see
morning fog or low stratus with the abundant precipitation of
late, but confidence is low at this point, given thick clouds in
the forecast. Fog that does form will likely be patchy in nature.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 11 AM MST Wednesday
     Bitterroot/Sapphire Mountains...Lower Clark Fork Region.

ID...None.
&&

$$



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