397 
FXUS65 KMSO 271132
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
432 AM MST Wed Feb 27 2019

.DISCUSSION...Light snow is spreading across Central Idaho and 
Western Montana currently, this is associated with Pacific moisture 
being pushed up by a upper level circulation off the Washington 
and Oregon coast. With the southerly winds in Idaho, expect the 
Camas Prairie and Salmon to warm into mid 40s with even the 
Southern Bitterroot approaching the upper 30s. The rest of us 
will see mid 20s as easterly winds continues to advect cooler air
across the Continental Divide. Precipitation will generally be 
light, with broad inch or 2 coverage. Higher terrain and mountain 
passes of Central Montana may see 2 to 4”. That said the Camas 
Prairie and Salmon will likely see a wintry mix of precipitation.

Light snow will continue over night Wednesday into Thursday, a 
second push of moisture will affect Western Montana in the 
afternoon through evening commute. The possibility of periods of 
moderate snow should not be ruled out and roads will become slick.
Highest accumulation will be Lolo Pass and Bitterroot Mountains 
where a total of 6 to 12” is possible. For the valleys, Missoula
and I-90 east could locally see up to 4”, elsewhere a broad 1 
to 3” is forecast. Once again, rain could mix in for the Camas 
Prairie and Lemhi County. 

Relatively moist northwest flow will be present over the Northern
Rockies Friday through Sunday, with an embedded cold wave re- 
introducing more arctic air to western Montana. The Flathead
Valley, Glacier Park region, and Seeley-Swan Valley appear to be 
most impacted by this next arctic intrusion, with the combination 
of light snow and gusty east/northeast winds creating blowing 
snow, low visibility, and hazardous snow covered roadways. Gusty
east/northeast winds will develop within the typical terrain
features, such as Hellgate Canyon (Missoula Valley) and Badrock
Canyon (Flathead Valley). The winds will undoubtedly produce some
very cold wind chill. In addition to frostbite risk for exposed
skin, newborn livestock will continue to be at-risk with daytime
temperatures more than 20 degrees below the seasonal average
(particularly near the Continental Divide). Meanwhile, conditions
will be a little showery over north central Idaho, with
temperatures only slightly cooler than the seasonal average.

Models depict a relatively dry pattern over the Northern Rockies
Monday through Tuesday, as upper flow shifts from northerly to
southwesterly. Daytime temperatures will warm a bit during this
time, however still well below the seasonal for most of the
region.

A surge of moisture embedded within southwest flow aloft is
anticipated to arrive over the Northern Rockies Wednesday and
interact with a relatively cold Pacific storm system through
Thursday. The net result of this interaction will be yet another
round of snow, particularly across northwest Montana (however,
confidence in specific location of best snow potential is low at
this point). The pattern itself seems plausible, considering that
it resembles the recent exceptional cold, snowy pattern over the
region.

&&

.AVIATION...Light precipitation associated with warm air overrunning
will spread across the forecast area this morning. Expect higher 
terrain being obscured and KMSO, KBTM, and KSMN to fluctuate back
and forth from IFR to MVFR conditions due to low ceilings and low
visibility due to moderate showers. KMSO may experience periods 
of blowing snow, further degrading visibilities to near zero at 
times, due to east winds gusting to 20 knots before slackening 
off in the afternoon. Conditions will only slightly improve 
overnight Wednesday before another surge of moisture spreads 
across the area Thursday. 

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$