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000
FXUS65 KMSO 161129
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
429 AM MST Sun Dec 16 2018

.DISCUSSION...

High pressure over central Montana this morning will drift
eastward during the next 24 hours, allowing an upstream
subtropical surge of moisture to move over north central Idaho
and along the Montana-Idaho border. Snow levels of 4500 to 5500
feet will be common, with several inches of dense snow over area
mountain passes and higher elevations. Most of western Montana
will miss out on precipitation over the next day, however
temperatures will slowly warm (even for area valleys).

A more significant subtropical moisture surge will move over the
Northern Rockies Tuesday through Wednesday, with over a foot of
new snow accumulation for high terrain along Montana-Idaho border.
Other high elevation areas (with the exception of southwest
Montana and Lemhi County Idaho) will receive 6 to 12 inches
accumulation by late Wednesday. Considering snow levels above 4000
feet, most valleys will see only rain or a wintry mix. The
pressure gradient will be intense during this time as well, with
winds gusting to 40 mph at times for Grangeville to top of
Whitebird Grade and Interstate 90 corridor Drummond to Homestake
Pass. The combination of snow and wind will create some hazardous
travel conditions at times over area mountain passes through
Wednesday as well.

High pressure is anticipated to surge west of the Northern Rockies
Thursday, with temperatures warming significantly across the
region. Models have begun to suggest that a quick clipper system
will move over the region by Friday and possibly bring snow levels
down to valley elevations for a brief time. It will be a wild ride
for temperatures and precipitation type if this forecast solution
stands. Mountains will once again be favored to receive up to a
foot of snow, while valleys may get a brief blast of snow
Thursday evening through Friday midday. It is probable that much
of any low elevation snow will quickly turn to ice and became a
significant travel impact for a short while.

Longer term models continue to suggest additional subtropical
moisture surges over the next week to ten days, with only minor
chances that any snowfall sticks in low and middle elevation
valleys.

&&

.AVIATION...Middle to upper level clouds will continue to spread
across the Northern Rockies today as a disturbance moves onto
Pacific Northwest coast. VFR conditions will prevail across area
TAF sites today with generally light winds expected. Attention
then turns to Sunday evening and Monday morning as shower activity
spreads into the area associated with a weak upper level
disturbance.

&&

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

$$