Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 021121
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
421 AM MST Fri Dec 2 2016

...Strong Winter storm system with multiple impacts likely Sunday
through Tuesday...

.DISCUSSION...Expect scattered snow showers to gradually diminish
through the morning hours across west central and southwest
Montana. These showers will bring little impacts or snow
accumulations for travelers this morning so the advisories in
southwest Montana have been cancelled.

There will be a brief halt to showers as the atmosphere stabilizes
under a transitory high pressure ridge. Early this evening the
next weather disturbance will nose its way into far northwest
Montana and spread southeastward through southwest Montana around
midnight and persist through Saturday afternoon. Mountain
locations will receive several inches of snow but amounts in the
valleys may be relatively light (around an inch) as daytime temps
approach 40 degrees. If temperatures don`t realize their maximum
potential then additional snow amounts are possible in the
valleys.

A much advertised powerful cold front will enter the Northern
Rockies early Sunday afternoon and impact the region through
Monday evening. Several impacts are expected

1. SUBSTANTIAL MOUNTAIN SNOWFALL amounts creating hazardous
driving conditions at times. Mountain passes, specifically Lolo,
Lookout, Marias and McDonald could receive 1-2 feet over 36 hours.
Up to a foot is possible over Lost Trail Pass with lighter
amounts over Homestake Pass.

2. Windy conditions are likely as the front moves through the
region Sunday afternoon and evening which could bring BLOWING AND
DRIFTING SNOW.


3.  IMPACTS FOR THE VALLEYS FOR THIS STORM... The main winter
impacts will start sometime late Sunday morning for northwest
Montana, as a powerful cold front enters the region. Moderate to
heavy snowfall (possibly 3-7 inches over 36 hours), with gusty
winds creating BLOWING SNOW, will be possible along the front.
This could create hazardous to dangerous driving conditions at all
elevations. The same conditions can be expected over the rest of
western Montana and north- central Idaho later in the day on
Sunday as the front slides to the southeast. A cold air mass will
settle in behind the cold front overnight Sunday into Monday
morning with continued snow showers under a northwesterly flow.
The valleys are expected to be shadowed out for a portion of this
storm system, but could still receive several inches of snow (2-4
inches over 36 hours) with the front and the light flow behind it.
The rest of the valleys of western Montana and north- central
Idaho will see lesser amounts.

MONDAY evening into TUESDAY, a pretty good shot of arctic air
from Alberta, Canada will move over the Continental divide into
western Montana. Any roads that may still be wet from the weekend,
could see a flash freeze as the air mass pushes through. Many
valleys will see high temperatures Tuesday in the teens across the
region, with potential sub zero lows Tuesday. In addition expect
strong northerly to northeast winds gusting to 30 mph at times in
Badrock Canyon into Kalispell as well as Hellgate Canyon through
the Missoula Airport. This could create our first impacts of this
winter from WIND CHILLS 10-15 BELOW ZERO Monday night into Tuesday
morning.

Temperatures will remain pretty cold Wednesday through Thursday
morning with single digit to sub zero temperatures likely in the
valleys of western Montana. Depending on the amount of snowfall
some favored valley areas such as the Seeley/Swan, Condon and into
Polebridge may have temperatures 5 to 15 degrees below zero.

The next weather disturbance looks to impact the Northern Rockies
around Thursday or Friday of next week. There is a lot of
uncertainty for timing and strength of this system due to model
inconsistency.

&&

.AVIATION...Snow showers have tapered off across the region, but
low clouds and mountain obscurations continue in most areas.
Northwest Montana was the first to clear out overnight and the
recent moisture, stable boundary layer, and building ridge are
causing stratus and fog to form. KGPI has fog this morning, and
there is little reason to expect anything better than low stratus
this afternoon with the building ridge. Other terminals will see
improving conditions with low and mid-clouds overnight preventing
fog, but mountain obscurations will remain throughout the day due
to the moist boundary layer.


&&

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

$$


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