Area Forecast Discussion
Issued by NWS Missoula, MT

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476
FXUS65 KMSO 191038
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
338 AM MST Sun Feb 19 2017

.DISCUSSION...Southwesterly flow continues to be the dominant
feature over the Northern Rockies this weekend. The first
disturbance continues to move through western Montana early this
morning with a few showers lingering behind the cold front in
north central Idaho. This feature did put down a couple of inches
of new snow in the higher terrain, but impacts to area roads
appear to be minimal. The few breaks in the clouds across north
central Idaho up into northwest Montana has allowed for the
development of patchy fog. This fog will dissipate by mid to late
morning.

The next disturbance will make its way into the region later today
and this evening causing an increase in shower activity. The
models continue to show enough instability across Idaho county
into southwest Montana to potentially produce a lightning strike.
The shower activity is anticipated to diminish during the
overnight hours.

Embedded disturbances will work with abundant moisture in
southwesterly flow to produce several rounds of precipitation
Monday and Tuesday. Snow levels are expected to start relatively
low on Monday at around 3000 feet, then quickly rise to around
5000 feet Monday afternoon into Tuesday before dropping back to
valley floors on Tuesday night. Mountain passes such as Lookout,
Marias, Lolo, and Lost Trail will likely see 5-10 inches of
snowfall leading to slick, snow packed roadways at times.

Potential valley rainfall amounts of 0.5 to 0.75 across NW
Montana and central Idaho with 0.2 to 0.4 across west
central Montana are forecast for Monday into Tuesday. Hydrologic
issues may become a problem with ponding on roadways and property,
along with debris flows possible on favored travel corridors
(such as Hwy 12 in Idaho).

Beginning Wednesday through the end of the week, a trough of low
pressure will set up over the Northern Rockies resulting in below
normal temperatures and a chance of daily snow showers as snow
levels remain at the valley floors.

Forecast models continue to show even colder air by next weekend
as arctic-type air drops into the region. This would be a dramatic
change from the recent mild temperatures with potential impacts
the area has not seen in several weeks.


&&

.AVIATION...The first disturbance will continue to exit the region
this morning with KGPI and KBTM having the best chance of being
impacted by low ceilings and reduced visibilities early this
morning. After the passage of this disturbance patchy fog will
develop across north central Idaho up into northwest Montana. A
second disturbance will make its way through the region later
today causing an increase in shower activity with the potential of
thunderstorms in Idaho county into southwest Montana this
afternoon.


&&

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

$$



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