Weather Service Report


393 
FXUS65 KMSO 141050
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
350 AM MST SUN FEB 14 2016

.DISCUSSION...The next wave of showers have pushed into the
Northern Rockies overnight with periods of snow being reported
across the higher terrain as well as in some lower elevation
locations. And while Winter Weather Advisory's continue for a good
swath of the area above 4000ft, forecast models along with recent
radar and satellite trends show the next push of moisture focused
a bit farther south than previously thought. So do not anticipate
snow amounts to be nearly as much and generally half of what was
forecast yesterday (1 to 3 inches vs. 2 to 6 inches) Regardless,
there will still be periods of travel impacts over the higher
terrain this morning, especially to those traveling over Lolo and
Lookout Pass. But lesser impacts are likely in the West Glacier
Region as well as the Butte/Blackfoot Region and these Advisory's
may end up being cancelled early.

All models continue to show a very strong upper level jet stream
slamming into the British Columbia coast tonight which will bring
a healthy feed of deep, subtropical moisture southeast into Idaho
and Montana. Forecast models have deviated little from their
depictions 1 to 2 inches total precipitation over the higher
terrain of the Mission, Swan, Bitterroot and Clearwater Mountains.
Locally up to 3 inches of liquid may be possible in the
Clearwater, Swan and Mission ranges through Monday. The snow level
during the heaviest precipitation appears to reside between 6000ft
and 6800ft, so much of the precipitation will fall as high
mountain snow with valley rain below 6000ft. This may promote
increased ponding of water in some valleys, the impacts of which
are further discussed below in the Hydrology section.

A weak high pressure ridge will try to nudge the jet stream and
storm track north into Canada on Tuesday. However a large low
pressure system approaching the west coast appears to keep a
steady flow of moisture over the region Tuesday and Wednesday with
limited potential for drying. However warm, above normal
temperatures will continue throughout the rest of this week in
this flow pattern. Precipitation should become more widespread by
late Wednesday as the approaching weather system moves inland. But
the snow level will remain high (+6500ft) and thus travel impacts
will be limited until the cold front sweeps through the region
Thursday evening. Thereafter models keep things unstable through
the weekend, but the consensus points towards a drying and warming
trend to begin after next weekend.

&&

.AVIATION...Occasional light snow may impact visibility and help
usher in temporarily lowered ceilings at all airfields today.
However conditions overall shouldn't be too bad for very long with
the most persistent snow showers impacting KMSO and KSMN. Area
terrain will be obscured at times in clouds and by transient
showers.

&&

.HYDROLOGY...Warm, above normal temperatures will keep the snow
level high and result in widespread valley/mid slope rain across
the region today through Tuesday. Increased ponding of water
could become problematic in some valleys where snow remains on the
ground and may further clog or hamper natural drainage. Even those
who have experienced recent melting may see standing water due to
much of the soil remaining quite saturated. 

The heavier precipitation will also bring about the possibility of
rock and/or mudslides along US-12 in Idaho and I-90 near Lookout
Pass in Montana. These issues are further highlighted in a
Hydrologic Outlook that can be viewed on our website at
www.weather.gov/missoula.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 3 PM MST this afternoon 
     Butte/Blackfoot Region.

     Winter Weather Advisory until noon MST today ABOVE 4000 FEET for 
     the Bitterroot/Sapphire Mountains.

     Winter Weather Advisory until noon MST today ABOVE 4000 FEET for 
     the Lower Clark Fork Region.

     Winter Weather Advisory until noon MST today ABOVE 4000 FEET for 
     the West Glacier Region.

ID...Winter Weather Advisory until 11 AM PST this morning ABOVE 4000 
     FEET for the Southern Clearwater Mountains.

&&

$$

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Western Regional Climate Center, wrcc@dri.edu