Weather Service Report


793 
FXUS65 KMSO 312132
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
232 PM MST SAT JAN 31 2015

...Wintry weather and slick roads to return beginning Sunday...

.DISCUSSION...
Most of the persistent fog from this morning has lifted this
afternoon, with a few lingering spots in valleys of central Idaho
and the Flathead Valley. A weak arctic is currently dragging along
the Continental Divide which has dropped some light snow and
created some slick roadways at times for the passes along the
divide. The drier arctic air has also funneled through Badrock
Canyon and has increased winds for the Kalispell and Flathead
Valley region this afternoon. A part of the arctic has also
funneled westward along Highway 200, causing locally breezy
conditions through the canyons. The light snow showers and winds
are expected to diminish this evening.

The first wave of more significant wet weather is expected
beginning mid-day tomorrow and continuing into early Monday.
Mountain passes will be impacted by several inches of accumulating
snow during this period, which will make for slick travel
conditions. Most valleys will begin as snow or a rain/snow mix,
but snow levels will warm from the south to the north which will
cause some of the lower elevation valleys of Central Idaho and
southwest Montana to transition into mostly rain by later Sunday.
However, wet valley roadways may be in danger of refreezing
overnight Sunday night, making them potentially hazardous.

Another, more potent wave is forecast to arrive Monday into Tuesday
which will impact the mountain passes with snow, and promote a
rain or a rain/snow mix for the valleys. Another swipe of arctic
air along the divide may push westward along Marias Pass on US-2
Tuesday which could cause any rain/snow mixture to freeze, causing
slick roads.

Next weekend another warm and wet atmospheric river type system
will impact the Northern Rockies. This will be a particularly warm
and wet system, especially for early February. Snow levels may
rise above 7,000 feet briefly with over an inch of precipitation
in about 24 hours. Portions of central Idaho will likely see
closer to 1.5 inches of precipitation. Due to the rising snow
levels and potential for heavy rain, concerned about increasing
risk from rock/mud slides in the long term as well as avalanche
conditions. While there is still considerable uncertainty due to
the long lead time of this event, there is good model agreement
among the ensembles so confidence is above average.


&&

.AVIATION...Ceilings over KGPI should continue to improve through
the afternoon but as the sun sets and winds weaken, ceilings will
begin to lower again tonight. Fog could once again be an issue at
KGPI Sunday morning but it may be more of a low stratus deck. KMSN
will continue to see the stratus deck through Sunday morning. A
weather system will move in on Sunday and will bring snow to
KGPI. Other terminals will see a wintry mix of rain/snow on Sunday
afternoon and evening.


&&

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

$$


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Western Regional Climate Center, wrcc@dri.edu