282 
FXUS65 KMSO 141007
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
407 AM MDT Fri Mar 14 2014

.DISCUSSION...The disturbance is anticipated to push into the
north central Idaho during the morning hours then into western
Montana during the afternoon. Snow levels will hold around the
4000 to 5000 foot mark during the bulk of the precipitation, so
valleys will have primarily rain while snow falls in the higher
elevations. Lookout, Lolo and Marias passes should experience the
biggest impact from this system as 4 to 6 inches of snow is
anticipated by Saturday morning. The best accumulation on roadways
will not occur until this evening after the sun sets. The snow
levels will fall during the overnight hours to most valley floors.
Snow accumulations will be light and limited to grassy locations.

A low amplitude ridge of high pressure will build back over the
region on Saturday into Saturday night. The models are indicating
some moisture stream over the top of the ridge into northwest
Montana. This moisture could cause lingering showers for the
Libby/Eureka area.

The ridge of high pressure is anticipated to slowly break down on
Sunday, with the next system arriving over the Northern Rockies by
Monday morning. Snow levels will initially be in the 5000 to 6000
feet range throughout Sunday night, dropping to around 4000 feet
by Monday afternoon. Much of the precipitation is likely to fall
during the day on Monday, with periods of hazardous travel
conditions over area mountain passes due to snow covered roadways
through early Tuesday. Blowing snow may also reduce visibility in
blowing snow over Marias Pass. Valley locations may also see some
snow overnight Monday, however little more than a dusting is
expected through Tuesday morning.

Extended range forecast models have begun to agree upon the next
high pressure ridge, expected to be present during the Wednesday
through Thursday time frame. As has been the case during the past
several days, the GFS pattern depiction past midweek has
vacillating wildly and been difficult to embrace. The ECMWF has
deviated slightly from previous model runs, now suggesting a
prolonged storm cycle from Thursday evening through Saturday
night. Despite the ECMWF depicting an open upper level wave
associated with this period, it is not uncommon for these systems
to deepen and intensify to a closed circulation upon reaching the
Continental Divide. In other words, the ECMWF storm strength is
questionably weak, however the pattern depicted is common for
spring time. The forecast broadly reflects the ECMWF forecast,
with a long period of precipitation and cool temperatures Thursday
evening through next weekend.

&&

.AVIATION...Cloud cover will continue to increase and lower
this morning as the next weather system approaches. Rain, snow, and
mountain obscurations will develop later this morning in north
central Idaho. This rain and mountain snow will move into western
Montana during the afternoon. The cold front associated with the
upcoming trough is expected to pass during the late Friday evening
with conditions to further deteriorate.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY from Noon today to 9 AM MDT Saturday for 
     Lolo Pass IN THE Bitterroot/Sapphire Mountains.

     WINTER WEATHER ADVISORY from Noon today to 9 AM MDT Saturday for 
     I-90 Lookout Pass to Haugan IN THE Lower Clark Fork Region.

     WINTER WEATHER ADVISORY from Noon today to 9 AM MDT Saturday for 
     Marias Pass IN THE West Glacier Region.

ID...WINTER WEATHER ADVISORY from 11 AM this morning to 8 AM PDT 
     Saturday for Lolo Pass IN THE Southern Clearwater Mountains.

&&

Smith/Zumpfe
Aviation - Smith

$$

Follow us on Facebook and Twitter!
https://www.facebook.com/US.NationalWeatherService.Missoula.gov
https://www.twitter.com/NWSMissoula