Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 281035

Area Forecast Discussion
National Weather Service Missoula MT
435 AM MDT Tue Mar 28 2017

.DISCUSSION...A few scattered showers will be present today with
high temperatures in the upper 40s to low 50s across western
Montana and central Idaho. Most of the showers will be fairly weak
and will mainly be focused over northwest Montana. Clouds will be
on the increase this evening as the next weather system begins to
approach the Northern Rockies.

The next weather system will be moving in during the day
Wednesday. A stream of moisture from the pacific will cause
steady periods of moderate rain for many valleys in central Idaho
and across northwest Montana valleys near the Idaho border.
Mountain passes along the Montana/Idaho border could see some wet
snow but little impact to road conditions is expected. On
Wednesday night, the trough of low pressure will begin to dig
further south and a stronger surge of moisture will move into
central Idaho and parts of west central Montana. Periods of heavy
rain overnight over central Idaho will cause ponding of water
issues and some rock slides as well. An area of concern for rock
slides will be along highway 12 leading to Lolo pass and over
highway 14 to Elk City.

The flow will become more northerly Thursday morning and
will allow for snow levels to drop around 5000 feet. High
elevation valleys of southwest Montana, Lemhi county, and central
Idaho could see periods of moderate wet snow. Lost Trail pass
will likely see winter driving conditions Wednesday morning when
road temperatures are still below freezing and will likely turn
into slush during the day. Lost trail pass could see 5 to 8
inches of snow Wednesday night through the day Thursday.

Rain and high elevation snow showers will linger across southwest
Montana and Lemhi County Idaho Thursday evening through early
Friday afternoon. Several inches snow accumulation is anticipated
over the high mountain passes, such as Lost Trail Pass, however
the snow is unlikely to stick to the roadway and create hazardous
winter driving conditions.

A relatively dry day is anticipated Saturday, however another
northwesterly oriented storm system is projected to follow quickly
for at least Sunday and Monday. This system is not expected to
bring much of a change in airmass or large amounts of

Further through the extended forecast, it appears that the
Northern Rockies remains stuck in a pattern of "36 hours of
shower activity followed by 24 hours of mostly dry conditions".


.AVIATION...Partial clearing expected for portions of Northern
Rockies air space today, however some patches of valley fog may
exist through 28/1600Z (including near KMSO, KGPI, and KSMN)
Shower activity will resume mainly north of KMSO after 29/0000Z,
however there is low probability of even vicinity showers for KGPI
or KMSO. Scattered terrain obscurations will be present through
29/0000Z, increasing in frequency thereafter.



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