239 
FXUS65 KMSO 282047
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
247 PM MDT Fri Mar 28 2014

...Significant Precipitation Tonight into Saturday...
...Snow accumulations above 6000 feet...

.DISCUSSION...Moisture is spreading through the Pacific Northwest
this afternoon and will arrive to Clearwater County in Idaho and
northwest Montana by this evening and into the rest of the region
by Saturday morning. Snow accumulations will mainly occur above
6000 feet with 6 to 10 inches possible, while moderate to heavy
rain amounts will fall below 6000 feet. Idaho and Clearwater
counties of north central Idaho are still on track to receive the
highest precipitation amounts with 0.75"-1.50". Rock and mudslides
are still a concern with the amount of rain expected in north
central Idaho and portions of northwest Montana. Snow levels are
tricky with this weather system due to its warm and moist nature.
There is concern that the heavy precipitation being shown by some
of the model guidance will allow for lower snow levels and
accumulations through Lemhi County Idaho and into southwest
Montana. Mountain pass locations above 6000 feet are expected to
become snow covered by late Saturday morning, but there will also
be an opportunity during the late morning and early afternoon for
snow to accumulate in Butte. Winter weather advisories have been
issued for the snow potential. 

Precipitation will decrease overnight on Saturday, but showers
will return for Sunday and there is the potential for some of
these to be intense snow showers especially south of I-90.

A brief area of high pressure is expected Sunday night into
Monday, which could reduce shower activity and possibly even
bring some breaks in the clouds. 

The forecast gets more uncertain for the Tuesday into Wednesday
time frame as forecast models begin to diverge on their solutions.
Most models are showing an area of low pressure moving well south
of western Montana and north central Idaho, taking all the
moisture well south of the region as well. This scenario would
likely result in mainly just nuisance showers. The European model
continues to bring this area of low pressure further north
however, placing the bulk of this moisture into southern Idaho
county, Lemhi county and southwest Montana. This scenario could
lead to a decent snowfall event, potentially even into the
valleys. Very few changes were made to the forecast for the time
being due to the uncertainty. The forecast could dry out again by
Thursday into Friday due to another ridge of high pressure.


&&

.AVIATION...A very moist weather system will begin to increase
cloud cover and shower activity in north central Idaho this
afternoon and western Montana tonight into Saturday. Low ceilings
causing the higher terrain to be obscured will become widespread.
Periods of heavy rain and high terrain snow will also cause
visibility reductions. Most airfields are expected to see
precipitation fall as rain, however KBTM could switch over to snow
around 29/1500z which could cause low ceilings/visibility and
possibly some accumulations on the runway. Precipitation will
begin to let up by Saturday evening.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY from 6 AM to 6 PM MDT Saturday 
     Butte/Blackfoot Region.

     WINTER WEATHER ADVISORY from Midnight tonight to 6 PM MDT 
     Saturday Bitterroot/Sapphire Mountains.

     WINTER WEATHER ADVISORY from 6 PM this evening to 6 PM MDT 
     Saturday for Marias Pass IN THE West Glacier Region.

ID...WINTER WEATHER ADVISORY from Midnight tonight to Midnight MDT 
     Saturday Night ABOVE 6000 FEET FOR THE Eastern Lemhi 
     County...Western Lemhi County.

&&

$$

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