942
FXUS65 KMSO 160632 AAA
AFDMSO

Area Forecast Discussion...UPDATED
National Weather Service Missoula MT
1232 AM MDT Sun Jun 16 2024

.UPDATE...The forecast remains on track, so only minor changes
were necessary to the previous discussion (below).

&&

...Snow Storm to hit Elevations of 4500 feet and Higher Tonight
into Monday...

.PREV DISCUSSION...

DISCUSSION...We expect the coldest part of the trough to rotate
south over our region later today, and eventually a piece of
energy in the middle atmosphere is expected to close off and
rotate over Lemhi County, ID, further lowering snow levels to the
north and west of its track. As such, today will be cool,
overcast, and breezy. Shower activity initially will be limited to
the Canadian border and will expand further in the late afternoon
south of I-90.

Overnight conditions get progressively cooler and with snow
levels lowering across the region down to about 5000 feet. There
is increasing confidence of a mid-level low pressure system
closing off and developing a deformation zone during the late
night hours. There is model consensus that this deformation zone
will develop over far southeastern Clearwater County into the
southern Bitterroot Valley, and eventually moving east of Missoula
along I-90 towards southwest Montana. Under the deformation zone,
snow levels will likely lower an additional 1000 to 1500 feet,
bottoming out around 4000 to 4500 feet. We have added Clearwater
County (southeastern portion) and the Bitterroot Valley to the
Winter Storm Watches for concerns involving back country users in
Idaho and the potential for power outages due to downed tree
limbs in the Bitterroot Valley. As little as 1 to 2 inches of
heavy wet snow will be sufficient on leafed tree branches to
cause breaks and/or potential power outages.

In general, Monday will be a wet and raw day. Plan accordingly for
any outdoor plans, as hypothermia can happen even in June.

Tuesday, a secondary wave drops out of Canada and scattered
showers redevelop. Snow levels rise above 6000 feet, but snow
showers will remain possible in Glacier National Park.

&&

.AVIATION...Cloud cover and precipitation will spread from north
to south today as a low pressure system in Washington circulates
and moves into Idaho and western Montana. Blustery winds will
exist this afternoon, with snow levels lowering this evening and
overnight. Precipitation in the form of rain is expected below
5000 feet, with snow expected above 5000 feet late Sunday into
Monday.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Watch from late tonight through Monday afternoon
     for Bitterroot/Sapphire Mountains...Butte/Blackfoot
     Region...Potomac/Seeley Lake Region.

     Winter Storm Watch from Monday afternoon through Tuesday evening
     for West Glacier Region.

     Winter Storm Watch from late tonight through Monday morning for
     Missoula/Bitterroot Valleys.

ID...Winter Storm Watch from Sunday evening through Monday afternoon
     for Southern Clearwater Mountains.

&&

$$