357
FXUS65 KMSO 290806
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
206 AM MDT Mon Apr 29 2024

.DISCUSSION...An upper trough along the West Coast will come onshore this
 morning and wobble through the Northern Rockies into Wednesday
ushering in cooler and unsettled conditions. A cold front will
concentrate precipitation this morning across north-central
Idaho/west-central Montana with 2-4 inches of snow above 5000
feet in locales such as Dixie, Lolo Pass, and Lost Trail Pass
eastward to Georgetown Lake. Watch for transient slush on pass-
level roadways and slippery conditions on backcountry roads.

Considerable instability showers (maybe even a few rumbles of
thunder) are anticipated later today as temperatures cool aloft,
with additional showers on Tuesday and Wednesday. Snow levels will
range from 2500-3500 feet by this evening lasting into Wednesday
but valley impacts should be limited to a dusting on non-paved
surfaces. A secondary disturbance may focus precipitation in
Glacier Park and along the Divide on Wednesday with a 45%
probability of over 4 inches of snow at Marias Pass. There is
still uncertainty with the track of the disturbance as the 25th to
75th percentiles range from 1 to 7 inches respectively at Marias
Pass. Once again, be cautious of intermittent slippery conditions
on pass-level roadways in the overnight and morning periods.
Daytime wind gusts of 20-30 mph will also be prevalent in valleys,
tapering off during overnight periods today through Wednesday.

It`s noteworthy that morning temperatures will be below normal throughout
the middle and end of this week. The lower valleys of western Montana and
higher valleys of north-central Idaho are projected to experience
temperatures in the upper 20s to lower 30s. Gardeners with sensitive
annuals outdoors should take necessary precautions.

Models suggest another disturbance dropping down from British
Columbia late Thursday into Friday, bringing more showers.
Ensemble clusters support an active weather pattern with
intermittent showers expected this weekend (May 4th-5th) through
the first full week of May.


&&

.AVIATION...An upper trough situated along the West Coast will come onshore
this morning and propel a cold front through the Northern Rockies today.
This cold front will concentrate precipitation this morning across
north-central Idaho and west-central Montana, with snow levels near 4000
feet (closer to 6000 feet in southwest Montana). Considerable
instability showers are anticipated later today continuing into
Tuesday as temperatures cool aloft. Snow levels drop to 2500 feet
this evening but valley impacts should be limited to a dusting on
non paved surfaces.

As precipitation occurs, expect reductions in ceiling and visibility, along
with mountain obscurations, although these effects will likely be
brief during afternoon and evening showers. Additionally, wind
gusts of 20-25 knots will be common at terminal sites, gradually
diminishing during overnight periods.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 6 PM MDT this evening for
     Bitterroot/Sapphire Mountains.

     Winter Weather Advisory from 6 AM this morning to 9 PM MDT this
     evening for Butte/Blackfoot Region.

ID...Winter Weather Advisory until 6 PM MDT /5 PM PDT/ this evening
     for Eastern Lemhi County...Northern Clearwater Mountains...
     Southern Clearwater Mountains...Western Lemhi County.

&&

$$