210
FXUS65 KMSO 270818
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
218 AM MDT Sat Apr 27 2024

.DISCUSSION...The Northern Rockies sits under a deep trough of
low pressure extending south through the Great Basin this
morning. This trough is one in a series of disturbances lined up
over the northeastern Pacific Ocean and moving towards the
northwestern U.S. In the near-term, rain will grace the forecast
for today, with the highest probability for precipitation being
across southwest Montana and Lemhi County due to a midlevel
circulation to the southeast sending moisture back up from the
south. Snow levels this morning will be around 5000 to 6000 feet,
so expect slushy or snowpacked roads over Lost Trail and Homestake
Passes. Winter Weather Advisories are in effect for elevations
above 6000 ft in the affected areas. Snow showers will occur at
lower elevations also, but if there`s any accumulation at all
below 6,000 ft it won`t be enough to warrant an advisory.

As todays trough of low pressure moves east overnight tonight,
upper level flow becomes westerly as the next disturbance moves
down the Canadian coast on Sunday. As it does, it will push
Pacific moisture onshore into the Pacific Northwest and,
eventually, into the Northern Rockies. Expect valley rain and high
elevation snow to continue into Sunday morning with an increase
in westerly winds in the afternoon with the passing of a weak cold
front. Chances for precipitation will again increase on Monday as
this next wave moves through the northwestern U.S. and into the
Northern Rockies, bringing pacific moisture, a cold front, and a
favorable position of the upper level jet.

The Northern Rockies will remain under an unsettled pattern
through the middle of next week. Ensemble solutions show good
agreement for cool, wet weather to continue through Wednesday.
Agreement starts to waver later in the week, when some solutions
begin to show a shift towards a drier pattern while others keep
the Northern Rockies under a strong trough.


&&

.AVIATION...A deep trough of low pressure will keep rain showers
in the forecast throughout the day today. The southeasterly nature
of the midlevel flow will result in increasing rainfall intensity
at KBTM, further dropping visibility and ceilings by about
27/1500Z this morning and lasting through about 27/2000Z.
Elsewhere, expect light rain for most of the day today. Snow over
the higher elevations will obscure terrain over the Continental
Divide and the Bitterroot and Clearwater Ranges.


&&

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

ID...Winter Weather Advisory until 6 PM MDT this evening for Eastern
     Lemhi County...Western Lemhi County.

&&

$$