Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/22/24

Area Forecast Discussion

National Weather Service Missoula MT

 212 PM MST Sun Jan 21 2024

.DISCUSSION...The persistent low pressure off the west coast
continues to introduce moist and mild conditions into the Northern
Rockies. While valley inversions remain, they are gradually
weakening as valleys slowly warm, moving away from the trapped
cold air. Despite the weakening inversions, sub-freezing
temperatures are still anticipated, especially in the valleys of
northwest Montana.

Showers are expanding in Washington and Oregon, and water vapor
imagery reveals approaching shortwaves, expected to arrive late
this afternoon and overnight. The temperature profile suggests a
wintry mix of freezing rain and snow in northwest Montana, and
light rain with pockets of freezing rain in the valleys south of
I-90.

Winter weather advisories have been reissued for northwest
Montana, anticipating very slick conditions tonight due to the
combination of freezing rain and snow.

Another shortwave disturbance on Monday afternoon through Monday
night brings another chance of a wintry mix in valleys and
mountain snow. Precipitation amounts may need adjustment in future
updates, given the recent challenges in model guidance.

A trough is forecast to move into the Northern Rockies on
Wednesday, initially with warmer conditions and higher snow
levels, but transitioning quickly into a northwesterly flow
pattern with lowering snow levels by Thursday.


&&

.AVIATION...Several rounds of light mixed precipitation is expected
across the Northern Rockies through Tuesday morning. For tonight,
the area with the highest probability for more widespread and
steady precipitation is across northwest Montana. While the
ceilings may stay elevated, freezing rain is likely in the valleys
up to around 5000 feet MSL. A quasi-saturated and sub-freezing
layer up to 9000 feet AGL could pose aircraft icing risk in
northwest Montana, especially late this afternoon to daybreak
Monday (00z to 12z Monday Jan. 22). Up to a 0.10 of ice accretion
is possible from Libby to the Flathead Valley and Glacier Region
through Monday. Another round of mixed precipitation is possible,
up to 40 percent Monday night across northwest Montana.




&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Monday for Flathead/Mission Valleys...Kootenai/Cabinet
     Region...West Glacier Region.

ID...None.
&&

$$