textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Winter Weather Advisories Issued: Travel impacts over Lookout Pass and Marias Pass by this afternoon.

- Slick Morning Commute: Valley rain and snow will develop early this morning, making for a messy and potentially icy start to the work week in northwest Montana including Kalispell.

- Colder with Snow Banding Midweek: A sharp cold front Tuesday night will bring gusty winds and quick-hitting snow showers through Wednesday.

Satellite imagery early this morning indicates a low pressure circulation off the Canadian coast sending Pacific moisture onshore and into the Northern Rockies. Radar returns indicate precipitation making its way across the Idaho Panhandle and into northwest Montana. Model guidance is in favor of this moisture plume thickening today and expanding south over the next 48 hours.

Winter Weather Advisories are in effect for higher mountain passes where travel impacts are most certain. Expect a wintry mix in the valleys, followed by a colder, windier period through the middle of the week.

Mountain Passes: Expect snow to begin this morning. Total accumulations of 4 to 8 inches are likely through Monday night, with higher amounts on the peaks. Blowing snow may reduce visibility.

Valleys: Light snow or a wintry mix will develop early this morning. Because temperatures will be near freezing, the morning commute could be slick. By this afternoon, most valleys will transition to a rain/snow mix or all rain as warmer air moves in. North-central Idaho valleys will see primarily rain below 4,000 feet.

A cold front pushes through Tuesday evening and rain will turn back to snow in the valleys late Tuesday night.

Wednesday will feature gusty westerly winds and convective snow showers. These snow bands can cause sudden whiteout conditions even if total accumulations remain modest. The trend has been for the snow bands to develop earlier in the day and focus farther south, potentially bringing the highest impacts from near Lost Trail Pass and south and east.

Colder air settles in for the remainder of the week. While the main moisture plume exits, the region remains in a northwest flow pattern. This means, off-and-on light snow showers will continue, especially in the mountains, and temperatures are forecast to be closer to seasonal averages.

Early indications show another weak disturbance possible by Saturday, keeping the unsettled trend alive.

AVIATION

Precipitation, starting in the form of snow, will affect KGPI this morning. Expect decreasing ceilings and periods of decreased visibility down to MVFR/IFR through about 23/1700Z. Precipitation will transition to rain this afternoon and expand to include terminals further south (KMSO, KBTM, KHRF) this evening. Expect obscured terrain across all mountain ranges of northwest and west-central Montana, as well as the Clearwaters in Idaho. Wind will accompany precipitation today. Southwesterly winds gusting to about 20-30 kts will be widespread, with gusts of 30-40 kts at KBTM.

MSO WATCHES/WARNINGS/ADVISORIES

MT...Winter Weather Advisory until 11 AM MST this morning for Kootenai/Cabinet Region.

Winter Weather Advisory from 5 AM early this morning to 5 AM MST Tuesday for West Glacier Region.

Winter Weather Advisory from 1 PM this afternoon to 9 AM MST Tuesday for Lower Clark Fork Region.

ID...None.