textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Slick Morning Travel (Today): Mainly above 4000 feet.

- Strong Winds (Late Sunday into Monday): Decent potential gusts over 40 mph in the valleys.

- Active Pattern Rest of Next Week: Snow levels to valley floors at times, gusty westerly winds.

Current Conditions and Short-Term Impacts (Today-Saturday): Widespread light to moderate precipitation continues early this morning, primarily from I-90 southward, as moisture wraps around a surface low over southwest Montana. While slick roadways have been reported at elevations above 5,000 feet, snow levels will gradually drop to 3,500-4,000 feet by sunrise. Travelers should prepare for winter driving conditions on mountain passes and higher-elevation routes (generally above 4,000 feet) through the morning. By late morning, warming temperatures will limit further road impacts to brief slush or snow cover during more intense passing showers.

An active northwest flow will persist through Saturday, characterized by periodic showers. However, impacts will remain minor due to light precipitation totals, seasonable temperatures, and snow levels rising back toward 5,000 feet by Saturday afternoon. Expect breezy conditions each afternoon,with westerly gusts of 20-30 mph common in valley locations.

Incoming Storm System (Sunday-Tuesday): Model guidance remains consistent in depicting an atmospheric river (AR) directed north of the region on Sunday, bringing steadier precipitation to northwest Montana. This AR is then progged to shift southward as a potent cold front crosses the region Monday. This transition will lower snow levels to valley floors. While accumulating snow is a concern, wind appears to be the primary hazard with this system. Probabilities for valley gusts exceeding 40 mph currently sit between 45-65%. Furthermore, the synoptic setup is favorable for mountain wave activity, which introduces the potential for localized gusts over 50 mph in some valley locations.

Extended Outlook (Late Next Week: March 12-14): The active pattern is expected to continue late next week as additional weak to moderate atmospheric rivers target the Northern Rockies. CPC guidance and ensemble clusters suggest a higher likelihood of below-normal temperatures and above-normal precipitation during this window. With snow levels potentially fluctuating near valley floors and persistent, gusty westerly winds, this period bears close monitoring for renewed winter travel impacts.

AVIATION

Widespread stratiform precipitation remains focused from the I-90 corridor southward early this morning. As a surface low shifts east and cold air advection increases mid-to-upper-level instability, precipitation will transition to numerous showers by mid-morning. Snow levels are progged to lower to 3,500-4,000 feet during this transition. While terminal ceilings and visibilities are expected to improve to VFR/high-end MVFR after 05/1800Z, frequent mountain obscurations will persist through the period.

Enhanced boundary layer mixing will result in westerly surface gusts of 15-25 knots, primarily affecting valley terminals through the afternoon. Expect these winds to diminish after 06/0200Z as the boundary layer decouples.

Showers will become more widely scattered tonight, though persistentnorthwest flow will maintain VCSH and lower ceilings near higher terrain. A secondary weak disturbance on Friday is expected to bring a renewed increase in shower activity and potential for localized MVFR conditions.

MSO WATCHES/WARNINGS/ADVISORIES

MT...Winter Weather Advisory until 9 AM MST this morning for Bitterroot/Sapphire Mountains...Butte/Blackfoot Region.

ID...Winter Weather Advisory until 9 AM MST /8 AM PST/ this morning for Eastern Lemhi County...Southern Clearwater Mountains... Western Lemhi County.