textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Moderate snow during a cold front passage this morning will lead to snow-covered roads in the mountains and high valleys, creating difficult travel for the morning commute.

Latest weather models show a narrow band of moderate snow moving through the region this morning. Snow is expected to fall at rates of 0.4 to 0.7 inches per hour from southern Idaho County eastward toward Butte. Consequently, a Winter Weather Advisory has been added for Georgetown Lake, MacDonald Pass, Anaconda, and I-90 east of Deer Lodge. Travelers and truck drivers should prepare for difficult driving conditions and visibility as low as one-half mile at times. While road temperatures are currently in the upper 30s at Homestake Pass, they will fall to near freezing by sunrise. Combined with westerly winds up to 15 mph, any moisture on the roads may quickly turn to black ice under the fresh snow.

A plume of moisture will continue to move across the Northern Rockies today before being pushed south and east by an incoming cold front. The heaviest moisture will focus on north-central Idaho, west-central and southwest Montana. Mountain passes along the Montana/Idaho border and the Continental Divide will see accumulating snow through today. While most valleys will see light rain this morning, the higher valleys from Drummond to Butte will see light accumulating snow. The Missoula and Bitterroot Valleys may see a brief changeover to light snow around sunrise, though little to no impacts are expected.

A passing area of high pressure will bring a break in the weather Tuesday, causing remaining showers to fade. On Wednesday, a weak system moving through southern Idaho may bring light snow to Lemhi County. Looking ahead to next weekend, a large storm system is expected to develop over the western United States. While there is still uncertainty regarding the exact path of this storm, it is likely to bring an active weather pattern and much-needed rain and snow to the region.

AVIATION

A weak atmospheric river will continue to stream moisture over the Northern Rockies through this morning, causing low clouds and light precipitation. KMSO, KSMN and KHRF will have the biggest impact from this moisture feed with reduced visibility and a low . KMSO, KSMN, KHRF and KBTM will see a brief period of rain changing over to snow by 09/1200Z, that will further reduce the visibility around the terminals. KBTM is the only terminals that will have accumulating snow this morning, with around 30% probability for a couple inches of snow by mid-morning.

MSO WATCHES/WARNINGS/ADVISORIES

MT...Winter Weather Advisory until 11 AM MST this morning for Bitterroot/Sapphire Mountains...Lower Clark Fork Region... West Glacier Region.

Winter Weather Advisory until 8 AM MST this morning for Butte/Blackfoot Region.

ID...Winter Weather Advisory until 11 AM MST /10 AM PST/ this morning for Eastern Lemhi County...Southern Clearwater Mountains... Western Lemhi County.