textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Weekend Warmth: Temperatures will trend upward, with widespread highs in the 40s and 50s likely. Riggins Idaho could be in the 60s.

- Minor Monday Morning Commute Hazard: A weak cold front brings light valley rain Sunday night into Monday. Localized black ice on roads where surfaces remain below freezing.

- Mid Next Week: High pressure returns, continued above-normal temperatures.

A ridge of high pressure moving over the Northern Rockies today through tonight is bringing plenty of warmth to the region. Most valleys are already breaking into the 40s and 50s this afternoon with minimal mixing.

Upper-level flow will turn southwesterly on Sunday as a weak cold front approaches. Better mixing is expected ahead of the front as southerly winds increase during the afternoon and evening. Consequently, the Camas Prairie of Idaho is anticipated to see gusts up to 40 mph Sunday afternoon. This increased mixing will help the majority of valleys reach the 50s; the exception will be northwest Montana, where thicker clouds and cooler air aloft will limit Sunday afternoon temperatures to the 40s.

Overall, readings will run approximately 15 to 20 degrees above seasonal averages. While confidence in reaching record warmth is relatively low, it cannot be ruled out. Daily records for Sunday for select stations include:

-Missoula: 60F (2020) -Kalispell: 54F (1971) -Butte: 57F (1934) -Orofino: 55F (2005)

The cold front is expected to push across the region late Sunday afternoon through the overnight hours. While the front will shift winds to the west, gusts do not appear significant. Widespread precipitation is expected, particularly north of the Highway 12 corridor. Snow levels will hover around 4000 feet during the frontal passage, bringing a couple of inches of new snow to the mountains; expect minor to moderate impacts over Lookout, Lolo, and Marias passes. Valleys are anticipated to remain all rain. However, road subsurface temperatures across portions of northwest Montana, specifically Highway 93 from Whitefish to Eureka and Highway 2 from West Glacier to Marias, remain well below freezing. Therefore, any wet roads have the potential to ice up by Monday morning.

A strong ridge of high pressure is expected to build over the region for the remainder of the work week. This ridge will bring significantly warmer temperatures, with the potential for daily records in the Wednesday/Thursday timeframe. While valley inversions will develop each day, northwest Montana holds the highest probability for fog and low stratus development due to recent light precipitation.

AVIATION

High pressure will be building over the Northern Rockies for the next 24 hours allowing for fair flying conditions at all terminals. Some mid to high level clouds will be streaming across the region, but should have little to no impacts.

MSO WATCHES/WARNINGS/ADVISORIES

MT...None. ID...None.