textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Widespread rain and mountain snow will impact the region throughout today.

- Evening Snow for Lost Trail and Homestake Passes: Snow will intensify late this evening and tonight, particularly over Homestake Pass and the Continental Divide, where travel may become difficult after sunset.

A Pacific trough is moving across the Northern Rockies this morning. Clouds will continue to lower and thicken, with precipitation spreading from west to east through the afternoon. Expect rain showers starting by mid-day for most Montana and Idaho valleys. Snow will begin for the higher terrain above 5,000-6,000 feet. Mountain passes like Lookout and Lolo will see wet snow initially with accumulating snow more likely by the evening commute.

The cold front will push through the region this afternoon and evening. As the front arrives this evening, rain will rapidly transition to snow along the Divide, including over Lost Trail and Homestake Passes. Visibility will be reduced, and travelers should be prepared for winter driving conditions.

The cold front clears to the east by Thursday morning, leaving the region in a colder, unstable air mass. Gusty westerly winds of 30 to 40 mph are expected, especially along the Continental Divide and through the Butte/Blackfoot region. Snow showers are also possible at valley floors during the morning hours, which may lead to a few slick spots before showers become more hit-or-miss.

The region remains under an unsettled weather pattern from Friday through Monday. Expect hit-or-miss snow showers to continue, primarily over the mountains. Breezy conditions will persist, likely peaking again on Sunday or Monday.

We are tracking a 30% probability of an Arctic weather system arriving as early as March 9th, or as late as the 12th. While the rest of the cluster ensemble members are not showing an Arctic system, they do show a colder and wetter pattern as opposed to where we have been. This remains the primary focus for potential high-impact winter weather in the extended forecast.

AVIATION

Conditions will deteriorate rapidly today as the Pacific system arrives. Expect widespread obscured terrain and MVFR ceilings and visibility in the valleys by this afternoon. Winds will shift to the west-northwest as the cold front passes, with gusts increasing to 20-30 knots. A rapid transition from rain to snow is looking more likely this evening as the front passing through KBTM. Snow levels lower to valley floors on Thursday with hit-or-miss showers and west winds.

MSO WATCHES/WARNINGS/ADVISORIES

MT...Winter Weather Advisory from 3 PM this afternoon to 9 AM MST Thursday for Bitterroot/Sapphire Mountains.

ID...None.