textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- High pressure breaks down early Monday.

- Colder temperatures and periods of rain and mountain snow expected this week.

A weak ridge of high pressure over the Northern Rockies will maintain dry conditions and seasonal temperatures through this afternoon. Patchy fog is possible Monday morning, but it is not expected to be as dense or widespread as Sunday morning's fog.

A low pressure system will move into the Pacific Northwest on Monday. Rain and mountain snow from this system will reach north-central Idaho by early Monday afternoon, spreading across the rest of the region overnight. A second storm system will move along the coast by mid-week, establishing a large area of low pressure over the western United States. Another strong low pressure system may arrive late in the week, but weather forecast models currently disagree on the exact track and impacts for the Northern Rockies.

Expect temperatures to run about 5 degrees below seasonal averages this week, along with periodic rain and snow. Snow levels will hover between 4,000 and 5,000 feet, bringing accumulating snow to the higher terrain and mountain passes, especially at night.

AVIATION

A weak ridge of high pressure will remain over the region today. High-level clouds will increase later today as a low pressure system approaches the region. Due to increased cloud cover tonight and light winds, widespread fog will not have the same level of impact on Monday morning.

MSO WATCHES/WARNINGS/ADVISORIES

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