MISSOULA — High pressure will continue to build over the western half of the United States this week.
High pressure is a very stable air mass, this means valley inversions, fog/ low lying clouds and deteriorated air quality is all possible as we move through out the week.
An air stagnation advisory has been issued for the Kootenai/Cabinet Region along with the Potomac/Seeley Lake Region through 11 am Saturday.
The forecast challenge this week will be pinning down those daytime temperatures. High pressure generally means clear skies resulting in cold nights and warm days. However, the topography for us here in western Montana allows for cold air to pool in valleys when strong high pressure builds during the winter months. The take away from this is, if locations can break free of valley inversions and cold air pools, highs will warm into the upper 30s to mid 40s. However, locations that can not break free will see highs remain only in the 20s.