A deep moisture plume from a Pacific storm system will bring mixed precipitation to Idaho on New Year’s Day, Expect a prolonged period of unsettled weather through next week.
Tonight: Clear and Cold
Mostly clear skies will allow temperatures to cool below freezing in most areas again tonight as high pressure maintains its grip on the region. This will be the last night of clear, cold conditions before the weather pattern shifts dramatically.
New Year’s Day: Mixed Precipitation Arrives
A deep moisture plume on the east side of a storm off the California coast will stream northward through California and Nevada into the region Thursday, continuing overnight into Friday. Snow levels will initially be near 4,500 feet Thursday morning but will rise above 6,500 feet by Thursday night.
Precipitation could start as a wintry mix, rain, freezing rain, or snow in some lower valleys where strong temperature inversions remain in place. The Baker Valley faces the highest probability for freezing rain with a 30% chance Thursday morning due to the persistent cold air trapped at the surface. I expect just rain in the Boise area. Some freezing rain is possible in the Ontario area Thursday morning.
Surface temperatures should rise above freezing in most areas during the afternoon, making rain the preferred precipitation type in valleys as the day progresses.
Mountain Snow Conditions for Ski Areas
Light snow in the mountains at elevations above 4,500 feet may bring 1 to 2 inches of accumulation to mountain communities before snow levels rise above 6,500 feet Thursday night and Friday. This initial snowfall will benefit higher elevation ski areas, though the rising snow levels will transition most resorts to rain by Friday…