Cool, breezy, and unsettled weather will persist through the weekend, bringing light mountain snow showers, gusty winds, and the threat of widespread frost or a light freeze to agricultural valleys by Saturday morning.
Frost likely in Scott Dorval's video forecast
Light mountain snow and gusty winds continue
The region will remain on the backside of a broad upper-level trough over the northern Great Plains into the weekend. Shortwave energy dropping out of Canada will maintain a 20 to 30 percent chance of showers over the west-central Idaho mountains on Friday. Snow levels will be down to mountain valley floors, but showers will be light, and any accumulation will total less than an inch.
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Otherwise, dry and breezy conditions are expected across southeast Oregon and southwest Idaho. Winds will ramp up in the afternoon, with gusts peaking around 30 mph across the Snake River Plain south and east of Boise.
A closed low off the California coast will draw the trough further south and west on Saturday. Cooler air aloft will increase instability over higher terrain along the Nevada border, supporting a 20 to 30 percent chance of afternoon showers. The environment will be borderline for thunderstorm development, topping out around a 10 percent chance along the border. Lower elevations will stay dry on Saturday, seeing slightly warmer temperatures and lighter winds.
Frost and freeze threat for agricultural valleys
Lower valleys will see a chance for frost tonight and freezing temperatures Friday night. For tonight, the wind, clouds, and borderline temperatures should limit frost formation, so forecasters have held off on issuing an official advisory, instead covering the threat with "patchy frost" wording in the forecast.
However, Friday night will likely see a widespread light freeze or frost, with low temperatures dropping to between 29 and 34 degrees from Ontario to Twin Falls and Jerome. Agricultural interests and home gardeners should take precautions to protect sensitive plants.
Unsettled weekend before a warming trend
A trough extending from a low centered over Canada will dig into the region Sunday into Monday, bringing cool, below-normal temperatures and a 30 to 50 percent chance of high-terrain precipitation. Showers will generally be light, with minimal accumulation anticipated. Snow levels will begin around 4,500 to 5,500 feet on Sunday, rising to 5,500 to 6,500 feet on Monday.
High pressure will then move into the region, bringing a steady warming trend through the end of next week. Temperatures will gradually warm toward normal, reaching the low 70s by Wednesday and Thursday. Lingering mountain showers are possible through Thursday with this warming trend, but forecast confidence is low (20 to 30 percent chance).
Tonight
Patchy frost after midnight. Otherwise, mostly clear, with frost possible and a low around 36. NW wind 5 to 10 mph becoming calm after midnight.
Friday
Patchy frost before 9am. Otherwise, mostly sunny, with a high near 56. Wiind NW 6-10 g20.
Friday Night
Mostly clear with valley frost likely, with a low around 33. Wind becoming calm after midnight.
Saturday
Mostly sunny, with a high near 59. Light NW breeze.
Saturday Night
Mostly clear with frost possible, with a low around 36. Wind becoming calm after midnight.
Sunday
Sunny, with a high near 61.
Sunday Night
Mostly clear, with a low around 37.
Monday
Mostly sunny, with a high near 62.
Monday Night
Mostly clear, with a low around 40.
Tuesday
Sunny, with a high near 67.
Tuesday Night
Partly cloudy, with a low around 43.
Wednesday
Mostly sunny, with a high near 71.
Wednesday Night
Mostly clear, with a low around 44.
Thursday
Sunny, with a high near 73.
