A flat shortwave trough will bring light rain to northern areas Saturday before the pattern turns highly active Monday night into Tuesday, with confidence remaining high for a major mountain snow event and potential valley snow chances later in the week.
The weekend will see gradual warming as a moist band shifts northward Saturday night through Sunday as a warm front ahead of a Pacific upper low approaching the California coast. Saturday will be mostly cloudy with highs near 56 degrees, while Sunday becomes gradually sunnier with temperatures reaching 58 degrees as southerly flow develops ahead of the approaching system.
The main event begins Monday as weather models continue showing remarkable consistency across multiple runs and ensemble suites. As the low off the California coast fills in and rejoins the main atmospheric flow, another low digging down the coast will help sling it over the area. The heaviest precipitation window remains Monday 5 p.m. through Tuesday 11 a.m., with precipitation chances rapidly increasing through Monday and reaching 50 to 95% by Monday night, highest over the mountains.
With southerly flow aloft, Monday temperatures will run 10 to 15 degrees above normal, keeping snow levels elevated at 4,500 to 6,000 feet Monday afternoon and evening. However, the current forecast carries 1 to 5 inches of snow in mountain valleys above 4,000 feet, and 6 to 12 inches above 6,000 feet from Monday 5 p.m. through Tuesday 5 p.m., with locally higher amounts along peaks. This could create hazardous travel conditions on mountain routes, especially along passes where winds may gust up to 30 mph across higher terrain. Lower valley locations will generally see 0.10 to 0.25 inches of rain during this same period.
Beyond Tuesday morning, precipitation chances remain elevated as the second low makes its way onshore, dropping temperatures and snow levels for the rest of the week. By Wednesday, temperatures will lean below normal with snow levels down to 1,500 to 2,500 feet - essentially valley floors. While precipitation won't be as significant as the Monday night event, showers will continue as the trough moves inland.
What makes the extended pattern particularly interesting is the strong ridging in the eastern Pacific extending up to the Aleutian Islands, which will keep the area in cool northwesterly flow aloft. This pattern will not only maintain cool temperatures but direct the storm track toward the region. Some weather models are hinting at another shortwave riding down the British Columbia coast Thursday and Friday, which could tap into Pacific moisture while maintaining a cold continental air mass - a favorable setup for another round of mountain and even valley snow.
Current probabilities show a 50 to 70% chance of measurable snowfall in the Snake Basin between Wednesday 5 p.m. and Friday 5 p.m. The chances of one inch of snow during that timeframe range from 10 to 35%, highest near the western Magic Valley and between Boise and Mountain Home. This represents a dramatic shift from the recent dry pattern to an active winter weather regime that could finally deliver significant snowfall to both mountains and valleys.
Mountain Snow Conditions for Ski Areas
This storm system represents the most significant snowfall event of the season for Idaho's ski areas. With 6 to 12 inches possible above 6,000 feet and substantial accumulations expected across all elevation levels, ski resorts should see dramatic improvements in base conditions. The timing provides fresh powder for Presidents Day weekend and beyond, though mountain travel may be hazardous during the Monday night through Tuesday morning period.
Friday Night
Mostly cloudy, with a low around 37. Light wind.
Saturday
Mostly cloudy, with a high near 56. SE wind 5 to 10 mph.
Saturday Night
Cloudy, with a low around 38. Light and variable wind.
Sunday
Cloudy, then gradually becoming mostly sunny, with a high near 58. Light and variable wind.
Sunday Night
Partly cloudy, with a low around 34.
Monday
A 20 percent chance of rain after 11am. Partly sunny & very mild, with a high near 58.
Monday Night
Rain. Low around 37. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.
Tuesday
A 50 percent chance of rain. Mostly cloudy, with a high near 50.
Tuesday Night
A chance of rain before 2am, then a chance of rain and snow. Mostly cloudy, with a low around 32. Chance of precipitation is 30%.
Wednesday
A chance of rain and snow. Partly sunny, with a high near 44. Chance of precipitation is 30%.
Wednesday Night
A chance of rain and snow. Mostly cloudy, with a low around 27. Chance of precipitation is 30%. A trace of snow possible.
Thursday
A chance of rain and snow. Mostly cloudy, with a high near 43. Chance of precipitation is 40%.
Thursday Night
A chance of rain and snow. Mostly cloudy, with a low around 30. Chance of precipitation is 40%. A trace of snow possible.
Friday
A chance of rain and snow. Mostly cloudy, with a high near 43. Chance of precipitation is 40%.
