Widespread rain and wind through Sunday

IDAHO FALLS, Idaho (KIFI) - A major storm system will bring widespread rain, gusty winds and mountain snow across southern Idaho on Saturday night and Sunday. Falling temperatures will drop high elevations into the mid-30s and 40s on Sunday, creating hazardous mountain driving conditions.

The National Weather Service issued a Winter Weather Advisory active from 6 p.m. Saturday through 5 p.m. Sunday. The advisory covers the Sun Valley Region and the Big Lost Highlands above 7,000 feet, where three to seven inches of snow is expected at Galena Summit. Across the broader region, weather forecasters report a 90% to 100% chance of receiving at least 0.25 inches of rain as a heavy precipitation band moves in late Saturday night and continues through Sunday night.

An upper-level low moving inland from the Pacific coast is driving the moisture across Idaho. Weather forecasters report an organized round of rain is expected to start in the Central Mountains, Wood River Valley and eastern Magic Valley after 6 p.m. Saturday before spreading eastward overnight. Lower elevations, including the Snake River Plain, will see rain showers mostly after 3 a.m. Sunday, accompanied by southeast winds gusting up to 20 mph.

Rainfall totals are expected to reach between 0.20 and 0.50 inches in the eastern Magic Valley and Challis area. The Snake River Plain and lower elevations of the Eastern Highlands and Central Mountains are expected to receive 0.50 to 0.80 inches of rain. High-elevation areas above 8,000 feet, including the Lost River Range, Copper Basin and the Wasatch Mountains near the Utah border, could see liquid precipitation totals reaching up to 1.25 inches. Sunday afternoon highs will reach near 48 degrees, with west winds gusting up to 24 mph on Sunday night.

Showers are expected to linger into Monday morning before conditions clear. Long-term weather models indicate uncertainty for Wednesday and Thursday due to a 60-40 split among forecast solutions regarding whether a high-pressure ridge will hold or flatten into zonal flow.

Conditions are expected to dry out from west to east beginning Monday morning as high pressure builds over the area. Skies will turn partly sunny with a high near 49 degrees on Monday, followed by patchy fog developing after 7 p.m. Monday night and low temperatures falling to around 33 degrees.