Significant pattern change brings widespread rain, mountain snow, and temps 20 degrees below normal

A potent cold-core low will push a strong cold front through the region Friday morning, ending the recent heat and bringing widespread showers, cooler temperatures, and the potential for significant precipitation and light mountain snow through the weekend.

Significant cool down for the weekend in Scott Dorval's video forecast Isolated thunderstorms will develop this afternoon through this evening, with the main focus along the Nevada border and western Magic Valley. Given the high-based nature of this activity, strong and gusty outflow winds will be the primary threat, with gusts up to 50 mph possible. On Thursday, the thunderstorm threat shifts into the central Idaho mountains as moisture increases ahead of the next major weather system. Temperatures will be about 5 degrees cooler than today.

The significant pattern change begins in earnest on Friday as a potent cold core low moves into the Northwest, dragging a strong cold front through southeast Oregon and southwest Idaho Friday morning. This system will usher in widespread showers and thunderstorms through Friday night. There is currently a 60 percent chance for the valleys to pick up over a tenth of an inch of rain, while the central mountains of Idaho could see higher amounts up to half an inch. The stronger storms could produce brief heavy rain as moisture values peak to the 90th percentile. Temperatures on Friday will drop sharply, landing around 10 degrees below normal.

Cool and showery conditions will continue Saturday and Sunday with a slight chance of thunderstorms as the upper low slowly moves overhead. Temperatures will run 15 to 20 degrees below normal, making for a dramatically different feel compared to the recent heat wave. Significant precipitation remains possible with this system, with amounts up to 1 to 1.25 inches possible over the central Idaho mountains and lesser amounts in eastern Oregon. With snow levels expected to drop into the 6,500 to 8,000-foot range by Sunday, light snowfall is likely over the west-central Idaho mountains, with accumulations up to 2 inches on the highest peaks above 7,500 feet.

Conditions will dry out with breezy conditions Monday and Tuesday as the system moves northeast. Temperatures will remain below normal under cool northwest flow aloft before a mostly dry Pacific shortwave trough digs over the area on Wednesday.

Tonight

A 20 percent chance of showers and thunderstorms after 3am. Increasing clouds, with a low around 63. NW wind becoming light and variable after midnight.

Thursday

A 20 percent chance of showers and thunderstorms before 9am. Increasing clouds and hot, with a high near 92. Wind becoming NW 5-10 mph.

Thursday Night

Cloudy, with a low around 64. Gusty evening breezes subsiding overnight.

Friday

Showers, with thunderstorms also possible after noon. High near 75. NW wind 5-15 mph. Chance of precipitation is 80%.

Friday Night

Showers likely and possibly a thunderstorm, then showers after midnight. Low around 53. West wind 6 to 11 mph becoming light and variable after midnight. Chance of precipitation is 80%.

Saturday

Showers likely, with thunderstorms also possible after noon. Partly sunny & unseasonably cool, with a high near 68. Chance of precipitation is 60%.

Saturday Night

Partly cloudy, with a low around 46.

Sunday

Partly sunny, with a high near 69.

Sunday Night

Mostly cloudy, with a low around 47.

Monday

Mostly sunny, with a high near 76.

Monday Night

Partly cloudy, with a low around 51.

Tuesday

Sunny, with a high near 82.

Tuesday Night

Mostly clear, with a low around 51.

Wednesday

Sunny, with a high near 84.

Significant pattern change brings widespread rain, mountain snow, and temps 20 degrees below normal

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