Strong thunderstorms are developing across the region this afternoon, bringing the threat of 50 mph outflow winds, small hail, and heavy rain through the weekend as temperatures plummet to around 20 degrees below normal Saturday and Sunday.
Clearing skies across southeast Oregon have allowed for surface heating and the initiation of thunderstorms this afternoon. Initial convective activity will be capable of producing strong, erratic outflow wind gusts up to 50 mph due to relatively dry low levels. However, as atmospheric moisture steadily increases overnight, this severe wind threat will gradually diminish and storms will transition to producing brief heavy rain and small hail.
Thunderstorm activity is expected to persist through the overnight hours and continue through Saturday across much of the forecast area. The best dynamics, moisture pooling, and overall chance for storms and heavier rainfall amounts will focus across southwest Idaho. The potential for heavier rainfall across the central Idaho mountains Saturday increases the risk for rock slides and localized flooding, especially near legacy burn scars like the Wapiti fire burn scar.
Precipitation amounts of 1 to 1.25 inches are possible over the central Idaho mountains through Sunday. Eastern Oregon can expect 0.25 to 0.75 inches, while the Snake River Plain will generally see between 0.25 and 0.50 inches. Above 6,500 feet, up to 3 inches of wet snow is possible Saturday night into Sunday. Temperatures will plummet to around 20 degrees below normal Saturday and Sunday, with several locations forecast to approach record low maximum temperatures both days. Near-record low temperatures are also possible across southeast Oregon Sunday morning.
Convective activity and overall precipitation chances will begin to taper off early Sunday as the system starts to exit the region. Gradual warming and drying will follow Monday and Tuesday as the weekend upper low moves away into central Canada, though a continuing chance of showers and thunderstorms will remain in the northern mountains. Another cold upper-level low will approach from the British Columbia coast on Wednesday, though forecast confidence beyond that point is low due to model disagreement on the track and intensity of this second system.
Tonight
Showers and possibly a thunderstorm. Low around 52. North wind 5 to 8 mph becoming calm. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Saturday
Showers and possibly a thunderstorm before noon, then a chance of showers and thunderstorms after noon. High near 68. Light west northwest wind becoming northwest 6 to 11 mph in the morning. Winds could gust as high as 23 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Saturday Night
A slight chance of showers before 2am, then a slight chance of showers after 4am. Cloudy, then gradually becoming partly cloudy, with a low around 46. Northwest wind 5 to 10 mph, with gusts as high as 22 mph. Chance of precipitation is 20%.
Sunday
A 30 percent chance of showers, mainly after noon. Partly sunny, with a high near 65. West northwest wind 5 to 10 mph, with gusts as high as 22 mph.
Sunday Night
A 40 percent chance of showers, mainly after midnight. Mostly cloudy, with a low around 47.
Monday
A 20 percent chance of showers before noon. Partly sunny, with a high near 72.
Monday Night
Mostly cloudy, with a low around 49.
Tuesday
Mostly sunny, with a high near 80.
Tuesday Night
Mostly clear, with a low around 52.
Wednesday
Sunny, with a high near 82.
Wednesday Night
Partly cloudy, with a low around 54.
Thursday
Mostly sunny, with a high near 87.
Thursday Night
Partly cloudy, with a low around 56.
Friday
Sunny, with a high near 86.
