Tuesday will bring another warm day across southwest Idaho and southeast Oregon, but changes are already starting to take shape as a stronger storm system approaches the Pacific Northwest.
Thunderstorm chances increase this afternoon, mainly across the higher terrain of central Idaho and portions of the Western Magic Valley. While many valley locations could stay dry, storms that do develop will be capable of producing gusty outflow winds up to 45 mph and small hail. Temperatures will remain about 5 degrees above normal, with valley highs climbing into the upper 80s to around 90 degrees.
Another round of showers and thunderstorms is possible Wednesday. Storm coverage is expected to increase across the central Idaho mountains during the afternoon, where some storms could produce heavy rain and small hail. Eastern Oregon will begin to feel the first push of cooler air as the larger system moves closer.
The biggest change arrives Thursday as a strong area of low pressure moves into the Pacific Northwest. Temperatures will fall quickly, with highs running 10 to 15 degrees cooler than Wednesday. Rain will become more widespread from west to east throughout the day, with southeast Oregon and the central Idaho mountains favored for some of the heavier rainfall. A few thunderstorms could also develop within the larger area of rain.
Cool, wet and unsettled weather continues into Friday. Around a half-inch of rain could fall in some locations between Thursday and Friday, with locally higher totals possible. Persistent clouds and rain will keep Friday especially cool, with valley highs only reaching the upper 60s to lower 70s.
The heaviest rain should begin shifting east by Saturday, but the unsettled pattern will stick around through early next week. Daily chances for afternoon showers and isolated thunderstorms will continue, especially over the mountains. Temperatures will gradually warm through the weekend and into Tuesday but are expected to remain slightly below normal for early September.
