A weak shortwave ridge of high pressure will transition through the Inland Northwest today. Mostly sunny skies are expected in Northcentral Washington today with increasing clouds late, light wind with afternoon high temperatures in the upper 70’s to lower 80’s.
By Thursday, the weak ridge exits allowing a Pacific area of low pressure to set up off the British Columbia coast with a series of shortwaves of moisture pivoting around the circulation, and funneling in more moisture into the region under the southwest flow aloft. With that being said, Thursday will be mostly cloudy with a 30% chance of showers mainly after noon, mild temperatures too, with daytime highs in the upper 70s to lower 80s and overnight lows in the upper 50s and lower 60’s.
Two low pressure systems and an elongated trough will near the west coast on Friday. One low will move towards Vancouver Island, the other toward Central/Northern California. The weaker low, the one going into California, will move inland Friday and bring an area of instability and moisture to the region. Showers will start in the Cascades and portions of Northcentral Washington in the morning and then become region wide by the afternoon and evening hours. There will be thunderstorms as well as cool air aloft mixes with our warm surface temperatures. The Wenatchee Valley and Columbia Basin will see mostly cloudy skies Friday with a 40% chance of showers and Thunderstorms with afternoon high temperatures in the lower 80’s. Some thunderstorms could contain lightning, gusty winds and hail.
A series of very weak weather systems will move through the state Saturday through mid-week with partly to mostly cloudy skies for Northcentral Washington, cooler afternoon highs too, with temperatures each day in the low to mid 70’s.