A weather pattern change is slowly underway. A shortwave storm system dropping down from British Columbia is riding down the front side of the de-amplifying positively titled ridge of high pressure over the Eastern Pacific. While cooler air is funneling in behind it, under sunny and breezy weather today, afternoon high temperatures today will still be well above normal near 90 degrees.
By Tuesday and Tuesday night, the weak positively tilted ridge continues to weaken and flattens to a zonal flow with jet stream positioned within close proximity, if not directly overhead of Washington and Idaho. Coupled with the passing of a cold front this weather pattern will allow dry and breezy/windy conditions, which will heighten concerns for spread of any new and existing fires. The Wenatchee Valley can expect sunny skies tomorrow with west wind 15-20 mph and highs in the mid 80’s.
On Wednesday, a rather large upper level area of low pressure sags southward down from Canada and a significant portion of it overhangs above Northeast Washington and North Idaho. The resulting tight pressure gradient produced at the surface by this change allows for continued robust breezy/windy conditions and much cooler conditions. Sunny skies again on Wednesday with west winds 10-15 mph with gusts to 30 mph, highs on in the mid 70’s.
Thursday, the coldest air ass of the week will settle over the Pacific Northwest with mostly sunny and much less wind with afternoon highs once again only in the mid 70’s.
Friday through Monday, the upper level trough sticks with us Friday and into the weekend. This will continue the unsettled weather pattern with showers and thunderstorms focused over the higher terrain and to a lesser extent, the lower elevations. The air mass will also begin modifying Friday, which will bring subtle warming into the weekend. Expect Northcentral Washington temperatures on Friday to be in the lower 80’s and lower to mid-80’s on Saturday with mostly sunny skies. By late Sunday into Monday, a more organized low will move through the Pacific Northwest. If this comes to fruition, a better chance of widespread showers will be possible in addition to some breezy conditions Sunday afternoon across the Columbia Basin, Waterville Plateau and Wenatchee Valley with a 20% chance of showers and high temperatures near 80 degrees.