A flat ridge of high pressure aloft will buckle as a weak Pacific weather system brushes through the Inland Northwest this afternoon and evening. This will lead to breezy westerly winds for the Columbia Basin, Wenatchee Valley and Waterville Plateau this afternoon out of the northwest 15-25 mph with gusts as high as 30 mph. Under mostly sunny skies today, expect another warm one, with afternoon high temperatures in the lower 90’s. The combination of the breezy winds and dry conditions this afternoon and early evening will elevate the risk of fire spread in grass and sagebrush, especially from the Central Cascade valleys into the Columbia Basin. Winds will gradually taper off overnight, while westerly downslope winds continue in the Cascades.
Behind the passage of the cold front, a broad upper trough will be over the Inland Northwest for Friday as a weak impulse rotates across northeast Washington and north Idaho in the afternoon. With this weak system, temperatures will cool back to seasonal levels with high temperatures tomorrow in the mid to upper 80’s.
By Saturday and the weekend, the broad trough shifts eastward, leaving a dry northwest flow over the region with mostly clear skies. Temperatures begin warming on Saturday too with daytime highs across Northcentral Washington in the lower 90’s. Confidence remains high for a strong warming and drying trend for the upcoming weekend and early next week.
High pressure over the Eastern Pacific will expand inland allowing the heat dome currently over the Desert Southwest to nose northward. In response, all global models support a 1-3-degree warming trend each day from Saturday through Tuesday. This will begin to feel quite warm compared to the cool weather we have become accustomed to for much of July and those sensitive to heat may want to check on those air conditioners.
Under sunny skies, Sunday will start off in the mid-90’s while Monday, Tuesday and Wednesday will jump into the upper 90’s. Greatest risk for triple digit heat will be in the lower Columbia Basin and along the Snake River Valley including Moses Lake, Othello, and Mattawa but Omak, Wenatchee, and Lewiston will be within a few degrees.
Spokane will now have a good shot of reaching 90 degrees by Monday. If this occurs, the 119-year-old record for the latest date to hit 90 will remain intact. The National Blend of Models gives Spokane International an 88% chance of hitting 90 on Monday which has come up from 20% two days ago.