A strong upper level ridge that’s been parked in the desert Southwest will amplify over the inland northwest today bringing hot and dry conditions with afternoon high temperatures expected to be over 100 degrees. Smoke and haze will also continue and will likely increase across the region throughout the day. The hot/dry weather will promote more smoke generation from local fires especially in the north Cascades. The light winds associated with the ridge will likely lead to a gradual increase in smoke over the region. Per coordination with various air quality agencies, several counties are under Air Quality Alerts including Chelan, Douglas, Grant and Okanogan counties until 10:00 a.m. Friday.
By Thursday, an increasingly unstable atmosphere is a concern especially Thursday afternoon where a Fire Weather Watch remains in place marking the beginning of a critical fire weather period. Several Excessive Heat Warnings and Heat Advisories remain in place beginning this afternoon and running through Thursday where we could see highs tomorrow near 106 degrees, which would break the old record of 104. By Friday, a weak cold front will move through kicking up our winds to around 10-20 mph and cooling us down slightly into the mid and upper 90’s. Also, by late afternoon a marine push associated with the main cold front will break through the Cascades and will sweep across the basin during the evening hours.
The hot, dry and breezy conditions of Friday alone will justify the current Fire Weather Watches…however, there is an added risk of thunderstorms developing during the day over the high Cascades and then forming over parts of the basin during the evening hours. These storms, if they occur at all, will likely be high based initially and promote dusty gust fronts with lightning but little rain.
By the weekend, Saturday will be noticeably cooler and downright comfortable after this week`s sweltering conditions with high temperatures back to or even slightly below normal. The cold front and associated trough will be gone by Sunday and the region will come under a weak zonal flow or weak ridging leading to mainly dry conditions through the middle of next week and increasing but not overly hot temperatures. Highs on Saturday will be in the lower 80’s, upper 80’s on Sunday and back to the 90’s for Monday and Tuesday.