Clear northerly flow to bring frost

Cool, dry weather is replacing the gusty winds that whipped across the Inland Northwest on Saturday night and Sunday, and forecasters are warning that a northerly flow is all but certain to bring the region’s frost-free growing season to an end this week. Highs today are expected to reach the upper 50s or lower 60s, but tonight’s lows should bring frost to most locations. The forecasted low for Spokane and Coeur d’Alene is 31. Mostly sunny weather is expected throughout the week with highs near 60 each day. A narrow ridge of higher air pressure, expected to reach toward the North Pole by mid-week, is turning the upper-level air circulation to flow out of the north this week, bringing colder-than-normal overnight temperatures, according to the National Weather Service. If frost doesn’t strike gardens tonight, the cold is sure to freeze sensitive plants by the end of the week when an arctic front is forecasted to plunge southward out of western Canada, bringing lows down to the upper 20s by Thursday night and then to the middle 20s by Friday night. The northerly flow also is bringing clean air to the region. This morning’s air quality index in Spokane was at 14, which was well into the good range for air quality and among the lowest readings to occur. In Spokane on Sunday, sustained winds of 26 mph and gusts to 40 mph were reported. Grant County Airport at Moses Lake reported sustained winds to 30 mph and gusts to 39 mph. The wind whipped up a dangerous dust storm in the upper Columbia Basin, closing Interstate 90 on Sunday between Ritzville and Moses Lake along with other roads and highways in the region. Eight people were injured in a five-vehicle accident late Saturday night. Power was out to 8,000 Avista Utilities customers and to about 1,500 Kootenai Electric customers. Most power had been restored by this morning. The dewpoint in Spokane this morning was 22 degrees, which is an indication of how cold and dry the atmosphere is in the wake of the northerly winds over the weekend. At 7 a.m., temperatures were 38 at the airport in Spokane, 41 in Coeur d’Alene and Sandpoint, 34 at Deer Park and 39 in Pullman.