A deep arctic air mass is forming in Alaska and Canada today, and is forecasted to move southward into the Inland Northwest starting about midday Sunday.
Lows could dip into the low single digits starting on Sunday night with the cold hanging around at least until Wednesday, according to the National Weather Service.
Daytime highs on Monday may only reach 11 degrees in Spokane and 10 in Coeur d’Alene before rebounding to the teens on Tuesday.
The cold could be accompanied by north to northeast winds, especially along the Purcell Trench in North Idaho and the Okanogan Valley, which typically become pathways for arctic air that hugs the ground and migrates through mountain openings.
Spokane city officials recommended that residents protect pipes from freezing. Warming centers for the homeless have been put on alert that they may be activated by the city.
The cold will follow a round of light snow and freezing fog in the Spokane area this morning that caused some problems for drivers.
The National Weather Service had cautioned drivers to slow down because roadways may become hazardous.
Freezing drizzle was falling in Spokane earlier in the morning before changing to light snow. Light fog had also settled over the area. By 10 a.m., the stratus clouds and fog were lifting and the drizzle and snow had subsided. Fog continued in Pullman.
The slight chance of snow flurries remained in the forecast for the rest of the day. Cloudy conditions were reported in Coeur d’Alene and other locations across Northeast Washington and North Idaho.
Forecasters said a weak frontal system was dropping southward out of Canada and carrying light amounts of precipitation today, and another frontal system on Saturday will continue the chance of snow at 20 percent.
In both cases, higher air pressure behind the fronts is expected to whip up cold north winds and bring arctic air to the region by Sunday night. A strong high pressure system along the West Coast has been creating the north-to-south flow in the weather this week and it will intensify Sunday.
Highs on Monday may only reach 10 to 12 degrees during the day with lows a few degrees above zero. Temperatures should start to rebound on Tuesday and Wednesday.
Before then, highs should reach the upper 20s today and lower 30s Saturday before the frigid air starts pouring across the Canadian border on Sunday and Sunday night. A low of 6 degrees is expected Sunday night. Tonight’s low should be about 21.
At 7 a.m., it was 21 at Spokane International Airport, 22 at downtown Spokane, 19 at Coeur d’Alene and Pullman and 17 at Deer Park.