A wildfire blazing about 20 miles northeast of Portland, Ore., exploded in size Sunday, forcing thousands from their homes and putting tens of thousands more on notice that they may have to flee. The Nakia Creek Fire covered roughly 1,565 acres as of Monday and was about 5 percent contained. Officials warned that the situation was “very dynamic” and anyone nearby should be prepared to evacuate. …There was no lightning on October 9 when the blaze began, and Washington State officials believe the fire was probably human-caused and is under investigation. …People living in more than 2,900 homes had been ordered to evacuate as of Sunday because of immediate danger. Residents of more than 33,000 other homes faced warnings that they may need to leave if fire conditions near them worsen. …Portland International Airport has gotten only 0.31 inches of rain since Sept. 1… Thirteen other large blazes are burning in Washington and seven are active in Oregon.