As a result, there were some power outages in the south Sound today (some still going on)





Last night, very cold, dry air surged southward out of Canada, pushing into Washington and Oregon.The pressures, temperature, and wind map for 8 AM this morning tells the story (below). The blue is cold air, with the primo stuff east of Cascades. Note the large pressure difference across the Cascades, which resulted in strong easterly winds in the Columbia Gorge and in Cascade mountain passes.You should, since we have usually high pressure at the surface right now. For example, at Ellensburg, in the central portion of the State,, reaching nearly 1040 hPa (mb).Does it feel kind of dry? It should, sicne e have some of the driest air in a very long time over us--yes the driest since the start of the year--as indicated by the very low dew point temperature at Sea Tac Airport. Dew point is a good measure of the amount of water vapor in the air (and it is the temperature at which air becomes saturated when cooled). This morning it got down below zero (in fact, -4F). Mama Mia...that is super dry. Even drier than the arid period last March when downslope winds started fires around western Washington.The large pressure difference across the Cascade resulted in easterly winds accelerating to 50-60 mph around Enumclaw and Tacoma today and similar winds around the Columbia Gorge and some of the highest hills in eastern WA (see below, click to expand).With very dry air above, the greenhouse warming effect of water vapor in the atmosphere will be lessened, and our temperatures should plummet tonight. Be prepared for lots of frost when you go out tomorrow morning--and some cooler areas away from water will drop into the teens.This cool dry air will slowly warm, but expect sunny skies and cool nights for the rest of the week.The cold air moving south has an Amazon Prime account and the delivery will be overnight. By tomorrow morning, the cold, dense air and associated high pressure will have moved southward through Nevada, setting up a large pressure difference across the Sierra Nevada (see map below for 5 AM Wednesday).Southern California will face a real challenge with a powerful Santa Ana wind descending to the ocean by 5 AM Wednesday (see below). The most severe winds (sustained 50 mph with gusts to 80 mph) will be east and north of downtown LA, but substantial winds will be felt southward down to San Diego.The winds will weaken a bit by 5 PM Wednesday (see below), but will be more than strong enough to sustain any fires that started earlier. It is crucial to turn off the power to a lot of folks in southern CA tomorrow. Turns out the Getty Fire was the result of trees on powerlines--just a taste of what is possible with the far more powerful winds overnight.