Today (Monday) dawned with relatively clear skies over Seattle, with some high level smoke that had come from California and a hint of smoke on the eastern horizon. The latter has our name on it.
A number of major and minor fires are burning now (see below), with the eastern slopes of the Oregon Cascades and southern Oregon being particular hot spots. There are some major fires over the eastern slopes of the Cascades, most of them lightning initiated.
Yesterday's MODIS satellite imagery showed the smoky impacts of the fires, with eastern WA getting the blunt of the Cascade fires because the winds were westerly...that is going to change today. Southwest Oregon is a smoke disaster.
Fire behavior varies during the day, with the more stable conditions at night often allowing the fires to "settle down". But during the day, the surface heating can cause the lower atmosphere to become less stable and to mix in the vertical, which can allow fires to explode (or at least to intensify). As fires intensify they can develop deep columns of smoke, often topped by pyrocumulus. This happened yesterday to several of the WA fires.
Yesterday, I was hiking to Burroughs Mt on the north side of Mt. Rainier (with Professor Dan Jaffe of the UW Bothell, one of our region's leading experts in atmospheric chemistry). As we left Sunrise, there was only some stable smoke on the horizontal, but during the next few hours several of the plumes went vertical and developed into mushroom clouds of white and black smoke (see below).
Some of the fire plumes were high enough and substantial enough to be picked up on regional weather radars (see below, the three blue-green areas are fires). The ability to follow fires with weather radars is one reason Senator Maria Cantwell is working to secure some weather radars along the eastern slopes of the Cascades.
Now the problem. For the last few days, western flow off the Pacific has kept air quality (and visibility) decent over western Washington. But during the next 48 h, building high pressure east of the Cascades will allow an area of low pressure (the thermal trough) to build northward out of California and the development of easterly (from the east) flow over the Cascades. Such easterly flow will move the eastern WA smoke over us and warm temperatures (particularly with flow descending the western slopes of the Cascades and thus warming by compression).
Here are the surface pressure predictions (with lower atmospheric temperatures and surface winds).
Red and brown indicate the warmest temperatures (the devil's colors).
8 AM Sunday.
Around 90F today and mid-90s tomorrow would be a good forecast. The big question is how much smoke will reduce the max temps.
And how much smoke? Here is the latest prediction of the Canadian Smoke Model (Firework), showing the surface smoke at 5 PM Sunday, Monday, and Tuesday.
Huge explosion of smoke over the Northwest during the next day with Beijing-like values over much of the area. Yes, red colors are the worst.
The USDA Forecast Service also runs a smoke model and it also shows smoke moving into western WA (5 PM Monday and Tuesday are shown)
Well, you get the message...expect heat and smoke, wherever you are in the region.
Want some good news? Cooling and onshore flow will occur on Wed. and Thursday. And temperatures should drop into a normal range for at least a week. The sun is weakening quickly now, so there is a good chance the real heat is over for the year. But no guarantees.
from Cliff Mass Weather and Climate Blog http://ift.tt/2wyNhMs
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