I have been forecasting around here for a long time and have never seen a situation like this, with ash falling around western Washington and a smoke cloud so dense one would think it is low stratus deck. No sun was visible this morning.
I am mean this is something new.
Outside my home there is ash on all horizontal surfaces. To illustrate, here is a photo taken by Logan Johnson, the head of the Seattle NWS office, from his home in Bothell. His car looks like it has a bad case of dandruff.
At the UW we have a device called a ceilometer, that can measure the base of clouds by shooting a laser vertically and measuring the return. Here is a plot of the last 48h (time in UTC--12:00 is 5 AM). Around 2-3 AM, it started to pick up a lot of stuff in the lower atmosphere....probably the ash fall.
The visible satellite photo this morning at 8:30 AM (below) shows dense smoke everywhere, with some high clouds above in places (particularly offshore). I never seen anything like this around here over the past 30 years.
The Seattle Space Needle cam showed sharply reduced visibility...and no sun.
And unfortunately, our low-level air quality, which held up yesterday, is rapidly declining (see plots of small particles...PM2.5.. at Seattle and Tacoma).
A regional summary of air quality over the Northwest is amazing with extremely poor (purple) and very poor (red) air quality at many sites. Northern Idaho and SW Oregon/NW CA are in very bad shape.
Now the bad news. As the surface heats up and vertical mixing increases, more of the smoke will be mixed down. Air quality will probably decline in western WA.
Why did the bottom drop out last night? Because the easterly flow (from the east) increased in the lower atmosphere as the the thermal trough moved northward. This is shown by a time-height cross section at Seattle-Tacoma Airport (time increases to the left, in UTC, temperature in red, winds in blue, heights are in pressure, 850 is roughly 5000ft)
This is clearly the worst smoke year in Seattle that anyone can remember.
from Cliff Mass Weather and Climate Blog http://ift.tt/2gKx7d5
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