A greater-than-expected amount of smoke came down from British Columbia into the Puget Sound region today and rapidly has dropped air quality across the region to between moderate to unhealthy. Given the south-southwestward trajectory of the Canadian wildfire smoke, the worst air quality this afternoon (unhealthy) has been just along and west of Puget Sound, with locations toward the foothills of the central Cascades actually having better air quality.
Of note, the strong push of smoky air down the Fraser River valley of British Columbia caused strong winds at Bellingham earlier today. The compressional heating of this downslope air flow caused a spike to 100 degrees at the Bellingham Airport, which set a new record for the warmest August day on record there.
Tonight and Friday, expect more wildfire smoke to move in, and we will also mix in a bit of central Washington smoke as well. The details as to where the worst smoke will be and when are murky just due to the nature of how smoke moves in and settles in the lowlands, but an Air Quality Alert has been issued for all of Western Washington except our far southern and southwestern counties until Saturday. Expect Friday’s smoke to be worse than today’s and folks who are more susceptible are warned to stay inside as much as possible.
After highs in the 90s in many areas today, morning lows Friday will be in the 60s – warmer than average. The urban areas around Seattle, in particular, will cool most slowly tonight given the abundance of concrete and buildings which cool off more slowly at night. Most of the night in urban areas will be in the 70s to low 80s, bottoming out only in the mid-to-upper 60s around daybreak. With smoke in the air, very difficult cooling conditions indeed for those without air conditioning. An Excessive Heat Warning is in effect for all of the Puget Sound region.
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Highs Friday will be near today’s highs except not as hot around Bellingham. While forecast models have plenty of mid-upper 90s around the central and south Sound Friday, the smoke in the air will probably shave several degrees off daytime high temperatures. My high of 95 for Seattle still is a daily record high for Friday, with the old record 92 back in 2002.
Central Washington will have highs in excess of 100 Friday. The coast will be cooler with highs in the 70s to near 80. This is a sign that more onshore flow will bring relief from the heat and smoke in the interior of Western Washington, eventually.
Saturday will be much cooler at the coast but still in the 80s to near 90 around much of Puget Sound south of Everett. The good news is that skies will clear of smoke through the day Saturday and we should have good air quality back by Saturday night.
Sunday will be much cooler with a few clouds, fresh air and highs in the 70s to low 80s.
A weak disturbance brings more clouds and the chance for a few showers on Monday. Highs will be in the 70s with a slight warming trend back to near 80 by the middle of next week. Smoke should not return anytime soon after this bout of bad air.
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