FastCast—Saturday, Aug. 20 to Friday, Aug. 26:
After two uncharacteristically muggy days in Western Washington, more typical summer weather is ahead for the region through Tuesday, although temperatures will be slightly above average. Through Tuesday, expect lowland highs in the upper 70s to low 80s and lows in the upper 50s to low 60s, much more comfortable than the very warm lows on Thursday and Friday mornings. Conditions in Eastern Washington will remain hot, with highs in the 90s to near 100 in the Columbia Basin. The Coast will be the coolest area of the state, with highs in the upper 60s to near 70. No rain is forecast for the lowlands, but some light showers are possible on the coast and in the mountains on Saturday. Conditions change on Wednesday. The lowlands will endure another heat wave, with temperatures from Wednesday to Friday reaching the upper 80s to low 90s across the area, hottest away from the water. Thursday will be the hottest day, with a higher likelihood of 90°+ temperatures in the lowlands. Lowland lows during the heat wave will be in the low to mid 60s. In Eastern Washington, late week highs will again reach the upper 90s to low 100s. Note: Seattle only needs 2 day with highs above 90° to set a new all-time record for most 90°+ days in a summer.
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Continue reading the full blog below!
Thursday and Friday were very odd days for Western Washington, particularly the Puget Sound Lowlands. These days were some of the muggiest days in recent memory for the area. Dewpoints reached the upper 60s to low 70s, incredibly rare for this region. Typical summer dewpoints are in the 50s, with dewpoints above the low 60s being relatively unusual.
Take a look at the maps below, showing peak dewpoints on Thursday (top) and Friday (bottom).
The dewpoint is the temperature where dew would form on the grass. Higher dewpoints = less comfortable outside.
Friday offered a few degrees of improvement from Thursday, but it was still quite abnormal for the region. Dewpoints near or above 70 degrees are nearly unheard of in the Seattle area, and for such readings to be widespread for two days in a row is one of the most unusual weather phenomena to occur in this area.
Why did this happen? This was the combination of monsoon moisture from the Southwest that brought increased humidity and heat being trapped under the constant mid to high level clouds of the past couple days. It is an odd combination that doesn’t usually occur in the Northwest.
There is good news though…normal temperatures are ahead! The NAM forecast for Saturday shows near average temperatures for Western Washington.
Temperatures on Saturday will be near average for the lowlands, with highs reaching the mid to upper 70s. The coast will be in the 60s, and Eastern Washington will yet again be in the low 90s to near 100. Portland will reach the low 80s.
These are just preliminary, and Western Washington temperatures will likely end up higher than this forecast. Generally, highs in the mid 80s to low 90s can be expected from Wednesday to Friday. The Olympia and Portland areas will reach the upper 80s to mid 90s, and Eastern Washington will reach the mid 90s to low 100s. The coast will be the place to beat the heat…with highs likely in the upper 60s to low 70s.
With a 60-80% chance of above average temperatures over most of the Pacific Northwest, it is likely that temperatures in the 80s will continue for a bit after the next heat wave.
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