Wednesday, August 17, 2016

Possible hot weather and decreased air quality later this week

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From our partners at the National Weather Service. Be careful out there, volunteers!

A Period of Hot Weather and Possible Decreased Air Quality
 Appears Increasingly Likely For Thursday through Saturday

This message is intended as an informational briefing for public safety decision makers. We ask that you continue to monitor latest information using the resources listed below. You are welcome to share this message with others in your organization. Please do not respond to this email. If you need to contact the office, please use the links and information below.

A period of hot weather is becoming increasingly likely Thursday through Saturday in Western Washington. Record high temperatures are possible in Seattle on all three days, and temperatures at night will only cool into the 60s.  There is the potential that maximum temperatures will be higher than currently forecast across the region. 

None at this time.

Offshore flow will strengthen on Thursday as high pressure develops over British Columbia. Air compressing as it comes down off of the Cascades and Olympics will gradually heat the air mass up starting early Thursday and continuing through early in the weekend. Temperatures on the coast and away from the water will likely peak on Thursday, while temperatures in the interior lowlands will likely peak on Friday. Temperatures in the interior on Saturday will likely only cool a couple of degrees from Friday's hot values.  Hot temperatures on Thursday will be accompanied by low relative humidity and breezy conditions -contributing to increased fire danger. Air quality may degrade somewhat on Friday and Saturday as a thermal trough moves into the interior lowlands and reduces circulation.

                      Seattle                  Bellingham            Olympia
Day             Hi/Lo/Rec/Yr         Hi/Lo/Rec/Yr       Hi/Lo/Rec/Yr

Thu 8/18      88/60/88/1991        87/56/86/1965     90/54/94/1981 
Fri   8/19      91/62/89/2015        86/58/84/1950     93/56/94/1961
Sat 8/20       89/63/87/1966        81/59/83/1958     88/56/92/1982

A prolonged period of warm to hot weather across the region will mainly impact people in urban areas who are in poor health. People living in high rise buildings without air conditioning will be most impacted.  Any fires that start on Thursday could grow rapidly in the hot, dry and breezy conditions.   A decrease in air quality Friday and Saturday could affect unhealthy individuals. At this time, impacts are expected to be moderate.

Confidence is high that a period of hot weather will develop on Thursday and will persist into Friday. Confidence is moderate that hot temperatures will persist in the interior into Saturday.

Confidence is moderate that the combination of hot temperatures, low relative humidity, and breezy conditions could contribute to a high fire danger across much of Western Washington.

Confidence is moderate that air quality will degrade somewhat starting on Friday and perhaps persist or worsen Saturday or Sunday.

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Thank you,
National Weather Service, Seattle WA

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