Thursday, 3 August 2017

Record high temperatures threaten the Pacific NW

Pacific Northwest threatened by hottest weather ever recorded; Seattle could hit 100
Jason Samsenow

26 November, 2014

An overpowering dome of hot air has entrenched itself over the Pacific Northwest and is primed to cook population centers like Seattle and Portland in record-crushing heat through Friday.

Excessive heat warnings blanket the western third of Northern California, Oregon and Washington state. High temperatures just inland from coastal locations are forecast to soar to between 100 and 110 degrees.

We are talking about one of the major sustained heat waves in a long time around here,” writes Cliff Mass, professor of meteorology at the University of Washington. He said that “there is a lot of confidence” temperatures will at least reach the mid-90s in Seattle and notes the GFS model projects a high of 100 on Thursday — a reading he can’t “remember ever seeing”.

Seattle has posted only three days in the triple digits in the last 123 years. The hottest temperature ever recorded in Seattle was set July 29, 2009, when the mercury reached 103 degrees.

If Seattle hits triple digits on Thursday or Friday, it’ll be the third time in the past 23 years — after reaching it only once in the first 100 years of weather observations,” notes The Seattle Weather blog. It has never before hit 100 in August.

The National Weather Service office serving Seattle said high temperatures are likely to be within five degrees of all-time highs.

Mass said in Seattle the heat wave would be “major” but that in Portland it would be “historic.”

In Portland, the National Weather Service office serving the region says the temperature could surge to 107 degrees or higher, which would match or exceed its hottest temperature on record (at any time of year) of 107, set in 1942, 1965 and 1981. Only smoke flowing into the region from British Columbia could put a lid on temperatures, preventing all-time highs. “With that said, several daily high temperature records will certainly be shattered in the interior,” the Weather Service said.

Statistics geek will find fascinating that the GFS model predicts temperatures near the surface in Portland to be seven standard deviations (7 sigma) from the mean Thursday. In plain English, this means that this is an incredibly rare and extreme heat situation.

Temperature difference from normal forecast Wednesday late afternoon by GFS model. (

The hottest temperatures in the region are expected in Oregon’s southern interior where highs could approach 120 degrees. Medford’s all-time record high of 114 degrees, set July 20, 1946, could be threatened.

These sweltering temperatures, 20 to 30 degrees above normal, are expected in a part of the country not accustomed to such heat. The New York Times reported Tuesday that only a third of Seattle has air-conditioning. Seattle is opening cooling centers to help its citizens find relief.

The heat is the result of an unusually intense high pressure system aloft, sometimes referred to as a heat dome. The core of the heat dome is forecast to drift northward allowing more moderate temperatures to replace the punishing heat this weekend.

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