Heat wave to bring 106 degrees to Portland, National Weather Service predicts

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    The National Weather Service has revised its forecast for Wednesday and Thursday in the Portland area, setting 106 degrees as the predicted high for those days and warning that one model had temps hitting a whopping 113 degrees.

    A high of 106 would be one degree short of tying the city’s record high temperature — 107 degrees, which was reached on Aug. 10, 1981; Aug. 8, 1981; and July 30, 1965.

    On Friday, the weather service had predicted a high of 101 on Wednesday and a high of 95 on Thursday.

    Additional computer modeling has added to the weather service’s belief that 106 degrees is possible, service meteorologist Will Ahue said.

    The model that predicted a high of 113 is one of dozens that meteorologists ran, Ahue said. The likelihood is “very low” that temperatures will reach quite that high, he said.

    “We have a strong upper level (high pressure) ridge building over the area with a strong thermal trough centering over the Willamette Valley,” Ahue said.

    He explained the phenomenon further in an email to The Oregonian/OregonLive:

    A strong upper level ridge of high pressure is forecasted to build into the Pacific Northwest next week. This ridge of high pressure will essentially place a large dome of hot air over the region. The reason for this is that the air under the ridge is sinking and as it sinks it is compressed and heats up. A strong upper level ridge will generally bring warm and dry conditions at the surface during the summer, especially without the influence of the marine air.

    The predicted high on Monday is 91, on Tuesday it’s 98 and on Friday it’s 99.

    The Portland area’s high temperature Saturday, Aug. 5, is expected to drop to 87 as “the high pressure shifts inland and the trough moves inland,” Ahue said in an interview. Earlier this week, the weather service had expected Friday to begin reflected the cooling trend.

    Also on Saturday, government officials said they are taking steps to prepare for the extreme heat.

    “We are opening discussions with TriMet, fire (and) the Portland Bureau of Emergency Management,” said Michael Cox, spokesperson for Mayor Ted Wheeler.

    “We’re going to try to get moving on some cooling centers,” Cox said.

    TriMet’s MAX trains are limited to 35 miles per hour when temperatures exceed 100 degrees, spokesperson Roberta Altstadt said. When temperatures exceed 90 degrees, the speed is reduced by 10 mph in high speed areas, she said, noting that MAX trains can hit 60 mph in those areas.

    When high temperatures hit the city, Portland Police Bureau officers typically “will check on people who they believe might be in distress and needing assistance,” spokesman Sgt. Chris Burley said, adding that officers sometimes are supplied with bottled water to hand out to people.

    Portland General Electric is expecting power to flow as normal. About two-thirds of PGE’s residential customers have some kind of air-conditioning in their home, spokesman Stan Sittser said. 

    “The electrical grid is built to handle extreme temperatures,” Sittser said. He added that “those high temperatures will put the grid to the test.”

    A lot of hydro power is available due to abundant rain and snow this winter, Sittser said. Also, some customers allow the company to adjust their power use during times of high electrical demand.

    — The Oregonian’s Carli Brosseau contributed to this report.

    –Allan Brettman

    abrettman@oregonian.com

    503-294-5900

    @allanbrettman

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