An abnormally early heatwave is in the forecast for the Pacific Northwest this weekend, which may bring record breaking highs — or at the very least multiple days of uncomfortable and potentially hazardous daytime and nighttime temperatures.
A strong ridge of high pressure is forecast to build over the West, pushing from the U.S.-Mexico border all the way north into Canada’s Northwest Territories. At the same time, this will force a trough of wet, cool air south in the eastern U.S. Sound familiar? This is the weather pattern that dominated U.S. weather for basically the entire winter.
What it means for the West now that we’re at the end of June is extreme heat that could span multiple days into next week. Though models tend to have a hard time with the strength and duration of these “blocked” weather patterns, they do suggest that the ridge is going to stick around through at least Wednesday next week, cranking up the temperature as it lingers over the region.
High temperatures in Pacific Northwest could run up to 35 degrees above average starting Saturday according to recent runs of the GFS model. The National Weather Service is forecasting actual high temperatures between 100 and 110 degrees every day from Saturday to Tuesday for Washington state east of the cascades.
In the meantime, an excessive heat watch is in effect for non-coastal areas of southwest Washington state and northwest Oregon from the coastal range to the Cascades. “This is abnormally early for a heat wave of this magnitude,” the Weather Service writes. They warn to avoid exertion outdoors, and to stay hydrated — and most importantly, do not leave pets or children unattended in cars, which when left in the heat can surge to temperatures over 150 degrees in fewer than 10 minutes.
Nearly all of Oregon and Washington are in some state of drought as of Thursday, according to the U.S. Drought Monitor. In lieu of rains, the additional heat this weekend and next week could dry out wildfire fuel even more. With dry thunderstorms in the forecast, lightning could ignite the region’s wildfire season in a matter of days.
— Daniel Swain (@Weather_West) June 24, 2015
The National Weather Service in Spokane, Wash., notes this weekend could be some of the biggest heat on record for the region. “If this verifies, the 102F at Spokane would not only be a record for the day,” the Weather Service writes. “It would be the hottest June day ever in Spokane (the current record is 101F set in 1992). That’s a significant record that could be broken. In fact, a number of locations could set their record for the hottest June day ever.”
However, there’s still a lot of uncertainty in the forecast, and models are pumping out a wide range of solutions in the strength of the ridge and potential cloud cover. And, the Weather Service notes, this exact forecast has busted before: “We had a similar hot forecast for this time of year 2 years ago, and some unexpected showers resulted in cooler temperatures than forecast.”
10-day GFS forecast raw numbers for Boise … temps max out at 108° … potential of at least 8 days 100°+ pic.twitter.com/nRRXjGwFxJ
— Ryan Maue (@RyanMaue) June 24, 2015
According to weather.com’s Jon Erdman, Salt Lake City; Reno, Nev.; Missoula, Mont.; and Portland, Ore., are at risk to break all-time June high temperature records.
In Boise, Idaho, the National Weather Service is forecasting highs over 100 degrees every day from Saturday until at least Tuesday. Highs on Sunday and Monday could push 110 degrees, and Boise’s all-time high temperature for any day is 111 degrees, most recently set on July 19, 1960.