A powerful ridge of high pressure will take control across the Western U.S. this weekend and into early next week, resulting in a late summer Northwest heat wave extending from the Pacific Coast into the Northern Rockies and high plains.
The heat will initially build near the west coast on Saturday and Sunday, including Portland and Seattle, before shifting across the entire Intermountain West on Sunday and Monday.
Take a look at the 500-millibar height anomalies projected for Monday. A strong ridge such as this during August can be referred to as a “heat dome”.
Numerous heat advisories and excessive heat warnings are already in effect across the Northwest, even west of the Cascades.
So just how hot is it going to get?
For many areas, highs will reach the mid 90s and into the low 100’s from this weekend through early next week. Record highs will certainly be a possibility.
On Saturday, the heat will arrive in Oregon with high temperatures topping out close to 100 in Portland and Eugene. Farther south, the heat will be even more extreme with a forecast high of 105 in Ashland and 110 in Medford!
On Sunday, the heat builds north into Washington and east into the Interior West and Northern Rockies.
High temperatures will reach the 90s in Seattle and around the Puget Sound region, with 100’s extending into central and eastern Washington, including Spokane, as well as into Boise and the western Snake River Plain of Idaho.
Farther east, 90s will become widespread across the valleys and plains of Montana as well.
By Monday, the ridge of high pressure will strengthen over the Intermountain West with upper 90s and 100’s across Eastern Washington, Eastern Oregon, and Southern Idaho and highs in the mid to upper 90s across much of Montana and Wyoming.
The heat will start to relax some along the Pacific Coast and surface winds switch to onshore.
What about in Canada? Yes, the heat will extend north of the border up into British Columbia and Alberta as well, especially on Sunday and Monday.
Here is a look at the Canadian Model projected temperatures across BC and Alberta on Sunday in Celsius. Remember, 30 degrees Celsius = 86 degrees Fahrenheit and 32 Celsius = 90 Fahrenheit, as a point of reference.
The hottest temperatures will occur across the interior valleys of BC and along the Canadian Prairies east of the Rockies. Vancouver is expecting a high of 29 C (84 F) on Sunday, before the heat relaxes on Monday.
The ridge of high pressure will start to weaken slightly and become less amplified starting on Tuesday. As a result, the heat wave will start to subside.
However, above average warmth is largely expected to continue across the Northwest U.S. outside of the coastal regions for the foreseeable future, quite possibly through the end of August.