The upper-atmospheric setup for the U.S. Northwest heat wave week of 5 July 2015. A strong dome of high pressure means continued record heat wave. Graphic: The Weather Channel

By Jon Erdman and Nick Wiltgen
4 July 2015 (The Weather Channel) – While it may not be quite as hot as last weekend in some areas, there appears to be no end in sight to this torrid heat wave in the West. June and even a few all-time record highs have already been shattered in parts of the interior Northwest, northern Rockies and Great Basin. The extreme heat is likely to last into next week and may end up breaking records for longevity as well. For example, the six-day period ending Thursday was the hottest stretch of six days on record dating to 1877 in Boise, Idaho. Through the holiday weekend, daily record high temperatures will be threatened in some cities, including Seattle, Yakima, and Spokane in Washington, Portland and Eugene in Oregon, and Helena, Montana. Medford, Oregon, tied its daily record on Wednesday (108 degrees). Eugene, Oregon, set daily record highs Wednesday (99 degrees), Thursday (101 degrees) and Friday (100 degrees). Seattle also set daily record highs on Thursday (93 degrees) and Friday (92 degrees). In Montana, daily records were set on Friday in Kalispell (95 degrees) and Helena (98 degrees). The culprit in this hot setup is a dome of high pressure aloft, surging northwestward to encompass a large area of the western states. The center of this high will shift around through the holiday weekend, but overall it will remain a dominant feature. This will allow the sizzling early-July sun to send temperatures soaring in the Pacific Northwest, northern California, interior Northwest and northern Rockies.  Highs well into the 90s and triple digits are expected in many lower-elevation locations west of the Continental Divide and inland from the Pacific Coast this holiday weekend and into next week. This includes the Salt Lake Valley, Idaho’s Snake River Plain, much of Oregon’s lower elevations east of the immediate coast, and areas to the east of the Cascades in Washington State. In particular, parts of the Columbia Basin and lower Snake River Valley will see particularly extreme and persistent heat. This includes cities such as Yakima, Kennewick, and Walla Walla in Washington as well as Lewiston, Idaho. Temperatures will surge towards the low to middle 100s through the holiday weekend. These very hot conditions have led to heat advisories for portions of the Northwest including Seattle, Portland, and Eugene. [more]

Western Heat Wave Enters Second Chapter; More Record Highs Through Holiday Weekend (FORECAST)