Significant heat will return to the western US this week while the South remains hot as a blocking weather pattern remains in place over the nation. A large heat dome will intensify slightly while drifting back to the west, becoming centered over the desert Southwest. The combination of a persistent 597-plus decameter ridge over the desert region will make for big heat in the foreseeable future. This heat dome will likely sit over the same spot through at least the end of July and likely into the start of August, keeping temperatures above average in most parts of the West and South.
Heat alerts this Monday span from southern Louisiana through much of Texas and across the desert Southwest. Those alerts will also be scattered up the West Coast and span as far north as western Washington. This indicates abnormally warm temperatures that may reach dangerous levels.
This Monday, temperatures will be up to 25 degrees above average in the Pacific Northwest, translating to highs generally into the 90s. In Seattle, the city is forecast to experience a high temperature of at least 88 degrees for 7 days in a row. That would break the current record of 5 days. Now while heat of this magnitude is uncommon for this region, it won’t be record-breaking in terms of daily temperatures. Highs will also be up to 20 degrees above normal in Texas with the exception of the Panhandle. Actual high temperatures in the state will be in the 100s in most areas. Some towns will even hit or exceed 110 degrees, including Dallas-Fort Worth area. Elsewhere west of the Rocky Mountains, high temperatures in the valleys will get into the 90s and 100s. In the desert, some areas may approach 120 degrees, which is record-breaking.
The heat will intensify slightly on Tuesday as geopotential heights of the upper-level ridge of high pressure top off at 600 decameters over the Four Corners states. It’s not often heights with any ridge reach 600 decameters, so that is a huge signal for big time heat. High temperatures across the West will remain in the 90s and 100s. In the desert, the 110s will be more common. Death Valley, one of the hottest places in the country, may even reach all the way up to 120 degrees. For a perspective, their all-time record high is 134 degrees from the year of 2013. On the other hand, the southern Plains will “cool down” closer to normal with highs still in the 100s in some areas, including in Dallas and Austin.
Temperatures will follow a very similar profile on Wednesday, with high temperatures across most areas into the 90s, 100s, and 110s. A few locations may even reach 120 degrees for a second day in a row. This will likely be the hottest day in Southern California as Los Angeles approaches the century mark. This heat will persist through the end of the month but highs in the 90s and 100s will be more commonplace while highs in the 110s become more scarce.