Major heat wave to swallow U.S. as records fall in Pacific Northwest


Large parts of the Lower 48 are expected to cook this week after a prolonged and punishing heat wave that set records across the Pacific Northwest edges to the east and south. Few regions will be spared as the heat spreads across different areas each day, scorching the Northern Rockies on Monday, the central states on Tuesday and Wednesday and the Northeast on Thursday.

There will be no escaping the heat in Texas, which has already endured a historically hot summer. Temperatures there are expected to remain above normal – with mostly triple-digit highs – throughout the week.

The heat wave has its roots in the Pacific Northwest, where it set longevity records in Seattle and Portland.

Combined with a historically severe drought, the heat has fueled dangerous conditions for the spread of wildfires in Northern California, where the new McKinney Fire is devouring the landscape. The fire, located in the Klamath National Forest, has burned down 51,468 acres and is entirely out of control.

2 die in McKinney Fire, now California’s biggest blaze this year

As the heat wave expands eastward, it will bring triple-digit heat to 43 million Americans. Heat advisories are already being issued in the Plains states, and it is likely that excessive heat warnings will be rolled out in some cities in the coming days.

Records plummet in Northwest and Northern California amid growing fire danger

Relief is finally coming to the Pacific Northwest after a week of scorching heat, though another day of triple-digit highs are expected in eastern parts of Washington and Oregon.

Seattle set a record for its longest stretch with highs at or above 90 degrees. The previous record was a tie between two five-day periods in 2015 and 1981. It hit 94 degrees on Tuesday, 91 on Wednesday, 94 on Thursday and Friday, and 95 on Saturday and Sunday.

Portland also had a record breaking spell of heat, with a full week of consecutive days at or above 95 degrees ending on Sunday. The previous record was a tie between a six-day span in 1941 and another in 1981. The city’s average high in July is 81.8 degrees, and yet three days between July 25 and the end of the month reached the mark of the century.

In Medford, Oregon, it was as high as 114 degrees on Friday, just one degree off its all-time high. Tri-Cities Airport near Kennewick, Wash., hit a high of 110 degrees Thursday, 112 Friday and 109 Saturday.

Warm weather across the West fueled a spate of wildfires in Oregon and Washington, but the McKinney Fire in northern California is the region’s most severe blaze. It burned an area roughly twice the size of Disney World, as high temperatures helped to parch the landscape and the ground is full of dry fuels available to burn.

How dry is this area of ​​California? The ERC, or Energy Release Component, is 97%. It is a number related to the amount of fuel per unit area available to burn. Values ​​above 80% reflect a propensity for dangerous forest fires; at 97%, explosive wildfire growth is possible.

High temperatures, amplified by the effects of human-induced climate change, are contributing to larger and more extreme wildfires. Eighteen of California’s 20 largest wildfires have occurred in the past two decades.

Extreme heat seeping eastward in the short term

As the Pacific Northwest heat wave subsides, the area responsible for high pressure – or heat dome – will sink to the southeast and be absorbed by another heat dome that extends from the Four Corners to Florida. The combined heat domes will at times bend to the northeast in the coming days.

Heat advisories have already been issued over the Plains, Ozarks and Corn Belt, encompassing St. Louis, Kansas City, Omaha, Des Moines, Sioux Falls and the Twin Cities.

The core of the heat will settle over the central states on Tuesday and Wednesday, and could expand into the northeast on Thursday.

Here are the day-to-day hotspots:

  • Many records between 90 and 105 degrees are predicted across the eastern Pacific Northwest and the northern Rockies from eastern Oregon to central Montana, including Billings, Helena, Great Falls and Missoula.
  • Triple-digit highs are forecast for much of the area from Texas (away from the coast) to western Nebraska. While predicted highs aren’t until the mid-90s in Missouri, heat indices are forecast to reach 100 to 110, including in St. Louis.
  • High temperatures of at least 100 degrees are predicted from Texas (away from the coast) to South Dakota, with heat indices of up to 105 to 110.
  • Highs in the 90s are expected to cover much of the South and Midwest, with a massive area posting heat indices of 100 to 105, including Dallas, Oklahoma City, Wichita, Omaha, Des Moines, Kansas City, St. Louis and Little Rock. Heat indices flirting with 100 could extend as far north as Minneapolis.
  • The heat is concentrated from Texas to Illinois, with widespread forecast peaks of 90s to 105s and heat indices of 100 to 110. The heat index could reach 100 as far north as Chicago and Detroit.
  • The heat is spreading in the northeast. Boston and Hartford, Connecticut, Both are expected to reach 96 degrees on Thursday, and Albany, NY, could climb to 98. That would tie a record set in 1955. Highs in the mid-90s are projected from DC to New York, with heat indexes of 5 to 10 degrees. upper.
  • Most of the southeast will be in the low to mid 90s, but oppressive humidity will push heat indices into the upper 90s or even near 100.
  • Across the plains, upper 90s or lower 100s are likely. Dallas, Austin and San Antonio should see highs of 103 or 104 degrees.

Plains to continue cooking in the longer term

Additionally, a look at the extended range suggests this heat dome could languish for a week or more, possibly until mid-August as it consolidates over the plains.

Here’s a look at how hot it could get:

  • The upper 90s to the lower 100s spread from Texas all the way north to the Canadian border, peaking at around 102 degrees in Rapid City, SD That would tie a record set in 1964.
  • Some cooler air sinks into the northern plains, but highs into the 90s and low 100s extend from Texas to Iowa.

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