A major pattern shift sets the stage for a dangerous heat dome in the West
Drought areas as of early July.
(CNN) — Yet another brutal heat dome is set to roast part of the United States starting this weekend as part of a major weather pattern change.
The East Coast was in the hot seat last week and the West is next up for a heat dome — a large area of high pressure that stalls over an area, trapping heat and driving up temperatures.
High temperatures are expected to soar 10 to 15 degrees higher than normal during the hottest month of the year — well into the triple-digits for some locations. The renewed blast of heat could also raise wildfire concerns.
Some of the most intense heat will center on the Rockies, where some daily records are likely to be tied or broken and a handful of locations could come within a few degrees of all-time high temperature records.
Hazardous extreme heat could also shift into the central US early next week as the heat dome expands, but it will take a few days for forecast confidence to grow.
Heat has long been the deadliest type of weather in the US, but the threat is rising. Heat waves are now longer lasting, more intense and more likely to occur due to emissions from the burning of fossil fuels.
A rapid attribution study found that the combination of extreme heat and high humidity seen in last week’s East Coast heat dome would have been impossible were it not for emissions of greenhouse gases.
Here’s what we know.
Where heat could topple temperature records
Ahead of the pattern change, the rest of this week will be seasonably toasty in much of the West. Temperatures will start to climb to more uncomfortable levels on Friday as a large area of high pressure develops. As it strengthens, the heat dome will also shift the jet stream — the river of air that dictates where stormy weather develops — out of the US and into southern Canada.
Widespread high temperatures in the upper 90s and low 100s Fahrenheit are likely on Saturday from the Rockies into eastern Oregon and parts of California. Areas right along the West Coast will dodge the worst of the heat.
Heat will intensify further on Sunday with high temperatures near 105 degrees forecast in some parts of Montana, Wyoming and the Dakotas.
Billings, Montana, is forecast to climb to around 103 degrees Saturday. The city could then threaten its all-time high temperature record of 108 degrees on Sunday.
Salt Lake City and Grand Junction, Colorado, are in similar situations. Salt Lake City’s all-time high temperature record is 107 degrees, and the city is forecast to top out around 103 degrees Saturday and 105 degrees Sunday. Grand Junction’s highs of around 104 degrees on Saturday and 106 on Sunday are nipping on the heels of the city’s all-time record of 107 degrees.
Heat expands next week
Sizzling conditions will creep farther east by Monday, reaching the foothills of the Rockies and into more of the Plains.
Monday and Tuesday could be the hottest days of the upcoming stretch for the Denver area where the high temperature could flirt with triple digits. The city’s all-time high temperature record is 105 degrees.
Heat will likely expand into parts of the Midwest Tuesday and Wednesday with the Northern Plains and Rockies remaining hot.
Minneapolis is forecast to climb well into the 90s next week which would be about 10 degrees hotter than normal.
Heat in the West and central US will likely stick around well into next week with the heat dome slow to break down over time.
Wildfire concerns
What the heat dome means for wildfire activity in the West is less clear-cut.
Wildfires have burned more than 3.3 million acres in the US so far this year, well above average. Most of this fire activity has been in the West, with destructive fires in parts of Colorado and Utah in recent weeks.
Typically, a heat wave like this would dry out vegetation and make it more susceptible to burning, but the drought-ridden region is already very dry.
Hot and dry conditions are concerning for fire starts but, since the heat dome is a large area of high pressure, gusty winds that would fan flames are less likely during this upcoming stretch.
The expanding heat dome may also help usher some moisture into parts of the Rockies next week as winds shift out of the south. That surge of moisture could help tamp down temperatures but might also support thunderstorm development and lightning strikes.
We’ll continue to monitor what this patten change could mean for wildfire activity.
CNN’s Andrew Freedman contributed to this story.
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