Massive Heat Dome Will Envelop Much of U.S. Next Week

Tom Moore
Published: July 14,2016
Since June, many regions of the U.S. have experienced periods of hot temperatures, but most heat waves have been relatively short-lived. That'll all change next week as a dome of high pressure builds in the upper atmosphere, providing favorable conditions for expanding heat across much of the nation.
By the second half of next week, summer heat will be the dominant weather theme as temperatures really soar.
(MORE: Check the Forecast for the Next 10 Days)

Sweltering Days Ahead

NOAA's 6- to 10-day outlook shows above-average temperatures are likely across most of the nation.

NOAA's latest 6- to 10-day temperature outlook clearly illustrates where the core of the heat will be centered next week. A large swath from the Plains and the Midwest to the Great Lakes has a 70-percent or higher chance of seeing above-average temperatures from July 19 to 23.
Additionally, heat indices – a measure of how hot it feels – will be dangerously high with values in the 110- to 100-degree range in some locations.
For example, Midwestern cities like Chicago and Minneapolis will see highs in the mid-90s by late next week with heat indices above 100 degrees. Low temperatures will be in the 70s. Plains cities like Wichita, Oklahoma City and Dallas will see highs exceeding 100 degrees with heat indices near 110. Lows will be in the upper 70s to near 80.
These conditions can be particularly dangerous for vulnerable groups such as the sick and the elderly. The National Weather Service offered useful heat safety tips that can be incorporated into a daily routine when extreme heat sets in.

• Job sites: Stay hydrated and take breaks in the shade as often as possible.
• Indoors: Check up on the elderly, sick and those without air conditioning.
• In vehicles: Never leave children or pets unattended – look before you lock.
• Outdoors: Limit strenuous activities and find shade. Drink plenty of water and avoid alcohol.

A massive dome of high pressure aloft means widespread heat across the nation next week.

Atmospheric Heat Dome

So far this summer, there have been a couple of high-pressure ridges aloft (bulges in the jet stream) that have prevailed across the U.S. One ridge was positioned around the Western U.S., and the other was in the Southeast. The Western ridge has occasionally expanded a bit to the north and east, while the Southeast ridge has expanded north and west, but only for short periods of time.
As next week progresses, we will see a bridging of these ridges resulting in one massive dome of high pressure. Beneath this dome, air sinks and warms, resulting in hot temperatures. Under these conditions, thunderstorm activity will become sporadic, so many areas will be dry.
The exception could be parts of the Northeast, especially New England, where this pattern sometimes allows cold fronts to back into the area from the northeast. Thunderstorms and somewhat cooler temperatures can result.
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