Massive Heat Dome Will Envelop Much of U.S. Later This Week

Tom Moore
Published: July 17,2016
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 during the second half of this week as a dome of high pressure builds in the upper atmosphere, providing favorable conditions for expanding heat across much of the nation.
By Thursday, summer heat will be the dominant weather theme as temperatures really soar.
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Sweltering Days Ahead

In addition to the hot temperatures, 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, Des Moines, Iowa, and St. Louis will see highs from the mid 90s to near 100 degrees during the second half of this week with heat indices above 100 degrees. Low temperatures will be in the 70s.

Forecast Maximum Heat Index Thursday

Plains cities like Wichita, Oklahoma City and Dallas will see highs near or exceeding 100 degrees with heat indices near 110. Lows will be in the upper 70s to near 80.
The sultry temperatures will also impact parts of the South late this week where highs will range from the middle 90s near 100 degrees, including Nashville and Raleigh.

Forecast Highs

By next weekend, the ridge of high pressure may nudge its way into the Northeast. This would allow very hot temperatures to engulf parts of the Northeast and mid-Atlantic regions. Highs in the middle to upper 90s are possible
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.

Atmospheric Heat Dome

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

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 this 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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