Dangerously Hot Temperatures Expected This Week as Massive Heat Dome Envelops Much of U.S.

Tom Moore
Published: July 18,2016
A massive dome of high pressure in the upper atmosphere will grip the nation's midsection this week, providing favorable conditions for dangerously hot temperatures.
In parts of the central U.S., heat index values will be up to 110 degrees (locally higher) at times this week. The heat will also spread toward the Northeast late this week into the weekend.
The National Weather Service has issued heat alerts for more than a dozen states in the central U.S.

Heat Alerts

(MORE: Check the Forecast for the Next 10 Days)
Here's a look at what to expect.

Sweltering Days Ahead

Central States
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 this week.

Forecast Maximum Heat Index Thursday

For example, Upper Midwest cities like Omaha, Nebraska, and Des Moines, Iowa, will see highs from the upper 90s to near 100 degrees during the second half of this week with heat indices well above 100 degrees. Low temperatures will be in the 70s, providing little relief at night.
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.
In the Great Lakes, Chicago and Detroit may see highs in the middle to upper 90s with heat index values topping 100 degrees Thursday-Saturday.

Forecast Highs

Eastern States
The sultry temperatures will also impact parts of the Southeast through late this week where highs will range from the middle 90s near 100 degrees, including Atlanta, Nashville, and Raleigh.
By late this week and into the 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.
Washington D.C. and Philadelphia may see highs in the upper 90s to near 100 degrees Friday or Saturday. Highs in the middle to upper 90s are possible in New York City.

Forecast Highs

Heat Safety Tips

The hot conditions this week will 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.
MORE: Hydrating Foods For Summer