Dangerously hot temperatures in the central US this week; heat spreads to Northeast by this weekend

Over 42 Million Under Heat Alert

By Tom Moore

A massive dome of high pressure in the upper atmosphere is gripping 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 115 degrees at times during the second half of this week. The heat will also spread toward the Northeast and mid-Atlantic late this week into the weekend.

This map shows the current "feels like" temperatures, or heat index.

Hot temperatures are also pushing into the Southwest, including southern California, through this weekend.

The National Weather Service has issued heat alerts for more than a dozen states in the central U.S., from Minnesota, the Dakotas and Wisconsin to Louisiana.

Heat alerts issued by the National Weather Service.

(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 100- to 115-degree range in some locations during the second half of this week.

(MORE: What is the Heat Index?)

The value displayed is the maximum "feels like" temperatures expected when humidity is factored in.

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 not much 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. Lows may only dip into the middle 70s.

(MORE: Four Things Extreme Heat Does to Your Body)

Forecast high temperatures for the second half of this week.

Eastern States

The sultry temperatures will also impact parts of the Southeast through this weekend where highs will range from the middle 90s to near 100 degrees, including Atlanta, Nashville and Raleigh. Nashville could see its first 100-degree reading since July 2012.

By late this week and into the weekend, the ridge of high pressure will nudge its way into the Northeast. This will allow very hot temperatures to engulf parts of the Northeast and mid-Atlantic regions. Some daily record high temperatures will be within reach.

Washington D.C. and Philadelphia may see highs in the upper 90s to near 100 degrees Friday-Sunday. Highs in the middle to upper 90s are possible in New York City.

If Washington, D.C. hits 100 degrees, it would be the first time that's happened there since July 2012.

Forecast Highs

Southwest Heat

The southwestern states will also heat up through this weekend as the dome of high pressure spreads its wings toward that region of the country.

Highs in the 90s are likely in the Los Angeles metro area through this weekend.

Across the interior of Southern California and into southern Nevada and Arizona, expect readings to top 110 degrees.

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

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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