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Here's why it will be so unbearably hot this weekend
(NWS NOAA)
A heat wave is coming.
Most of the US will be gripped by dangerously high temperatures this weekend. According to the National Weather Service, some places will see temperatures as much as 10 to 15 degrees Fahrenheit above average for this time of year.
The temperatures are expected to be so much higher than normal because of a meteorological event called a heat dome. That is when a dome of high pressure in the upper atmosphere traps warm air beneath it. Under the dome, the air sinks toward the ground, becomes more compressed, and heats up even more — often to dangerous levels, as are expected this weekend.
The heat dome, which is expected to be especially large this time, will envelop the Midwest first and then move eastward over the weekend. This is why eastern Missouri and southern Illinois are expected to see a high of 100 degrees on Friday. New York is expected to see a high of 97 degrees Fahrenheit on Saturday, according to Weather.com.
This heat dome formed largely because of the jet stream, LiveScience reports. This time of year, the jet stream is farther north, passing roughly over the border between the US and Canada. It effectively prevents cooler air from pushing southward into the country.
But that's not all. Not only is the heat expected to be unbearable in parts of the country, but the humidity will make it feel worse — in other words, the heat index, which factors in humidity and raw temperature, will increase. For example, the heat index in eastern Missouri is forecast to be 105 to 112 this weekend.
The heat dome is a high-pressure mass. Because air flows clockwise around the center of high-pressure systems in the northern hemisphere, the heat dome will suck up humid air behind it from the Gulf of Mexico as it moves east.
The Midwest #heat advisories originate via air from the warm & humid Gulf of Mexico combining w/crop moisture- yuck! pic.twitter.com/no5J2sGtqb
— Eric Blake (@EricBlake12) July 21, 2016
In other parts of the country, such as the Midwest, the heat dome will be compounded by a weather phenomenon known as corn sweat, NBC news reports. That happens when water is released from the leaves of crops such as corn into the atmosphere, making it extra muggy.
While eastern cities, like New York, will most likely be spared the effects of corn sweat, they are still likely to be hotter than the surrounding areas because of the "urban heat island effect." Heat in urban areas is absorbed by concrete and asphalt and trapped between tall buildings. The heat is also enhanced by vehicles, factories, air conditioners, and pollution. As a result, cities are generally 1.8 to 5.4 degrees Fahrenheit warmer than their surroundings, according to the US Environmental Protection Agency.
A lot of things are coming together to make it really hot this weekend, so be sure to take precautions to be safe and follow the advice from the National Weather Service: Stay indoors, limit strenuous activities outside, drink lots of water, don't leave anyone alone in a car, and find a local cooling center if you don't have access to air conditioning.
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