Following on the heels of the hottest June in the history of the lower 48 states, an extended, intense and widespread heat wave is likely to develop next week.
The heat wave will start in the Plains states and parts of the intermountain West, eventually spreading to the West Coast, South and Midwest by Thursday, July 21. The heat wave is also likely to seep northward into southern Alberta and Ontario.
Cities like Dallas, Denver, Oklahoma City, Kansas City, Chicago, Minneapolis, Fargo and eventually New York City and Washington, D.C. may experience sizzling heat and stifling humidity by the end of the week.
During the height of the heat wave, a majority of the contiguous U.S. is likely to see high temperatures well above 90 degrees Fahrenheit, or 32 degrees Celsius. There will also be areas that will see temperatures climb into the 100s Fahrenheit, or above 38 degrees Celsius.
Another hazard may also be found along the northern fringe of the heat dome, from southern Canada across the northern Great Lakes states and into New England. Atmospheric disturbances tend to ripple across the outer edges of such weather patterns, triggering large complexes of severe thunderstorms.
While this is an extended range forecast with details that are subject to change, the warning signs for a major heat wave are present, and have been for several days, in several of the main computer models used to help predict the weather.
Both the European, or ECMWF, and the GFS models are showing the extreme heat developing early in the week and growing more intense and widespread as the week goes on.
One parameter meteorologists look at to judge the severity of a hot or cold streak is the height of a given pressure surface in the atmosphere.
With hot air masses, a particular pressure surface will be found higher in the atmosphere, since hot air rises and causes a bulge to develop that pushes pressure surfaces above where they would normally be located. On the other hand, cold air masses feature below average heights.
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