A large heat dome will dominate the weather pattern through early next week over the Eastern US. This large area of high pressure will reach heights upwards of 591 decameters at times, which signifies an atmosphere that is conducive for dangerous heat. The center of this dome will drift from over the Mississippi Valley to Mid-Atlantic and central Appalachian Mountains over this weekend. This ridge of high pressure will then weaken mid-next week as a new pattern change takes place and forces the ridge to weaken. Despite its weakening, it will still remain in tact fairly well over the southeastern US, so above-average temperatures will likely takeover this region in the mid-range time period.
Heat Advisories and Excessive Heat Watches and Warnings are in place across a large amount of land in the Midwest. This includes Chicago, St. Louis, Des Moines, Kansas City, and Minneapolis. These heat alerts are in place by the National Weather Service to warn how dangerous this heat can be.
On Friday, record highs may fall across portions of the Upper Midwest as high temperatures soar into the 90s across much of the region. Closer to the Canadian Border in northern Minnesota, it will be a tad cooler into the 70s and 80s. Farther south and west into the Central Plains, highs in the 100s will become commonplace. In both the Midwest and Northern Plains, temperatures will be 15 to 25 degrees above average. Across the East overall, high temperatures in the 80s and 90s can be expected, except for the Northeast where it will be cooler into the 60s and 70s thanks to an upper-level disturbance passing through from the north.
The heat will begin to expand into the Northeast while continuing to dominate across the Midwest and Northern Plains where highs will be 15 to 25 degrees above average for a second day straight on Saturday. Most areas east of the Continental Divide will experience high temperatures in the 80s and 90s. The only exception will be in portions of the Dakotas and northern Minnesota. Most areas will not break a record daily high, but one or two locations will still be at risk in the Upper Midwest. That includes Madison, Wisconsin where temperatures will soar into the mid 90s.
On Sunday, the heat and humidity will continue to pump into the Midwest and now the Northeast. This heat will remain dangerous. Most locations that will experience high temperatures in the 90s will also see heat indices in the 100s. Staying in an air-conditioned environment is the best key of advice. If you are outside, try to cool off in a pool and be sure to drink plenty of water. About a dozen record highs are forecast to be tied or broken on Sunday, including in Chicago, Des Moines, St.Louis, Cleveland, and even a few locations in the Northeast. The only difference between Saturday and Sunday is that the Northeast will become hotter. High temperatures in this part of the country will soar into the mid to upper 80s to the low to mid 90s, except for Maine where it will remain seasonable warm.
That will change on Monday. A cold front will dig through the Upper Midwest and Northern Plains, dropping high temperatures down into the 70s. Meanwhile, most areas in the Southern Plains, Southeast, Midwest, southern Great Lakes, and Northeast will get in on high temperatures in the 90s. Even localized locations in the Mid-Atlantic and along the I-95 corridor in the Northeast may top off at 100 degrees. This will definitely break the record high temperatures. In some of these cities, the lowest record high out of all of June occurred on this date, so it will make it slightly easier to break. About 2 dozen cities, mainly in the I-95 corridor, are at risk for breaking their record high.
On Tuesday, the heat will continue to become eroded. Much of the Plains, Midwest, Great Lakes, northern Mid-Atlantic, and New England will cool off with high temperatures generally in the 70s and 80s. This air will be more seasonable, and even up to 10 degrees below average in the Plains. The Mid-Atlantic will continue to bake, however, as this area experiences temperatures of up to 15 degrees above normal. That means another day of highs mainly in the 90s will be ahead.
For the latter half of next week, temperatures will become seasonably warm across most of the East, with high temperatures generally at or up to 5 degrees above average thanks to the weakening heat dome.