A ridge of high pressure present across most of the country will be responsible for intense heat across portions of the eastern US or at least above average temperatures. Combine that with humidity and instability in the environment and that will allow for thunderstorms to develop, thus making for a toasty yet unsettled weekend for many across this part of the country.
High temperatures across the East will range from up to 10 degrees above normal across most of the Midwest, Great Lakes, and from the Gulf Coast through the interior Northeast. Meanwhile the Southeast and portions of the East Coast will feel quite nice with temperatures closer to slightly below average.
High temperatures in the 80s and 90s will be commonplace for most on Saturday. While the Northern Plains and the Mid-Mississippi River Valley bakes with temperatures into the 90s, storms and cloud cover will keep portions of the central Midwest cooler yet still in the 80s.
Not only will it be hot but it will also be humid. Dew points will generally range from 65 to 75 degrees across the eastern US. The only exception is across coastal sections of the Mid-Atlantic where the air mass will feel quite pleasant thanks to dew points in the 50s to low 60s, which is quite unusual for mid-July. Dew points of this magnitude will reach as far south as the Raleigh, North Carolina area.
As an almost daily occurrence in the South during the summertime, hit or miss showers and thunderstorms will pop up across the Gulf Coast states as well as into the Mid-Mississippi River Valley during the afternoon before dissipating in the evening thanks to the sunshine and instability. An easterly wind coming off of the Atlantic Ocean will stabilize the atmosphere and prevent much convection from occurring, however, in the Mid-Atlantic and the Carolinas.
Into the Midwest, especially the greater Chicago area, flash flooding will be a concern on Saturday as heavy rain and thunderstorms affect the region during the morning hours before a separate area of thunderstorms forms to the south and east during the latter half of the day.
Interior portions of the Northeast, including northern New England, may also have to dodge showers and storms, mainly in the afternoon. There may even be a few isolated storms that produce damaging winds and small hail in portions of New York and Pennsylvania thanks to wind shear crossing through overhead.
On Sunday, the heat will build over the Southern Plains as the dome of high pressure drifts to the west, allowing for widespread high temperatures into the upper 90s to low 100s. Temperatures to the north and east will also be quite toasty into the 80s and 90s in the Midwest, Northeast, Mid-Atlantic, South, and Southeast.
Meanwhile in the Northern Plains and interior Northwest, the first of two cold fronts will allow for relief from the heat, cooler temperatures down to over 10 degrees below average in some locales. Since it is July, however, it will still be mild with high temperatures in the 70s to low 80s.
Dew points, or humidity, will increase across the Eastern Seaboard on Sunday, especially in the Mid-Atlantic where on Saturday the dry air made the heat bearable. Now while it will increase, it won’t be dramatic. This added moisture will bring that feels-like temperature up by a few degrees.
No question more storms develop across parts of the eastern US on Sunday. Multiple clusters of rain and thunderstorms will already be present by daybreak on Sunday, including across interior portions of the Northeast and back into the Mid-Mississippi River Valley. The convective activity won’t be as widespread as on Saturday with storms becoming more isolated across the Southern Tier — except for the Florida Panhandle and southern Georgia — while storms become a bit more common from the Ohio River Valley through southern New England.
Flash flooding will be a concern with some of these storms, especially in the Midwest region. There may also be a severe component to a few of the storms in the northern Mid-Atlantic and southern New England regions. The main risk will be damaging winds with any of these storms that turn severe thanks to the wind shear present in the atmosphere.
A more substantial cold front will be responsible for big changes in the weather across the eastern US by mid-next week, bringing a more widespread area of storms to the midwestern US on Monday, then to the East Coast on Tuesday. Seasonable temperatures and drier air will then follow for the latter half of the week, but the pattern will remain active across the nation’s midsection.