Heat and humidity will continue across the central and southern states as an upper ridge expands over much of the country. As the ridge expands eastward over the next few days, much of the eastern third of the country will see a resurgence of the record breaking heat experienced last weekend.
A cold front slowly pushing through the Great Lakes on Thursday and Friday should drop far enough southeastward to provide portions of the Upper Midwest some relief from the extreme heat by the end of the forecast period. Areas of thunderstorms are expected as the tail end of the front stalls across the Northern Plains. To the west of the upper ridge, active monsoonal flow will drag moisture up along the Gulf of Baja toward the Desert Southwest and Four Corner states. The increased moisture will result in numerous late afternoon/early evening showers and thunderstorms across the region.
Heat and humidity will continue to be the story across the central and southern states as a resilient upper ridge expands over much of the country. A huge area of Excessive Heat Warnings and Heat Advisories have been issued across the Midwest where the combination of high temperatures and dewpoints will bring heat index values into triple digits and make for extremely dangerous conditions. As the ridge expands eastward over the next few days, much of the eastern third of the country will see a resurgence of the record breaking heat experienced last weekend. In addition to the heat, scattered afternoon thunderstorms are expected across a moist and unstable air mass in place from the Gulf Coast to the Tennessee Valley.
There is a slight risk of severe thunderstorms from the northern and central High Plains to the central Great Lakes and Ohio Valley. Yesterday, there were over 340 reports of hail and high winds over the East Coast and northern Plains. One apparent path of severe weather stretched from west central lower Michigan to northern Virginia with another concentration in Vermont and New Hampshire.
At 200 AM PDT the center of Tropical Depression Four-E was located about 620 miles south of the southern tip of Baja California. Movement was toward the west-northwest near 13 MPH and this general motion is forecast to continue today. A turn toward the west is expected by Friday. Maximum sustained winds were near 35 MPH with higher gusts. Some strengthening is expected during the next 48 hours and the depression is forecast to become a tropical storm later today.