A dome of high pressure over the Southeastern U.S. is causing two interconnected weather problems. Beneath the dome, air is sinking and heating up, producing hot and humid conditions; afternoon highs have been in the mid to upper 90s F with heat indexes above 100. Along the outer rim of the dome, winds are moving clockwise, drawing Gulf of Mexico moisture northward through the Heartland, eastward across the southern Great Lakes and then southeastward to the Mid-Atlantic Region.
This rim of moisture, caught between the hot central dome and the cooler air to its north and west, is feeding bands of thunderstorms, some of which have spawned tornadoes. Training over the same swath, the storms are also dropping heavy rain and producing regional floods; last evening, the worst of the conditions were affecting Greater Chicago and no doubt sending travel disruptions across the country.
Today, moisture from Tropical Storm Bill in the western Gulf will add fuel to the fire. Pulled inland along the edge of the dome, this copious moisture is expected to produce torrential rain in eastern Texas and Oklahoma, exacerbating the floods that have been plaguing the region. Further north, the plume of moisture is expected to stay south of Chicago, cutting eastward through the Ohio Valley and into southern New England. Until the dome breaks down, this stormy pattern will continue.
