Weather on the Rim

Over the past week, a massive dome of high pressure has brought extreme heat to the southern U.S.; in the past few days, this atmospheric ridge has drifted westward and has bulged further to the north. Within the dome, where the air is sinking, hot, humid conditions and light winds prevail.

The weather action is along the rim of this ridge where this tropical air converges with cooler, drier air of the High Plains and Upper Midwest. Thunderstorms develop in this collision zone and, due to clockwise flow around the edge of the dome, these storms move in that direction. Lying near the west edge of the rim, the Front Range of Colorado is experiencing an early monsoon season; the heavy rains of that period generally occur in August, in response to similar high pressure over the Southern Plains. In the past week, bands of thunderstorms have also brought torrential rains to the Northern Plains and Upper Midwest as the dome has pushed into those areas. Florida, initially encased within the dome, experienced record high temperatures as the usual sea breeze was shut off; since the ridge has shifted northwestward, this onshore flow has redeveloped in South Florida, producing heavy rains across that region. Meanwhile, as this persistent dome has shunted cold fronts into Canada, the Northeast remains trapped in a stationary trough, with cool, damp conditions more typical of spring.

Last evening, a ripple in the north rim of the dome produced a cluster of thunderstorms which had enough punch to invade the ridge. Moving south, they reached Central Missouri about 10PM, producing strong winds and heavy rain. This morning, the air is noticeably cooler and drier than it has been; unfortunately, the ridge is expected to build back from the south and hot, humid conditions should redevelop by this afternoon.