Overall, the Southeastern U.S. has been exceptionally dry over the last two weeks other than some places getting the typical summertime pulse thunderstorms. The coverage of storms today has been a little more widespread across the Southeast due to a weak frontal boundary that has helped to spark up some activity with the help of daytime heating.
You can thank the persistent deep-layer high pressure ridge over the Southeast for the very hot and dry conditions that have been in place this month. The locations that have been most inundated by heavy rain have been along that “ring of fire,” which is the area right around the suppressing ridge. From Texas/Oklahoma through the Ohio Valley into the Northeast are the locations that have had well-above average rainfall, especially over the last 14 days.
Percentage Of Normal Rainfall Over The Last 14 Days:
Much of the eastern half of the U.S. is going to either remain or become more unsettled in the coming days. As I discussed last night in my article, after a couple more days of excessive heat, the Southeast ridge is going to weaken and break down as a trough digs unusually far to the south and ridging builds over the Pacific Northwest into Canada. A rather active northern jet stream (a fast-moving column of air in the upper-levels of the atmosphere) is currently located in the northern U.S. and will begin pushing pretty far southward.
In response to this digging trough and active jet stream, surface low pressure will develop and move across the Ohio River/Tennessee Valley and northeastward, dragging a cold front well into the Southeast, which will bring an increased risk of heavy rain/stormy conditions this weekend for the Southeast, Ohio/Tennessee Valley, and into parts of the Great Lakes and Mid-Atlantic/Northeast.
WPC’s 3-Day Rainfall Map For Tonight Through Saturday Night:
It’s likely that this cooler pattern will persist right into July, but as I mentioned last night, I’m not ruling out that the Southeast ridge won’t try to build back in, which could warm areas farther south back up. The region located between the two air masses could be the zone for heavy precipitation into July. Getting the details ironed out on that possible location will take some time. Please stay updated at Firsthand Weather.