By Alex Sosnowski, Expert Senior Meteorologist
Aug 30, 2012; 9:30 PM ET
Drenching rain from Isaac is aiming for Arkansas, Missouri, Tennessee and the Ohio Valley states into the Labor Day weekend.
Isaac has unloaded over 10 inches of rain in a significant part of southeastern Louisiana and southwestern Mississippi thus far. Meteorologist Meghan Evans has more statistics on Isaac.
The arrow of that rain, although diminishing, is aiming northward.
Cities in the path of Isaac as a rainstorm include Little Rock, Memphis, St. Louis, Louisville, Indianapolis, Cincinnati and Springfield, Ill.
Soon after heat builds over the region, a rainstorm from the diminishing tropical system Isaac will take an arced path from the lower Mississippi Valley to the Ohio Valley.
There is the potential for a general 2 to 4 inches of rain reaching as far to the northeast as central areas of Illinois, Indiana and Ohio.
In the core of the storm, local amounts of 6 to 8 inches are possible in the Ohio Valley with the potential for a foot of rain in eastern parts of Arkansas and southeastern Missouri.
Eventually, some moisture in the form of steady rain or spotty showers and thunderstorms will reach into the Northeast as well.
There is no doubt that the rain will be greatly beneficial to these areas from a hydrological and agricultural standpoint. However, there will be a rather abrupt northern and western edge to the rainfall, and heavy rainfall could be rather spotty in part of the Tennessee Valley.
Chicago and Detroit will be on the northern edge of the rain. A front dropping in from Canada may scoop up some of the moisture at the last minute.
In addition, while the ground will soak up a tremendous amount of rain, too much could fall too fast for the ground to absorb leading to flash flash flooding in some locations. Paved and concrete surfaces absorb virtually no water so the risk of urban flooding is elevated in the downpours.
Even though the tropical system is aging, it still brings the risk of locally severe thunderstorms, near and south and east of the center. The greatest risk is for damaging wind gusts, but a couple of brief tornadoes could be produced.
While there is a risk of severe weather, a repeat of widespread damaging winds from another iStorm, Ike from 2008, is not likely to be repeated over the Ohio Valley.
Motorists are reminded to avoid driving through flooded roadways and to slow down on wet highways to reduce the risk of hydroplaning and to provide a buffer for emergency braking.
The rain will follow a late-summer heat wave in progress over much of the Midwest. Temperatures have peaked in the 90s from Little Rock to Cincinnati.
Unfortunately, Isaac’s rain will not reach everywhere with many areas in the Plains missing out.
Temperatures soared above 100 degrees in Nebraska and the Dakotas Wednesday. Pierre, S.D., recorded their latest 110-degree temperature Wednesday. The high in Pierre was 111.
Triple-digit heat was reaching Kansas City and Omaha Thursday.
During Friday, temperatures will peak well into the 90s in Chicago for the second day in a row and are forecast to reach the 90s in Detroit.