Flooding downpours to linger in wake of Claudette

Parts of the southeastern United States will get a break from heat and humidity this week, but other areas are likely to face more downpours that can lead to flooding in the wake of damage caused by Tropical Storm Claudette this past weekend.

Claudette dropped up to a foot of rain in parts of Mississippi and spawned several tornadoes that tore up some communities. A tornado that hit East Brewton, Alabama, Saturday morning was rated as an EF2 and injured 20 people, according to National Weather Service survey crews.

Gusty winds well away from the Gulf Coast knocked down trees. A tree that fell onto a home in Tuscaloosa, Alabama, claimed the lives a 24-year-old man and a 3-year-old boy on Saturday, according to The Associated Press. A multiple-vehicle crash along Interstate 65 in Butler County, Alabama, amid the storm Saturday killed 10 people, including eight children, the AP reported.

Claudette emerged over the western Atlantic Monday after it strengthened back into a tropical storm over eastern North Carolina early in the morning. The storm moved off the coast of North Carolina and Virginia and accelerated east-northeastward at 28 mph as a cold front moved across the eastern U.S., and began ushering in a push of cooler and less humid air to the region.

The front associated with the leading edge of cooler and less humid air set up numerous downpours and thunderstorms across the South on Tuesday night. This is the same front that spawned a tornado in the suburbs of Chicago during Sunday night. AccuWeather forecasters say some communities in the South can be hit with flash flooding and damaging wind gusts as storms erupt.

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Drier air is forecast to continue to sweep southward and eastward on Wednesday, but only to a certain point. Drier air will not reach into the Gulf of Mexico or well off the southern Atlantic coast, AccuWeather Meteorologist Randy Adkins said.

"As this front pushes southward and eastward a bit on Wednesday, storms will shut off over northern parts of Louisiana, Mississippi, Alabama, Georgia and South Carolina, as well as western and central portions of North Carolina," Adkins stated.

However, farther south, the risk of downpours and locally gusty storms will continue along the I-10 corridor through the end of the week.

"Since this front will stall along the Gulf coast and the flow of moist air from the Gulf is forecast to persist, showers and thunderstorms are likely to repeat over and over in some communities to the point where there is a risk of flooding," Adkins explained.

This repeating downpour pattern is referred to as a "training effect" and can unload inches of rain over many hours, causing flooding in low-lying and poor drainages areas such as streets, highways and neighborhoods.

Some parts of the Gulf Coast and the coasts of Georgia and South Carolina as well as the northern part of the Florida Peninsula may pick up 4-8 inches of additional rain this week.

The risk of flooding will occur over portions of the Gulf Coast that were hit with several inches of rain from Claudette over the weekend.

"It is in these areas that were hit with heavy rain this weekend and then more rain this week, where the risk of flooding is greatest," AccuWeather Meteorologist Brandon Buckingham said.

The downpours could persist and hamper cleanup efforts in some locations that were hit with tornadoes in southern Alabama and southwestern Georgia this past weekend.

On the other hand, for some locations, the push of dry air will bring relief from summertime humidity that much of the South is known for. For people living near and north of I-20, the reduction in humidity will be noticeable and especially so for areas in northern Georgia, upstate South Carolina and much of North Carolina. In these locations, dew point temperatures can drop into the 50s F.

The dew point is the temperature to which the air must be cooled to become saturated. When dew points are high, people may feel uncomfortable with a sticky feeling from lingering perspiration. Some people with respiratory ailments may have difficulty breathing. When dew points are low, moisture from the skin evaporates very quickly and some people with respiratory problems may have fewer issues.

During the summertime, a dew point temperature in the upper 60s is common for Atlanta and a dew point temperature near 70 is common in Charlotte, North Carolina. In South Florida, a summer dew point temperature in the middle to upper 70s is typical.

"During most episodes of dry air in June, July and August, dew point temperatures may dip into the lower 60s and provide noticeable relief, but when dew point temperatures dip as low as they are expected to be at midweek across the interior south, the weather can be especially delightful and comfortable for some people," Adkins said.

The drier the air becomes, the more likely temperatures will be to dip at night as well. Midweek nighttime low temperatures are forecast to be in the middle 60s around Atlanta and near 60 in Charlotte. High temperatures are forecast to be within a few degrees of 80, instead of the upper 80s to near 90, which is more typical for the latter part of June.

Later in the week, the cooler and drier air is forecast to retreat northward and allow a more typical pattern of warm and humid conditions to set up across the interior South.

The new pattern will also lead to showers and thunderstorms letting up some along the Gulf and southern Atlantic coasts -- or at least allow them to become less concentrated over the area. However, moist air flowing in from the Gulf of Mexico and the Atlantic may lead to numerous showers and thunderstorms, more so than an average summer day, across the Southeast in general.

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