The second-worst category of drought has spread to include a large swath of southern Arkansas, the National Weather Service said Thursday.

The latest U.S. Drought Monitor, which reflects conditions through Tuesday, shows about 14 percent of the state under extreme drought. The area comprises all or part of the southern-most row of counties as well as Bradley, Drew, Lincoln, Cleveland and Desha counties.

Only about 5 percent of the state was under an extreme drought last week.

John Robinson, warning coordination meteorologist for the weather service in North Little Rock, said the increase was "no surprise" given a lack of rain, but some relief is likely on the way.

Thunderstorms are possible over most of Arkansas Thursday night through Friday night.

"The moisture content of the atmosphere is greater than normal for this time of year, suggesting that there will be some locally heavy downpours," Robinson said in an email. "What we do not want to see, however, is all the rain come down at once. When the ground is dry and hard as it is now, especially in southern Arkansas, too much rain all at once leads to too much runoff and not enough rain soaking into the ground."

None of Arkansas is under the worst category of drought, exceptional. Nearly 30 percent is under at least a severe drought and nearly 40 percent is under at least a moderate drought.

A year ago, conditions were far worse with extreme drought covering about 42 percent of the state.