Doyle Rice

USA TODAY

Powerful tornadoes, giant hail, damaging winds and drenching rain are forecast to strike Oklahoma, Texas and Kansas late Tuesday, AccuWeather predicts.

The storms, expected near Dallas, Oklahoma City and Tulsa, Okla., and Wichita, Kan., could be the biggest severe weather outbreak to strike so far this year, with the largest number of reports of tornadoes, large hail and damaging winds, AccuWeather said. Hail could exceed 3 to 4 inches in diameter.

A tornado watch was posted for the area, meaning conditions are favorable for tornadoes to develop. The watch was in effect until later this evening.

Almost 11 million people from southern Nebraska to central Kansas, and central Oklahoma and into northern Texas could be at "moderate risk" to experience severe storms, the Storm Prediction Center (SPC) said. Several school systems in Oklahoma closed for the day due to the threat, according to the Daily Oklahoman. The worst of the storms are expected to hit in the evening.

Moderate risk is the second-highest of the five categories the center uses for predicting severe weather, according to weather.com.

Cities including San Antonio and Austin were in a "slight" risk area for severe storms Tuesday.

The types of storms expected Tuesday "have the greatest potential to produce numerous tornadoes," including wedge tornadoes at least as wide as they are tall that could move along the ground for an extended period of time, AccuWeather's Andrew Gagnon said.

Additional isolated strong storms could rattle the Ohio Valley and Mid-Atlantic regions, including New York City, Washington, Baltimore, Philadelphia and Cincinnati, but the storms should not be as destructive as those in the central U.S.

Voters going to the polls in primary elections states such as Maryland, Delaware and Pennsylvania could encounter some heavy rain and a few thunderstorms in the late afternoon and early evening.

Another chance of thunderstorms enters the forecast Thursday evening and remains through Saturday. The Storm Prediction Center forecasts the possibility of yet another round of potentially severe thunderstorms Friday for parts of Oklahoma and North Texas.