A persistently cold weather pattern has kept severe thunderstorms at bay so far this spring. Tornadoes and reports of damaging winds and hail from thunderstorms have been quite scarce. Most notably, a tornado has yet to form in Oklahoma, the latest in the calendar year on record.

But the weather pattern is undergoing a major rearrangement this week. High pressure off the Southeast coast is pumping warm, humid air into the central and eastern United States, which will set the stage for thunderstorms to erupt as cooler, drier air from the West barges east.

Throughout this week, storms capable of producing damaging winds, large hail and some tornadoes are possible, especially late Tuesday through early Thursday. Each day, the risk of violent weather is expected to intensify and affect more people.

On Monday, the risk of severe storms is at most, “slight” — level 2 on the National Weather Service’s 1-to-5 scale. But the risk rises to “enhanced” — or level 3 — in some areas by Tuesday and Wednesday.

On Monday, the Weather Service has placed a narrow strip from western Texas to southeast North Dakota under an elevated risk of severe storms. About 5 million people live in this area, which includes Lubbock and Amarillo in Texas; Sioux City, Iowa; and Sioux Falls, S.D.

On Tuesday, the threat of severe weather consolidates over west central Oklahoma, Kansas, southeast Nebraska, Iowa and western Wisconsin, but affects nearly 10 million people, including those in Wichita, Omaha, Des Moines and Madison. The Weather Service office serving Omaha warned of a “substantial severe weather threat” with “all modes of severe storms possible.”

By Wednesday, the severe weather risk area expands southward, from central Texas to western Illinois, affecting a population of almost 25 million people, including Dallas, Oklahoma City and Kansas City.

Thursday may present one more opportunity for some vigorous storms over the central U.S., but the risk should diminish by Friday as the responsible storm system zips northward into Canada.

Because it’s been such a quiet severe-weather season so far, Weather Service offices are doing their best to raise awareness about the threat.

The Weather Service office serving central Oklahoma, in Norman, called for “a busy severe weather week.” It dispatched tweets describing the meaning of its risk outlooks and how to interpret them. “Outlooks involve uncertainty about storm development, timing, location and threat. They are NOT precise forecasts,” one graphic embedded within a tweet said.

The Weather Service office serving Wichita conducted a live Twitter question-and-answer session Monday afternoon about the severe weather threat. “We think the highest probabilities for severe storms in the Wichita area will be Wed aftn-evening,” it replied to a question about the day of greatest concern.

While the Weather Service worked to prepare its constituents for the potentially dangerous weather, storm chasers welcomed the start of more turbulent conditions and were reportedly headed toward the Plains in droves.