Two tornadoes passing through Oklahoma this evening left at least four people dead and destroyed dozens of houses, according to state and local officials.
News of the storm system gave the search for survivors in Joplin new urgency.
The storms are predicted to move into the Joplin area between 8 p.m. and 2 a.m. tonight, according to Bernie Rayno, expert senior meteorologist at Accuweather.com.
The city is still staggering from the EF-5 tornado that tore through the city on Sunday, the deadliest single tornado in more than 50 years.
Rayno said that a strengthening jet stream combined with "directional sheer," meaning changing wind speeds at different atmospheric heights, are textbook factors in tornado creation.
"There are not enough quotes to describe what could happen tonight," Rayno told ABC News.
The threat of more tornadoes comes as search and rescue teams struggle to find survivors. More than 750 people were injured in the storm Sunday that caused widespread devastation to the small midwestern town.
Want to help? Here is a list of organizations.
A Joplin, Mo., Tornado Recovery Facebook page has been created for people reaching out for information about lost loved ones.
Details have emerged that the massive tornado may have had two cyclones inside -- called "a multiple vortex."
"You don't go to bed at night thinking something like this would happen," Gov. Jay Nixon said this morning. "I was down here for graduation on Saturday, gym was filled with 4,000 of the happiest people you're ever going to see and the next thing I hear is that we've got a tornado coming and 24 hours later we're down here looking at this."
President Obama said this morning that he will visit the tornado-ravaged state of Missouri this weekend after he returns from Europe.
Speaking from the Ambassador's House in London, where he and Michelle Obama arrived earlier today, Obama called the outbreak of tornadoes "devastating and heartbreaking," while he reassured those affected by the storms that "every ounce of resources the federal government may have" will be used in recovery efforts.
"Our thoughts and prayers are with the families who are suffering at this moment," Obama said. "And all we can do is let them know that all of America cares deeply about them and that we are going to do absolutely everything we can to make sure that they recover."
Obama also acknowledged that more storms are headed for the region today, as a warning of new tornado outbreaks was issued for the central region of the United States by an Oklahoma storm prediction center. Long-form, long-track, very powerful tornadoes are expected throughout Tuesday.
The greatest threat for tornadoes stretches from Dallas to Kansas City, according to the report. The area includes Joplin, Mo., where rescue workers are racing to salvage survivors from the wreckage left by a tornado that destroyed an estimated 30 percent of the city on Sunday.
The massive Joplin tornado was rated as an EF-5, the strongest classification, with winds ranging above 200 mph. The nearly mile-wide funnel touched down at 5:41 p.m. CT Sunday and blasted a six mile wide path through the city and left trapped survivors crying out for help this morning.
The tornado that struck Flint, Mich., on June 8, 1953 and killed 116 people had been the deadliest single tornado on record since the National Oceanic and Atmospheric Administration began keeping track of tornado fatalities in 1950.
The lethal twister has also made 2011 the deadliest year for tornadoes since 1953, with 454 deaths from 1,000 tornadoes so far, according to NOAA.
April also set a record as the deadliest month with 361 tornado-related deaths, according to NOAA's records.