Updating an alert from earlier in the week, the National Weather Service on Friday warned Central Plains states of a massive storm this weekend expected to bring heavy rain, large hail, severe thunderstorms, blizzards and flooding.
A system moving in from California and moisture from the Gulf of Mexico will combine to create problems, forecasters said.
"This is a very large and powerful system that will impact a large area of the country," forecaster Lynn Maximuk said in a service advisory. "Some areas will see severe weather, some will see heavy rains, some will see blizzard conditions and some will see combinations of various conditions as we move through the weekend."
National Weather Service forecast offices in Colorado, the Dakotas, Nebraska, Kansas, Iowa, Illinois and Indiana have issued winter storm warnings and watches for the cold side of the storm system, with severe thunderstorms a possibility in eastern Kansas, Missouri and western Kentucky.
Some areas, such as southwest Kansas, will start the weekend with the possibility of severe thunderstorms and could end with blizzard conditions.
On Wednesday, forecaster Mike Looney said that "warmer temperatures over the past few days have really increased the rate of melting snow" from recent weeks.
"The presence of saturated soils in many areas is compounded by the fact soil is frozen a few inches below the surface," he added. "Since frozen soil can't absorb the moisture, it's all turning to runoff."
"As temperatures get warmer, the snow, holding 1-3 inches of water, melts that much faster, so it won't take much rain to cause really significant flooding," Looney said.
"Quiet little streams are already becoming raging torrents," Looney said of localized flooding earlier this week, "and those conditions are only going to get worse as temperatures rise and rain moves in."