A storm system hovering over a broad swath of the Plains could dump a month's worth of rain over some areas in just four or five days — potentially causing serious flash flooding.
Copious amounts of rain are forecast through early next week. About 3 million people are under a flooding alert with flash flooding possible in parts of Texas, Oklahoma, Kansas and Nebraska, according to The Weather Channel. Rainfall totals in some parts of the High Plains could approach all-time monthly April records, meteorologists added.
The stagnant weather pattern will likely drop at least 3 inches of rainfall through Tuesday night from Texas to parts of South Dakota, while other parts of Texas as well as Kansas and Oklahoma could receive 5 to 8 inches or more over a four-day period.
That's more than some of those areas get in all of April, or even May. The last time North Platte, Nebraska, saw that much rain at this time of year was April 1915 — when 7.1 inches fell — setting a monthly precipitation record, according to the National Weather Service.
The most North Platte ever got in total in May was 8.01 inches in 1962, the NWS said.
Garden City, Kansas, could get up to twice the average April monthly precipitation.
The extreme amount of rainfall is due to a sluggish weather pattern that is parked over the Plains, with an area of low pressure stuck between areas of high pressure to the northwest and northeast of it.
Thunderstorms, starting Saturday night, will hit parts of Oklahoma and Texas through Monday or Tuesday, The Weather Channel said. There's a threat of some severe thunderstorms, accompanied by hail and high winds, and tornadoes, too.
About 13 million people are under a wind advisory.
To add to the misery: Heavy, wet snow — up to a foot in some areas — will hit parts of the High Plains and Rockies, affecting about 3 million people under a winter storm warning.
In Colorado, 845 flights were canceled Saturday into or out of Denver International Airport. Around 10 inches of snow accumulation was expected through Sunday, the airport said.
"Overall, heavy rain and localized flooding will be the biggest concern from this system," said Weather Channel Lead Forecaster Michael Palmer.