A weather pattern known as an omega block will affect weather throughout much of the nation this weekend.
CNN Weather and Climate Department
A weather pattern known as an omega block will affect weather throughout much of the nation this weekend.

Story highlights

Warmer weather for the Midwest and Northeast; storms and flooding in the Plains

An April snowstorm dusts the Colorado Rockies

More than 700 flights canceled at Denver International Airport

Atlanta CNN —  

The weather will shake things up this weekend with effects across the country.

The North will have a nice weekend as it finally begins to feel like springtime. Meanwhile, the Plains and Mountain West will have to deal with severe storms, flooding and a snowstorm. Why the shake-up? Thank (or blame) a stall in the weather pattern called an omega block.

The jet stream generally flows west to east in the Northern Hemisphere. Sometimes it takes major turns north and south, essentially getting stuck in the same pattern and slowing the movement of weather. The shape of the jet stream that blocks weather from moving will look like the Greek letter omega (Ω). This pattern is expected to take shape and persist into next week.

Under the omega, high pressure will allow warm air to build. The Midwest and Northeast will gladly welcome this warmth after starting April with record low temperatures and snow.

Welcomed warmth

Highs will reach the 70s over in the Midwest this weekend, up to 20 degrees above average. The warmth shifts into the Northeast by Sunday and Monday, allowing temperatures to reach the 60s, and 70s in the Mid-Atlantic. Areas along the Atlantic Coast will not warm quite as much as a north wind keeps temperatures closer to average.

Above average temperatures for the Midwest and Northeast this weekend.
Above average temperatures for the Midwest and Northeast this weekend.

Severe storms and flooding in the Plains

A low from the Pacific Northwest stalls out in the Mountain West this weekend as it runs into the omega block. This will keep the Rockies and Plains stormy for several days.

Moisture feeding north from the Gulf of Mexico will fuel heavy rain in western portions of the Central Plains for several days. The nearly stationary nature of the heavy rain could bring flash flooding

Rainfall accumulations of 4 to 7 inches are likely through the weekend from Texas to Nebraska, with isolated higher amounts possible. This is significant as many locations in the Plains average under 3 inches of rain for the entire month of April.

This warm moist flow from the Gulf is also conducive for severe thunderstorms. The Storm Prediction Center has highlighted areas east of the southern and central Rockies with a slight risk for severe storms Friday and Saturday, with south-central Texas the focus of storms Sunday. These storms could bring large hail, strong winds and isolated tornadoes.

April snowstorm for the Rockies and High Plains

The low hanging out in the Mountain West will also have a wintery side. Add some elevation and cold air to the mix, and we are looking at a significant snowstorm in the central Rockies and High Plains. Several days of heavy wet snow will hamper travel and may cause downed tree branches and power lines.

Winter storm warnings posted by the National Weather Service stretch throughout the Colorado Rockies and into southern Wyoming. By Sunday morning higher elevations will see 2 to 4 feet of snow, over a foot in the lower foothills and 8 to 14 inches in the Denver metro area.

United Airlines canceled all of it flights in and out of Denver International Airport. Over 700 Denver flights have been canceled for Saturday, according to flightaware.com.

As with every snowstorm, uncertainties remain in the forecast. Keep up-to-date over the weekend for the latest changes.

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