Pattern Change This Week in Plains, Rockies Will Include Spring Snow for Some

 Jonathan Erdman

Published: April 11, 2021

A pattern change will bring markedly chillier air to the Rockies and Plains states as far south as Texas in the week ahead, and that could also wring out spring snow in a few areas, including Denver.

The colder pattern arrived in the Pacific Northwest this weekend and resulted in several daily record lows on Sunday, including Seattle (34 degrees), Portland, Oregon (32 degrees), Eugene, Oregon (31 degrees), Pendleton, Oregon (23 degrees), Spokane, Washington (23 degrees), and Yakima, Washington (21 degrees).

This chiller air will filter into the Rockies, then plunge southward through the Plains early this week. Widespread record mid-April cold isn't expected, but it will certainly squelch any recent spring fever.

Daytime highs in the 40s are expected from the northern Great Lakes into parts of the Plains as far south as parts of western Kansas, western Nebraska and eastern Colorado. Parts of the Rockies won't rise out of the 30s.

The Texas Panhandle and western Oklahoma will likely struggle to rise out of the 50s.

(MAPS: 10-Day U.S. Forecast Highs and Lows)

Widespread frost and freeze conditions are possible midweek from the western Great Lakes into the Northern and Central Plains, Rockies and Great Basin.

Slightly below average morning lows will extend into parts of the Midwest and South later this week.

Forecast Morning Lows

This generally cool pattern could seep into parts of the Midwest and Deep South and linger this week and possibly beyond, as the latest 6- to 10-day temperature outlook from NOAA's Climate Prediction Center indicates.

Extended-Range Temperature Outlook

The reason this cooler air may hang around: a traffic jam in the upper-level winds, which steer weather systems, is expected to develop.

Namely, high pressure aloft will nose into western Canada. That will trap a swirl of low pressure aloft over the West.

This configuration of high pressure north of low pressure – known to meteorologists as a Rex Block – blocks the normal flow of weather systems moving west to east, similar to a giant rock in a stream.

So once the cooler air flows south, it might take some time to move out.

Spring Snow For Some

That slow-moving swirling low in the West and just-cold-enough air will combine to wring out some wet snow in parts of the Rockies, High Plains and Northern Plains near the Canadian border.

In fact, at least some light snow could fall for several days in Wyoming, western Nebraska, western South Dakota, northwestern Kansas and Colorado, including the Front Range from Denver to Cheyenne.

For now, this doesn't appear to be nearly the magnitude of mid-March's Winter Storm Xylia, which dumped feet of snow in the Front Range and High Plains of Wyoming and Colorado.

But there will likely be some accumulations, and that could lead to slushy or snowy travel next week.

Snow and Rain Outlook

One of Warmest Starts to Spring

This change will reverse what has broadly been one of the warmest early-spring periods on record in the nation's midsection.

According to the Southeast Regional Climate Center, a couple dozen cities in the upper Midwest and Plains have had a top-five warmest start to spring, including International Falls, Minnesota, and Sioux Falls, South Dakota.

Spring temperature anomalies (in degrees Celsius) from March 1 - April 6, 2021. Parts of the northern and central Plains have had one of their warmest starts to spring on record.

One week ago, Bismarck, North Dakota, reached 83 degrees on April 3.

Denver soared to the low 80s on both April 4 and 5 after smashing their March monthly snow record – 34 inches – largely from Winter Storm Xylia.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.