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Corn Belt frost possibilities in mid-April eyed, forecaster says

A monster Rex block weather pattern is on the horizon.

As U.S. farmers head to the fields for spring planting of corn and soybeans, a rainy and cold weather pattern is set to arrive soon.

Beginning this week, the Corn Belt planting progress could be delayed by rainfall. 

As of Sunday, the U.S. had 2% of the corn crop planted, equal to the five-year average, according to the USDA.

In that Crop Progress Report Monday, USDA data showed that Kansas farmers had seeded 2% of this year’s corn crop. Missouri and North Carolina farmers have planted 1% of their corn crops.

Frost Temps

After this week’s weather, the Corn Belt weather will cool near the April 15-16 time frame. 

How cool? 

A frost or a freeze is not being ruled out, according to David Tolleris,

The culprit is what’s being called a monster Rex block weather pattern.

It’s made up of a high pressure system sandwiched between two low pressure systems. When one of the low pressure systems moves below the high pressure system, it blocks the high pressure. That means the system is stuck and will not be able to move for a long time.

Rex blocks are characterized by a high-pressure system located pole-ward of a low-pressure system. The Rex block will remain nearly stationary until one of the height centers changes intensity, unbalancing the high-over-low pattern, according to the National Weather Service (NWS).

The NWS definition further explains that “Unsettled, stormy weather is usually found near the low pressure while dry conditions are typical with the high-pressure. Strong, particularly persistent Rex blocks can cause flooding near the low-pressure part of the block and short-term drought under the high-pressure part.” 

Corn Belt Impacts

Tolleris explains that this week’s low pressure weather pattern is entering from the Pacific Ocean, moving through the central Plains (Missouri, Illinois, Ohio, and Kentucky and eventually to Pennsylvania). However, that low pressure pattern is expected to keep repeating itself to form a block for the high pressure system.

“It means that Canada’s Prairie region will miss much-needed rains. In the next two weeks, the maps show that there are several weather systems that are going to keep going underneath the high pressure block,” Tolleris says.

For the next week, those low pressure systems will bring rain to Iowa, Illinois, and Indiana.

Eventually, that the energy will shift to the East Coast. So, on April 15, when this shift occurs, there will be a big storm on the East Coast, bringing heavy rain and some snow to the New England mountain areas.

This will also pull down a lot of cold air from Canada into the Midwest, Tolleris says.

“From April 15-25, multiple cold air masses will be dropping out of Canada. The pattern will turn dry, but temperatures will drop. The Midwest temperatures will be below normal for a significant portion of the middle of April,” Tolleris says.

As long as the blocking pattern stays in Greenland and eastern Canada, the Midwest is not going to warm up, Tolleris says.

“The possibility exists for freezing temperatures in the Midwest, once the pattern shifts to the East Coast. That’s a real possibility.”


Beginning Friday, weather for the Southern and Southeastern states will turn wet and continue through next week. 

The cold fronts that will drop down from the East Coast will stall out and produce rain events, Tolleris says.

“From east Texas through the Carolinas into Virginia, wet weather is expected next week,” Tolleris says. 

While Midwestern corn and soybean plantings could get delayed, the blocking pattern will break down, and a return to a more normal pattern is expected by the end of this month. 

“The traditional May 10 cutoff date for planting is not threatened,” Tolleris says. 

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