Ag Weather Forum

Polar Vortex Makes a Visit

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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Polar vortex-source cold shows signs of blanketing the north-central and eastern U.S. with a Mother's Day weekend freeze. (Tropical Tidbits graphic)

Hello Polar Vortex. It's been awhile. The high-northern-latitude pool of very cold air was absent through most of the 2019-20 winter. However, there is still enough northern cold to be a problem feature in the North America weather scene if the atmospheric patterns permit. And indeed, the polar vortex has moved south into the continental U.S. It is set to bring hard freeze conditions to much of the north-central and eastern U.S. during the Mother's Day weekend. A wide area of the continental U.S. east of the Rockies, from western Nebraska to the Mid-Atlantic coast and from the U.S.-Canadian border in northern North Dakota south to northern Alabama is in the potential blanket of this cold.

This oncoming freeze potential is enough to force the large accomplishments in U.S. corn and soybean planting into at least a temporary backseat due to the potential for crop-delaying and even crop-killing cold. The cold is also a threat to both hard red and soft red winter wheat. These crops are well into their jointing and heading reproductive phases. Air temperatures at freeze level or a few degrees colder for only two hours can injure the new wheat florets and reduce the yield. Wheat in the central and Southern Plains has already been damaged by hard freezes on several occasions in April.

The extent of the cold air influence is notable. The cold air flow covers almost the entire continental U.S. east of the Rockies. There is a strong angle of the cold air extending southeast from the North Dakota-Manitoba border to the Ohio Valley and the eastern U.S. That places the Midwest squarely in the path of the cold. And, freeze warnings cover almost the entire Midwest into the Midsouth and the Mid-Atlantic region.

Coverage of this cold pattern, however, is also spreading into the Plains. Freeze warnings are in effect during the weekend into north-central Kansas. Frost and freeze watches are also noted farther west and southwest in southwestern Kansas and eastern Colorado as of Saturday morning, May 9. This event is not unprecedented; for example, a hard killing freeze May 9-10, 1981, caused extensive damage to the Plains winter wheat crop.

The Northern Plains will also be targeted by this cold wave with several days of very cold conditions. This includes prospects for snow and strong winds. And for the northern tier of crop country, this pattern adds to the pressure of trying to get some crop -- any kind of crop -- in the ground. And time is running out.

More details on how this cold snap could affect young plants are in this article by DTN's Emily Unglesbee:… .

Bryce Anderson can be reached at

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