How ice forms and why it has been falling in Green Country

TULSA, Okla. — Oklahoma is no stranger to ice, but many wonder why we get freezing rain and sleet versus good old-fashioned snow. Wintry precipitation is not only dependent on surface temperatures, but those readings at cloud level as well.

When shallow cold air is in place, warmer air at cloud level causes raindrops to form. As they fall into sub-freezing air, those liquid drops may freeze on contact (freezing rain) or in the air before hitting the ground (sleet).

In the case of particularly strong forcing in the atmosphere, upward lift in the warm air above can cause thunderstorms, creating an instance of “thunder-sleet.” Those thunderstorms grew to such heights that droplets within those storms were brought to below-freezing temperatures aloft, enabling hail to form and fall to the ground. This is why some of our ice pellets in the heaviest downpours were larger hail was mixed with sleet.

Freezing rain is more likely on Wednesday night as that shallow Arctic air continues to erode except at the very surface where temperatures may stay below freezing if and when precipitation arrives. This can create big problems if enough freezes on contact. That glaze is what can stick to trees and powerlines. The highest threat of this icing is in southeast Oklahoma before we thaw out Thursday afternoon.