Early weather outlook shows tornado outbreak unlikely this month

DES MOINES — State Climatologist Justin Glisan says the initial, long-term forecast for December indicates warmer temperatures and more precipitation, but there’s nothing to suggest there’s an amped up threat of a tornado outbreak like the one two years ago.

“December 15th, 2021, that was an extreme event,” Glisan says. “We had a serial derecho and 63 tornadoes — the largest tornado outbreak for Iowa for any month and the largest December outbreak for the United States in the observational record.”

The latest Drought Monitor nearly all of Iowa has some level of drought, with some areas in extreme drought. Glisan says there is the potential for more precipitation to fall in December, but the old adage that it’s too dry to rain is true in SOME cases when thunderstorms hit dry pockets of air. “We saw this in western Iowa as the drought started in May and June of 2020. You would have thunderstorms approach the state and then just either break up or go around because there was no low level moisture to work with,” Glisan says. “Now in these larger scale low pressure systems they’re able to have more access to large scale moisture pools and hence you do see wider spread snowfalls or rainfalls.”

The seasonal outlook indicates abnormally wetter conditions along the southern coast of the U-S and that may provide the moisture weather systems sweeping across Iowa draw from and generate rain or snow.