The Ottumwa Courier

October 12, 2012

Models firm up severe weather threat

MATT MILNER
CNHI

OTTUMWA — Forecasts for Saturday show the severe weather threat has stretched south from earlier models, but southern Iowa is still very much at risk.

The highest risk areas stretch from central and southeastern Iowa down through western Missouri, eastern Kansas and northeastern Oklahoma. The Storm Prediction Center says the forecasts show a "nearly continuous" line of storms forming along that line and moving east in the afternoon and evening hours.

That's both good and bad news. It limits the tornado and large hail threat to earlier in the day, when the cells are more widely separated. More thunderstorms in a line means they all are using the same heat and humidity to sustain themselves. In essence, they're competing with each other for limited resources.

Supercells generally do best when they don't have other thunderstorms adjacent to them. That way they monopolize the local energy. Forecasters expect the line of storms to transform the threat from large hail and tornadoes to strong, straight-line winds.

Of course, it doesn't take a tornado to do serious damage. A storm that moved through Ottumwa in June knocked the Chief Wapello statue from the courthouse. It didn't involve a tornado, but the damage was more widespread.

The threat from storm winds is expected to last through Saturday night.