The National Weather Service issued a Tornado Watch for portions of Iowa on Monday as conditions favoring severe thunderstorms developed. Forecasts indicate that any storms that form could become strong and dangerous.
The watch area includes parts of southwest and central Iowa, specifically mentioning Polk County and the Des Moines and Ames areas. This particular watch remains in effect until midnight.
Additional tornado watches extend into northern and northwest Iowa, though with earlier expiration times. A Severe Thunderstorm Watch was also issued for eleven northwest Iowa counties through 11 p.m. Earlier tornado warnings in northern Iowa and for Cass County have since expired.
Primary threats associated with the storms include the potential for a few tornadoes, some of which could be intense. Damaging winds with gusts possibly reaching 75 mph are expected, along with widespread large hail, some potentially reaching three inches or the size of apples.
Storm development is most likely during the late afternoon and evening hours, roughly between 3 p.m. and 10 p.m., with a more favorable period around 7 p.m. Uncertainty exists regarding storm initiation due to atmospheric conditions, but a dry line moving from Nebraska is identified as a potential trigger.
The state is divided into different risk zones, with areas north of Highway 20 facing a moderate (Level 4 of 5) severe weather risk. Most of the rest of the state, including central and southern areas, is under an enhanced (Level 3 of 5) risk.
Impacts have already been noted, with the Fort Dodge Regional Airport reporting a peak wind gust of 76 mph Monday afternoon.
Following the passage of the storms, temperatures are expected to drop significantly on Tuesday, with highs in the mid-60s under mostly sunny skies. The next chance for rain is forecast to arrive on Wednesday.
