It’s well known what will happen Sunday afternoon and evening. A cold front, or a trough strongly resembling a cold front, will push its way through eastern Iowa. But all the little details surrounding this event, as usual, remain in question.
First things first, there is a slight risk for extreme northern Iowa today. But it’s expected the bulk of the severe weather will remain in the Minneapolis area. That’s where the Storm Prediction Center has posted a moderate risk for storms and tornado watches were posted Saturday Afternoon.
For most of Iowa, there is little if any chance for storms. Despite a weakening cap in parts of northern Iowa, the warm front is well to our north and that will likely be the focus of storms in Minnesota. Here, we will just deal with the oppressive heat and humidity.
So now we turn to Sunday. On paper, the scenario is relatively straight forward. The final chapter of this storm system will push through as the cold front makes its way through Iowa. But there’s a catch.
The front does not have a lot of forcing behind it (after all, it IS summer). This creates a weak boundary rather than a strong cold front with a lot of cool air behind it. This means the overall “clash of the air masses” might not be that strong.
Because the front, or if it weakens enough, trough is not strong, our persistent cap must weaken before organized storms can develop. This would delay severe weather until 4pm or perhaps even later, closer to sunset.
At any rate, the chase team will continue to monitor the situation and monitor any changes in the forecast later tonight. Once the new outlook comes out at 1AM, we will provide a brief update on the situation and any changes in our current thinking.