Flood Warning: When rivers will crest and how high the water will get

The Eric Factor: Why we look back at history before forecasting what’s to come

We are setting the stage for a possible severe weather day. And heading into September, it may be one of the last days this year that we have both a flash flood threat and a damaging wind threat at the same time.

It would be easy for me to get on the air this morning and just broad-brush the possibilities. But the forecast becomes more valuable with some context. And that's why it's important to look back at the past before trying to figure out what's going to happen in the future.

That's where the Meteorology department at St. Louis University comes in. A few years ago, a research project developed software that looks at current weather patterns and compares them with those in history. The closer the connection, the more we can look at what happened and factor that into our forecasts.

So let's look at a few maps concerning our potential for severe storms and flooding rain.

severe1

The map above shows the chance of having a severe weather report within 68 miles of any point on the map. In Northeastern Iowa, there's a greater than 50/50 chance of seeing at least one instance of severe weather. But keep in mind, that's not a forecast, it's a map that shows the historical probabilities. severe2

The next map shows where heavy rain has occurred using the 15 most-similar weather patterns to our current weather. A wide swath of 2"+ rains fell from Northern Missouri into Michigan. Not only do our computer models show heavy rainfall on the way, but our historical perspective does too! That's why heavy rain with flash flooding is a pretty significant risk later today.

-Meteorologist Eric Sorensen