The Reasons for the Miss. Flooding

There haven't been any recent flooding rains in the Mississippi Valley, but the rivers there are flooding this week. Why? Well, first of all, rivers lag considerably behind local creeks when it comes to flooding. The NWS [JessePedia] says, of the Wabash River (see Julie's experience yesterday): "PORTIONS OF THE WABASH RIVER REMAINS IN FLOOD DUE TO THE HEAVY
RAINFALL OVER THE PAST WEEKEND."

And if you look at the NOAA past rainfall chart for January 13th, you can see the rain they are referring to:

But 2 to 3 inches of rain isn't that impressive, and when you look at past river conditions, it may have just been the nail in the coffin. The government maintains creek and river gauges which measure the height of the water hourly. Check out this animation of hourly river flood conditions for the last 10 days:

Notice that the Mississippi Valley has been above flood stage for the entire period, in fact if you go all the way back to January 1st, much of it still was, especially southern Indiana. Why? Because of the amount of rain in the last 30 days, which is quite impressive, showing 6-10 inches over much of the Mississippi Valley...

RAINFALL - LAST 30 DAYS

But even more importantly, this is significantly above normal, to the tune of 3-5 inches:

INCHES ABOVE NORMAL RAINFALL - LAST 30 DAYS

In addition, when you look at an animation of hourly Daily Percentiles at these gauges (in other words, how does today's gauge height compare to the same day in past years?), you see a similar story although near the end of the animation, you're seeing a quick decrease in blue and black as small creeks have receded but the major river stations are now flooding.