WEEKEND RAINS IMPACT FLOOD RISK ON THE MISSISSIPPI...

March 31, 2020

The next few days the weather looks to be nice and quiet as March goes out like a lamb. That's a good thing after a wet weekend for much of my area and the upper Midwest. In this graphic from the Midwest Climate Center you can see where the rains were most substantial. Large parts of the regions saw 1-2" of rain. Some spots around the Quad Cities picked up more than 4".

That, combined with other systems since February 29th has given much or the region north of I-80 into central Minnesota and Wisconsin 1.5 to 2 times the normal precipitation expected during that 30 day period.

 As of March 29th soil moisture is ranked in the the top 90-99 percent . The ground is in a very squishy state.

Heavy precipitation in Minnesota and Wisconsin over the weekend is causing the Mississippi to rise upstream. As the water works its way downstream it will bring a mid to late April crest in my area. The next 2-3 weeks just how much precipitation falls up north will be critical to how high that crest gets.

In the Quad Cities there is a 60% conditional threat that the river will reach the major stage of 18 feet. Chances are about 40 percent of a 19 foot crest and close to 20 percent for a 21 foot crest. The all-time record set last year was 22.7'.

 

NOAA's spring flood outlook does show much of the area from Dubuque to Keokuk with moderate chances of  a major crest at some point this spring.

The GFS does show well above normal precipitation the next 2 weeks in the upper Midwest where the current crest is developing. Here, the forecast departures are up to 3" above the norm

That along with depleted frost levels and above normal temperatures in the period April 6-13th certainly points to crests being moderate to significant on the Mississippi when they do occur. Heavy rains locally preceding or accompanying the crest would be the worst case scenario. This would also bring other rivers into flooding play such as the Iowa, Cedar, Rock, etc.

Needless to say there are far too many unknowns to make concrete forecasts but at least on the Mississippi the odds are higher than normal of another significant crest this spring. Still several weeks before that would happen so plenty of time to fine tune the details.

 

Meantime, a couple decent days ahead with seasonal highs and some sun to boot! I like it, Roll weather...TS

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© 2019 Terry Swails