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2021 Spring Flooding Thread


Geoboy645
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I figured it was time to start this thread as we come up on the first spring flooding outlooks of the year. As of right now Spring Flooding could be a major concern across most of the sub. With an above-average snowpack with high water equivalency and deep frost depth this year could be an above average year for flooding. A quick melt by either a sharp warmup or a rainy cutter could potentially lead to March 2019 or April 1965 style flooding quite easily. Interesting thing to note that most analog years to this one pattern wise featured major flooding in the Midwest during Spring. 1965,2008, and 2011 are the most notable ones. If there is a plus it's that soil conditions aren't nearly as wet as last year and snowpack is average to below-average across the headwaters of the northern major rivers. River Basins I would particularly pay attention to this year are the Illinois, Rock, Fox (Illinois), Fox (Wisconsin), Wisconsin, Des Plaines, Wabash, Southern Cedar, Iowa and Des Moines, and Mississippi. When it comes to the Great Lakes I wouldn't be shocked if Lake Michigan-Huron starts breaking lake level records again after this spring. Especially if we get more snow to the east in Michigan. Overall this year is looking like a potentially bad one for the Midwest. 

TLDR: Bad flooding year possible for the Midwest.

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Watching the IL river basin fill up with snowpack over NE IL and NW IND

many of the top ten crests on the upper IL river from PIA upstream have occurred in the past 15 years with over 100 years of history 

Urban growth of the SW burbs the past 20 years not helping with any increased runoff 

 

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We were dealing with a moderate drought here in northeast Indiana and the lake levels are very low. Somewhere along the line we were upgraded to Abnormal but we still have a lot of storage to fill along the watersheds. With this prolonged cold the snow is piling up though and I feel like by the end of next week even more will have accumulated.

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22 hours ago, A-L-E-K said:

not really seeing any signs of a thaw imminent, the long the cold holds, the more ice jamming of rivers will compound things down the road

That was a problem briefly in 2014.  3-5" of snowpack water didn't cause any major flooding later on because the thaw was very dry.  2013 didn't have as much snowpack, but there were a few major early spring rainstorms and April was bad.  It seems like it only takes one widespread 2-3" rainstorm to cause significant flooding if the ground still has frost after snowmelt.  When the frost and snow is gone but little green-up has occurred it seems to only happen with two or three of those widespread 2-3" rain events in close succession.  Soil is somewhat sandy here though so that helps a little when the ground isn't frozen.

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22 hours ago, A-L-E-K said:

not really seeing any signs of a thaw imminent, the long the cold holds, the more ice jamming of rivers will compound things down the road

Plus, the closer we get to spring,  odds increase of a warm spell that could melt things all at once rather then gradual if this was say Jan 1st

 

 

 

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https://www.weather.gov/ncrfc/LMI_ROF_NFP_SpringHydroOutlook. The NCRFC just came out with their first spring flooding outlook. They are pretty much thinking the same thing when it comes to what areas are likely to flood this spring. They are definitely a little more conservative with their wording though. Which makes sense I guess considering that we are still in mid-february.What was especially interesting was the note that the SWE for the Illinois/Wisconsin snowpack is actually in the top 10 highest ever for that area. Basically if your south of the latitude of the Iowa/Minnesota state line your going to have a higher flood potential than north of it.

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Take it for what it's worth, but the CFSv2 is showing a signal for above normal precip in March. If that comes to fruition and we have a flip to above normal temps and an accompanying snow pack release, it could get ugly. Granted, it is also consistently showing near normal temps, but it would only take three or four days of above normal temps.

summaryCFSv2.NaPrec.202103.gif

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This will only grow with todays system and Thursday..keep in mind even if it warms up for a brief time a lot of the melting and any rainfall will just get absorbed into the snowpack at first priming for a big release

getting very worried about IL river  flooding here and upstream with the upper basin and tributaries with deep snowpack

even the LES isn't helping, eastern cook county used to drain into the lake, now every drop flows this way 

 

 

nsm_depth_2021021505_Midwest.jpg

nsm_swe_2021021505_Midwest.jpg

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Fairly strong signal for March being wetter than average in much of the region.  Southern areas will obviously thaw more quickly than farther north.  Right now I'd say that thawing looks somewhat gradual with northward extent at least in the shorter term (like not suddenly blasting into the 50s/60s) but all in all, certainly potential for issues down the road.

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Now that the melt looks to start over the next week it'll be very interesting seeing how the rivers respond. Fortunately it looks to initally be a slow melt which should minimize flooding at least for the moment. At least here everyday this week looks to be 30's and 40's at least at somepoint in the day. Adding some sun and you got yourselves great conditions for long slow snowmelt.

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3 inches along OH river the next five days...running high from snowmelt

.plus very heavy  rains over the TN valley, .this water can be stored in KY lake but will eventually need to be released into the OH river

 

OH river forecast  as of yesterday, crest at Cario IL 35.7 on march 4th (without most of the rain shown below) 

flood stage 40

record 61.7

 

 

Day 11 image not available

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1 hour ago, janetjanet998 said:

3 inches along OH river the next five days...running high from snowmelt

.plus very heavy  rains over the TN valley, .this water can be stored in KY lake but will eventually need to be released into the OH river

 

OH river forecast  as of yesterday, crest at Cario IL 35.7 on march 4th (without most of the rain shown below) 

flood stage 40

record 61.7

 

 

Day 11 image not available

Oh boy I guess its the annual let's flood the Tennessee valley week. Right on schedule too. 

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I figured I'd put this here. I have been eyeing the Huntington County river gauges this week. I was not worried about flooding per se, but ice jams causing flooding. Yesterday afternoon, I noticed a gauge spiking on the Salamonie River.  I was getting ready to go check it out when I received a call from IWX about the same thing.  I took the UAV with me and caught some footage of the ice breaking up. There was a mile or so of sheet ice behind a low head dam, with chunk ice piling up behind it.  I got there just as the strong current and chunk ice caused the sheet ice to break up. (apologies about You Tube degrading the video quality)

I love my job.

 

 

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