Thursday, January 27, 2011

Foggy Friday Morning....Spring Flood Outlook

We are going to be in the throws of some dense fog by morning.

The melting through Thursday has added enough moisture to the lower levels to create foggy conditions over central Iowa. The fog is expected to move in after 2 AM. It should lift with the warmer temperatures and some sunshine by mid Friday morning.

Highs Friday are expected to be in the middle to upper 30s again. Enjoy the melt before we head into the freeze of next week. Much colder air is on the way by Monday.

Flood Outlook

The National Weather Service released their first flood outlook of the year today. It basically shows higher chances for flooding along the Mississippi in eastern Iowa...and in the Sioux-land area of western Iowa.

Here are the highlights:
* Current information suggests that the greatest risk of significant flooding is along the Mississippi, Big Sioux and Floyd Rivers. Along the Mississippi River, there is greater than 50% chance of major flooding from the Minnesota border all the way down to Burlington. At many locations along the Mississippi, the risk exceeds 70%. Similar risk levels exist along the Big Sioux and Floyd Rivers.

* Of less concern but still worthy of mention, the risk of flooding is near to above normal at most other locations in Iowa, especially for north central, northeast and east central Iowa including but not limited to portions of the Cedar, Iowa, Winnebago, Wapsipinicon and Upper Iowa Rivers.

* Also worthy of mention, the rivers across the remainder of the state, including the Des Moines and Skunk River basins, the risk is near to above normal. Keep in mind the aforementioned above normal risk of significant flooding along the Big Sioux and Floyd Rivers however.

** Important note #1: the risk of flooding may change significantly between now and the spring thaw. We obviously have a lot of winter to go yet. Iowa tends to receive a lot its winter snowfall between now and the end of the season. Things can change a lot either for the better or worse. Recall last year we were all quite concerned about significant flooding along the Des Moines River basin due to the indicated high risk of significant flooding. Ideal snow melt conditions led to a relatively minimal flood however.

** Important note #2: stream levels across much of Iowa are above to much above normal for this time of year. They have been persistently high since last fall. Soil moisture is also near to above normal statewide. An extreme example of the elevated stream levels is the Mississippi River in northeast Iowa, where some locations are reporting the highest river levels they have ever seen for this time of year.
This all means that we will be more vulnerable than normal to flooding and flash flooding, regardless of if the snow melt flooding occurs, at least into late spring.

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