The featured graphic above truly tells the rainfall story across northern Iowa over the last few days. The data being shown is MRMS Q3 data, which combines data from NWS radars and rain gauges to generate regional rainfall estimates. This creates a desirable product, allowing estimates to be widespread in coverage, but also keeping it more accurate than the traditional data itself via rain gauge corrections. Northeast Iowa by far has seen the most rain this week, with 8-10+” being estimated over areas of Chickasaw, Bremer, and Fayette counties. Areal Flood Warnings remain in effect through this morning as many roads continue to flood, or have been closed or washed out. Some relief should be seen through the early work week with generally sunny skies expected, however another round of heavy rain is possible on Wednesday, which may exacerbate the already saturated grounds in these areas, once again leading to flooding.
Several rivers are expected to exceed flood stage and produce moderate-to-major flooding. Flood warnings are currently in effect for the following sites:
- Maquoketa River
- Manchester: xyz flooding occurring (xx’), flood stage is 14′. Minor flooding (15.3′) is expected, 1.3′ over flood stage. — Rise to 15.3 feet this morning. Fall below flood stage this evening.
- Mississippi River
- Rock Island: xyz flooding occurring (xx’), flood stage is 15′. Moderate flooding (17.2′) expected, 2.2′ over flood stage. — Rise above flood stage Sunday evening…and continue rising to 17.2 feet Tuesday morning. Fall below flood stage Thursday.
- Turkey River
- Garber: Moderate flooding occurring (22.47′), flood stage is 17′. Major flooding (25′) expected, 8′ over flood stage. — The river will continue rising to near 25.0 feet by today. The river will fall below flood stage Monday morning.
- Wapsipinicon River
- Anamosa: No flooding occurring (7.82′), flood stage is 14.5′. Major flooding (22′) expected, 7.5′ over flood stage. — Rise above flood stage Tuesday morning…and continue rising to 22.0 feet Wednesday. Fall below flood stage Saturday morning.
- DeWitt: Minor flooding occurring (11.29′), flood stage is 11′. Major flooding expected (12+’), 1+’ over flood stage. — Rise to 11.7 feet this morning. The river will fall below 10 feet by Tuesday morning before rising again. A second crest above 12 feet is expected around the end of the month.
- Independence: Minor flooding occurring (12.02′), flood stage is 12′. Major flooding expected (18′), 5′ over flood stage. — Rise above flood stage this morning…and continue rising to 18.0 feet Monday. Fall below flood stage Wednesday morning.
Flood watches are currently in effect for the Cedar River at Cedar Falls, the Mississippi River at Burlington, Camanche, Gladstone, Illinois City, Keithsburg, New Boston, and Muscatine. These sites have mainly been blanketed out of caution due to high rates upstream; limited confidence has been noted in these points actually reaching flood stage. Nonetheless, worth monitoring.
The charts below show this year’s year-to-date precipitation in red. The black is the climatological average, blue is the “extreme high” for the site, dark red is the “extreme low”, with 2015 and 2016 plotted as well for reference. The story is quite different at each site. Burlington, Des Moines, and Waterloo are generally hovering around average, whereas Decorah is trending along the “extreme high” and Sioux City much below average. Additional rainfall is expected later this week which will help some areas and hurt areas with already saturated grounds.