Probabalistic Hydrologic Outlook - March 11, 2021

Use the links below to find the Graphical Probabilities and the Numerical Probabilities respectively.
 

Graphical Hydrologic Outlooks	Spring Flood Risk 2-Pager  (Mar 11th, 2021)	Statistical Hydrologic Outlook (Mar 11th, 2021)
Images below are examples which link to the Wapsipinicon River near DeWitt. Find all other locations in the Quad Cities Hydrologic Service Area in the drop down menu below.       Select Location: Mississippi River at Dubuque L&D 11Mississippi River at DubuqueMississippi River at Bellvue L&D 12Mississippi River at Fulton L&D 13Mississippi River at CamancheMississippi River at Le Claire L&D 14Mississippi River at Rock Island L&D 15Mississippi River at Illinois City L&D 16Mississippi River at MuscatineMississippi River at New Boston L&D 17Mississippi River at KeithsburgMississippi River at Gladstone L&D 18Mississippi River at BurlingtonMississippi River at Keokuk L&D 19Mississippi River at Gregory LandingMaquoketa River at ManchesterMaquoketa River at MaquoketaWapsipinicon River at IndependenceWapsipinicon River at AnamosaWapsipinicon River at De WittCedar River at VintonCedar River at Cedar RapidsCedar River at ConesvilleIowa River at MarengoIowa River at Iowa CityIowa River at Lone TreeIowa River at Columbus JunctionIowa River at WapelloIowa River at OakvilleEnglish River at KalonaSkunk River at SigourneySkunk River at AugustaDes Moines River at KeosauquaDes Moines River at St FrancisvilleFox River at WaylandPecatonica River at FreeportRock River at ComoRock River at JoslinRock River at MolineGreen River at GeneseoLa Moine River at Colmar   Go

Flood Outlook

Updated 3/19/2021

The majority of the snow across the region has melted and as the bulk of it melted slowly, rivers were generally able to take the runoff with rises staying within the banks. There were a few rivers that saw rises from snowmelt runoff cause some minor flooding, but these were limited to localized areas and generally just caused minor lowland and farmland flooding.

The snowmelt runoff is currently working down the Mississippi River, with peak levels due to the snowmelt water expected through March 25th. These peak levels are anticipated to stay below flood stage. However, additional rain is expected in the next week so river levels could rise to higher levels after the snowmelt crest moves through. With the river running at higher levels, runoff from heavy rains would bring a higher risk for flooding to occur.

The weather pattern is expected to stay active in the coming weeks, which could bring rain, additional snow or a combination of both to areas across the region. Any additional precipitation will have an impact on the flood risk as any areas that receive heavy rain or heavy snow will have the risk increase. 

Key Points:

• Flood risk this season continues to be lower than previous years. 
   
• The majority of area rivers have a below normal risk of reaching flood levels of moderate or major flood severity. 

• As the snow has melted favorably across the local area as well as across the majority of the Upper Mississippi Watershed, flooding due to snowmelt was limited to a few locations.  The flood risk for the remainder of the spring months turns toward additional spring precipitation. 
   
• Soil conditions are favorable to reduce the flood risk.  Thawed soils and near to below normal soil moisture indicates soils will have the ability to absorb water from precipitation this spring.

                                                              Advanced Hydrologic Prediction Service (AHPS)

Observed Conditions	Forecast Conditions	Long-Range Outlooks

Flood Category definitions:

• Minor Flooding - minimal or no property damage, but possibly some public threat or inconvenience.
• Moderate Flooding - some inundation of structures and roads near streams. Some evacuations of people and/or transfer of property to higher elevations may be necessary.
• Major Flooding - extensive inundation of structures and both primary and secondary roads. Usually significant evacuations of people and/or transfer of property to higher elevations.  

Many factors are have been considered when determining the overall flood risk for the Spring, with the combination of these influences factoring into the final determination. These factors are discussed in detail below.

Information Current as of 3/19/2021

Seasonal Precipitation

Precipitation this winter has averaged above normal for much of the NWS Quad Cities Hydrologic Service Area (HSA), however the larger-scale Upper Mississippi River watershed has averaged near to below normal precipitation. 

Below you will find graphics of the precipitation accumulated this winter season (left) and how this amount of moisture compares to normal in percentage (right). These graphics are courtesy of the Midwest Regional Climate Center.

River Conditions

Streamflow analysis from the United States Geological Survey indicates the majority of the Upper Mississippi River watershed has rivers running at near to above normal streamflows. The higher flows are occurring as snowmelt runoff and recent rainfall runoff is moving through the river systems, which has caused rises in river levels. While these flows will drop as the snowmelt runoff works through these river systems, the period of time when the rivers are running at higher levels will cause an increased risk for flooding because the stream levels will already be running at higher levels. This essentially means that the river doesn’t have as much capacity to hold higher amounts of runoff. 

Iowa	Illinois	Missouri

Soil Conditions

Soils across much of the Upper Mississippi River watershed are near normal or drier than normal. The drier soils will help reduce the threat for flooding if and when heavy rains occur this spring.

Snow Cover and Liquid Water Content

Temperatures through the first half of March allowed for an almost perfect melt of the snow across the region, which greatly reduced the amount of runoff entering the river systems simultaneously. It ended up taking 2 weeks to melt the 8-16 inches of snow that was on the ground as of late February as warm temperatures were observed during the day, but dropped below freezing at night which slowed the melting process.

Snowmelt runoff did cause rises on many rivers, but the slow pace of running into the rivers kept the majority of rivers below flood stage even with the surges of water in the river systems. The peak flows due to snowmelt will move down the Mississippi River between Dubuque, IA and Gregory Landing, MO through March 25th. However, additional rain is expected through the end of March, so with river levels being high with the ongoing snowmelt crest moving through, the risk for reaching flood levels will be a bit higher through the end of March and higher levels could be reached beyond the snowmelt crest.

Current Snow Depth Current Snow Water Equivalent

Images courtesy of the National Operational Hydrologic Remote Sensing Center (NOHRSC)

Frost Depth

Observations show that no frost remains in the soils for much of the region. Where there is frozen ground still is limited to the central and northern portions of Minnesota and Wisconsin. This is significant as new rain or snow across the region this spring will have the potential to be filtered into the ground rather than converted to 100% runoff.

Frost Depths - North Central River Forecast Center

Regional Frost Depths as of March 19, 2021

Ice Jam Flooding

Ice jamming is no longer a threat as ice has melted in all area rivers.

Drought

According to the U.S. Drought Monitor, there are no local areas observing drought conditions, however portions of the Midwest are seeing Abnormally Dry to Severe Drought conditions.

Archived Recordings and Situation Reports:

Feb 11, 2021 Webinar Recording	Feb 25, 2021 Webinar Recording	Mar 11, 2021 Webinar Recording

2021 Spring Flood Outlook #1 Document	2121 Spring Flood Outlook #2 Document	2121 Spring Flood Outlook #3 Document

River and Streamflow Information:

• National Weather Service: water.weather.gov
• US Geological Survey: water.usgs.gov/waterwatch
• Corps of Engineers: rivergages.com 

Flood safety and flood insurance information:

• NWS Flood Safety: www.floodsafety.noaa.gov
• National Flood Insurance Program: www.floodsmart.gov

Precipitation, temperature, and soil moisture information:

• National Operational Hydrologic Remote Sensing Center: www.nohrsc.noaa.gov
• NWS Graphical 7-Day Forecast: https://graphical.weather.gov/sectors/uppermissvly.php
• NWS Climate Prediction Center: www.cpc.ncep.noaa.gov
• US Drought Portal: www.drought.gov 

Questions or Comments

If you have questions or comments about this spring flood and water resource outlook please contact:

Jessica Brooks
Service Hydrologist
National Weather Service
9040 Harrison St
Davenport, IA 52806
Email: jessica.brooks@noaa.gov