2020 Spring Flood Outlook #3 (updated Mar. 12, 2020)

Probabalistic Hydrologic Outlook

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

Graphical Hydrologic Outlooks	2-Pager on Spring Flood Risk	Statistical Hydrologic Outlook
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

Overall, there has been a noticeable improvement in the latest probabilities for flooding compared to the outlook released on February 28th, especially on the Mississippi River.  The probabilities of reaching major flood stage on the Mississippi River have dropped substantially (e.g. KHBI2 probability of major flood dropped from 94% to 59%).  This drop was due to a prolonged period of dry weather across much of the Mississippi River Valley and a favorable snow melt.  However, it remains important to note that the overall risk of flooding remains high through the Spring.

The severity of any flooding will depend on additional rain and snow that fall this Spring.  There will also be a risk for long duration flooding this season if soil moisture across the region stays very wet.

• The highest concern for flooding this spring remains on the Mississippi River. The risk of major flooding is above normal for the entire reach of the river from Dubuque, IA through Gregory Landing, MO, but has dropped compared to the previous outlook.  Confidence continues to be low in exactly how severe flooding would be at specific locations.
   
• Potential for widespread flooding is near normal for all rivers across the area, but is dependent on additional Spring precipitation.
   
• Additional snowfall and heavy Spring rains would increase the threat for higher flood categories.  Conversely, little or no additional snowfall and lighter Spring rains would decrease the flood threat.

                                                              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.

• A large portion of the Upper Mississippi River watershed continues to observe extremely wet soil conditions. The flood risk will remain elevated until soils dry out.
• There is no snow in the watersheds of all local tributary rivers, which lowers the risk for flooding on rivers across Iowa, Illinois, and northeast Missouri. However, snowpack does remain in the upper portions of the Mississippi River watershed, which may lead to additional rises on the Mississippi river as it melts.

Seasonal Precipitation

Little to no measurable precipitation fell across the Midwest and portions of the Mississippi River Valley from the end of Meteorological Winter to 
mid March, giving the soils a chance to dry out and for snow to melt at a favorable pace. Only recently did the area see a period of long duration 
moderate rainfall, with three quarters to one inch of rain observed on March 09. This generally led to in-bank rises along rivers. Otherwise, 
precipitation across the area has generally been below normal. 

As mentioned in previous outlooks, the primary driver for our Spring flood potential is the above normal precipitation observed in the upper 
Mississippi River Valley over the winter. That precipitation plays a part in raising the risk for flooding on the Mississippi River, while having 
lesser influence on local rivers.

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

River levels remain near to well above normal across the majority of the Upper Mississippi River watershed. While dry conditions over the
second half of February and early March did allow for river levels to recede slightly, recent rainfall, snow melt and subsequent runoff
have caused rises on many rivers. 

The significance of high streamflows to flood risk is that a river with higher water levels will have less space for additional water.
As a result, flood levels can be reached with lesser runoff than it would take given normal river levels for late winter/early spring.

Iowa	Illinois	Missouri

Soil Conditions

Wet soils have persisted through the winter months as moisture from last fall was locked into the soils during the cold season.
The wettest soils are currently observed across Minnesota, Wisconsin, northern Iowa and northern Illinois as of early March.
To the south, ground thawing contributed to soils drying out across much of Iowa and Illinois. However, recent rains have introduced
additional saturation.

The threat for river rises from snowmelt or spring rainfall runoff due to very wet soils remains high for the Mississippi River as the
entire watershed is experiencing wet to nearly saturated soils. Where soils are saturated, little runoff will be able to be absorbed
by the soils, so water from both snowmelt and rainfall would efficiently move into the river system. Local watersheds have a
slighly elevated risk for high runoff from spring rains as these watersheds are observing wetter than normal soils.

Snow Cover and Liquid Water Content

The latest analysis shows snowpack remaining in Minnesota and Wisconsin mainly north of Interstate 94. Much of the snow along and
south of Interstate 94 that was present in the previous outlook melted over the past week thanks to warm temperatures in the
Mississippi River Valley region. This snowmelt is working through rivers in Minnesota, Wisconsin and northeast Iowa per latest
forecasts. In the snowpack that remains, liquid water content generally ranges from 3 to 6 inches. Isolated pockets of 8 inches or
greater were still observed in northern Wisconsin around the upper basin of the Wisconsin River.

The rapid melt that occurred last week with the dry weather and warm temperatures will bring rises through March, with many locations
expected to experience some degree of flooding. The rate at whichthe remaining snowpack melts may contribute to the severity of
flooding that occurs. The watersheds for the local rivers have no snow cover, which lessens the risk for additional flooding concerns. Unless local
snowpack builds significantly, any local river flooding will be the result of spring rains.

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

Frost Depth

Temperatures were above normal across the region this winter into early March, with only limited periods of extreme cold. This led to
little to no frost depth over much of the mid-Mississippi River Valley. Further into northern Iowa, Wisconsin and Minnesota, frost
depths ranged from 6 inches to as much as 22 inches where colder temperatures and snowpack have persisted.

The depth of frozen ground contributes to the flood risk by implying any frozen ground will cause efficient runoff from snowmelt or
rainfall. The depth of frozen ground is also a factor to how long it might take for the ground to thaw. Shallower frozen ground leads to
an early thaw, allowing the ground to dry out and infiltration of runoff.

Frost Depths - North Central River Forecast Center

Regional Frost Depths as of March 12, 2020

Ice Jam Flooding

The warmer weather this winter has into early March has limited river ice. As of mid March, there is little to no ice cover on area rivers, thus diminishing 
the threat for ice jam flooding. It is possible that cold air will return still, but without a long period of extreme cold, the risk for development of thick river ice 
will be low. This keeps the risk for spring break-up ice jams low.

Drought

According to the U.S. Drought Monitor, there are no areas in the Midwest under drought conditions.

The latest outlook from the Climate Prediction Center favors a high probability of below normal temperatures and above normal
precipitation in the upper Mississippi River Valley through the end of March.

Looking at the outlook through May, temperatures across the Upper Midwest look to have equal chances for Above, Near, or Below normal.
This may mean a similar pattern which has been observed through winter will continue, with changes from warmer to colder occurring
frequently. Normal high temperatures are now above freezing. The impact to the remaining snowpack will depend on how warm daily highs get, and 
if lows drop below freezing during the overnight hours.

Precipitation outlooks for the next three months do indicate higher potential for above normal precipitation, but keep the highest risk
for above normal precipitation generally to the south and east of the region. This indicates a more active weather pattern could come
into play later in the spring.

8 to 14 day Temperature Outlook	8 to 14 day Precipitation Outlook

March Temperature Outlook	March Precipitation Outlook

Archived Recordings and Situation Reports:

March 12, 2020 Webinar Recording

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
9050 Harrison St
Davenport, IA 52806
563-391-7094 ext 493
Email: jessica.brooks@noaa.gov