Flood Potential Outlook
Issued by NWS Quad Cities, IA IL

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IAC011-019-031-045-055-057-061-087-095-097-101-103-105-107-111-113-
115-139-163-177-183-ILC011-015-067-071-073-085-109-131-155-161-177-
187-195-MOC045-199-201800-

Probabilistic Hydrologic Outlook
National Weather Service Quad Cities IA IL
947 AM CST Thu Mar 07 2019

...Above to Well Above Normal Risk for Flooding this Spring...

.2019 Spring Flood and Water Resources Outlook...

This is the second of two planned Spring Flood and Water Resource
Outlooks for 2019 for the the Quad Cities Hydrologic Service Area,
which covers portions of eastern Iowa, northwest and west central
Illinois, and extreme northeast Missouri. Rivers included in this
outlook are the Mississippi River and its tributaries from above
Dubuque, Iowa to below Gregory Landing, Missouri. The primary
tributary systems include the Maquoketa, Wapsipinicon, Cedar, Iowa,
Skunk, North Skunk, and Des Moines Rivers in Iowa; the Fox River in
Missouri; and the Pecatonica, Rock, Green, and La Moine Rivers in
Illinois. This outlook is for the time period from late February
through May.

.Flood Outlook Overview...

The potential for widespread flooding remains high this spring as
soils are nearly saturated and frozen, while cold and active weather
has allowed the snowpack to increase across northern Iowa,
Minnesota, and Wisconsin in the past 2 weeks. Additionally, the
weather pattern is expected to stay active in the near future with
two significant storm systems showing signs of bringing some warmer
air and rainfall locally, and possibly additional heavy snow across
the northern parts of the Upper Mississippi River basin.

Along the Mississippi River, the probabilities for more severe
flooding have risen due to the increased snowpack. It is now likely
that much of the mainstem Mississippi River will have a high chance
of reaching major flood stage levels, with a potential for some
locations to reach levels near previous record crests. The occurrence
of near record levels will depend on the rate of the snowmelt along
with receiving additional spring rains.

On the larger tributaries, the rivers with source regions in the
deep snowpack will have well above normal chances for flooding this
season. Rivers with higher flood threats include the Cedar,
Pecatonica, lower Rock, Iowa above Coralville Reservoir, and the Iowa
below the confluence with the Cedar River. The remainder of area
rivers will have near or above normal chances for flooding this
season.

To note, even a gradual snowmelt with little rainfall this spring
assures at least minor flooding for many rivers across the region.

Main Points:

* Current conditions support a chance for high impact flooding this
  spring, as well as widespread minor flooding.
* Saturated soils or frozen ground will contribute to high amounts
  of runoff from snowmelt and spring-time rains.
* Due to a deep snowpack across much of the region, snowmelt alone
  will likely cause most rivers to reach levels near or above flood
  stage. Confidence is high on widespread minor flooding, with lower
  confidence on the severity of peak crests.
* Ice action in the rivers will continue to be a factor in potential
  flooding as many rivers remain ice covered.
* The rate of the snowmelt and additional spring rains will be
  essential to the severity of flooding that occurs this spring. A
  fast snowmelt and any significant spring rains will increase the
  potential for high impact flooding this season.

Many factors are considered when determining the overall flood risk
for the upcoming spring season. the combination of these influences
factor into the final determination. These factors are discussed in
detail below.

.Seasonal Precipitation: Above to Well Above Normal

The winter season ended with total precipitation amounts being above
to well above normal across the local area as well as the entire
Upper Mississippi River basin. A large area from central Iowa into
southern Minnesota through northeast Wisconsin had observed total
amounts upwards of 200 percent of normal.

Some of the winter precipitation has been rain, but overall, the
entire region has also observed above normal snowfall for the season.
Portions of the region have received 20 to near 40 inches above
normal.

The wet conditions this winter followed a wet autumn season. So
overall, conditions across the region have been wetter than normal
for much of the last 6 months.

.Snow Cover and Liquid Water Content: Above to Well Above Normal

The snowpack is extensive across the region, with complete coverage
extending from southwest Iowa to southeast Wisconsin and all areas
north of that line. Snow depths range from a few inches on the
southern edge of the snowpack and quickly increase going north, with
the majority of the region measuring amounts in excess of one foot.
The deepest snow is currently being observed over northern Wisconsin
with amounts over 30 inches. These depths are anywhere from 2 to 24
inches above normal for early March.

The water equivalent of in the snow is quite impressive, with
widespread amounts of 2 to 6 inches of liquid in the snowpack. There
are even some locations in region that exceed 6 inches. Along the
southern periphery of the snowpack, liquid water content is
generally 1 to 3 inches.

The rate that this snowpack melts will be a primary determination
of the severity of flooding that occurs.

.Soil Conditions: Well Above Normal

Little changes have occurred in soil conditions since late February.
Soils across all of Iowa into southern Minnesota, Wisconsin and
northern Illinois are nearly saturated, ranking in the 90 to 99th
percentile of soil moisture rankings. The areal extent of the
saturated soils is concerning as it would imply excessive amounts of
runoff from snowmelt, rainfall, or a combination of the two will
impact most rivers in the area, leading to an enhanced threat for
flooding.

.Frost Depth: Near to Above Normal

Frost depths range from 6 to 12 inches from southern Iowa into
northeast Illinois to 3 feet in parts of Minnesota and Wisconsin. The
frozen ground across the northern parts of the Upper Mississippi
River basin will likely cause high snowmelt and rainfall runoff
amounts into the Mississippi River system this spring.

Locally, the frozen ground will also play a part to increase runoff
and the threat for flooding into tributaries and smaller creeks and
streams through March.

.River Conditions: Above Normal

River levels are generally running above normal for this time of
year. They have remained at elevated levels since September.

The continuation of cold temperatures across the midwest has kept
ice on many area rivers. Ice action has had an impact on river levels
and has caused flooding on some rivers through the winter months,
helping to keep levels above normal.

.Ice Jam Flooding:

Where rivers are still ice covered, high amounts of runoff from
either snowmelt or moderate to heavy rain could cause ice to break-
up and form ice jams. Any ice jams will have the potential to cause
flooding. This will remain a threat until all area rivers are ice
free.

.Looking ahead:

Active weather is expected through the middle of March with the
potential for several large storm systems to impact the region with
both rain and snow. This could further build up the snowpack in some
areas, promote melting across the southern fringe of the snowpack,
and if soils are able to thawed, will further saturate the ground.
Looking to the second half of March, a drier weather pattern is
favored, with below normal temperatures looking to continue through
the remainder of March. Of note, average temperatures rise
considerably through the month of March. By the end of the month,
normal temperatures for most areas are above freezing. Therefore a
forecast of near normal temperatures will be promoting snowmelt.

The longer into the spring that the snow remains, the higher the
potential for a rapid snowmelt. A faster snowmelt will promote an
increased chance for a higher degree of flooding.

.Summary:

All factors in consideration for flooding potential are indicating
the probabilities are high for spring flooding along the Mississippi
River, as well as tributary rivers in eastern Iowa and western
Illinois. A lesser probability for flooding exists for smaller
rivers in northeast Missouri and west central Illinois. These
factors would also indicate that the potential does exist for high
impact flooding to occur. The occurrence of significant flooding
will be dependent on how fast the snowpack melts, as well as if the
region receives additional heavy rains this spring. A gradual melt
with little additional precipitation would cause flooding to be much
less severe.

Ice jam flooding will be a possibility as long as ice remains in the
rivers and cold air is anticipated across the area.

.Numerical Weather Outlooks...

The numerical weather outlook provides long-range probabilistic river
outlooks for river basins in the NWS Quad Cities service area. This
outlook is divided into three parts, the first part for the
probabilities of minor, moderate and major flooding, the second part
for high water and the final part for low water.

In Table 1 below, the current (CS) and historical (HS) or normal
probabilities of exceeding minor, moderate and major flood stages
are listed for the valid time period.

CS values indicate the probability of reaching a flood category
based on current conditions.

HS values indicate the probability of reaching a flood category
based on historical or normal conditions.

When the value of CS is greater than HS, the probability of
exceeding that level is higher than normal. When the value of CS
is less than HS, the probability of exceeding that level is lower
than normal.

...Table 1--Probabilities for minor, moderate and major flooding...
                    Valid Period:  03/11/2019 - 06/09/2019

                                       :    Current and Historical
                                       :     Chances of Exceeding
                                       :       Flood Categories
                                       :      as a Percentage (%)
                      Categorical      :
                   Flood Stages (ft)   :   Minor    Moderate   Major
Location           Minor   Mod   Major :  CS   HS   CS   HS   CS   HS
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Mississippi River
Dubuque LD11        16.0   17.0   20.5 : >95   40  >95   32  >95   10
Dubuque             17.0   18.0   21.5 : >95   49  >95   39  >95   11
Bellevue LD12       17.0   18.0   20.0 : >95   32  >95   19  >95   10
Fulton LD13         16.0   18.0   20.0 : >95   48  >95   27  >95   11
Camanche            17.0   18.5   20.5 : >95   42  >95   28  >95   11
Le Claire LD14      11.0   12.0   13.5 : >95   46  >95   30  >95   12
Rock Island LD15    15.0   16.0   18.0 : >95   57  >95   46  >95   19
Ill. City LD16      15.0   16.0   18.0 : >95   56  >95   42  >95   19
Muscatine           16.0   18.0   20.0 : >95   59  >95   42  >95   19
New Boston LD17     15.0   16.5   18.5 : >95   61  >95   48  >95   23
Keithsburg          14.0   15.5   17.0 : >95   61  >95   46  >95   24
Gladstone LD18      10.0   12.0   14.0 : >95   62  >95   45  >95   21
Burlington          15.0   16.5   18.0 : >95   61  >95   44  >95   25
Keokuk LD19         16.0   17.5   19.0 : >95   31  >95   23   90   10
Gregory Landing     15.0   18.0   25.0 : >95   62  >95   37   38   <5

:Maquoketa River
Manchester Hwy 20   14.0   17.0   20.0 :  50   22   21   16   12    8
Maquoketa           24.0   26.0   28.5 :  67   18   48   13   26    8

:Wapsipinicon River
Independence        12.0   13.0   15.0 :  27    8   13    7    7   <5
Anamosa Shaw Rd     14.5   18.0   21.5 :  89   26   25   12    7   <5
De Witt 4S          11.0   11.5   12.5 : >95   68  >95   64  >95   45

:North Skunk River
Sigourney           16.0   18.0   21.0 :  78   55   51   40   12   11

:Skunk River
Augusta             15.0   17.0   20.0 :  65   46   50   32   18   14

:Cedar River
Vinton              15.0   18.0   19.0 : >95   20   50    8   36    6
Palo Blairs Ferry   12.5   15.5   17.0 : >95   30   44    7   23   <5
Cedar Rapids        12.0   14.0   16.0 : >95   32   93   19   66    9
Cedar Bluff         16.0   20.0   26.0 : >95   32   61    9    6   <5
Conesville          13.0   15.0   16.5 : >95   56  >95   22   52    8

:Iowa River
Marengo             15.0   17.0   19.0 : >95   67  >95   48   38    6
Iowa City           23.5   24.5   26.0 :  21    6   16   <5   <5   <5
Lone Tree           16.0   18.5   22.0 :  30   14    8    6   <5   <5
Columbus Jct        23.0   25.0   26.5 :  74   14   36    5   20   <5
Wapello             21.0   25.0   27.5 : >95   53   42    7   16   <5
Oakville            11.0   15.0   20.0 : >95   51   39    7   <5   <5

:English River
Kalona              14.0   16.0   18.0 : >95   48   31   33    9   13

:Des Moines River
Keosauqua           22.0   25.0   27.0 :  17    9    7   <5   <5   <5
St Francisville     18.0   22.0   25.0 :  71   43    9    6   <5   <5

:Fox River
Wayland             15.0   18.0   20.0 :  32   28    9   10   <5   <5

:Pecatonica River
Freeport            13.0   14.0   16.0 : >95   43   91   23   24   <5

:Rock River
Como                12.5   15.5   18.0 :  86   24   25    8   <5   <5
Joslin              12.0   14.0   16.5 : >95   57  >95   38   66   17
Moline              12.0   13.0   14.0 : >95   56  >95   32   82   23

:Green River
Geneseo             15.0   16.5   18.0 :  46   25   28   16   14    9

:La Moine River
Colmar              20.0   22.0   24.0 : >95   64   54   43   22   19

Legend
CS = Conditional Simulation (Current Outlook)
HS = Historical Simulation
ft = Feet


In Table 2 below, the 95 through 5 percent columns indicate the
probability of exceeding the listed stage levels (ft) for the valid
time period.

...Table 2--Exceedance Probabilities...

                               Chance of Exceeding Stages
                                  at Specific Locations
                          Valid Period: 03/11/2019 - 06/09/2019
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Dubuque LD11         21.2   21.6   22.5   24.4   26.2   28.6   29.5
Dubuque              23.0   23.5   24.5   26.1   27.5   29.8   30.6
Bellevue LD12        20.6   20.9   21.6   23.1   24.2   26.0   26.5
Fulton LD13          21.2   21.5   22.4   24.2   25.8   28.3   29.3
Camanche             21.8   22.2   23.1   24.8   26.3   28.8   29.8
Le Claire LD14       15.0   15.3   16.1   17.8   19.5   22.2   23.4
Rock Island LD15     20.1   20.4   21.2   22.6   24.3   26.5   27.5
Ill. City LD16       20.5   20.8   22.2   24.1   25.8   27.8   28.6
Muscatine            22.2   22.4   23.8   25.2   26.8   28.6   29.4
New Boston LD17      21.3   21.6   22.6   23.9   25.6   27.3   28.0
Keithsburg           18.3   19.0   20.0   21.0   23.2   25.1   25.7
Gladstone LD18       15.0   15.9   17.0   18.3   20.7   22.7   23.3
Burlington           19.1   19.9   21.2   22.3   24.7   26.0   26.2
Keokuk LD19          18.1   19.0   20.3   21.5   24.2   26.2   26.9
Gregory Landing      20.3   21.2   22.6   23.9   26.1   27.6   28.3

:Maquoketa River
Manchester Hwy 20    10.1   10.5   11.5   13.9   15.8   20.7   21.3
Maquoketa            19.6   20.6   22.9   25.7   28.6   30.2   32.6

:Wapsipinicon River
Independence          9.1    9.5    9.9   10.8   12.1   13.4   15.7
Anamosa Shaw Rd      13.7   14.3   15.1   16.2   18.0   19.9   22.2
De Witt 4S           12.5   12.7   12.9   13.3   13.5   13.9   13.9

:North Skunk River
Sigourney            14.5   15.0   16.5   18.0   19.6   21.5   21.8

:Skunk River
Augusta              12.8   12.9   13.5   17.0   19.4   21.2   23.4

:Cedar River
Vinton               15.1   15.3   16.3   18.0   19.9   21.0   21.3
Palo Blairs Ferry    13.2   13.3   14.0   15.3   16.9   17.8   18.2
Cedar Rapids         13.8   14.0   15.2   17.7   20.6   22.4   23.3
Cedar Bluff          17.2   17.6   18.7   21.1   23.8   25.4   26.2
Conesville           15.0   15.2   15.6   16.6   17.6   18.3   18.7

:Iowa River
Marengo              17.7   17.9   18.3   18.8   19.2   19.6   19.7
Iowa City            19.4   19.4   19.5   19.7   22.9   25.3   25.9
Lone Tree            13.2   13.4   14.0   14.4   16.8   18.3   19.0
Columbus Jct         21.0   21.2   22.6   24.5   26.0   27.3   28.1
Wapello              22.1   22.3   23.3   24.8   26.2   28.3   29.6
Oakville             11.8   12.0   13.0   14.4   15.8   17.8   19.1

:English River
Kalona               14.1   14.3   14.9   15.4   16.3   17.9   19.2

:Des Moines River
Keosauqua            17.7   18.3   19.3   20.3   21.5   22.5   26.1
St Francisville      16.0   16.6   17.8   19.2   20.6   21.8   24.6

:Fox River
Wayland              11.4   11.7   12.1   12.5   15.8   17.8   19.2

:Pecatonica River
Freeport             13.8   14.1   14.4   15.1   16.0   16.5   17.0

:Rock River
Como                 12.0   12.5   13.2   14.1   15.5   16.5   16.7
Joslin               14.7   15.2   16.3   17.5   19.1   19.9   20.3
Moline               13.2   13.5   14.2   15.3   16.4   17.3   18.0

:Green River
Geneseo              13.5   13.5   13.8   14.7   17.0   18.7   21.2

:La Moine River
Colmar               20.7   20.9   21.0   22.3   23.6   25.3   25.9


In Table 3 below, the 95 through 5 percent columns indicate the
probability of falling below the listed stage levels (ft) for the
valid time period.

...Table 3--Non-Exceedance Probabilities...

                            Chance of Falling Below Stages
                                 at Specific Locations
                          Valid Period: 03/11/2019 - 06/09/2019
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Dubuque LD11          5.1    5.0    4.9    4.7    4.7    4.6    4.5
Dubuque               8.0    7.9    7.8    7.7    7.7    7.6    7.6
Bellevue LD12         5.2    5.0    4.8    4.6    4.5    4.3    4.3
Fulton LD13           6.2    5.9    5.6    5.0    4.9    4.8    4.8
Camanche              9.6    9.5    9.4    9.2    9.2    9.1    9.0
Le Claire LD14        5.6    5.6    5.3    5.1    4.9    4.8    4.8
Rock Island LD15      8.2    8.1    7.9    7.4    6.9    6.0    5.7
Ill. City LD16        6.6    6.5    6.4    6.2    5.6    4.8    4.7
Muscatine             8.2    8.1    8.0    7.8    7.5    6.8    6.7
New Boston LD17       8.2    8.1    7.9    7.5    6.6    5.4    5.0
Keithsburg            9.4    9.3    9.3    9.1    8.0    6.9    6.8
Gladstone LD18        3.8    3.8    3.7    3.7    3.5    2.6    2.5
Burlington           10.1   10.0   10.0   10.0    9.7    8.6    8.6
Keokuk LD19           6.0    5.9    5.9    5.9    5.7    4.9    4.8
Gregory Landing       8.8    8.7    8.6    8.4    7.5    6.9    6.8

:Maquoketa River
Manchester Hwy 20     4.5    4.5    4.4    4.2    4.1    4.0    4.0
Maquoketa            12.5   12.3   11.8   11.5   11.2   11.0   11.0

:Wapsipinicon River
Independence          5.6    5.5    5.4    5.3    5.1    5.0    5.0
Anamosa Shaw Rd       6.9    6.8    6.4    6.1    5.8    5.5    5.3
De Witt 4S            8.1    7.9    7.4    7.0    6.5    6.1    6.0

:North Skunk River
Sigourney             6.6    6.4    5.8    5.2    4.9    4.6    4.6

:Skunk River
Augusta               4.9    4.6    3.9    3.0    2.5    2.1    2.0

:Cedar River
Vinton                4.3    4.2    4.0    3.7    3.3    3.1    2.9
Palo Blairs Ferry     5.2    5.1    4.7    4.2    4.0    3.6    3.5
Cedar Rapids          5.1    4.9    4.7    4.4    4.3    4.1    4.0
Cedar Bluff           6.8    6.7    6.2    5.6    5.4    5.1    4.9
Conesville            7.9    7.8    7.5    7.0    6.5    6.2    6.1

:Iowa River
Marengo               9.3    9.1    8.6    8.1    7.6    7.3    7.2
Iowa City            11.0   10.9   10.7   10.6   10.3    9.7    9.6
Lone Tree             8.4    7.6    6.7    5.9    5.3    4.7    4.6
Columbus Jct         13.7   13.6   13.1   11.2   10.5   10.1    9.9
Wapello              15.2   15.1   15.1   14.0   13.2   12.7   12.6
Oakville              5.0    4.9    4.9    4.2    3.4    3.1    3.0

:English River
Kalona                5.0    5.0    4.6    4.4    4.2    4.0    4.0

:Des Moines River
Keosauqua            15.4   14.9   14.1   12.7   12.0   11.4   11.2
St Francisville      13.1   12.7   11.8   10.0    9.0    8.0    7.7

:Fox River
Wayland               2.4    2.3    2.2    2.0    1.9    1.9    1.8

:Pecatonica River
Freeport              8.1    7.8    6.7    5.8    5.1    4.8    4.7

:Rock River
Como                  6.6    6.1    5.6    4.8    4.3    4.0    4.0
Joslin                9.4    8.7    8.0    7.1    6.3    5.9    5.9
Moline               10.0    9.7    9.4    8.9    8.5    8.3    8.3

:Green River
Geneseo               4.7    4.6    4.5    4.3    4.0    3.7    3.7

:La Moine River
Colmar                5.5    5.3    4.6    3.8    3.5    3.2    3.1

These long-range probabilistic outlooks contain forecast values that
are calculated using multiple season scenarios from 30 or more years
of climatological data, including current conditions of the
river, soil moisture, snow cover, and 30 to 90 day long-range
outlooks of temperature and precipitation. By providing a range of
probabilities, the level of risk associated with long-range planning
decisions can be determined. These probabilistic forecasts are part
of the National Weather Service`s Advanced Hydrologic Prediction
Service.

Visit our web site at http://www.weather.gov/dvn for more weather and
water information.

The next outlook will be issued near the end of March.

$$

Brooks



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