Flood Potential Outlook
Issued by NWS Quad Cities, IA IL

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Probabilistic Hydrologic Outlook
National Weather Service Quad Cities IA IL
1120 AM CST Thu Feb 15 2018

...2018 Spring Flood and Water Resources Outlook...

This is the first of two planned Spring Flood and Water Resource
Outlooks for 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, and Des
Moines Rivers in Iowa; the Fox River in Missouri; and the
Pecatonica, Rock, and La Moine Rivers in Illinois. This outlook is
for the time period from late February through May.

...The Risk for Flooding this Spring is Slightly Below Normal to
Normal...

.Flood Outlook Summary...

Lower than normal seasonal precipitation combined with dry soils and
near to below normal river streamflows suggests below normal
potential for flooding. However, deep frost will cause increased
runoff from any snowmelt or additional rains this spring, which
raises the potential for flooding slightly.

Main Points:

* Seasonal precipitation, current snow liquid water content, and
  river streamflows are near or below normal
* Cold temperatures this season allowed for deep frost development
* Despite dry conditions, deep frost could promote increased runoff
  given rapid snowmelt, significant spring rains, or a combination of
the two
* Significant spring rains will be needed for high impact flooding
  this season

NOTE: A heightened risk for flooding is not an indicator of severity.

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: Below Normal

Winter precipitation has been below normal. With the exception of
parts of northwest Illinois, the local area is up to 10 inches below
normal for accumulated snowfall this season. Looking at the entire
Upper Mississippi River Basin, much of the area is 0 to 20 inches
below normal for snowfall. Iowa had the 5th driest December on
record, while Illinois had the 7th driest. Also, the northern part
of Missouri only received 25% of the normal precipitation amounts
for the month of December. Snowfall in early February occurred with
many areas receiving 6 to 12 inches of new snow. However, the snow
had a low liquid water content so the precipitation amount did not
have a high impact on the seasonal totals.

.Snow Cover and Liquid Water Content: Near to Below Normal

Liquid water content in the current snowpack is generally measuring
less than one inch. There is an area from southwest Minnesota into
northern Wisconsin that has higher amounts of 2 to 4 inches of
liquid. However, this is a rather small portion of the entire Upper
Mississippi River Basin so even a rapid melt of this snow is not
expected to cause significant flooding.

.Soil Conditions: Below Normal

Moisture content in the soils across the local area are measuring
near to below normal. The driest conditions are being observed
across northeast Missouri, southeast Iowa, and into central Illinois
with values ranking in the 5th to 30th percentiles.

.River Conditions: Near to Below Normal

Measurements from USGS streamgages are indicating streamflows are
near to below normal across the area. This leads to a lesser chance
for flooding as the lower river levels will result in increased
capacity for additional runoff from snowmelt and spring rains.

.Frost Depth: Above Normal

The winter as a whole has had temperatures average below normal. A
few periods of well below normal temperatures back in December and
January allowed the ground to freeze to depths of 1 to 2 feet across
much of the Upper Mississippi River Basin, with up to 4 foot depths
in parts of Minnesota and Wisconsin. The deep layer of frozen ground
will prohibit percolation of snowmelt water and early spring rains,
which will have the potential to cause escalated runoff and raise
the threat for increased streamflows.

.Drought: Abnormally Dry to Moderate Drought

Abnormally dry to moderate drought conditions are ongoing from
Missouri into eastern Iowa and northwest Illinois. The driest
conditions are currently from northern Missouri into southeast Iowa.

.Ice Jam Flooding: Near Normal

Many area rivers remain ice covered. Ice jam flooding remains
possible over the next month if jams form as the ice breaks up.
While any ice covered river will have the potential for ice jams and
subsequent flooding, rivers that will be more susceptible to this
potential are the Rock, Edwards and other smaller rivers in
Illinois, and portions of the Iowa and Skunk Rivers in Iowa.

.Weather Outlooks:

An active weather pattern will be in place through the end of
February. However, the local area is expected to be on the northern
fringe of where the heaviest precipitation will fall as the storm
track is expected to be centered over the Ohio River Valley. As for
temperatures, Iowa, Illinois, and Missouri will be placed between
the colder air to the northwest and warmer air to the southeast, so
temperatures may be variable for the remainder of February.

Looking into March, the outlook is for a higher chance for below
normal temperatures, with no clear signal for above, near or below
normal precipitation.

.Numerical River Outlooks:

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:  02/18/2018 - 05/19/2018

                                       :    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 :  36   48   28   35   11   10
Dubuque             17.0   18.0   21.5 :  41   51   30   42   16   12
Bellevue LD12       17.0   18.0   20.0 :  23   32   17   22    9   10
Fulton LD13         16.0   18.0   20.0 :  37   49   20   30   15   11
Camanche            17.0   18.5   20.5 :  31   45   23   31   16   13
Le Claire LD14      11.0   12.0   13.5 :  34   48   27   32   16   16
Rock Island LD15    15.0   16.0   18.0 :  48   56   38   50   20   20
Ill. City LD16      15.0   16.0   18.0 :  40   55   34   42   20   20
Muscatine           16.0   18.0   20.0 :  47   56   34   42   19   19
New Boston LD17     15.0   16.5   18.5 :  56   59   38   51   24   27
Keithsburg          14.0   15.5   17.0 :  62   59   35   48   25   24
Gladstone LD18      10.0   12.0   14.0 :  64   57   34   45   21   21
Burlington          15.0   16.5   18.0 :  49   56   34   45   24   24
Keokuk LD19         16.0   17.5   19.0 :  28   32   21   21   13   11
Gregory Landing     15.0   18.0   25.0 :  61   61   32   38   <5   <5

:Maquoketa River
Manchester Hwy 20   14.0   17.0   20.0 :  13   17   11   13   <5   <5
Maquoketa           24.0   26.0   28.5 :  14   21   <5   16   <5    6

:Wapsipinicon River
Independence        12.0   13.0   15.0 :  11   13    6    8    5    6
Anamosa Shaw Rd     14.5   18.0   21.5 :  16   24   10   14   <5   <5
De Witt 4S          11.0   11.5   12.5 :  72   67   56   63   18   28

:North Skunk River
Sigourney           16.0   18.0   21.0 :  42   59   24   42   <5   10

:Skunk River
Augusta             15.0   17.0   20.0 :  27   38   15   28    6   14

:Cedar River
Vinton              15.0   18.0   19.0 :  13   18   <5    6   <5   <5
Cedar Rapids        12.0   14.0   16.0 :  16   25    9   13   <5    7
Conesville          13.0   15.0   16.5 :  46   53   13   21   <5    7

:Iowa River
Marengo             14.0   15.5   18.5 :  73   74   49   62   <5    5
Iowa City           22.0   23.0   25.0 :  <5    8   <5    7   <5   <5
Lone Tree           15.0   16.5   18.0 :  12   26    6   15   <5   11
Columbus Jct        19.0   22.0   23.0 :  38   52   14   21   11   12
Wapello             20.0   22.0   25.0 :  55   62   28   45   10   11
Oakville            10.0   12.0   19.0 :  36   52   14   22   <5   <5

:English River
Kalona              14.0   16.0   18.0 :  40   55   19   33    7   15

:Des Moines River
Keosauqua           22.0   25.0   27.0 :   6    9   <5   <5   <5   <5
St Francisville     18.0   22.0   25.0 :  23   35   <5    5   <5   <5

:Fox River
Wayland             15.0   18.0   20.0 :  11   25   <5   10   <5   <5

:Pecatonica River
Freeport            13.0   14.0   16.0 :  43   38   28   26   11   10

:Rock River
Como                12.5   15.5   18.0 :  30   21    7    9   <5   <5
Joslin              12.0   14.0   16.5 :  67   49   43   28   12   16
Moline              12.0   13.0   14.0 :  68   51   46   32   25   23

:Green River
Geneseo             15.0   16.5   18.0 :  22   24   12   17    9    9

:La Moine River
Colmar              20.0   22.0   24.0 :  52   66   39   44   17   21

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: 02/18/2018 - 05/19/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Dubuque LD11          9.9   11.3   12.7   14.8   17.4   20.5   23.9
Dubuque              11.7   13.0   14.2   16.5   19.0   22.1   25.4
Bellevue LD12        10.5   11.6   12.6   14.4   16.9   19.9   22.5
Fulton LD13          10.1   11.5   13.4   14.9   17.5   20.7   23.3
Camanche             12.1   13.0   14.2   15.5   18.2   21.8   24.7
Le Claire LD14        7.6    8.4    9.3   10.2   12.3   15.3   17.6
Rock Island LD15     10.5   11.4   13.1   14.8   17.3   20.7   22.3
Ill. City LD16        9.5   10.9   12.8   14.3   17.1   21.2   23.3
Muscatine            11.2   12.4   14.4   15.9   19.1   22.3   23.9
New Boston LD17      11.2   12.4   14.1   15.4   18.3   21.9   23.5
Keithsburg           10.9   11.8   13.4   14.3   17.0   19.4   20.7
Gladstone LD18        6.5    7.7    9.4   10.3   13.4   16.4   18.0
Burlington           11.9   12.8   14.3   15.0   17.9   20.7   22.1
Keokuk LD19           8.3    9.3   11.3   12.3   16.7   20.1   21.8
Gregory Landing      10.4   11.2   14.0   15.4   19.2   22.4   24.2

:Maquoketa River
Manchester Hwy 20     6.1    6.6    7.7    8.8   10.8   17.4   19.7
Maquoketa            13.2   13.7   14.7   16.7   19.6   24.3   25.4

:Wapsipinicon River
Independence          6.1    6.3    7.0    7.7    8.7   12.2   16.4
Anamosa Shaw Rd       7.5    8.3    9.8   11.3   13.3   18.0   19.8
De Witt 4S            8.4    8.9   10.7   11.7   12.1   12.8   13.2

:North Skunk River
Sigourney             6.6    9.7   12.7   14.8   18.0   19.4   20.3

:Skunk River
Augusta               3.2    5.7    8.0   11.8   15.1   17.6   20.9

:Cedar River
Vinton                7.5    8.3    9.4   11.2   13.2   15.4   16.5
Cedar Rapids          6.0    6.4    6.9    8.3   10.6   13.3   15.1
Conesville            9.5   10.0   11.3   12.7   14.3   15.7   16.1

:Iowa River
Marengo               9.8   10.8   13.3   15.5   16.5   17.8   18.1
Iowa City            12.4   13.4   15.1   17.6   19.6   19.7   20.1
Lone Tree             7.8    9.7   11.5   12.9   14.1   15.5   17.3
Columbus Jct         13.7   14.4   16.5   18.1   20.7   23.2   24.1
Wapello              15.9   16.6   18.8   20.3   22.6   24.9   26.0
Oakville              5.0    5.7    7.6    9.1   10.6   13.4   14.4

:English River
Kalona                7.5    8.4   12.0   13.2   15.4   17.3   18.4

:Des Moines River
Keosauqua            13.1   14.9   17.0   18.1   19.3   21.1   23.1
St Francisville      10.3   12.7   15.2   16.3   17.8   19.8   22.0

:Fox River
Wayland               1.9    2.7    4.6    7.8   11.2   15.5   16.9

:Pecatonica River
Freeport              8.1    9.1   10.4   12.6   14.6   16.0   17.0

:Rock River
Como                  7.0    7.7    9.0   11.2   12.8   14.3   15.9
Joslin                9.7   10.2   11.3   13.6   15.0   16.9   19.4
Moline               10.5   10.9   11.6   12.9   14.0   15.3   18.1

:Green River
Geneseo               8.0    8.8   10.6   12.1   14.4   17.4   20.7

:La Moine River
Colmar                6.7   10.1   13.7   20.6   22.8   24.9   25.7


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: 02/18/2018 - 05/19/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Mississippi River
Dubuque LD11          4.7    4.6    4.6    4.6    4.4    4.3    4.2
Dubuque               7.7    7.6    7.6    7.6    7.4    7.4    7.3
Bellevue LD12         4.3    4.3    4.2    4.2    3.9    3.8    3.7
Fulton LD13           4.6    4.6    4.6    4.5    4.4    4.4    4.3
Camanche              8.9    8.9    8.9    8.9    8.8    8.8    8.8
Le Claire LD14        4.6    4.6    4.6    4.6    4.5    4.5    4.4
Rock Island LD15      5.0    4.9    4.8    4.7    4.6    4.4    4.2
Ill. City LD16        4.1    4.0    3.9    3.8    3.8    3.6    3.5
Muscatine             6.3    6.3    6.2    6.2    6.2    6.1    6.0
New Boston LD17       4.1    4.1    3.9    3.9    3.8    3.6    3.4
Keithsburg            5.9    5.9    5.8    5.8    5.7    5.6    5.5
Gladstone LD18        1.6    1.6    1.5    1.4    1.4    1.2    1.1
Burlington            8.1    8.0    7.9    7.9    7.8    7.8    7.6
Keokuk LD19           3.5    3.5    3.3    3.2    3.0    2.7    2.5
Gregory Landing       6.4    6.4    6.4    6.3    6.3    6.3    6.3

:Maquoketa River
Manchester Hwy 20     3.8    3.8    3.8    3.8    3.8    3.8    3.8
Maquoketa            10.4   10.3   10.2   10.1   10.1   10.0    9.9

:Wapsipinicon River
Independence          4.9    4.9    4.8    4.8    4.8    4.8    4.8
Anamosa Shaw Rd       4.9    4.9    4.9    4.9    4.8    4.8    4.8
De Witt 4S            5.5    5.5    5.4    5.3    5.3    5.2    5.1

:North Skunk River
Sigourney             3.4    3.4    3.4    3.3    3.3    3.2    3.0

:Skunk River
Augusta               1.0    1.0    0.9    0.9    0.8    0.8    0.8

:Cedar River
Vinton                2.5    2.5    2.4    2.4    2.3    2.2    2.2
Cedar Rapids          3.6    3.6    3.6    3.5    3.5    3.4    3.4
Conesville            5.9    5.8    5.7    5.6    5.5    5.4    5.3

:Iowa River
Marengo               6.1    6.0    5.9    5.9    5.9    5.8    5.7
Iowa City            10.2   10.2   10.2    9.9    9.1    9.0    9.0
Lone Tree             5.2    5.2    5.1    5.0    4.3    3.9    3.7
Columbus Jct          9.7    9.6    9.5    9.4    9.2    8.9    8.8
Wapello              11.9   11.8   11.6   11.5   11.3   11.0   10.8
Oakville              1.7    1.6    1.4    1.3    1.1    0.9    0.7

:English River
Kalona                3.5    3.5    3.4    3.4    3.4    3.3    3.3

:Des Moines River
Keosauqua            10.8   10.6   10.5   10.3   10.2   10.2   10.1
St Francisville       7.1    6.8    6.6    6.4    6.2    6.2    6.0

:Fox River
Wayland               1.5    1.5    1.4    1.3    1.2    0.8    0.8

:Pecatonica River
Freeport              5.2    5.1    4.8    4.7    4.4    4.0    3.9

:Rock River
Como                  4.6    4.6    4.3    4.2    4.1    3.7    3.5
Joslin                6.5    6.4    6.1    5.8    5.6    5.0    4.6
Moline                8.8    8.6    8.5    8.5    8.3    8.1    8.0

:Green River
Geneseo               4.3    4.1    3.9    3.7    3.2    3.0    2.8

:La Moine River
Colmar                2.9    2.8    2.6    2.4    2.2    2.1    1.9

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-day to 90-day long range weather
outlooks of temperature and precipitation. By providing long-range
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 (AHPS).

Information in this outlook has been collected from numerous
sources, including the United States Geological Survey (USGS), the
US Army Corps of Engineers (USACE), the Midwest Regional Climate
Center (MRCC), and the National Operational Remote Sensing Center
(NOHRSC).

Further weather and water information, including the statistical
data available in graphical format, can be found at the following
location: http://www.weather.gov/dvn. Additional information can be
found at the North Central River Forecast Center`s website at:
http://www.crh.noaa.gov/ncrfc.

This is the first Spring Flood and Water Resources Outlook for 2018.
the next updated outlook will be issued March 1, 2018. Regular long-
range probabilistic outlooks are issued near the end of the month
through the remainder of the year.

$$

Brooks






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