Flood Potential Outlook
Issued by NWS Omaha/Valley, NE

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FGUS73 KOAX 151818
ESFOAX
NEC003-023-025-039-053-055-067-095-107-109-119-127-139-141-147-151-
153-155-159-167-IAC071-085-133-137-145-155-DDHHMM-

Probabilistic Hydrologic Outlook
National Weather Service Omaha NE
1211 PM CST Thu Feb 15 2018

...Spring Flood Outlook...

...There is Above-Normal Risk for Spring Flooding due to ice jams,
otherwise, the risk for spring flooding is near normal...

This flood outlook is for the National Weather Service (NWS)
Omaha/Valley Hydrologic Services Area. This area includes eastern
Nebraska and portions of southwest Iowa including the following
rivers and their tributaries:

Missouri River from Decatur to Rulo
Niobrara River from Verdel to the Missouri River
Big Blue River from Surprise to the Kansas border
Elkhorn River from Neligh to the Platte River confluence
Platte River from Duncan to the Missouri River confluence
Other tributaries to the Missouri River in Iowa and Nebraska

                 ** Current Flood Outlook Highlights **
.Overview: This year there are two important aspects to the spring
flood outlook. The first is the risk of flooding due to ice jams.
Along area rivers, significant ice cover remains in place. While this
condition isn`t uncommon, it has been several years since thick ice
has been observed in eastern Nebraska. This coupled with the
potential for below-normal temperatures through the end of February
could lead to a later-than-normal ice breakup. The other aspect to
this year`s outlook is the general flood risk due to snowmelt, past
precipitation and soil conditions. This year that element of flood
risk is near normal.

                  ***********************************
                  ** Summary of Current Conditions **
                  ***********************************

.Mountain Snowpack: To date the snowpack in the headwaters of the
Missouri River is at 137% of normal. The snowpack in the headwaters
of the Platte River is at 89% of normal.

.Plains Snowpack: Appreciable snow cover remains across much of
eastern Nebraska and western Iowa. In northeast Nebraska the water
content of the snow ranges from 0.3 inches to one inch.

.Ice Jam Threat: Recent ice thickness measurements indicate there is
anywhere from 12 to 18 inches of ice on the Lower Platte River. This
risk is conditional and will depend on timing of breakup and eventual
ice movement. For now, persons along the Platte, Elkhorn and Loup
Rivers should remain vigilant to this flood potential.

.Soil Conditions: Soil moisture is near normal for most areas with
some areas of northeast Nebraska reporting above-normal soil
moisture. Reports indicate frost depths range from 8 to 14 inches.
Each year frost is a conditional threat.  The contribution of frost
to overall flood threat depends on the presence of frost during
periods of heavy spring rain. In most years, the frost is gone prior
to spring rains.

.Current River Conditions: This time of year the amount of water in
rivers is mostly unknown due to ice cover and those effects. For the
rivers we have real-time flow information for, most are in the normal
to above normal category.

.Climate Outlook for the next two weeks: The latest forecast favors
below-normal temperatures and above-normal precipitation.

.Climate Outlook for March through May: The latest forecast favors
equal chances for below-near-above normal temperatures and equal
chances for below-near-above normal precipitation.

Below is some river specific information related to this years
outlook.

                ***************************************
                * Missouri River from Decatur to Rulo *
                ***************************************

Overview: There is a greater than 50% chance for minor flooding along
the Missouri River below Nebraska City. Areas upstream of Nebraska
City are less likely to reach flood stage, especially above the
Platte River confluence.

                      Average                  Recent Streamflow
                     Streamflow    Long-term       as a % of
                    Past 14 Days   mean flow    long-term mean
---------------------------------------------------------------------
Missouri River:
  at Decatur           20,276        19,500         104%
  at Omaha             22,829        19,600         116%
  at Nebraska City     30,489        26,300         116%
  at Rulo              30,209        27,600         109%

                    ********************************
                    * Other rivers across the area *
                    ********************************

Most rivers across the area have a near normal threat of flooding
over the next 90 days. Due to favorable antecedent conditions,
the following rivers have an above-normal threat for reaching or
exceeding minor flood stage.

Elkhorn River (due to ice jams)
Lincoln Creek near Seward
Platte River (due to ice jams)
Salt Creek (downstream of Lincoln)
Wahoo Creek

* An updated spring flood outlook will be issued on March 1st.


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 more 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:  02/17/2018  - 05/18/2018

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Niobrara River
Verdel               7.0    9.0   10.0 :  <5   <5   <5   <5   <5   <5
:Ponca Creek
Verdel              13.5   15.0   17.0 :   7    8    5    6   <5   <5
:Elkhorn River
Neligh              11.0   12.0   14.0 :  <5   <5   <5   <5   <5   <5
Norfolk             12.0   13.0   17.0 :  <5   <5   <5   <5   <5   <5
:North Fork Elkhorn River
Pierce              12.0   14.0   16.0 :   9   10    6    8   <5   <5
:Elkhorn River
Pilger              12.0   14.0   15.0 :   5   <5   <5   <5   <5   <5
West Point          12.0   16.0   18.7 :  12    6   <5   <5   <5   <5
Winslow             18.0   20.0   24.0 :  10   <5   <5   <5   <5   <5
:Logan Creek
Uehling             18.0   19.0   21.0 :  11   <5    9   <5   <5   <5
:Maple Creek
Nickerson           11.5   13.0   17.0 :  <5   10   <5   <5   <5   <5
:Elkhorn River
Waterloo            17.0   18.0   21.0 :  <5   <5   <5   <5   <5   <5
:Platte River
Duncan               8.0    9.0   10.0 :   5    6   <5   <5   <5   <5
:Shell Creek
Columbus            20.0   21.0   22.0 :   9    5    5   <5   <5   <5
:Platte River
North Bend           8.0   12.0   15.0 :  10   13   <5   <5   <5   <5
Leshara              8.0   10.0   12.0 :  14   17   <5   <5   <5   <5
Ashland             20.0   22.0   26.0 :   9    6   <5   <5   <5   <5
:Salt Creek
Roca                19.0   21.5   23.0 :   6    7   <5   <5   <5   <5
Lincoln (N 27th S   20.5   26.5   29.0 :   7    8   <5   <5   <5   <5
Greenwood           20.0   24.0   31.0 :  23   18    6    7   <5   <5
:Wahoo Creek
Ithaca              19.0   22.0   23.0 :  17   37    7    9   <5   <5
:Salt Creek
Ashland             16.0   20.0   23.0 :  31   32   10    9    5   <5
:Platte River
Louisville           9.0   11.0   12.0 :  11    7   <5   <5   <5   <5
:Big Blue River
Surprise             7.0   10.0   12.0 :  13   10   <5   <5   <5   <5
:Lincoln Creek
Seward              15.0   17.0   20.0 :  34   23    8    6   <5   <5
:Big Blue River
Seward              18.0   22.0   27.0 :  15    9   <5   <5   <5   <5
:West Fork Big Blue River
Dorchester          15.0   22.0   24.4 :   6   22   <5   <5   <5   <5
:Big Blue River
Crete               21.0   25.0   29.0 :  28   29   <5    6   <5   <5
:Turkey Creek
Wilber              12.5   16.0   21.0 :  33   32   <5   <5   <5   <5
:Big Blue River
Beatrice            18.0   26.0   32.0 :  12   22   <5   <5   <5   <5
Barneston           20.0   27.0   33.0 :   7   13   <5    6   <5   <5
:Little Blue River
Fairbury            18.5   20.0   23.0 :  <5   <5   <5   <5   <5   <5
:Maple River
Mapleton            21.0   24.0   27.0 :   5    5   <5   <5   <5   <5
:Little Sioux River
Turin               25.0   28.0   34.5 :   6    8    5    6   <5   <5
:Soldier River
Pisgah              28.0   29.0   30.0 :  <5   <5   <5   <5   <5   <5
:Boyer River
Logan               21.0   22.0   25.0 :   6    5    5    5    5   <5
:Weeping Water Creek
Union               25.0   28.0   30.0 :   6   11   <5   <5   <5   <5
:East Nishnabotna River
Red Oak             18.0   22.0   27.0 :  22   36   10   16   <5    6
:West Nishnabotna River
Hancock             14.0   19.0   23.0 :  31   34   12   25    5    5
Randolph            19.0   22.0   24.0 :  34   42    8   14    5    5
:Nishnabotna River
Hamburg             25.0   27.5   33.0 :  22   44    7   12   <5   <5
:Little Nemaha River
Auburn              22.0   23.0   27.0 :   9   13    7   11   <5   <5
:North Fork Big Nemaha River
Humboldt            28.0   29.5   31.0 :  <5   <5   <5   <5   <5   <5
:Big Nemaha River
Falls City          27.0   30.0   36.0 :   6   13   <5    8   <5   <5
:Nodaway River
Clarinda            23.0   26.0   29.0 :   6    7   <5   <5   <5   <5

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: 02/17/2018  - 05/18/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Niobrara River
Verdel                3.5    3.6    3.8    4.0    4.2    4.5    5.0
:Ponca Creek
Verdel                5.5    6.1    7.5    8.2    9.3   12.2   14.7
:Elkhorn River
Neligh                3.8    4.3    5.0    6.3    7.5    8.4    9.2
Norfolk               3.6    3.8    4.2    5.3    6.3    7.5    9.5
:North Fork Elkhorn River
Pierce                2.8    3.2    3.6    5.9    8.3   11.8   14.3
:Elkhorn River
Pilger                8.3    8.5    8.7    9.2    9.7   10.6   11.9
West Point            8.5    8.7    9.1    9.8   10.7   12.5   13.2
Winslow              11.5   11.9   12.8   14.2   15.7   18.1   19.2
:Logan Creek
Uehling               9.7   10.2   11.6   13.3   16.1   18.4   19.6
:Maple Creek
Nickerson             5.0    5.2    6.0    7.2    8.5   10.2   10.7
:Elkhorn River
Waterloo              7.1    7.3    8.1   10.2   12.4   14.6   15.4
:Platte River
Duncan                4.3    4.4    4.6    5.1    6.2    7.1    7.9
:Shell Creek
Columbus              8.7    8.8   10.1   15.2   17.6   19.8   20.9
:Platte River
North Bend            5.0    5.2    5.5    6.4    7.1    7.9    8.7
Leshara               5.0    5.2    5.7    6.7    7.5    8.4    9.2
Ashland              17.0   17.1   17.5   18.4   19.0   19.9   20.4
:Salt Creek
Roca                  1.7    2.8    4.6    7.3   13.8   18.2   19.7
Lincoln (N 27th S     2.5    4.5    6.1   10.1   14.5   18.1   21.6
Greenwood             2.4    4.3    6.9   12.2   18.5   22.4   25.1
:Wahoo Creek
Ithaca                3.5    3.8    6.2    9.9   14.6   21.8   22.3
:Platte River
Louisville            5.2    5.3    6.2    7.0    8.1    9.1    9.5
:Big Blue River
Surprise              2.6    2.8    3.2    4.0    5.7    7.5    8.8
:Lincoln Creek
Seward                6.8    7.3   11.1   13.6   15.5   16.6   18.2
:Big Blue River
Seward                3.7    4.3    7.7   11.7   15.5   19.1   20.3
:West Fork Big Blue River
Dorchester            4.1    4.7    7.0   10.6   12.7   14.6   15.5
:Big Blue River
Crete                 9.6   10.5   14.3   18.5   21.4   23.3   23.9
:Turkey Creek
Wilber                2.9    5.1    7.7   10.9   13.2   14.8   15.8
:Big Blue River
Beatrice              5.3    5.9    8.5   11.0   14.7   18.4   19.5
Barneston             5.6    6.4    9.4   12.2   16.0   18.8   22.0
:Little Blue River
Fairbury              7.5    7.7    9.0   11.6   14.1   15.4   17.4
:Maple River
Mapleton              6.3    7.3    8.8   11.2   12.8   14.8   21.2
:Little Sioux River
Turin                 9.0    9.4   11.5   16.5   19.2   22.4   27.7
:Soldier River
Pisgah                6.3    6.9    7.9    9.4   10.7   11.9   16.6
:Boyer River
Logan                 7.9    8.3    9.6   12.1   15.8   19.7   23.0
:Weeping Water Creek
Union                 4.2    5.4    7.6    9.5   16.4   21.6   25.7
:East Nishnabotna River
Red Oak               7.3    8.0   10.9   12.7   16.6   21.7   24.2
:West Nishnabotna River
Hancock               5.4    6.4    7.9    8.8   16.3   20.1   23.0
Randolph             10.4   11.4   14.0   16.3   20.5   21.6   23.8
:Nishnabotna River
Hamburg              11.1   12.3   17.1   22.1   24.6   26.8   28.8
:Little Nemaha River
Auburn                7.0    9.7   12.4   14.2   16.8   21.3   23.8
:North Fork Big Nemaha River
Humboldt              4.6    5.3    6.8    8.3   13.2   17.3   20.1
:Big Nemaha River
Falls City            6.2    8.4   11.3   14.9   20.8   24.0   28.2
:Nodaway River
Clarinda             11.4   11.7   13.0   13.9   18.8   21.1   23.7

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--Nonexceedance Probabilities...

                            Chance of Falling Below Stages
                                 at Specific Locations
                          Valid Period: 02/17/2018  - 05/18/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Niobrara River
Verdel                3.4    3.4    3.4    3.4    3.3    3.3    3.3
:Ponca Creek
Verdel                4.8    4.8    4.8    4.8    4.8    4.7    4.0
:Elkhorn River
Neligh                0.9    0.8    0.7    0.5    0.3    0.3    0.2
Norfolk               2.9    2.9    2.8    2.7    2.6    2.5    2.5
:North Fork Elkhorn River
Pierce                2.6    2.6    2.6    2.5    2.3    2.2    2.1
:Elkhorn River
Pilger                7.1    7.1    7.0    6.9    6.5    6.3    6.3
West Point            7.0    7.0    7.0    6.8    6.5    6.4    6.3
Winslow               8.8    8.8    8.8    8.7    8.5    8.4    8.4
:Logan Creek
Uehling               3.8    3.8    3.8    3.8    3.7    3.6    3.5
:Maple Creek
Nickerson             1.0    1.0    1.0    1.0    1.0    1.0    1.0
:Elkhorn River
Waterloo              3.3    3.3    3.3    3.2    2.9    2.7    2.6
:Platte River
Duncan                4.1    4.1    4.1    3.9    3.4    3.4    3.4
:Shell Creek
Columbus              0.6    0.6    0.6    0.6    0.6    0.5    0.5
:Platte River
North Bend            3.7    3.6    3.6    3.5    3.0    2.9    2.8
Leshara               4.1    4.1    4.1    3.9    3.5    3.2    3.2
Ashland              15.3   15.3   15.3   15.1   14.8   14.6   14.5
:Salt Creek
Roca                  1.7    1.7    1.7    1.7    1.7    1.7    1.6
Lincoln (N 27th S     2.5    2.5    2.5    2.5    2.5    2.4    2.4
Greenwood             2.4    2.4    2.4    2.4    2.4    2.3    2.3
:Wahoo Creek
Ithaca                3.5    3.5    3.5    3.5    3.5    3.4    3.4
:Platte River
Louisville            3.8    3.8    3.7    3.6    3.3    3.1    3.0
:Big Blue River
Surprise              1.3    1.3    1.3    1.3    1.3    1.2    1.2
:Lincoln Creek
Seward                3.9    3.9    3.9    3.8    3.8    3.7    3.6
:Big Blue River
Seward                1.6    1.6    1.6    1.6    1.6    1.5    1.5
:West Fork Big Blue River
Dorchester            2.6    2.6    2.6    2.6    2.5    2.5    2.4
:Big Blue River
Crete                 7.9    7.9    7.9    7.9    7.8    7.8    7.7
:Turkey Creek
Wilber                1.6    1.5    1.5    1.1    0.9    0.6    0.5
:Big Blue River
Beatrice              3.4    3.4    3.4    3.4    3.3    3.2    3.2
Barneston             4.2    4.1    3.9    3.8    3.7    3.6    3.6
:Little Blue River
Fairbury              6.5    6.5    6.5    6.5    6.3    6.3    6.2
:Maple River
Mapleton              5.1    5.1    5.1    5.1    5.1    5.0    5.0
:Little Sioux River
Turin                 7.1    7.1    7.1    7.1    7.1    7.0    7.0
:Soldier River
Pisgah                3.6    3.6    3.6    3.6    3.5    3.4    3.3
:Boyer River
Logan                 3.3    3.3    3.3    3.3    3.3    3.2    3.2
:Weeping Water Creek
Union                 2.8    2.8    2.8    2.8    2.8    2.8    2.8
:East Nishnabotna River
Red Oak               5.6    5.6    5.6    5.6    5.5    5.5    5.4
:West Nishnabotna River
Hancock               1.2    1.2    1.2    1.2    1.2    1.2    1.2
Randolph              7.7    7.7    7.7    7.6    7.6    7.4    7.4
:Nishnabotna River
Hamburg               6.7    6.7    6.6    6.6    6.5    6.1    5.7
:Little Nemaha River
Auburn                3.2    3.2    3.2    3.2    3.2    3.2    3.2
:North Fork Big Nemaha River
Humboldt              1.8    1.8    1.8    1.8    1.8    1.8    1.7
:Big Nemaha River
Falls City            3.7    3.7    3.7    3.7    3.7    3.6    3.6
:Nodaway River
Clarinda             10.6   10.6   10.6   10.6   10.5   10.5   10.5

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 weather.gov/oax for more weather and water
information.

$$





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