Flood Potential Outlook
Issued by NWS Bismarck, ND

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PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
225 PM CDT THU AUG 28 2015


...Flood and Water Resources Outlook...

This probablistic flood outlook is for the Missouri and James River
basins of North Dakota and covers the period of late August through
late November.

The following message has four sections. The first provides some text
on the highlights of this outlook and conditions affecting the local
hydrology. The second section gives the current and normal/historical
risks of flooding as determined by the Ensemble Streamflow Forecast
model of the National Weather Service. The third section gives the
current probabilities for reaching flood stage at the listed forecast
locations. And finally, the fourth section covers the risk of the
river sites falling below the listed stages.

...Flood Outlook Highlights...
In general, risks presented below tend to reflect a seasonally
normal probability of widespread flooding. This generally should be
interpreted as a relatively low risk of problematic high water along
the medium to larger rivers and streams.

...Current Conditions...
Most rivers and streams tend to have near normal streamflow for this
time of year. Reservoirs are a mixed bag with some near their full
supply level and others well below FSL, but all have their
full flood storage available if needed. Soil moisture levels remain
adequate, and are not considered a risk.

...Weather Outlook...
The near term, 6-10 and 8-14 day outlooks show the region has a
slightly greater than normal chance of precipitation and above
normal temperatures. Looking longer term into the climate outlooks,
a strengthening El Nino is expected through the fall and last well
into winter, if not next spring. This is noticeable in the winter
outlooks where the region is expected to have a well above normal
chance for above normal temperatures. However, in the shorter
one-month and three-month outlooks for September through November,
not enough effects from the still developing El Nino are expected
to significantly change the natural variability of climate for the
region.


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 = 08/29/2015  - 11/27/2015

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Pipestem Creek
Pingree             11.0   13.0   15.0 :  <5   <5   <5   <5   <5   <5
:James River
Grace City          12.0   14.0   15.0 :  <5   <5   <5   <5   <5   <5
Lamoure             14.0   16.0   18.0 :  <5   <5   <5   <5   <5   <5
:Cannonball River
Regent              22.0   24.0   26.0 :  <5   <5   <5   <5   <5   <5
:Cedar Creek
Raleigh             12.0   14.0   16.0 :  <5   <5   <5   <5   <5   <5
:Cannonball River
Breien              10.0   20.0   23.0 :  15    8   <5   <5   <5   <5
:Beaver Creek
Linton              12.0   14.0   16.0 :  <5    7   <5   <5   <5   <5
:Little Muddy River
Williston           10.0   12.0   14.0 :  <5   <5   <5   <5   <5   <5
:Little Missouri
Marmarth            18.0   23.0   30.0 :  <5   <5   <5   <5   <5   <5
:Little Missouri River
Medora              15.0   18.0   20.0 :  <5   <5   <5   <5   <5   <5
Watford City        20.0   24.0   30.0 :  <5   <5   <5   <5   <5   <5
:Knife River
Manning             15.0   17.0   20.0 :   5    5   <5   <5   <5   <5
:Spring Creek
Zap                 14.0   18.0   20.0 :   8    6    6    5   <5   <5
:Knife River
Hazen               21.0   24.0   25.0 :   8    6    6   <5   <5   <5
:Heart River
Mandan              17.0   23.0   28.0 :  <5   <5   <5   <5   <5   <5
:Apple Creek
Menoken             15.0   16.0   17.0 :  <5   16   <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 = 08/29/2015  - 11/27/2015
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Pipestem Creek
Pingree               4.8    4.8    4.8    4.8    5.0    5.5    6.7
:James River
Grace City            4.2    4.2    4.2    4.2    4.4    5.5    6.3
Lamoure               7.5    7.5    7.5    7.5    7.5    8.1    9.2
:Cannonball River
Regent                5.2    5.2    5.2    6.0    7.5    9.6   10.6
:Cedar Creek
Raleigh               1.1    1.1    1.2    2.4    5.2    6.6    7.4
:Cannonball River
Breien                2.4    2.5    3.1    5.2    8.5   10.8   12.1
:Beaver Creek
Linton                4.3    4.3    4.4    4.7    7.4    9.6   10.9
:Little Muddy River
Williston             4.7    4.7    4.7    4.7    5.5    7.4    8.1
:Little Missouri
Marmarth              1.6    1.6    1.6    1.7    4.9   10.1   10.8
:Little Missouri River
Medora                2.3    2.3    2.3    2.6    6.1   11.0   11.6
Watford City         -0.0   -0.0   -0.0    0.3    3.8    7.4    8.4
:Knife River
Manning               6.4    6.4    6.4    6.4    8.2   10.2   14.7
:Spring Creek
Zap                   5.0    5.0    5.0    5.0    6.6   11.2   19.1
:Knife River
Hazen                 1.6    1.6    1.6    1.6    6.9   15.4   24.2
:Heart River
Mandan                0.0    0.0    0.0    0.0    3.5    8.4   15.4
:Apple Creek
Menoken               5.3    5.3    5.3    5.3    6.4    9.8   14.3

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 = 08/29/2015  - 11/27/2015
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Pipestem Creek
Pingree               4.8    4.8    4.8    4.8    4.8    4.8    4.8
:James River
Grace City            4.2    4.2    4.2    4.2    4.2    4.2    4.2
Lamoure               7.3    7.2    7.0    7.0    6.9    6.9    6.9
:Cannonball River
Regent                5.2    5.2    5.2    5.2    5.2    5.2    5.2
:Cedar Creek
Raleigh               0.3    0.3    0.3    0.3    0.3    0.3    0.3
:Cannonball River
Breien                2.3    2.3    2.3    2.3    2.3    2.3    2.3
:Beaver Creek
Linton                4.2    4.2    4.2    4.2    4.2    4.2    4.2
:Little Muddy River
Williston             4.7    4.7    4.7    4.7    4.7    4.7    4.7
:Little Missouri
Marmarth              1.5    1.4    1.4    1.4    1.4    1.4    1.4
:Little Missouri River
Medora                2.1    2.0    2.0    2.0    2.0    2.0    2.0
Watford City         -0.2   -0.2   -0.2   -0.3   -0.3   -0.3   -0.3
:Knife River
Manning               6.4    6.4    6.4    6.4    6.4    6.4    6.4
:Spring Creek
Zap                   5.0    5.0    5.0    5.0    5.0    5.0    5.0
:Knife River
Hazen                 1.6    1.6    1.5    1.5    1.5    1.5    1.5
:Heart River
Mandan               -0.3   -0.4   -0.5   -0.5   -0.6   -0.6   -0.6
:Apple Creek
Menoken               5.0    5.0    4.6    4.6    4.6    4.6    4.6

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.govis for more weather and water
information.

The next outlook will be issued toward the end of next month.

$$


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