Flood Potential Outlook
Issued by NWS Bismarck, ND

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FGUS73 KBIS 222014
ESFBIS
NDC001-007-011-015-021-025-029-031-033-037-041-043-045-047-051-
053-055-057-059-065-083-085-087-089-093-103-105-302200-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
215 PM CST WED NOV 22 2017


...FLOOD AND WATER RESOURCES OUTLOOK...

This probabilistic Flood and Water Resources outlook is for
the Missouri and James River basins of North Dakota and covers
the period of late November through late February, 2018.

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...
Given the time of year, the overall risk of widespread flooding is
normally very low and this year is no exception. Overall though the
risk is very near its normal for this time of year. What is not
included in the below tables though is the risk ice related high
water. While this is not often a problem, fast rising water levels
associated with the initial freezing over of a river is common,
especially on the Missouri River itself.

...Current Conditions...
Larger reservoirs remain near normal for this time of year due
to an abundance of moisture over the past couple of years. However,
stock dams, rivers, and small wetlands have been slow to recover
and are normal to well below normal for this time of year. Soil
moisture across North Dakota has rebounded over the past few
weeks, but is still considered slightly below normal. Given the
current weather forecasts and short-term climate outlooks, the
area is still almost a month out from having low enough soil
temperatures to lock in the soil conditions critical to
understanding its likely impact on spring runoff.

...Weather Outlook...
The CPC outlooks tend to reflect an above normal temperature and
precipitation pattern for the 6-10 and 8-14 day period which
transitions into a slightly above normal chance for below normal
temperatures and above normal precipitation for December. That
cooler and wetter expectation is also carried into the
3-month (winter) outlook covering December through February.

All of the above is generally consistent with this being a La Nina
affected winter. However, this is not to suggest that this is an
expectation for a winter reminiscent of some of the more recent
severe winters. Those more severe winters, like 2008-2009, or
2010-2011 also had some other factors that affect winters in the
Northern Plains. Those climate influences are expected to moderate
this year`s La Nina patterns.

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.


                 Probabilities for Minor, Moderate, and Major Flooding
                          Valid Period: 11/25/2017  - 02/23/2018

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
: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 :  <5   <5   <5   <5   <5   <5
:Beaver Creek
Linton              12.0   14.0   16.0 :  <5   <5   <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 :  <5   <5   <5   <5   <5   <5
:Knife River
Hazen               21.0   24.0   25.0 :  <5   <5   <5   <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   <5   <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: 11/25/2017  - 02/23/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Pipestem Creek
Pingree               4.9    4.9    4.9    4.9    4.9    4.9    4.9
:James River
Grace City            4.2    4.2    4.2    4.2    4.2    4.2    4.2
Lamoure               6.7    6.7    6.7    6.7    6.8    6.8    6.8

:Cannonball River
Regent                4.6    4.7    4.9    5.4    5.5    6.1    6.8
:Cedar Creek
Raleigh               0.7    0.8    0.8    1.0    1.6    2.4    2.5
:Cannonball River
Breien                2.5    2.5    2.8    3.1    4.0    4.6    5.0
:Beaver Creek
Linton                4.3    4.3    4.3    4.3    4.6    4.9    4.9
:Little Muddy River
Williston             4.6    4.6    4.6    4.6    4.9    5.1    5.4
:Little Missouri
Marmarth              1.1    1.1    1.1    1.1    1.9    2.4    3.0
:Little Missouri River
Medora                1.5    1.5    1.5    1.5    2.3    3.2    4.0
Watford City         -0.8   -0.8   -0.8   -0.6   -0.2    0.3    0.5
:Knife River
Manning               6.3    6.3    6.3    6.3    6.3    6.5    7.0
:Spring Creek
Zap                   5.0    5.0    5.0    5.0    5.2    5.4    5.7
:Knife River
Hazen                 1.2    1.2    1.2    1.2    1.8    2.7    2.9
:Heart River
Mandan               -0.4   -0.4   -0.4   -0.4   -0.4   -0.1    0.3
:Apple Creek
Menoken               4.3    4.3    4.3    4.3    4.3    5.0    5.1

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
                          Vslid Period:  11/25/2017  - 02/23/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Pipestem Creek
Pingree               4.9    4.9    4.9    4.9    4.9    4.9    4.9
:James River
Grace City            4.2    4.2    4.2    4.2    4.2    4.2    4.2
Lamoure               6.6    6.6    6.6    6.6    6.6    6.6    6.6
:Cannonball River
Regent                4.4    4.4    4.4    4.4    4.4    4.4    4.4
:Cedar Creek
Raleigh               0.7    0.7    0.7    0.7    0.7    0.7    0.7
:Cannonball River
Breien                2.4    2.4    2.4    2.4    2.4    2.4    2.4
:Beaver Creek
Linton                4.3    4.3    4.3    4.3    4.3    4.3    4.3
:Little Muddy River
Williston             4.5    4.5    4.5    4.5    4.5    4.5    4.5
:Little Missouri
Marmarth              1.0    1.0    1.0    1.0    1.0    1.0    1.0
:Little Missouri River
Medora                1.4    1.4    1.4    1.4    1.4    1.4    1.4
Watford City         -1.1   -1.1   -1.1   -1.1   -1.1   -1.1   -1.1
:Knife River
Manning               6.3    6.3    6.3    6.3    6.3    6.3    6.3
:Spring Creek
Zap                   5.0    5.0    5.0    5.0    5.0    5.0    5.0
:Knife River
Hazen                 1.1    1.1    1.1    1.1    1.1    1.1    1.1
:Heart River
Mandan               -0.5   -0.5   -0.5   -0.5   -0.5   -0.5   -0.5
:Apple Creek
Menoken               4.3    4.3    4.2    4.2    4.2    4.2    4.2


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/bis for more weather and water
information.

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

$$

ajs



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