Flood Potential Outlook
Issued by NWS Bismarck, ND

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FGUS73 KBIS 261805
ESFBIS

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
105 PM CDT FRI APR 26 2019


...SPRING FLOOD AND WATER RESOURCES OUTLOOK...

This probability based Flood and Water Resources Outlook is for the
Missouri and James River basins of North Dakota and covers the
period from late April through late July. These routine outlooks are
issued every month, on or around the fourth Thursday of the month.

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...
Only the Missouri River west of Williston has a high probability
of exceeding flood stage over the coming three months. The rest of
the Missouri and James river basin are near normal. The primary
reason for this difference is that runoff from spring snowmelt has
already occured in all but the headwaters area of the Missouri and
Yellowston rivers in Montana. Once that snowpack begins to melt in
earnest, it is quite likely that at least minor flooding will occur
along the Missouri River west of Williston.

...Current Conditions...
Most rivers and streams are near their normal water levels for
the post spring snowmelt flood season. Wetlands, lakes, and
reservoirs also tend to be at early summer levels with no
significant water issues being reported.



...Weather Outlook...
The near term 6-10 and 8-14 day outlooks depict an enhanced
chance for cooler than normal and above normal precipitation.
Looking farther into the future, the one-month outlook for May
favors warmer than normal temperatures with an equal chance of
either below normal, near normal, or above normal precipitation.
And lastly, the three-month outlooks reflect an equal chance for
above normal, near normal, and below normal temperature with a
slightly enhanced chance for above normal precipitation south
and west of the Missouri River.


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.


                 Chance of Exceeding Stages at Specific Locations
                     Valid Period:  04/27/2019  - 07/26/2019

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Pipestem Creek
Pingree             11.0   13.0   15.0 :   6   <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 :  12   <5    5   <5   <5   <5
:Missouri River
Williston           22.0   24.0   26.0 :  95   27   22   17    7    7
: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 :  16   14   <5   <5   <5   <5
:Beaver Creek
Linton              12.0   14.0   16.0 :  22   18    9    8    5    5
:Little Muddy River
Williston           10.0   12.0   14.0 :  38   42   11   16   <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 :   9   13    5    7   <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   11   <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    8   <5   <5   <5   <5
:Apple Creek
Menoken             15.0   16.0   17.0 :  34   39   21   26   10   11

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: 04/27/2019  - 07/26/2019
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Pipestem Creek
Pingree               6.1    6.1    6.1    6.1    8.0    9.6   11.1
:James River
Grace City            6.2    6.2    6.2    6.2    8.5   10.9   12.6
Lamoure               9.6    9.6    9.6    9.6    9.6   14.6   16.5
:Missouri River
Williston            22.0   22.4   22.8   23.3   23.9   25.4   27.1
:Cannonball River
Regent                5.3    5.3    6.1    6.7    7.8    9.5   10.8
:Cedar Creek
Raleigh               2.1    2.5    3.8    4.9    6.0    6.6    7.3
:Cannonball River
Breien                4.3    4.8    6.7    7.7    9.1   10.9   11.6
:Beaver Creek
Linton                5.3    5.3    5.6    8.3   11.0   13.7   15.7
:Little Muddy River
Williston             4.8    4.8    5.6    8.3   10.5   12.1   12.4
:Little Missouri
Marmarth              2.1    2.1    2.1    3.7    7.6   13.8   16.7
:Little Missouri River
Medora                3.3    3.3    3.3    5.2    8.8   14.7   17.6
Watford City          0.6    0.6    0.6    2.5    5.1   10.0   12.7
:Knife River
Manning               6.3    6.3    7.2    8.3    9.8   13.0   14.1
:Spring Creek
Zap                   5.1    5.1    5.1    6.9    8.6    9.9   11.1
:Knife River
Hazen                 1.2    1.3    3.1    7.5   11.1   14.9   18.4
:Heart River
Mandan                0.1    0.1    1.4    3.9    6.1    8.6   13.0
:Apple Creek
Menoken               6.1    6.1    6.1   11.8   15.6   16.9   17.9

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--Nonexceedance Probabilities...

                            Chance of Falling Below Stages
                                 at Specific Locations
                          Valid Period:  04/27/2019  - 07/26/2019
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Pipestem Creek
Pingree               5.6    5.5    5.5    5.5    5.5    5.5    5.5
:James River
Grace City            5.3    5.3    5.3    5.2    5.2    5.2    5.2
Lamoure               8.5    8.4    8.2    8.2    8.1    8.1    8.1
:Cannonball River
Regent                5.2    5.2    5.2    5.2    5.2    5.2    5.2
:Cedar Creek
Raleigh               1.3    1.3    1.3    1.2    1.2    1.1    1.1
:Cannonball River
Breien                3.2    3.2    3.1    3.1    3.0    3.0    3.0
:Beaver Creek
Linton                4.7    4.6    4.5    4.4    4.4.   4.4    4.4
:Little Muddy River
Williston             4.7    4.7    4.7    4.6    4.5    4.5    4.5
:Little Missouri
Marmarth              1.6    1.5    1.4    1.3    1.3    1.2    1.2
:Little Missouri River
Medora                2.3    2.2    2.1    2.0    2.0    1.9    1.9
Watford City         -0.0   -0.1   -0.2   -0.4   -0.4   -0.5   -0.5
:Knife River
Manning               6.3    6.2    6.1    6.1    5.5    5.5    5.5
:Spring Creek
Zap                   5.0    5.0    5.0    5.0    5.0    5.0    5.0
:Knife River
Hazen                 0.9    0.8    0.7    0.5    0.3    0.3    0.3
:Heart River
Mandan               -0.3   -0.5   -0.6   -0.9   -1.1   -1.4   -1.5
:Apple Creek
Menoken               5.2    5.1    5.0    5.0    4.6    4.5    4.4

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.


$$

ajs


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