Flood Potential Outlook
Issued by NWS Bismarck, ND

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FGUS73 KBIS 262045
ESFBIS
NDC009-013-023-049-061-069-075-079-101-302200-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
340 PM CDT THU OCT 26 2017

...FLOOD AND WATER RESOURCES OUTLOOK...

This probability based Flood and Water Resources Outlook is
for the Souris (Mouse) River basin of North Dakota and covers the
period of late October through late January, 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...
This issuance of the monthly probabilistic Hydrologic Outlook
finds the region with little risk of widespread river flooding,
which is normal for this time of year.

...Current Conditions...
Reservoirs are already near, or below winter drawdown levels in the
basin. Relatively drier conditions over the early part of fall have
also lowered soil moisture to slightly below normal levels.
Similarly, many wetlands across the region have also fallen to below
the levels seen in the last few years even though many remain above
long-term historical levels.

...Weather Outlook...
The CPC outlooks pretty are pretty consistent going into
November with a well above normal chance for below normal
temperatures and above normal precipitation. However, the one-month
graphics suggest overall uncertainty with November as the region
is generally in the equal chances category for both temperature
and precipitation. Similarly, the three-month outlook covering
November through January is fairly neutral but the Winter Outlook
covering December through February outlook suggests cooler and
wetter than normal.

...Important Note On Substantive Changes... Beginning January 1st of
2016, the National Weather Service converted all river gage data in
the Souris River basin of North Dakota to feet above Mean Sea Level
using the North American Vertical Datum of 1988. This included raises
in flood stage definitions by up to one foot at individual locations
in order to continue working with whole numbers. More information on
this can be had by contacting Service Hydrologist Allen Schlag
at 701-250-4495.

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 of the model
predicting a rise to 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: 10/29/2017 - 01/27/2018

                                       :    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
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
Des Lacs River
  Foxholm         1651.0 1653.0 1654.0    <5   <5   <5   <5   <5   <5
Souris River
  Sherwood        1623.0 1625.0 1630.0    <5   <5   <5   <5   <5   <5
  Foxholm         1573.0 1576.0 1578.0    <5   <5   <5   <5   <5   <5
  Minot 4NW       1562.0 1565.0 1570.0    <5   <5   <5   <5   <5   <5
  Minot Brwy Brdg 1551.0 1553.0 1557.0    <5   <5   <5   <5   <5   <5
  Logan           1536.0 1538.0 1540.0    <5   <5   <5   <5   <5   <5
  Sawyer          1524.0 1526.0 1528.0    <5   <5   <5   <5   <5   <5
  Velva           1507.0 1512.0 1517.0    <5   <5   <5   <5   <5   <5
Wintering River
  Karlsruhe       1509.0 1511.0 1512.0    <5   <5   <5   <5   <5   <5
Souris River
  Towner          1454.0 1456.0 1458.0    <5   <5   <5   <5   <5   <5
  Bantry          1440.0 1441.0 1443.0    <5   <5   <5   <5   <5   <5
Willow Creek
  Willow City     1442.0 1446.0 1448.0    <5    5   <5   <5   <5   <5
Souris River
  Westhope        1414.0 1418.0 1420.0    <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: 10/29/2017 - 01/27/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
Des Lacs River
  Foxholm           1639.3 1639.3 1639.3 1639.3 1639.5 1639.8 1640.1
Souris River
  Sherwood          1607.6 1607.9 1608.3 1608.4 1608.6 1608.7 1608.7
  Foxholm           1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5
  Minot 4NW         1551.0 1551.0 1551.0 1551.0 1551.0 1551.2 1551.3
  Minot Brwy Brdg   1537.9 1537.9 1537.9 1537.9 1538.3 1538.8 1539.4
  Logan             1520.0 1520.0 1520.0 1520.0 1520.1 1520.3 1520.9
  Sawyer            1506.7 1506.7 1506.7 1506.7 1507.2 1507.7 1507.9
  Velva             1490.2 1490.2 1490.2 1490.2 1490.5 1491.3 1491.6
Wintering River
  Karlsruhe         1502.8 1502.8 1502.8 1502.8 1502.8 1503.3 1503.8
Souris River
  Towner            1445.7 1445.7 1445.7 1445.7 1445.7 1445.7 1445.8
  Bantry            1431.9 1431.9 1431.9 1431.9 1431.9 1431.9 1431.9
Willow Creek
  Willow City       1436.0 1436.0 1436.0 1436.0 1436.0 1436.3 1436.6
Souris River
  Westhope          1409.8 1409.8 1409.8 1409.8 1409.8 1409.8 1410.1


...Table 3--Nonexceedance Probabilities...

                            Chance of Falling Below Stages
                                 at Specific Locations
                        Valid  Period: 10/29/2017 - 01/27/2018
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
Des Lacs River
  Foxholm           1639.2 1639.1 1639.0 1639.0 1639.0 1639.0 1639.0
Souris River
  Sherwood          1605.5 1605.5 1605.5 1605.5 1605.5 1605.5 1605.5
  Foxholm           1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5
  Minot 4NW         1550.9 1550.9 1550.8 1550.7 1550.7 1550.7 1550.7
  Minot Brwy Brdg   1537.5 1537.3 1536.9 1536.7 1536.7 1536.7 1536.7
  Logan             1520.0 1519.9 1519.8 1519.8 1519.8 1519.8 1519.8
  Sawyer            1506.7 1506.7 1506.6 1506.6 1506.6 1506.6 1506.6
  Velva             1490.2 1490.2 1490.2 1490.2 1490.2 1490.2 1490.2
Wintering River
  Karlsruhe         1502.8 1502.8 1502.8 1502.8 1502.8 1502.8 1502.8
Souris River
  Towner            1445.0 1444.9 1444.8 1444.8 1444.8 1444.8 1444.8
  Bantry            1431.2 1431.1 1431.0 1431.0 1431.0 1431.0 1431.0
Willow Creek
  Willow City       1436.0 1436.0 1436.0 1436.0 1436.0 1436.0 1436.0
Souris River
  Westhope          1409.4 1409.4 1409.4 1409.4 1409.4 1409.4 1409.4

These long-range probabilistic outlooks contain forecast values that
are calculated using historical conditions from 30 or more years of
climatological data...and 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 near the end of next month.

$$
ajs



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