Flood Potential Outlook
Issued by NWS Bismarck, ND

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FGUS73 KBIS 261542
ESFBIS
NDC009-013-023-049-061-069-075-079-101-302200-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
1041 AM CDT FRI MAY 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 May through late August.

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 comes
just as the last spring flood warning has been cancelled for the
Souris River. Accordingly, water remains fairly elevated in the
downstream area from Towner to Westhope, but the bottom line is
that flood concerns are now in the near normal to slightly below
normal range.

...Current Conditions...
Rivers and lakes are all at near normal levels for this time of
the year and pose no concerns. Soil moisture levels are likely
near normal to below normal across most of the Souris River Basin
in North Dakota due to a fairly dry month of May.

...Weather Outlook...
The near term 6-10 and 8-14 day outlooks suggest a greater than
normal chance of above normal temperatures and also favor belown
normal chances for precipitation. Looking out at the longer term
one-month and three-month outlooks, there is an equal chance for
below normal, near normal, or above normal temperatures, and an
equal chance for above normal, near normal, or below normal
rainfall.


...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: 05/28/2017 - 08/26/2017

                                       :    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    10   <5    6   <5   <5   <5
  Foxholm         1573.0 1576.0 1578.0     9   19   <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    13   28   <5    6   <5   <5
  Bantry          1440.0 1441.0 1443.0    13   28   <5   17   <5   <5
Willow Creek
  Willow City     1442.0 1446.0 1448.0    <5    9   <5   <5   <5   <5
Souris River
  Westhope        1414.0 1418.0 1420.0     7   24   <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: 05/28/2017 - 08/26/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
Des Lacs River
  Foxholm           1640.5 1640.5 1640.5 1640.5 1641.4 1642.5 1643.5
Souris River
  Sherwood          1606.7 1606.7 1606.9 1608.7 1613.7 1622.3 1626.0
  Foxholm           1566.5 1566.5 1566.5 1566.5 1570.4 1572.4 1574.0
  Minot 4NW         1551.4 1551.4 1551.4 1551.5 1553.6 1555.8 1556.8
  Minot Brwy Brdg   1540.4 1540.4 1540.4 1541.2 1542.9 1544.0 1544.3
  Logan             1521.7 1521.7 1521.7 1523.1 1526.3 1529.3 1530.4
  Sawyer            1508.2 1508.2 1508.2 1509.5 1511.8 1515.3 1516.6
  Velva             1492.0 1492.0 1492.0 1492.9 1495.8 1499.8 1502.3
Wintering River
  Karlsruhe         1503.7 1503.7 1503.7 1503.9 1504.5 1505.0 1505.6
Souris River
  Towner            1448.3 1448.3 1448.3 1448.9 1452.4 1454.5 1455.2
  Bantry            1434.5 1434.5 1434.5 1434.7 1438.0 1440.3 1441.0
Willow Creek
  Willow City       1437.0 1437.0 1437.0 1437.0 1437.7 1439.2 1441.2
Souris River
  Westhope          1412.0 1412.0 1412.0 1412.0 1412.0 1412.9 1416.1

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
                        Valid  Period: 05/28/2017 - 08/26/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
Des Lacs River
  Foxholm           1639.8 1639.7 1639.7 1639.7 1639.6 1639.6 1639.6
Souris River
  Sherwood          1606.5 1606.4 1606.3 1606.2 1606.2 1606.2 1606.2
  Foxholm           1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5
  Minot 4NW         1551.3 1551.3 1551.1 1551.1 1551.1 1551.1 1551.1
  Minot Brwy Brdg   1539.6 1539.4 1538.7 1538.6 1538.5 1538.5 1538.5
  Logan             1521.0 1520.8 1520.2 1520.1 1520.1 1520.1 1520.1
  Sawyer            1507.9 1507.8 1507.3 1507.2 1507.2 1507.2 1507.2
  Velva             1491.7 1491.5 1490.8 1490.7 1490.6 1490.5 1490.5
Wintering River
  Karlsruhe         1503.2 1502.9 1502.8 1502.8 1502.8 1502.8 1502.8
Souris River
  Towner            1446.5 1446.2 1445.9 1445.7 1445.7 1445.7 1445.7
  Bantry            1432.7 1432.5 1432.0 1431.9 1431.8 1431.8 1431.8
Willow Creek
  Willow City       1436.2 1436.0 1436.0 1436.0 1436.0 1436.0 1436.0
Souris River
  Westhope          1410.6 1410.3 1410.1 1410.0 1409.9 1409.9 1409.9

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 June, 2017.

$$
ajs


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