Flood Potential Outlook
Issued by NWS Bismarck, ND

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FGUS73 KBIS 221846
ESFBIS
NDC009-013-023-049-061-069-075-079-101-302200-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
145 PM CDT WED MAR 22 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 March through late June.

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
as the onset of the major spring melt appears on the horizon. In that
sense, the below numbers should not be misinterpreted as the forecast
for the next few weeks. Rather, they are still the risk for the
entire 90-day effective period of this model run and include the
potential for higher water than what is currently included in the
near-term deterministic model runs.

While much of the very southern and western parts of the Souris River
basin have lost much of their snowpack, the central and northern
snowpack is still impressive and will begin to melt in earnest over
the coming week.

Increased discharges from Alameda Dam in Saskatchewan and Lake Darling in
North Dakota were initiated to increase storage of a robust snowpack
above Alameda. These increased flows are already working their way through
the Souris River and are only expected to go higher as runoff refills
these reservoirs. There are no significant precipitation events in
the near-term forecast for the region that would add much in the
way of runoff.

...Current Conditions...
Rivers and lakes remain frozen over for the most part with only the
Souris River immediately below Lake Darling having lost its ice cover.
Reservoirs are below their normal levels for this time of year in
anticipation of strong runoff from the remaining snowpack. Soil
moisture is well above normal due to a wet fall in some areas of the
Souris River basin, and are now likely a mixture of well frozen in
areas of little to no snow cover, to nearly unfrozen in areas with
the heaviest snowpack.

...Weather Outlook...
The near term 6-10 and 8-14 day outlooks depict above normal
temperatures and a near normal amount of moisture. 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 a slightly enhanced chance for above normal
precipitation.


...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: 03/26/2017 - 06/24/2017

                                       :    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    7   <5   <5   <5   <5   <5
Souris River
  Sherwood        1623.0 1625.0 1630.0    87   11   20   <5   <5   <5
  Foxholm         1573.0 1576.0 1578.0   >95   30  >95   13   <5   <5
  Minot 4NW       1562.0 1565.0 1570.0    61   11   14    6   <5   <5
  Minot Brwy Brdg 1551.0 1553.0 1557.0     7    5   <5   <5   <5   <5
  Logan           1536.0 1538.0 1540.0   >95   16    6    5   <5   <5
  Sawyer          1524.0 1526.0 1528.0     6    7   <5   <5   <5   <5
  Velva           1507.0 1512.0 1517.0    38   15   <5   <5   <5   <5
Wintering River
  Karlsruhe       1509.0 1511.0 1512.0   >95    6   <5   <5   <5   <5
Souris River
  Towner          1454.0 1456.0 1458.0   >95   60  >95   25   <5    5
  Bantry          1440.0 1441.0 1443.0   >95   55  >95   37    7    6
Willow Creek
  Willow City     1442.0 1446.0 1448.0   >95   39   75   16   <5   <5
Souris River
  Westhope        1414.0 1418.0 1420.0   >95   46  >95   23  >95   16
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: 03/26/2017 - 06/24/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
Des Lacs River
  Foxholm           1647.9/ 1648.0/ 1648.2/ 1648.3/ 1648.7/ 1650.1/ 1651.2
Souris River
  Sherwood          1622.5/ 1622.9/ 1623.9/ 1624.2/ 1624.9/ 1625.5/ 1626.0
  Foxholm           1576.1/ 1576.1/ 1576.3/ 1576.5/ 1576.9/ 1577.5/ 1577.7
  Minot 4NW         1561.3/ 1561.4/ 1561.7/ 1562.4/ 1563.2/ 1565.8/ 1567.0
  Minot Brwy Brdg   1546.9/ 1547.0/ 1547.2/ 1547.5/ 1548.3/ 1550.6/ 1552.5
  Logan             1536.2/ 1536.3/ 1536.4/ 1536.8/ 1537.3/ 1537.7/ 1538.1
  Sawyer            1521.8/ 1521.9/ 1522.1/ 1522.4/ 1523.0/ 1523.7/ 1524.7
  Velva             1506.3/ 1506.4/ 1506.5/ 1506.7/ 1507.4/ 1508.2/ 1509.0
Wintering River
  Karlsruhe         1509.1/ 1509.1/ 1509.2/ 1509.2/ 1509.4/ 1509.6/ 1509.7
Souris River
  Towner            1456.9/ 1456.9/ 1456.9/ 1457.0/ 1457.2/ 1457.4/ 1457.7
  Bantry            1442.2/ 1442.2/ 1442.2/ 1442.3/ 1442.6/ 1442.8/ 1443.1
Willow Creek
  Willow City       1445.8/ 1445.9/ 1446.0/ 1446.2/ 1446.5/ 1447.1/ 1447.5
Souris River
  Westhope          1421.3/ 1421.4/ 1421.5/ 1421.9/ 1422.6/ 1423.2/ 1423.5

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: 03/26/2017 - 06/24/2017
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
Des Lacs River
  Foxholm           1640.8/ 1640.6/ 1640.3/ 1640.2/ 1640.2/ 1640.1/ 1640.1
Souris River
  Sherwood          1607.9/ 1607.8/ 1607.2/ 1606.8/ 1606.4/ 1606.3/ 1606.3
  Foxholm           1566.6/ 1566.6/ 1566.6/ 1566.6/ 1566.6/ 1566.6/ 1566.6
  Minot 4NW         1554.4/ 1554.2/ 1551.5/ 1551.4/ 1551.3/ 1551.3/ 1551.3
  Minot Brwy Brdg   1543.2/ 1543.1/ 1541.0/ 1540.2/ 1539.9/ 1539.7/ 1539.7
  Logan             1527.2/ 1526.8/ 1522.5/ 1521.5/ 1521.3/ 1521.1/ 1521.1
  Sawyer            1512.8/ 1512.3/ 1509.0/ 1508.1/ 1508.0/ 1507.9/ 1507.9
  Velva             1496.8/ 1496.4/ 1492.5/ 1491.9/ 1491.8/ 1491.6/ 1491.6
Wintering River
  Karlsruhe         1504.2/ 1504.2/ 1504.0/ 1503.6/ 1503.5/ 1503.4/ 1503.4
Souris River
  Towner            1452.9/ 1452.9/ 1449.6/ 1447.7/ 1447.1/ 1446.7/ 1446.6
  Bantry            1437.0/ 1437.0/ 1435.7/ 1433.6/ 1433.2/ 1432.9/ 1432.8
Willow Creek
  Willow City       1436.0/ 1436.0/ 1436.0/ 1436.0/ 1436.0/ 1436.0/ 1436.0
Souris River
  Westhope          1409.9/ 1409.9/ 1409.9/ 1409.8/ 1409.8/ 1409.8/ 1409.8

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 on April 27, 2017.

$$
ajs



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