Flood Potential Outlook
Issued by NWS Bismarck, ND

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FGUS73 KBIS 291912
ESFBIS
NDC009-013-023-049-069-075-079-101-021715-

Probabilistic Hydrologic Outlook
National Weather Service Bismarck ND
112 PM CST Thu Feb 29 2024

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

This Spring Flood and Water Resources Outlook is for the Souris
River Basin of North Dakota, covering the period of 4 March through
2 June, 2024. This is the second of a three-part Spring Flood and
Water Resources Outlook series.

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...
The flood risks within the Souris River Basin of North Dakota remain
well below normal across the North Dakota portion of the Souris
River Basin, generally due to a well below normal Snow-Water
Equivalent (SWE) in the snowpack. While the overall risk for
widespread flooding is below normal, melting snow this winter across
much of the North Dakota portion and at least extreme southern
Saskatchewan portion of the basin has wetted the surface of the
ground and created a near impermeable layer of frozen soil that
should be expected to significantly enhanced runoff in the event of
an early spring rain. This enhanced runoff potential will remain in
place until such time as the soils begin to thaw, most likely in mid
to late March. Overall though, without at least normal to above
normal precipitation going forward, increased and expanded drought
designations are more likely to be a concern than flooding.

...Snowpack Conditions...
Overall SWE content of the snowpack across the Souris River Basin of
North Dakota is below, to well below normal for this time of year.
To a somewhat lesser degree, the same can be said for the Souris
River Basin in Saskatchewan. Overall, most of the Souris River Basin
has well under an inch of SWE with one-quarter to one-half of an
inch common in North Dakota, and up to one inch across much of the
Saskatchwan portion of the basin. That being said, all it would take
is one significant snow storm to bring the SWE up to around 1.5
inches of water, which is roughly the low-end of normal for the
Souris River Basin of North Dakota. Note: There is a system expected
to be centered on the Canadian portion of the Souris River Basin
next week that would most likely not bring it quite up to normal for
this time of year, but it is likely to bring it within easy reach of
normal if another similar event were to occur in the next few weeks.

...Soil Conditions...
Soil moisture values across the Souris River Basin are very high in
the soil down to about 4 inches (0-10 cm), but begin to fall rapidly
the deeper one looks. By the time one averages out the soil moisture
to a depth of around 40 inches (100 cm) the overall soil moisture is
normal to slightly elevated. Frost depth is highly variable this
year as a mix of very warm weather in December and a good part of
January has helped prevent extensive freezing of the soil, but up to
30 inches of frost depth has been observed in some areas.

...Current Drought Conditions...
The U.S. Drought Monitor reflects D0 (Abnormally Dry) in the western
portion of the Souris River Basin of North Dakota which increases to
D2 (Severe Drought) in Towner County. Given the time of year, no
significant impacts are noted with the current drought designations.
However, concerns with increased drought designations going into
spring are warranted, especially since climate outlooks and
near-term forecasts do not favor a change in existing trends anytime
soon.

...Reservoirs and Natural Wetlands...
Lake Darling above Minot along with the Canadian reservoirs behind
Grant Devine and Rafferty Dams have their full flood control
storage available for spring runoff. The majority of natural
wetlands and lakes also are at, or near normal water levels for this
time of year as the drier than normal latter half of summer and
early fall took a toll on water levels in 2023.

...Weather Outlook...
The Climate Prediction Center 6-10 day outlooks favor near normal in
the western part of the state to warmer than normal temperatures for
central and eastern North Dakota. Precipitation for the same period
is expected to be below normal in the northwestern two-thirds of the
state and slightly above normal in the southeastern one-third of the
state. The weeks 3-4 outlooks favor above normal temperatures
state-wide, with an equal chances designation for above normal, near
normal, or below normal precipitation for all but the southeastern
corner which has a slight favoring for above normal precipitation.
Overall, North Dakota is favored for an above normal temperature
outcome during March, with an equal chance for above normal, near
normal, or below normal precipitation. The longer 3-month outlook
for March, April and May combined favors above normal temperatures
with an equal chance for above normal, near normal, or below normal
precipitation. In general, this is consistent with the expectation
that the El Nino affected winter season will fade into an ENSO
neutral pattern by late spring to early summer. One trend in nearly
all of the outlooks for temperature and precipitation is a sharp
gradient from one extreme to the other, often right through the
middle of the Souris River Basin. A slight shift (70 miles) one way
or the other could have large impacts on the overall outcomes.

...Ice Conditions...
After recent warm weather, not all rivers remain covered in ice.
Lakes and wetlands are generally still ice covered, but thickness is
generally less than normal and reports of an early softening of ice,
especially near the shoreline, are common.

In Table 1 below, the current (CS) and historical (HS) or normal
probabilities of exceeding minor...moderate...and major flood stage
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 greater 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: 03/04/2024 - 06/02/2024
                                       :    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
Foxholm           1651.0 1653.0 1654.0 :  <5   <5   <5   <5   <5   <5
:Souris
Sherwood          1623.0 1625.0 1630.0 :  <5   10   <5    5   <5   <5
Foxholm           1573.0 1576.0 1578.0 :   8   37    5   16   <5   <5
Minot             1562.0 1565.0 1570.0 :  <5   16   <5    6   <5   <5
Minot             1551.0 1553.0 1557.0 :  <5   <5   <5   <5   <5   <5
Logan             1536.0 1538.0 1540.0 :   7   19   <5   <5   <5   <5
Sawyer            1524.0 1526.0 1528.0 :  <5    7   <5   <5   <5   <5
Velva             1507.0 1512.0 1517.0 :  <5   16   <5   <5   <5   <5
:Wintering
Karlsruhe         1509.0 1511.0 1512.0 :   5   14   <5   <5   <5   <5
:Souris
Towner            1454.0 1456.0 1458.0 :  34   56    9   28   <5   <5
Bantry            1440.0 1441.0 1443.0 :  34   55   16   40   <5    8
:Willow Creek
Willow City       1442.0 1446.0 1448.0 :  34   47   <5   19   <5   <5
:Souris
Westhope          1414.0 1418.0 1420.0 :   9   49   <5   21   <5   17

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: 03/04/2024 - 06/02/2024
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Des Lacs
Foxholm            1639.5 1639.7 1640.4 1641.5 1642.3 1644.4 1645.3
:Souris
Sherwood           1608.3 1608.8 1610.2 1612.6 1616.2 1619.2 1620.2
Foxholm            1571.0 1571.0 1571.0 1571.0 1571.0 1571.4 1576.2
Minot              1554.1 1554.1 1554.1 1554.3 1554.8 1556.4 1561.8
Minot              1542.8 1542.8 1542.8 1542.9 1543.4 1544.2 1546.3
Logan              1526.6 1526.6 1526.6 1526.8 1528.2 1532.6 1536.8
Sawyer             1512.0 1512.0 1512.0 1512.4 1514.4 1520.4 1522.5
Velva              1496.0 1496.0 1496.0 1496.4 1498.7 1503.7 1506.9
:Wintering
Karlsruhe          1503.6 1503.8 1504.0 1505.8 1507.5 1508.7 1509.0
:Souris
Towner             1447.6 1448.2 1449.9 1452.7 1454.3 1455.7 1456.6
Bantry             1433.1 1433.4 1435.3 1438.4 1440.3 1441.5 1442.1
:Willow Creek
Willow City        1437.4 1437.4 1437.5 1439.4 1443.7 1444.9 1445.7
:Souris
Westhope           1410.7 1410.7 1411.0 1411.8 1412.7 1413.8 1415.7

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: 03/04/2024 - 06/02/2024
LOCATION              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Des Lacs
Foxholm            1639.3 1639.2 1639.0 1638.9 1638.8 1638.7 1638.7
:Souris
Sherwood           1606.5 1606.5 1606.4 1606.2 1606.1 1605.8 1605.8
Foxholm            1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5
Minot              1551.2 1551.0 1550.9 1550.8 1550.7 1550.6 1550.6
Minot              1541.5 1541.4 1541.3 1541.2 1541.1 1541.1 1541.0
Logan              1521.0 1520.2 1520.1 1520.0 1519.9 1519.8 1519.7
Sawyer             1507.9 1507.5 1507.2 1506.9 1506.6 1506.6 1506.5
Velva              1491.7 1491.5 1490.7 1490.2 1490.2 1490.2 1490.2
:Wintering
Karlsruhe          1503.6 1503.4 1503.4 1503.2 1503.0 1503.0 1503.0
:Souris
Towner             1444.4 1444.4 1444.4 1444.4 1444.4 1444.4 1444.4
Bantry             1430.4 1430.3 1430.2 1430.2 1430.2 1430.2 1430.2
:Willow Creek
Willow City        1436.9 1436.9 1436.8 1436.7 1436.1 1436.1 1436.1
:Souris
Westhope           1410.1 1410.0 1409.9 1409.8 1409.5 1409.3 1409.2

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 on 15 March.


$$

Schlag


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