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Flood Potential Outlook
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
000
FGUS73 KBIS 091654
ESFBIS
NDC009-013-023-049-069-075-079-101-111700-
Probabilistic Hydrologic Outlook
National Weather Service Bismarck ND
1054 AM CST Thu Mar 9 2023
...SPRING FLOOD AND WATER RESOURCES OUTLOOK...
This Flood and Water Resources Outlook is for the Souris River basin
of North Dakota, covering the period of 13 March through 11 June,
2023. This outlook is the third and final in a series of three
Spring Flood Outlooks intended to refine and define the overall risk
of flooding associated with the annual spring melt season. The
National Weather Service go back to our regularly scheduled release
of Flood and Water Resources Outlooks on 23 March, the fourth
Thursday of every 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...
The flood risks within the Souris River Basin of North Dakota have
essentially remained unchanged since the February 23rd issuance of
the probabilities. Overall flood risk can still be split into two
distinct areas this year. The first begins where the Souris River
comes across the border with Canada near Sherwood and extends on
down through Minot on over to Velva. In this stretch of the Souris
River, flood risks are slightly below to near normal this year. This
is largely due to the snowpack and its associated Snow-Water
Equivalent (SWE), which tends to decrease the farther north and west
one looks from Minot. This near normal risk of flooding includes the
Des Lacs watershed. Starting at roughly Velva and going downstream
through Towner and on up to Westhope, the snowpack and SWE are above
normal. The above normal snowpack in this area is responsible for
the near normal to slightly greater than normal risk of flooding.
This area also includes the Wintering River and Willow Creek
watersheds.
What continues to exert a great influence on overall flood risk are
the exceptionally dry and warmer than normal soils underlying the
snowpack. These warm and dry soils are expected to allow
infiltration of a much larger than normal fraction of meltwater
generated and rainfall received during the critical spring melt
season. Those living near areas that have historically experienced
spring flooding should still be vigilant for conditions that may
produce an unusually fast melting of the snow, and especially if
heavy rains are expected during, or shortly after, snowmelt has
commenced.
One significant risk for flooding that is not included in the below
probabilities are ice jams. Ice jams and flooding associated with
them tend to defy mathematical prediction, but there are indicators
that can help one understand if the risk of an ice jam is different
than normal. The Souris and its tributaries have generally been
below normal levels this winter. Low water levels combined with an
early thick blanket of snow have most likely limited ice thickness
and overall ice load in the rivers. This would suggest the risk of
ice jams, while certainly not zero, are also somewhat below normal
going into this spring. What can increase the risk of ice jam
formation are an abrupt change from colder than normal weather to
well above normal temperatures with rapid runoff from an early
spring rain. Importantly though, the details of the spring melt
season are still too far in the future for narrowing this down at
this point in time.
...Snowpack Conditions...
Overall SWE content of the snowpack across the Souris River Basin
has changed very little over the past several weeks and remains non-
uniform in depth and SWE. In general, the headwaters area of
Saskatchewan is below to near normal in SWE, with an overall value
of something less than two inches. Snowpack and SWE content tends to
increase to near normal where the Souris River flows into North
Dakota near Sherwood, and continues to increase the farther
downstream one looks. By the time one gets to just east of Minot,
the SWE is generally above normal with between three and four inches
of SWE common, and locally above four inches is possible.
...Soil Conditions...
Soils across the basin remain quite dry. Along with the soils being
dry, the insulating effect of the early snow has kept the soils
under the snow warmer than one would expect based on the overall
colder than normal December and slightly warmer than normal January.
These warm and dry soils will allow infiltration of rainfall and
meltwater from the spring snowmelt season under all but the most
extreme of melt conditions.
...Current Drought Conditions...
Despite a near normal snowpack in the upper portion of the Souris
River Basin of North Dakota and above normal SWE content in the
eastern and southern part of the basin, the basin wide Moderate
Drought (D1) designation continues to hold steady this winter.
Depending on how the spring melt unfolds, it is possible we will see
rapid improvement in the drought designations in response to
adequate streamflow and substantial replenishment of soil moisture.
Or, in the somewhat unlikely event of an extreme melt pattern which
minimizes replenishment of soil moisture, drought conditions may
still worsen going through spring.
...Reservoirs and Natural Wetlands...
Lake Darling above Minot along with the Canadian reservoirs behind
Grant Devine and Rafferty Dams have near normal to somewhat below
normal water levels for this time of year. The same can be said for
most wetlands and natural bodies of water as the drier than normal
latter half of summer and early fall took a toll on water levels in
2022.
...Weather Outlook...
In the 6-10 and 8-14 day outlooks, a cooler than normal weather
pattern is expected to continue while the above normal moisture is
favored to transition towards a more normal precipitation pattern.
Looking at the weeks 3-4 outlook, the cooler than normal pattern is
favored to continue while precipitation is split between equal
chances for below normal, near normal, and above normal for the
western half of North Dakota, while the eastern half is slightly
favored for below normal precipitation. The three-month outlook for
March, April, and May favors a retention of the cooler than normal
pattern, while all of North Dakota falls under the equal chances for
below normal, near normal, or above normal precipitation.
One key thing to remember as the region goes through March is that
the historical normal daily high temperatures in the Minot area is
27.0 degrees Fahrenheit on March 1st, but steadily rises to an
average of 46.6 degrees on March 31st. So even if the region were to
remain cooler than normal through March, below normal temperatures
now include weather patterns that could create a gentle melt
conditions.
...Ice Conditions...
All small lakes and wetlands are covered with ice now of variable
thickness. Lakes and rivers with substantial snow cover are likely
to have thinner ice due to the insulating effect of the deeper snow.
Snow cover and generally lower water levels in the river this winter
are also likely to lessen the overall amount of ice in those streams.
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: 03/13/2023 - 06/11/2023
: 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 : 22 37 6 16 <5 <5
Minot 1562.0 1565.0 1570.0 : 7 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 : 12 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 : 12 17 <5 <5 <5 <5
:Wintering
Karlsruhe 1509.0 1511.0 1512.0 : 26 14 <5 <5 <5 <5
:Souris
Towner 1454.0 1456.0 1458.0 : 89 60 28 28 <5 <5
Bantry 1440.0 1441.0 1443.0 : 91 59 60 40 <5 8
:Willow Creek
Willow City 1442.0 1446.0 1448.0 : 35 47 <5 19 <5 <5
:Souris
Westhope 1414.0 1418.0 1420.0 : 23 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: 03/13/2023 - 06/11/2023
Location 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:Des Lacs
Foxholm 1641.5 1641.9 1642.5 1643.5 1645.0 1647.2 1648.3
:Souris
Sherwood 1612.7 1613.3 1614.3 1615.3 1618.1 1620.1 1621.2
Foxholm 1570.6 1570.7 1570.8 1571.0 1572.4 1573.3 1576.6
Minot 1554.4 1554.7 1554.8 1555.3 1557.0 1561.1 1564.5
Minot 1543.0 1543.2 1543.3 1543.6 1544.4 1546.4 1548.7
Logan 1527.1 1527.5 1527.9 1529.0 1532.2 1536.9 1537.6
Sawyer 1512.6 1513.1 1513.7 1515.3 1518.9 1522.8 1523.4
Velva 1496.7 1497.2 1498.2 1501.0 1504.8 1507.2 1508.2
:Wintering
Karlsruhe 1506.6 1507.2 1507.8 1508.4 1509.0 1509.6 1509.9
:Souris
Towner 1453.8 1454.0 1454.4 1455.5 1456.2 1456.9 1457.4
Bantry 1439.8 1440.0 1440.4 1441.3 1441.8 1442.4 1442.9
:Willow Creek
Willow City 1438.1 1438.2 1438.8 1439.6 1443.6 1444.8 1445.4
:Souris
Westhope 1411.8 1412.1 1412.4 1413.0 1413.9 1415.6 1417.4
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: 03/13/2023 - 06/11/2023
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:Des Lacs
Foxholm 1638.6 1638.6 1638.6 1638.6 1638.6 1638.6 1638.6
:Souris
Sherwood 1606.2 1606.2 1606.2 1606.2 1606.2 1606.2 1606.2
Foxholm 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5
Minot 1550.6 1550.6 1550.6 1550.6 1550.6 1550.6 1550.6
Minot 1541.1 1541.1 1541.1 1541.1 1541.1 1541.1 1541.1
Logan 1519.9 1519.9 1519.9 1519.9 1519.9 1519.9 1519.8
Sawyer 1506.7 1506.7 1506.7 1506.6 1506.6 1506.6 1506.6
Velva 1490.2 1490.2 1490.2 1490.2 1490.2 1490.2 1490.2
:Wintering
Karlsruhe 1503.0 1503.0 1503.0 1503.0 1503.0 1503.0 1503.0
:Souris
Towner 1444.4 1444.4 1444.4 1444.4 1444.4 1444.4 1444.4
Bantry 1430.2 1430.2 1430.2 1430.2 1430.2 1430.2 1430.2
:Willow Creek
Willow City 1436.1 1436.1 1436.1 1436.1 1436.1 1436.1 1436.1
:Souris
Westhope 1408.9 1408.9 1408.9 1408.9 1408.9 1408.9 1408.9
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 23 March.
$$
Schlag
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- Page last modified: Sep 6th, 2022 18:00 UTC