Text Products for ESF Issued by BIS

Flood Potential Outlook
Issued by NWS Bismarck, ND
Versions: 1 2 3 4 5 6 7 8 9 10 11 12
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FGUS73 KBIS 251925
ESFBIS
NDC009-013-023-049-069-075-079-101-271900-

Probabilistic Hydrologic Outlook
National Weather Service Bismarck ND
225 PM CDT Thu Apr 25 2024

...FLOOD AND WATER RESOURCES OUTLOOK...

This Flood and Water Resources Outlook is for the Souris
River Basin of North Dakota, covering the period of 29 April through
28 July, 2024. This is a monthly issuance of the 90-day flood risks
for the Souris River Basin of North Dakota. These probabilities are
updated on or around, 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...
With essentially zero snowpack remaining in the North Dakota portion
of the Souris River basin, the region has largely dodged normal
amounts of spring time flooding. Without a significant snowpack, the
basin is generally in the range of well below normal, to slightly
below normal risk of flooding over the next 90s days. What risk is
present in the below tables is due to the region now entering its
summer, severe thunderstorm season where heavy rains can pose
problems. However, in general the risks are still well below normal
for this time of year.

...Snowpack Conditions...
While there may be a few drifts of snow in protected areas, no
signficant snowpack exists overall in the Souris River basin of
North Dakota.

...Soil Conditions...
Soil moisture values across the Souris River Basin are mostly near
normal with the exception of the Turtle Mountain area where it is
generally below the 30th percentile.

...Current Drought Conditions...
Most of the Souris River basin of North Dakota is depicted as in D0
(Abnormally Dry), with a small sliver of western Long Creek
watershed shown as in D1 (Moderate Drought) in the very northwest
corner of the state.

...Reservoirs and Natural Wetlands...
Lake Darling above Minot along with the Saskatchewan reservoir of
Grant Devine are generally at their summertime full supply level.
However, Rafferty and Boundary dams in Saskatchewan are not expected
to reach their full supply level this summer without the help of
some timely rainfall. The majority of natural wetlands and lakes
also are at, or near normal water levels going into spring.

...Weather Outlook...
Near term, as in the next few days, rain is expected over most of
North Dakota. This should put the region on track to enter May with
at least a stable position on the drought front. The 6-10 and 8-14
day outlooks favor an above normal temperature and precipitation
pattern. The strength of this above normal temperature and
precipitation pattern slightly wanes in the weeks 3-4 outlooks
before all of the Souris River basin in North Dakota slides into the
equal chances category for above normal, near normal,
or below normal temperature and precipitation for the entirety of
May and again in the 3-month outlook for May, June and July.

...Ice Conditions...
No ice is known to exist along the Souris River and its tributaries
in North Dakota.


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: 04/29/2024 - 07/28/2024
                                       :    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    6   <5   <5   <5   <5
Foxholm           1573.0 1576.0 1578.0 :   8   30   <5   12   <5   <5
Minot             1562.0 1565.0 1570.0 :  <5    8   <5   <5   <5   <5
Minot             1551.0 1553.0 1557.0 :  <5   <5   <5   <5   <5   <5
Logan             1536.0 1538.0 1540.0 :  <5   10   <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    9   <5   <5   <5   <5
:Wintering
Karlsruhe         1509.0 1511.0 1512.0 :  <5    6   <5   <5   <5   <5
:Souris
Towner            1454.0 1456.0 1458.0 :  20   48    9   19   <5   <5
Bantry            1440.0 1441.0 1443.0 :  20   49   15   33   <5   <5
:Willow Creek
Willow City       1442.0 1446.0 1448.0 :  12   35    7   10   <5   <5
:Souris
Westhope          1414.0 1418.0 1420.0 :  13   47    6   20   <5   12

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: 04/29/2024 - 07/28/2024
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Des Lacs
Foxholm            1639.5 1639.5 1639.5 1640.7 1642.4 1644.2 1645.7
:Souris
Sherwood           1606.8 1606.9 1607.5 1610.0 1612.4 1618.0 1620.4
Foxholm            1567.9 1568.3 1569.0 1570.5 1571.0 1571.6 1574.5
Minot              1551.2 1551.4 1551.8 1553.6 1554.7 1556.1 1558.3
Minot              1541.5 1541.6 1541.6 1542.6 1543.1 1544.1 1544.8
Logan              1521.2 1521.8 1523.2 1525.7 1527.1 1531.5 1533.6
Sawyer             1507.9 1508.2 1509.5 1511.2 1512.5 1518.6 1520.0
Velva              1491.5 1492.0 1492.8 1495.3 1496.6 1504.2 1505.4
:Wintering
Karlsruhe          1504.3 1504.3 1504.3 1504.5 1506.8 1508.1 1508.6
:Souris
Towner             1449.8 1449.8 1449.8 1451.5 1453.1 1455.6 1456.3
Bantry             1436.0 1436.0 1436.0 1436.8 1439.0 1441.4 1441.9
:Willow Creek
Willow City        1436.9 1436.9 1436.9 1437.1 1438.0 1444.3 1446.8
:Souris
Westhope           1411.1 1411.1 1411.1 1411.8 1412.5 1415.5 1418.5

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: 04/29/2024 - 07/28/2024
LOCATION              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Des Lacs
Foxholm            1639.4 1639.3 1639.1 1639.0 1638.9 1638.9 1638.9
:Souris
Sherwood           1606.6 1606.4 1606.2 1605.8 1605.8 1605.8 1605.8
Foxholm            1566.5 1566.5 1566.5 1566.5 1566.5 1566.5 1566.5
Minot              1551.0 1550.9 1550.9 1550.8 1550.7 1550.7 1550.7
Minot              1541.4 1541.3 1541.3 1541.2 1541.1 1541.1 1541.1
Logan              1520.5 1520.1 1520.0 1519.9 1519.8 1519.8 1519.8
Sawyer             1507.6 1507.2 1506.8 1506.7 1506.6 1506.6 1506.6
Velva              1491.3 1490.7 1490.2 1490.2 1490.2 1490.2 1490.2
:Wintering
Karlsruhe          1504.0 1503.6 1503.2 1503.0 1503.0 1503.0 1503.0
:Souris
Towner             1446.1 1446.0 1445.6 1445.1 1445.0 1444.9 1444.9
Bantry             1432.0 1431.9 1431.4 1431.0 1430.9 1430.8 1430.8
:Willow Creek
Willow City        1436.7 1436.6 1436.1 1436.1 1436.1 1436.1 1436.1
:Souris
Westhope           1410.8 1410.4 1410.1 1409.8 1409.7 1409.7 1409.7

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 by the end of May.


$$

Schlag
National Weather Service Weather Forecast Office
