Flood Potential Outlook
Issued by NWS Bismarck, ND
Issued by NWS Bismarck, ND
559
FGUS73 KBIS 222258
ESFBIS
NDC001-007-011-015-021-025-029-031-033-037-041-043-045-047-051-053-
055-057-059-061-065-083-085-087-089-093-103-105-230700-
Probabilistic Hydrologic Outlook
National Weather Service Bismarck ND
558 PM CDT Thu Aug 22 2024
...FLOOD AND WATER RESOURCES OUTLOOK...
This Flood and Water Resources Outlook is for the James and
Missouri basins of North Dakota, covering the period of 24 August
through 22 November, 2024. This is a routine monthly issuance of
flood probabilities for NWS forecast locations. These probabilities
are
issued 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 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...
Flood risk across the Missouri and James River basins in North
Dakota remains very low, which is normal for this time of year.
Streamflow on some of the smaller tributaries west of the Missouri
River have seen some ups and downs though as drought has steadily
crept into western North Dakota. Out east, on the James River and
Pipestem Creek watersheds, an unusually wet summer has kept water
levels elevated at both Pipestem and Jamestown dams, which has in
turn kept the James River below Jamestown elevated due to higher
than normal releases from the dams.
...Missouri and Yellowstone Rivers...
Above normal spring and early summer rains largely made up for
deficits in winter snowpack early this spring, but water levels in
both rivers have since fallen while remaining in the near-normal
range for this time of year. Nonetheless, Missouri River mainstem
reservoirs of Lake Sakakawea and Lake Oahe are higher than expected
early on this spring.
...Snowpack Conditions...
No snowpack exists within either the Missouri or James River basins
of North Dakota.
...Current Drought Conditions...
Timely and abundant rainfall east of the Missouri River corridor
continues to keep drought at bay in central North Dakota and the
James River Basin. However, west of the Missouri River and on up
through Williams and Divide counties, drought designations have
slowly expanded and gained in strength. Given the weather outlooks,
this trend is likely to continue west and north of the Missouri
River over the coming weeks and months.
...Reservoirs and Natural Wetlands...
Streamflow, natural wetlands and small water features generally have
normal to above normal water levels for this time of year.
...Soil Conditions...
Soil moisture values, which were well above normal for most of late
spring and early summer, are now a mixture of below normal south and
west of the Missouri River, and above normal east and north of the
Missouri River. This suggests areas east and north of the Missouri
River will continue to see crops and native vegetation well
supported by existing soil moisture, but crops and native vegetation
south and west of the Missouri River are likely to start showing
stress due to recent above normal temperatures and below normal
precipitation.
...Weather Outlook...
The near term 6-10 and 8-14 day outlooks generally favors below to
near normal temperatures with below to near normal precipitation.
Weeks 3-4 outlooks favor above normal temperatures with below normal
precipitation. Overall, the month of September in in the equal
chances designation for above normal, near normal or below normal
temperatures and precipitation. Looking longer term, the 3-month
outlooks for September, October and November favor above normal
temperatures with the equal chances designation for precipitation.
...Ice Conditions...
No ice exists on any river or stream 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.
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: 08/24/2024 - 11/22/2024
: 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
-------- ----- ----- ----- : --- --- --- --- --- ---
:Pipestem
Pingree 11.0 13.0 15.0 : 6 <5 <5 <5 <5 <5
:James River
Grace City 12.0 14.0 15.0 : 5 5 5 <5 <5 <5
LaMoure 14.0 16.0 18.0 : 6 <5 5 <5 <5 <5
:Missouri River
Williston 22.0 24.0 26.0 : <5 8 <5 <5 <5 <5
:Cannonball River
Regent 22.0 24.0 26.0 : <5 <5 <5 <5 <5 <5
:Cedar Creek
Raleigh 12.0 14.0 16.0 : <5 <5 <5 <5 <5 <5
:Cannonball River
Breien 10.0 20.0 23.0 : 10 13 <5 <5 <5 <5
:Beaver Creek
Linton 12.0 14.0 16.0 : <5 10 <5 7 <5 5
:Little Muddy River
Williston 10.0 12.0 14.0 : <5 23 <5 8 <5 5
:Little Missouri River
Marmarth 18.0 23.0 30.0 : <5 <5 <5 <5 <5 <5
Medora 15.0 18.0 20.0 : <5 <5 <5 <5 <5 <5
Watford City 20.0 24.0 30.0 : <5 <5 <5 <5 <5 <5
:Knife River
Manning 15.0 17.0 20.0 : <5 7 <5 <5 <5 <5
:Spring Creek
Zap 14.0 18.0 20.0 : <5 13 <5 6 <5 5
:Knife River
Hazen 21.0 24.0 25.0 : <5 12 <5 10 <5 8
:Heart River
Mandan 27.0 33.0 38.0 : <5 7 <5 <5 <5 <5
:Apple Creek
Menoken 15.0 16.0 17.0 : 14 17 11 11 8 7
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: 08/24/2024 - 11/22/2024
Location 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:Pipestem
Pingree 5.4 5.4 5.4 5.4 6.9 8.6 11.5
:James River
Grace City 5.1 5.1 5.1 5.1 6.0 7.2 13.2
LaMoure 9.3 9.3 9.3 9.3 9.6 12.8 15.6
:Missouri River
Williston 15.3 15.3 15.4 15.4 15.6 15.7 17.4
:Cannonball River
Regent 5.2 5.2 5.3 6.4 7.8 9.1 10.0
:Cedar Creek
Raleigh 1.0 1.1 1.1 3.1 4.6 6.0 7.7
:Cannonball River
Breien 2.1 2.2 2.5 5.1 7.4 9.8 13.3
:Beaver Creek
Linton 4.5 4.6 4.6 5.2 6.6 8.9 11.2
:Little Muddy River
Williston 4.6 4.6 4.6 4.6 4.7 5.8 7.8
:Little Missouri River
Marmarth 1.2 1.2 1.2 1.2 2.0 5.3 6.9
Medora 1.8 1.8 1.8 1.8 3.7 6.1 7.6
Watford City 7.2 7.2 7.2 7.6 9.4 11.1 12.2
:Knife River
Manning 6.3 6.3 6.3 6.4 7.3 9.9 12.9
:Spring Creek
Zap 4.8 4.8 4.8 4.8 5.5 9.1 11.6
:Knife River
Hazen 0.7 0.7 0.7 1.1 3.1 16.5 18.9
:Heart River
Mandan 9.5 9.5 9.5 9.6 11.4 23.1 25.0
:Apple Creek
Menoken 6.1 6.1 6.1 6.1 8.8 16.1 17.7
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: 08/24/2024 - 11/22/2024
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:Pipestem
Pingree 5.1 4.9 4.7 4.7 4.7 4.7 4.7
:James River
Grace City 4.8 4.6 4.4 4.4 4.4 4.4 4.4
LaMoure 8.1 6.9 6.8 6.8 6.8 6.8 6.8
:Missouri River
:Cannonball River
Regent 5.0 4.8 4.7 4.7 4.7 4.7 4.7
:Cedar Creek
Raleigh 0.3 0.3 0.3 0.3 0.3 0.3 0.3
:Cannonball River
Breien 2.0 2.0 2.0 2.0 1.9 1.9 1.9
:Beaver Creek
Linton 4.4 4.4 4.4 4.4 4.4 4.4 4.4
:Little Muddy River
Williston 4.5 4.5 4.5 4.5 4.5 4.5 4.5
:Little Missouri River
Marmarth 1.1 1.1 1.1 1.1 1.1 1.1 1.1
Medora 1.6 1.5 1.5 1.5 1.5 1.5 1.5
Watford City 7.1 7.1 7.1 7.1 7.1 7.1 7.1
:Knife River
Manning 6.2 6.2 6.2 6.2 6.2 6.2 6.2
:Spring Creek
Zap 4.8 4.8 4.8 4.8 4.8 4.8 4.8
:Knife River
Hazen 0.6 0.6 0.6 0.6 0.6 0.6 0.6
:Heart River
Mandan 9.3 9.2 8.7 8.6 8.5 8.4 8.4
:Apple Creek
Menoken 5.2 4.9 4.5 4.4 4.3 4.3 4.3
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 September.
$$
Schlag