Probabilistic Hydrologic Outlook
National Weather Service Bismarck ND
1012 AM CST Thu Feb 27 2025
...SPRING FLOOD AND WATER RESOURCES OUTLOOK...
This Spring Flood and Water Resources Outlook is for the Missouri
and James River basins of North Dakota, covering the period of 1
March, 2025 through 30 May, 2025. This is the second in a series of
three Spring Flood Outlooks covering flood probabilities for NWS
forecast locations. The next outlook will be issued on March 13th.
Below is the full schedule for this series of outlooks.
First edition - Thursday, February 13th, 2025.
Second edition - Thursday, February 27th, 2025.
Third edition - Thursday, March 13th, 2025.
After the above Spring Flood and Water Resources Outlooks, the NWS
expects to revert back to its normally scheduled monthly release of
Flood and Water Resources Outlooks on, or about, 27 March, 2025.
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...
In general, all forecast locations in the Missouri and James River
basins are below historically normal risk levels of flooding. Some
of this lack of risk is due to an absence of normal levels of
Snow-Water Equivalent (SWE) in the snowpack through the winter.
Another is that the area has been unseasonably warm as of late and
that has been melting what snow was on the ground.
In short, the Snow-Water Equivalent (SWE) remaining is not only
below normal in all areas, but the dry to very-dry soils in the
region have been taking in much of the meltwater. Going forward,
these dry soils are expected to continue to temper runoff from
melting snow and rainfall as the region goes into early spring.
...Snowpack Conditions...
One of the two areas with significant remaining SWE in the James and
Missouri River basins of North Dakota is in the upper James River
basin. This, however, is still a less than imposing amount of water
and is unlikely to create major problems.
Another area with a fair amount of SWE remaining is Williams County.
In particular, western and eastern Williams County had over two
inches
of SWE and due to the terrain sheltering it, there should be a fair
amount of snow remaining even though it is likely to melt slowly due
to the protection from direct sunlight. This would include the White
Earth River.
Outside of the area listed above, most of the remaining portions of
the James and Missouri River basins of North Dakota are down to a
trace of SWE.
...The Missouri and Yellowstone rivers west of Williston...
This may be the most active area in the near-term. The Yellowstone
River basin in Montana is undergoing a similar warm spell with a
robust snowpack. Runoff into the Yellowstone has initiated ice
break-up and ice jams in the Miles City area of Montana. These
conditions are steadily going to be moving downstream and will find
its way into the Yellowstone and Missouri Rivers west of Williston
over the coming week, or so. This will bear watching until such time
as those areas are largely free of river ice.
...The Little Missouri River...
The Little Missouri River has also been receiving enough runoff to
enhance the risk of ice jams. This threat is also expected to remain
until such time as the local and upstream runoff passes, probably
until the first week of March before the risk begins to wane.
...Current Drought Conditions...
Drought remains a concern across much of North Dakota with a large
pocket of D3 (Extreme) drought centered on McKenzie and northwest
Dunn counties. D1 and D2 levels of drought cover most of the areas
west of the Missouri River and south of I-95 east of Highway 83.
North and east of these areas, drought designations rapidly diminish
and are near normal.
...Reservoirs and Natural Wetlands...
Streamflow values have trended upward over the last week of February
due to melting snow, but this trend is largely over in the near-term
as the region exhausts its supply of snow.
...Soil Conditions...
While the upper inch or two of the soil is now saturated from
melting snow, overall soil moisture values remain well below normal
across much of western and south central North Dakota. These dry
soils are expected to continue to reduce runoff and produce less
streamflow than expected from early spring rains as they continue to
thaw.
...Weather Outlook...
The near term 6-10 day weather outlooks favors near normal to above
normal temperatures with near normal precipitation. In the
slightly longer 8-14 day outlooks, the region is slightly favored
for above normal temperatures with near normal to below normal
precipitation. Again, looking a little longer term, the weeks 3-4
outlooks favor above normal temperatures, with an equal chances
designation for above normal, near normal, or below normal
precipitation.
Looking even longer term at the three-month outlooks (Mar-May),
there is a slight favoring for below normal temperatures across
western North Dakota with an equal chances designation for above
normal, near normal, or below temperature and precipitation for the
remainder of the state.
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: 03/01/2025 - 05/30/2025
: 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 12 <5 <5 <5 <5
:James River
Grace City 12.0 14.0 15.0 : 6 15 <5 9 <5 8
LaMoure 14.0 16.0 18.0 : <5 17 <5 8 <5 <5
:Missouri River
Williston 22.0 24.0 26.0 : <5 27 <5 10 <5 8
: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 9 <5 5 <5 <5
:Cannonball River
Breien 10.0 20.0 23.0 : 14 58 <5 <5 <5 <5
:Beaver Creek
Linton 12.0 14.0 16.0 : 6 41 <5 31 <5 13
:Little Muddy River
Williston 10.0 12.0 14.0 : 5 66 <5 32 <5 10
:Little Missouri River
Marmarth 18.0 23.0 30.0 : <5 6 <5 <5 <5 <5
Medora 15.0 18.0 20.0 : <5 18 <5 8 <5 6
Watford City 20.0 24.0 30.0 : <5 14 <5 5 <5 <5
:Knife River
Manning 15.0 17.0 20.0 : <5 20 <5 <5 <5 <5
:Spring Creek
Zap 14.0 18.0 20.0 : <5 25 <5 14 <5 8
:Knife River
Hazen 21.0 24.0 25.0 : <5 43 <5 25 <5 23
:Heart River
Mandan 27.0 33.0 38.0 : <5 20 <5 <5 <5 <5
:Apple Creek
Menoken 15.0 16.0 17.0 : 26 55 7 52 <5 34
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: 03/01/2025 - 05/30/2025
Location 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:Pipestem
Pingree 5.5 5.5 5.5 5.7 8.3 10.5 11.2
:James River
Grace City 4.3 4.3 4.3 4.8 6.6 9.9 12.8
LaMoure 7.0 7.0 7.0 7.2 8.6 11.4 13.1
:Missouri River
Williston 15.7 15.9 16.4 17.0 18.2 18.7 21.3
:Cannonball River
Regent 5.2 5.5 6.1 7.0 7.9 9.4 11.1
:Cedar Creek
Raleigh 1.3 1.8 2.9 4.0 4.9 5.8 6.0
:Cannonball River
Breien 2.8 3.7 4.5 6.7 8.1 10.5 11.1
:Beaver Creek
Linton 4.7 4.8 5.1 6.4 8.5 10.8 12.3
:Little Muddy River
Williston 4.6 4.6 5.1 5.7 6.9 8.2 9.8
:Little Missouri River
Marmarth 1.1 1.2 1.7 2.5 3.8 8.9 12.6
Medora 1.4 1.4 2.4 3.1 4.1 9.5 13.2
Watford City 7.1 7.2 8.2 9.1 10.1 13.4 16.4
:Knife River
Manning 6.1 6.1 6.1 6.7 7.9 8.5 10.5
:Spring Creek
Zap 4.6 4.6 4.7 5.2 6.2 8.7 9.3
:Knife River
Hazen 0.3 0.4 0.9 2.5 4.8 6.3 11.5
:Heart River
Mandan 9.2 9.7 10.8 12.1 15.6 17.8 20.0
:Apple Creek
Menoken 5.1 5.1 5.2 6.8 15.2 15.9 16.0
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: 03/01/2025 - 05/30/2025
LOCATION 95% 90% 75% 50% 25% 10% 5%
-------- ------ ------ ------ ------ ------ ------ ------
:Pipestem
Pingree 5.5 5.5 5.5 5.5 5.5 5.5 5.5
:James River
Grace City 4.3 4.3 4.3 4.2 4.2 4.2 4.2
LaMoure 7.0 7.0 7.0 7.0 7.0 7.0 7.0
:Missouri River
:Cannonball River
Regent 4.7 4.7 4.7 4.7 4.7 4.7 4.7
:Cedar Creek
Raleigh 0.1 0.1 0.0 0.0 0.0 0.0 0.0
:Cannonball River
Breien 1.9 1.9 1.9 1.9 1.8 1.8 1.8
:Beaver Creek
Linton 4.5 4.5 4.4 4.4 4.3 4.3 4.3
:Little Muddy River
Williston 4.4 4.4 4.4 4.4 4.4 4.4 4.4
:Little Missouri River
Marmarth 1.0 1.0 1.0 1.0 1.0 0.9 0.8
Medora 1.3 1.3 1.3 1.3 1.2 1.1 1.1
Watford City 7.0 7.0 7.0 7.0 7.0 6.8 6.7
:Knife River
Manning 6.1 6.1 6.1 6.0 6.0 6.0 6.0
:Spring Creek
Zap 4.6 4.6 4.6 4.6 4.6 4.6 4.6
:Knife River
Hazen 0.3 0.3 0.3 0.3 0.2 0.1 0.0
:Heart River
Mandan 9.1 9.1 9.1 9.0 8.9 8.8 8.8
:Apple Creek
Menoken 4.9 4.7 4.4 3.9 3.7 3.5 3.5
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 13 March.
$$
Schlag
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