National Weather Service

March 12, 2020

This Spring Flood and Water Resources Outlook is for the Missouri
and James River basins of North Dakota and covers the period from
mid-March through mid-June. This outlook is the last update in the
Spring Flood and Water Resources Outlook series. After this update,
the NWS will revert back to the regular monthly issuance on the
fourth Thursday of each month.

…Flood Outlook Highlights…

In the James River Basin, only modest amounts of the SWE have been removed from the countryside. Even if visually the snowpack appears to be considerably depleted, the runoff has not yet reached Pipestem Creek or the James River. Much of the meltwater generated is still trapped on the countryside and is expected to begin showing up in earnest during the latter half of March. Downstream of Jamestown has seen only modest amounts of water making its way into the James and Maple Rivers. While it would have
been beneficial to see the latest warm spell last a few more days to
help remove more SWE from the countryside, it would appear that this
area will now be entering a week or more of suspended animation.
This suspension of the melt and potential for adding more SWE over
the coming days are part of what is keeping the risk for flooding
substantially elevated at points along the lower James River in
North Dakota.

The Prairie Pothole region, including at least parts of Sheridan,
Wells, Kidder, Stutsman, Logan, McIntosh and Dickey counties have
enough SWE to suggest overland flooding will continue to be a
concern going into spring.

East of the Missouri River and south of I-94, Apple Creek near
Menoken is currently seeing higher water levels due to the recent
loss of the snowpack. While the cooler weather is likely to keep
Apple Creek below flood stage, it will be sensitive to any rainfall
over the coming few weeks. Beaver Creek near Linton has been
relatively quiet thus far even though some runoff is starting to be
observed at the gage and like Apple Creek, it will need some
rainfall in the near term if it wants to make a run at even minor
flooding. Other area streams such as Burnt Creek, Hay Creek, and
Painted Woods Creek have experienced at least some runoff and are
considered at a near normal to below normal risk of flooding due to
the wet soils.

The probability of flooding across western and central North Dakota
has generally held steady or trended slightly upward. The upward
revisions are generally associated with streams that are currently
receiving substantial runoff from snowmelt over that past couple of
weeks. These streams are very susceptible to minor flooding with
only modest amounts of additional rainfall over the near term.
However, these risks will fall quickly as the streams reach their
initial crest in the coming week or two. Other streams, such as the
Cannonball River, are also just very susceptible to minor flooding
during early spring rains.

In the northwest corner of North Dakota, streams like the Little
Muddy River have a somewhat below normal, but relatively high
probability of minor flooding. This risk is mostly centered around
those streams susceptibility to heavy spring rains as snow water
equivalent (SWE) is not a concern in that area of the state. Other
small streams in the area, such as the White Earth River, Little
Knife River, and Deep Creek in McLean County have a below normal
risk of flooding going forward.

Farther to the south and west of the Missouri River, forecast points
on the Knife River and Spring Creek are now below normal for spring
flood risk. Again, this is due to the the early loss of most of the
region`s SWE and any significant flooding from this point on will
certainly have a heavy rain component.

South of I-94 and still west of the Missouri River, forecast points
and small streams like the Heart and Cannonball rivers along with
Cedar creek are now considered near normal to below normal risk for
reaching Minor flood stage. Again, the early loss of the snowpack in
these watersheds is driving the risk down even though wet soils
continue to be a potential problem. This tends to be true as well
for the Green River, Big Muddy, and Sweet Briar Creek watersheds.

 

And lastly, the Missouri River itself.   With little plains and
perfectly average mountain snowpack, the Yellowstone and Missouri
rivers of western North Dakota are right around normal risk of
minor flooding. The slightly enhanced risk observed in the
probability tables is more a reflection of current conditions where
ice cover and modest runoff are combining to cause minor flooding
west of Williston. Once the ice cover is gone, near normal risk of
high water will hold through the spring and be mostly controlled by
the rate of melt in the mountain snowpack. Below Garrison Dam, the
Missouri River has lost its ice cover all the way down through the
Bismarck/Mandan area. With the loss of ice cover, risk of flooding
in this stretch is at a minimum and would require very significant
spring rains.

Overall, while western and central North Dakota has thus far been
under a very favorable weather pattern for producing a gentle melt,
some of that appears destined for change. The current weather
outlook is suggesting a shift towards a much more active, cooler,
and wetter pattern during the next couple weeks. Mid range outlooks
suggest that will be followed by a stretch of above normal
temperatures towards the last week of March and early April. Ice jams
defy mathematical predictions, but are known to increase during
early and rapid spring runoffs where the ice becomes mobilized, only
to get stuck at some downstream constriction such as bridges and
bends in the river. The slow and gentle melt much of western and
central North Dakota has experienced thus far would suggest the
risk of ice related high water is fading, and fading quickly.

 

…Current Conditions…
Frozen and wetter than normal soils remain a concern across the
entire state. However, SWE is only a true concern in the James River
basin. Warm weather over the past couple of weeks has removed most
of the SWE west of the Highway 83 corridor. Not surprisingly, some
streams have already experienced minor flooding and several others
are relatively high due to the runoff. Ice jams have not yet been a
problem in western and central North Dakota, most likely due to the
modest amount of runoff and gentle melt conditions. So far most
streams have not risen enough to mobilize the ice cover and this is
allowing the ice to slowly degrade in place.

…Weather Outlook…
The near term 6-10 and 8-14 day outlooks have a strong signal for
below normal temperatures and slightly above normal precipitation.
Looking farther into the future, the week 3-4 outlooks suggest the
cooler and wetter than normal pattern will end during the third
week of March where an above normal temperature signal would put
daytime highs well up into the realm of restarting the snowmelt.
And lastly, the three-month outlooks for March, April, and May
reflect an equal chance for above normal, near normal, and below
normal temperature and precipitation.