Unseasonably Warm Weather on the Way

 ...UNSEASONABLY WARM WEATHER ON THE WAY...

Much of North Dakota will be going into late February with
consecutive days of unseasonably warm temperatures in the forecast.
Highs well above freezing across the southwest and south-central are
likely with those warm temperatures decreasing to around freezing,
or just above freezing in the northwestern and north-central
counties. In short, the modest snowpack south and west of a line
from Williams County, through southern Ward County, and on down to
Jamestown will melt over the remainder of February into early March.

In general, there is not enough water in the above snowpack to
warrant significant concerns with flooding. However, there are some
concerns with ice stability and the potential for ice jams on some
of North Dakota`s larger rivers.

By geographic area, here are the concerns and most likely effects of
the incoming warm weather:

The Souris River Basin...
The Souris River Basin is the least likely of the major watersheds
of western and central North Dakota to experience significant
melting.  However, it has some of the most snow and water equivalent
in the snowpack. Temperatures in this area will be high enough to
see at least some melting of the snow, but the heaviest snowpack in
the Turtle Mountain area should also prove to be the most resilient.
Nonetheless, an early softening of the ice along the shorelines of
rivers and lakes can create hazardous conditions for recreational
users on the Souris and small lakes in the area. This will be
magnified where direct sunlight enhances the warming on exposed
shorelines.

The James River Basin...
Only the James and Pipestem watersheds above Jamestown have a near
normal snowpack, especially in the headwaters area.  This snowpack
will likely gradually melt and produce some runoff into both the
James River and Pipestem Creek towards late February, but the
potential for minor flooding would appear to be normal to slightly
below normal. The James River below Interstate 94 does not have much
water in the snowpack, and little risk of flooding is expected.

Missouri River Tributaries below Garrison Dam...
The thin snowpack in these watersheds are not likely to create
flooding and only modest runoff can be generated without more
precipitation, and there are only very modest chances of relatively
minor amounts of precipitation going through late February. It is
likely these watersheds, including the Knife, Heart, and Cannonball
rivers along with Painted Woods, Apple, and Beaver creeks will lose
their snow with only minor rises in those streams. It is not
expected that rises in these streams will be enough to break up the
ice, but safe access to river ice will likely decrease going into
late February and early March.

The Missouri and Yellowstone rivers west of Williston...
This may be the most affected waters going forward. The Yellowstone
River basin in Montana will be undergoing a similar warm spell and
it also has a more robust snowpack. As this snowpack melts, runoff
will make it into the Yellowstone and Missouri rivers of eastern
Montana and western North Dakota. Non-trivial rises in these streams
should be expected, along with a high potential for increasingly
unstable ice. As the region gets closer to the end of February,
recreational users of these rivers along with people who live near
them should be vigilant for the potential of higher flows and ice
jams.

The Little Missouri River...
At least a modest amount of runoff should be generated in the Little
Missouri River along its path from Wyoming and on up through western
North Dakota. High water is not expected, unless enough flow is
generated to begin breaking up the river ice. While this is a
relatively low concern for now, there is at least a nominal risk of
ice jams.

The Missouri River below Garrison Dam...
Due to recent extreme cold weather, the ice cover on the Missouri
River below Garrison Dam is about as much as ever develops during a
given winter. Even with the incoming warm weather, it will take a
few weeks to clear the Missouri River of its ice all the way down
through the Bismarck/Mandan area. This leaves this portion of the
river vulnerable to ice jams, especially if one or more of its
tributaries were to generate enough flow to try and discharge its
ice load into the Missouri River before the Missouri is itself
largely ice free. Since there does not appear to be sufficient water
in the local snowpack to make this a reasonable outcome, one will
need to monitor the weather forecast for large rainfall events.
Importantly, there is NO such large rainstorm in the current
forecast.