ESFBIS 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.
