A large dump of snow is expected to fall on North Dakota today -- and when it melts, we all know where it will go.
The United States National Weather Service said Sunday by the time the snow finally stops falling later tonight, Fargo, Grand Forks and Minot could all have more than 35 centimetres of new snow, possibly as much as 40 cm.
And there is at least a 20 per cent chance of snow each day this week in North Dakota.
Meanwhile, Environment Canada's forecast Sunday for Manitoba was bad, but not that bad -- with Winnipeg expected to get up to four cm by this morning, but up to 12 cm of heavy, blowing snow in Morris and Emerson.
Provincial officials have been nervously watching the North Dakota numbers.
And given what they had to say Sunday -- that anything up to 20 cm would be within their own somewhat-gloomy forecasts -- we may all be getting nervous.
"The provincial forecasting centre is monitoring this storm development closely, and our regional flood-response team is working with municipal officials on the ground in Morris, Emerson and other Red River Valley communities," said an official Sunday.
"Precipitation of up to 20 cm before the Red River crests is within the predictions for a normal weather scenario in the provincial flood outlook," said the provincial spokesman.
The U.S. National Weather Service expected close to double that amount: "A major winter storm will impact the north-central United States through Monday morning, where total snow accumulations of 6 to 12 inches will be common.
"Some locales in central North Dakota could experience more than 15 inches of new snow. Strong, gusty winds will also lead to considerable blowing and drifting snow and near-blizzard conditions, creating hazardous travel conditions."
An inch is equivalent to 2.54 centimetres.
Jay Doering, dean of graduate studies at the University of Manitoba and a civil engineer with expertise in watershed modelling, said Sunday only the province has the data necessary to know how much of a problem that snow will be -- but it will indeed be a problem.
"Any precipitation that falls in the Red River Watershed will flow towards the City of Winnipeg," Doering said.
"Part of that flow will pass through the city and part will be diverted into the Red River Floodway. The level of protection offered by the floodway is approximately for a one-in-700-years flood. Protection for residents of the Red River Valley who built dikes around their houses or put their houses up on pads are protected to a 1997 flood event plus two feet," he said.
"While the additional precipitation will increase flows, we should still be within existing levels of protection for residents of the Red River Valley. However, increased precipitation increases the probability, severity and duration of road closures.
On the Assiniboine River, flow is diverted at the Portage Diversion to Lake Manitoba," Doering pointed out. "The peak flow predicted for the Portage Diversion is approximately 18,000 cfs (design capacity is 25,000 cfs). The diversion was pushed to convey 34,000 cfs during the 2011 flood. Any additional precipitation in the Assiniboine River Watershed will increase flows."
Last week, Infrastructure and Transportation Minister Steve Ashton said in Manitoba's third flood forecast moderate to major flooding was expected for the Assiniboine and Souris rivers -- with unfavourable conditions, the towns of Melita and Souris will need additional flood protection. The flood risk hadn't changed dramatically for the Red River Valley. Along the Red River, the risk remained as of mid-week at moderate to major.
There could also be major flooding through the Assiniboine Valley to Brandon with unfavourable weather conditions, although it's expected to be at levels much lower than those of 2011.
On the Red south of Winnipeg, the province says Highway 75 will be closed as it was in 2009. The main route south to the U.S. was closed for 36 days in 2009 and 44 days in 1997. No Red River Valley communities are expected to lose road access and no communities currently face evacuation.