Lyndsay Morrison, staff writer
April 20, 2011 — With rivers continuing to rise in parts of Manitoba and Saskatchewan, The Weather Network takes a look at the science behind spring flooding in the southern Prairies.
Generally, the more snow that falls over the winter, the more snow that has to melt in the spring. Parts of Alberta and Saskatchewan saw above normal precipitation this winter, while Southern Manitoba saw below normal amounts.
Between November 17th and February 3rd, Winnipeg did not see a single day above the freezing mark. In an average year, the city sees about seven or eight days above zero.
The cold led to a frozen ground, which in return could not absorb the snowmelt and rain when temperatures finally warmed up again. However, as temperatures warm up and the rain starts to fall, that’s when ice jams become a problem.
As temperatures rise, frozen rivers start to swell, breaking the layer of ice on top of the river. Chunks of ice float downstream and often pile up, acting as obstructions. Officials believe that the ice jam season is now over on both the Red and Assiniboine.
It's important to know that the Souris and Qu'appelle Rivers both meet up with the Assiniboine. The Assiniboine meets up with the Red River in a part of Winnipeg known as “The Forks.”
When the snow begins to melt, all of the water ends up in the same place. To make matters worse, the Red River flows northward. If the Dakotas get hammered with snow, southern Manitoba will eventually have to deal with the melt. Also, waters that flow northward are often slowed by ice.
Be sure to tune in to The Weather Network on TV for the latest on the flood situation across the Prairies. Next week, Natalie Thomas will be reporting live from southern Manitoba.
With files from Natalie Thomas