Record high snow pack levels in the upper Fraser and Nechako river basins has increased the chances of flooding along the two rivers, according to the latest information released by the B.C. River Forecast Centre.
Snow pack levels in the upper Fraser basin were 52 per cent above normal and 65 per cent above normal in the Nechako River basin.
"What we're seeing along the upper Fraser and Nechako is exceptionally high snow packs," River Forecast Centre head Dave Campbell said. "This is the highest we've seen since we started recording. That does indicate increased flood risk for those regions."
By this time of year, approximately 95 per cent of the snow which will accumulate during the winter has fallen, Campbell said. Because of that, the April snow pack data is key in predicting potential spring freshet flooding, he added.
"[But] snowpack is one piece of the flood risk puzzle," Campbell said. "Whether we see flooding will depend on the weather. The weather drives it more than the snow pack."
An extended stretch of warmer weather during mid-May to June can trigger flooding even during normal snow pack years, he said. Several days of widespread, extremely wet weather also have the potential to trigger flooding on its own, or in combination with several days of warm weather.
However, if the region gets seasonably dry, normal weather during the melting period, then there is little risk of flooding, Campbell said.
The high level of snow is the result of a second year of La Nia conditions in the Pacific Ocean, Campbell said. The weather pattern resulted in temperatures 0.5 C to 1.5 C below normal across the province, and large amounts of snow, he said.
"Over the last six weeks, February to the beginning of April, we've had a number of systems with a lot of snow," Campbell said.
The overall snowpack for the Fraser River is 31 per cent above normal, comparable to 2007 -year which saw significant flooding across the province.
Across north-central B.C., the snow packs in the Peace, Columbia, Kootney and Skeena-Nass river basins are 25 per cent above normal or higher.
Environment Canada and the U.S. National Weather Service are predicting La Nia conditions to end by mid-April. Environment Canada's 30-day temperature forecast is predicting cooler than average temperatures across most of B.C., transitioning to warmer than average temperatures for most of the province through the summer.
