Declining La Niña conditions may point to better weather ahead

Cooler than normal conditions indicated in the short term, but signs of changing atmospheric pattern may be a sign of better weather ahead

La Niña conditions in the Pacific Ocean were observed to weaken through March. Weather patterns through the month were consistent with typical patterns observed during La Niña events. Wetter than normal weather was observed across most of British Columbia, with very wet conditions in the Lower Fraser, Columbia and Kootenay regions. Temperatures across the province were 0.5 to 1.5 ºC cooler than normal.

Snowpack

Combined cooler and wetter weather through March has led to significant growth of snow packs throughout the province. Snow packs are above normal throughout the province.

The snow basin index for the entire Fraser River basin is 131 per cent of normal. This is the 5th highest April 1 snowpack observed since 1953, and is similar to levels observed in 2007.

Okanagan-Kettle

104 per cent of normal

Similkameen

110 per cent of normal

Outlook

By April 1, about 95 per cent of the annual B.C. snowpack has typically accumulated. For most areas, the transition from snow accumulation to snow melt generally occurs in the middle of April, and therefore the April 1 snow survey is considered to be the key survey of the year for assessing the impact of snow pack on seasonal water supply and flood risk.

With above normal snow packs through most of the province, above normal spring runoff volume is expected in most basins across the province. Conditions in the Okanagan-Kettle basin have improved since February with the current snow pack at near normal levels. Therefore near normal seasonal runoff is expected for the Okanagan basin.

Snowmelt driven rivers in British Columbia generally reach their peak levels in May and June.

La Niña conditions across the equatorial Pacific Ocean have been weakening and the Climate Prediction Centre with the U.S. National Weather Service (NOAA) is predicting the La Niña event to break down by late-April. NOAA suggests that atmospheric patterns are still indicative of La Niña conditions, and this is consistent with current seasonal weather forecasts from Environment Canada.  The current 30-day deterministic temperature forecast from Environment Canada is for cooler than normal temperature across the province, except the far north and north-east. The current three-month forecasts transition into warmer than normal temperatures through most of the province into the summer, and below normal precipitation over the same period.

The River Forecast Centre continues to monitor snow and weather conditions across the Province and when conditions warrant, provides advisories through media releases and on the River Forecast Centre website:  http://bcrfc.env.gov.bc.ca/.

 

The May 1 snow bulletin is expected to be released on May 8, 2012.