The provincial snowpack was almost one-third below normal as of May 1, the Lower Thompson region was at 0 (zero) per cent of normal, and snowmelt is taking place earlier than usual, according to the most recent Snow Survey and Water Supply Bulletin published by the province.
The May 1 snow survey for British Columbia shows that the provincial snowpack is still below normal, averaging 71 per cent of normal across the province. This is down from the April 1 survey, which showed an average provincial snowpack of 79 per cent of normal, but is up from the same point a year ago, when the snowpack stood at 66 per cent of normal for the province.
The survey notes that by mid-April, annual snow accumulation in B.C. has reached its maximum level, adding that there was very little mountain snow accumulation in April.
Snowmelt is trending earlier than normal, with 15 per cent of the peak total snowpack at automated stations having melted by May 1; usually only five per cent of the annual B.C. snowpack has melted by then. Snowmelt has continued through the first week of May, and as of May 8 approximately 27 per cent of the total snowpack had melted.
A below normal spring freshet hazard is expected due to low snowpack. However, low snowpack, early snowmelt, and warm seasonal weather forecasts are pointing towards elevated drought hazards this spring and summer.
The May 1 survey was the province’s fifth Snow Survey and Water Supply Bulletin of the year, and was released on May 8. The only region of B.C. with an above average snowpack was the Liard region, at 128 per cent of normal; next closest was the North Thompson region, at 84 per cent of normal.
The Lower Thompson region — which includes Lytton, Ashcroft, Cache Creek, Clinton, and Merritt — had been sitting at 83 per cent of normal as of April 1, but by May 1 had dropped to 0 (zero) per cent of normal.
The Lower Thompson is one of four areas comprising the Middle Fraser region, which was at 62 per cent of normal on May 1 (down from 75 per cent on April 1). The survey notes that there was not enough data to calculate a Snow Basin Index for the Chilcotin region. The South Thompson region, which includes Kamloops, was at 72 per cent, down from 86 per cent on April 1.
Temperatures in April ranged from slightly above normal to above normal (+0.5 C to +2.5 C) throughout B.C. Precipitation was slightly below normal to below normal for April throughout most of the province, although slightly above normal precipitation was measured at Kamloops.
Environment and Climate Change Canada is forecasting a greater likelihood of above normal temperatures for most of B.C. from May through July. May is forecast to be wetter than normal for parts of northern B.C., with drier conditions in the southern parts of the province. This drier than normal trend is forecast to linger into the summer for southern B.C.
Seasonal volume runoff forecasts are normal (85 to 105 per cent of normal) for the Upper Fraser, North and South Thompson Rivers, and the Thompson River. With below normal snowpack across most regions, seasonal flood hazards are expected to be reduced this season. However, the May survey notes that while snow is one significant aspect to seasonal flooding in B.C., weather during the freshet season plays a key role, and flooding is possible in years with low snowpack.
“In areas with low snowpack, key flood risks shift towards heavy precipitation events, either short-duration events or prolonged periods of wet weather," states the report. "It is important to note that May and June are wet months through the B.C. Interior with the potential for extreme precipitation patterns. . . Therefore, precipitation poses a flood risk through the spring even with limited snowpack.”
The Snow Survey and Water Supply Bulletin is conducted by the province’s Ministry of Water, Land and Resource Stewardship and uses data from 40 manual snow courses and 113 automated snow weather services around B.C. The next report is due out on or about May 22.
