The majority of snow packs in the province of British Columbia remain below normal after a generally cooler and unsettled April, weather-wise, says the latest snow bulletin from the BC River Forecast Centre.
April temperatures were generally near normal across the province, with areas of coastal BC seeing slightly above normal temperatures, and areas in north-eastern and eastern BC experiencing slightly below normal temperatures. Precipitation patterns were also near normal for most areas of the province through April, with areas in central, northern and eastern BC experiencing some below-normal precipitation. Within the general seasonal weather through April, several cooler weather systems impacted many areas with late-season snow accumulation, particularly in the Rocky Mountains.
The East Kootenay snowpack stands at 70 per cent of normal.
Snow basin indices for May 1st are fairly similar to those for April 1st. One significant pattern this year is the difference between low-to-mid elevation and upper elevation snow. Particularly through the South Interior, snow below 1600m has almost completely disappeared as of early-May. This trend is 2-3 weeks ahead of when these regions would normally be snow-free (for many locations this was near-record early melt). Conversely, cooler weather patterns have led to very limited melt at higher elevations (>1600m); upper elevation melt is 1-2 weeks behind normal. Snowpack gradients across elevation is unusual Snow Survey and Water Supply Bulletin – May 1st, 2019 1. Every effort is made to ensure that data reported on these pages are accurate. However, in order to update the graphs and indices as quickly as possible, some data may have been estimated. Please note that data provided on these pages are preliminary and subject to revision upon review. this year, with a rapid change from no snow to deeper snow packs occurring over a few hundred meters of elevation difference in many regions. These conditions have developed due to extremely warm weather in late-March which kicked off ripening of mid-elevation snowpack, followed by cooler weather which has provided insufficient energy delivery to upper elevation snow to fully ripen and begin melting. In central, eastern and northern BC, this gradient is less pronounced, with current snowlines around the 1000-1200 m elevation level.
Seasonal forecasts from Environment and Climate Change Canada favor a high likelihood of above normal late-spring to early-summer temperatures (May-June-July) across western British Columbia, and no strong indication of favoured temperature patterns for elsewhere in the province. Forecasts have eased since last month which had been indicating a high likelihood of warmer spring and summer temperatures across the province. While warmer temperature patterns were not dominant in April, recent and current weather patterns have shifted towards ridging across BC, ushering in a period of warmer weather. This will see increased snowmelt, including the onset of melt from higher elevation areas across the province over the next week.
According to the report, annual snow accumulation usually reaches maximum levels in med-April.
At this stage in the season there is no elevated flood risk present in the current snowpack across the province. Close to normal seasonal flood risk is expected in the Peace, Liard, Upper Fraser and North Thompson regions. Elsewhere, snowpacks pose below-normal risk for snowmelt driven flooding.
However, other factors can effect blood risk, including heavy spring rains.
There will be one more season flood risk forecast released by the River Forecast Centre on May 22, 2019