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Rapid beginning to snow melt season

Snow melt has been observed at most of the automated snow weather stations (ASWS) across the province since early April.

The province’s snow melt freshet season is now underway.

Snow melt has been observed at most of the automated snow weather stations (ASWS) across the province since early April, indicating a melt season that is about two weeks in advance of normal.

At mid-elevations the early season melt has been rapid, and several ASWS have shed 30-50 per cent of peak accumulated snow in the past two weeks. At higher elevation ASWS, the transition has been slower, with five to 10 per cent of the total snow pack melting since April 1.

“This snow melt has led to the continuing rise of freshet flows in snow melt dominated rivers of the province,” said Nelson Jatel, Okanagan Basin Water Board water stewardship director.

“Stream flow is well above normal for this time of year in most rivers, though flow rates are currently about one-third to one-half of average peak flow levels, and less than this in watersheds with extensive high-elevation terrain.”

A strong high pressure system is developing off the coast, and is expected to move north through this week, bringing seasonally hot temperatures to southern and central British Columbia. Temperatures are expected to reach potentially record breaking mid to high 20s. Freezing levels are expected to be well above 3,000 metres for the southern half of the province, with overnight temperatures remaining above zero.

Snow melt rates are expected to climb through the week, with rapid melt at mid-elevations (<1500m), and daily melt rates in the 20-40 mm range. At high elevation melt rates will gradually increase as the snow pack ripens, with daily melt rates in the 10-25 mm range.

“River levels across the province are expected to rise through the week in response to the hot temperatures and rapid snow melt,” said Jatel.

“As it is still early in the freshet season, most rivers have sufficient capacity to contain this melt. In areas of the province with higher seasonal snow basin indices or particularly high forecasted temperatures, including the Okanagan and adjacent areas (Kettle, Similkameen, Central Interior) rapid rises in streamflow are possible this week, with the potential for localized flooding.”

Elsewhere in the province smaller stream and river systems may also experience quick rises in stream flow.

The River Forecast Centre continues to monitor conditions and will provide updates as conditions warrant.

Watch The Morning Star for the next Provincial River Outlook later this month.