High Streamflow Advisory - Howe Sound and Sea to Sky

Sep 16, 2021
Affected Communities: 
District of Squamish, Electoral Area C, Electoral Area D, Village of Pemberton

The River Forecast Centre is issuing a High Streamflow Advisory for:

  • West Vancouver Island
  • South Vancouver Island
  • Sunshine Coast
  • Howe Sound and Sea-to-Sky including the Lillooet River
  • North Shore Mountains
  • Metro-Vancouver
  • Fraser Valley tributaries including the Chilliwack River

A strong storm system is approaching the coast and expected to arrive Friday morning. The storm is forecast to provide moderate to heavy precipitation for western and southern Vancouver Island, the Sunshine Coast, Howe Sound, the Lower Mainland and the Lower Fraser Valley on Friday. The heaviest precipitation rates (up 5 to 10 mm per hour) are expected to occur Friday afternoon and rainfall totals could reach 150 mm or more in the mountains. There is still uncertainty in the exact location of the heaviest rainfall amounts.

The upcoming storm will mark a significant shift in streamflow runoff conditions which have been dominated by low flow drought conditions through most of the summer. Rivers are expected to rise rapidly in response to rainfall on Friday, with peak flows occurring late Friday through Saturday. Current hydrologic modelling is indicating the potential for streamflow in the 2-year to 20-year flows in some areas which can lead to localized issues and flooding.

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

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