Flood Watch issued for Howe Sound

The River Forecast Centre has upgraded to a Flood Watch for Howe Sound and the Sea to Sky Corridor including Squamish and Pemberton.

 

A multi-day atmospheric river continues to impact coastal British Columbia. From Wednesday, March 18 through Friday March 20, moderate to very heavy rainfall totals are likely for the South Coast, with an additional 50-150+ mm possible across the region. The next few days of rainfall arrive on top of previous totals ranging up to approx. 100-120 mm at lower elevations and 150-170 mm at higher elevations from the initial pulse of the storm in the past 96 hours.

 

Freezing levels are expected to remain elevated at approx. 2000-2500 m (possibly up to 3000 m in some areas) for the duration of the storm. The earlier phase of the storm deposited a substantial amount of mountain snowpack. Fresh snow is more susceptible to melting than older, established snowpack. Significant melt of mountain snowpack is likely, with melt rates possibly reaching or exceeding 30-50 mm snow water equivalent per day across multiple elevation bands. Rain-on-snow and snowmelt are expected to be substantial contributions to runoff, in addition to precipitation.

 

As of March 18, many rivers across the South Coast are at or near a fairly modest (up to 1-2 year return period) initial peak in response to the most recent round of precipitation. However, additional rapid rises are expected as precipitation rates increase later this evening, continuing into Friday. River levels are already elevated and soil is saturated as the next round of the storm begins, which will likely mean a faster and more dramatic flow response.

 

The storm’s extremely long duration, heavy precipitation rates, and potentially significant rain-on-snow and snowmelt contributions all increase the flood hazard associated with this event. Flows are expected to rise very quickly as precipitation increases, and peaks may be prolonged, possibly extending from Thursday into Saturday. Peaks may reach or exceed 2-5 year return periods in many systems, with potential for peaks up to 10-20 year return periods or higher in rivers that receive the heaviest runoff.

 

Please be prepared for challenging driving conditions and potential road washouts, and check local conditions on DriveBC.ca. Please avoid driving through flood waters or across road washouts.

 

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

 

March 18, 2026