The BC River Forecast Centre is issuing a High Streamflow Advisory for the South Coast including:

• North Shore
• Howe Sound
• Sunshine Coast
• Fraser Valley including Chilliwack

A Pacific storm system is forecast to bring warm temperatures and heavy rainfall to the South Coast over the next 24 hours. The heaviest rainfall will arrive on the South Coast by early Wednesday evening. Rainfall totals are forecast to range from 50 to 150 mm by Thursday morning for the affected areas noted above. Freezing levels are expected to reach 2200 m on the North Shore. Further details on the storm can be found at the Avalanche Canada weather blog.

Temperatures at the Upper Squamish Automated Snow Weather Station (elevation 1387 m) have been above freezing since Tuesday morning. Mild temperatures in the region are expected to persist through to Thursday evening, potentially reducing the high elevation snowpack and leading to increased streamflows along the North Shore and Howe Sound.

Depending on the intensity and timing of the system, river levels are expected to rise quickly by Wednesday evening, with peak flows by Thursday morning as an additional flush of snowmelt runoff arrives by late Thursday morning. Higher flows are expected to persist through Thursday afternoon. As the system leaves the region Thursday, flows should slowly recede through Friday.

Localized flooding in low-lying areas is possible as a result of this event. Wide-spread flooding is not expected. The public is cautioned to stay clear of rivers during rain events due to quickly flowing water and potentially unstable riverbanks.

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

A High Streamflow Advisory means that river levels are rising or expected to rise rapidly, but that no major flooding is expected.  Minor flooding in low-lying areas is possible.