High Streamflow Advisory Upgraded to Flood Watch for Howe Sound; Advisory Issued for Lillooet River near Pemberton

Oct 14, 2021
Affected Communities: 
District of Squamish, Electoral Area C, Electoral Area D, Village of Pemberton

The Highstreamflow Advisory issued by the BC River Forecast Centre has been upgraded to a Flood Watch for Howe Sound, effective October 15, 2021.

The River Forecast Centre is uprading to a flood watch for:

  • North Shore Mountains
  • Metro Vancouver
  • Howe Sound
  • Sunshine Coast

The River Forecast Centre is maintining the High Streamflow Advisory for:

  • Fraser Valley - north
  • Fraser Valley - south
  • Vancouver Island

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

  • Lillooet River near Pemberton (and tributaries)

A moderate atmospheric river event is expected to impact the region starting Friday, bringing an extended period of rainfall across south-west British Columbia. Environment and Climate Change Canada is forecasting 75-150 mm of total rainfall for most areas over the two-day period from Friday to Sunday. Higher rainfall amounts are possible, particularly over higher terrain, with the potential for localized amounts in the 150-250 mm range. Temperatures are expected to rise, with freezing levels forecast to peak around 2500 m by later Friday. Recent snow accumulation at elevation has occurred over the past few weeks, with 5-40 mm of snow water equivalent currently being observed at automated snow weather stations throughout the region. Most of the snow on the ground is expected to melt during this event and will contribute additional runoff to rivers.

Rivers are expected to rise rapidly on Friday and into Saturday in response to rainfall, with peak flows expected on Saturday. Larger rivers, including the Squamish River, will likely experience peak flows on Sunday. Current modelling is indicating the potential for flows in the 2-year to 5-year flows in most rivers through the region, and potentially higher depending on the rainfall rates and amounts that ultimately occur.

The most recent model results forecast potential flows at greater than 20-year return period for rivers on the north Shore, Howe Sound and Sunshine Coast.

View the advisory here.

Details of the COFFEE and CLEVER Model forecasts can be found at:

http://bcrfc.env.gov.bc.ca/fallfloods/map_coffee.html, and http://bcrfc.env.gov.bc.ca/freshet/map_clever.html

The public is advised to stay clear of the fast-flowing rivers and potentially unstable riverbanks during the high-streamflow period.

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

 

BC River Forecast Centre
Ministry of Forests, Lands, Natural Resource Operations and Rural Development


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.

A Flood Watch means that river levels are rising and will approach or may exceed bankfull.  Flooding of areas adjacent to affected rivers may occur.

A Flood Warning means that river levels have exceeded bankfull or will exceed bankfull imminently, and that flooding of areas adjacent to the rivers affected will result. 

Inside the SLRD > Notices > Emergency Notice Weather Noticess > High Streamflow Advisory Upgraded to Flood Watch for Howe Sound; Advisory Issued for Lillooet River near Pemberton