A high streamflow advisory has been issued by the River Forecast Centre for the Central Coast, including the Bella Coola River and Atnarko River, Thursday, June 3, 2021 at 8:15 a.m.
The advisory comes following a week of the warmest temperatures of the season, and a forecast of rain for the weekend.
“There is a risk that rain on a melting snowpack will increase the flows for the Atnarko and Bella Coola Rivers. This is not predicted to a severe or heavy rainfall event like typical fall storms, but since flows are already relatively high from snowmelt, the rivers are vulnerable to any additional precipitation input,” notes the advisory.
According the forecast centre the automated snow weather station 3C08P Burnt Bridge Creek (elevation 1329 m) reached maximum temperatures of 18C over the past two days and remained above zero for five consecutive days.
The April 1st Snow Basin Index for the Central Coast was 146 per cent of normal, indicating a higher than normal snowpack for the region. The 3C08P Burnt Bridge Creek station is melting snow quickly with approximately 1/3rd of the seasonal snow remaining.
“The larger river systems in the region are rising and expected to stay at higher levels longer than the typically flashy flow events in the fall. The Atnarko River near the Mouth (08FB006) was flowing at approximately 180 m3/s (between two-year and five-year flow) (Thursday) morning,” noted the advisory.
“The Bella Coola River above Hammer Creek (08FB011) is approximately 435 m3/s (nearing a 2-year flow). The recent atmospheric river event that affected the North Coast did not impact areas around Bella Coola and the recent rises have been driven by snowmelt alone.”
A moderate storm system is forecast to approach coastal B.C. on Friday, June 4 through Sunday, June 6.
Environment and Climate Change Canada is forecasting precipitation totals for the event of 30-60 mm for Bella Bella and 20-30 mm further inland at Bella Coola.
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.
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.