Special Weather Statement & High Streamflow Advisory
October 28, 2022
Special Weather Statement
Environment Canada has issued a special weather statement for:
- Fraser Valley - central including Chilliwack
- Fraser Valley - east including Hope
- Fraser Valley - west including Abbotsford
Heavy rain and strong wind are expected from Saturday night to Sunday night.
An atmospheric river will bring continuous rain and mild temperatures to the south coast from Saturday night to Sunday night. Significant amounts of rainfall will fall during this period and rainfall warnings are likely to be issued as the event nears. The mild temperatures will elevate snow levels and precipitation along the highway passes will fall as rain.
Strong southeast winds are expected to develop through the Strait of Georgia for Saturday night and Sunday.
High Streamflow Advisory
The River Forecast Centre has issued a High Streamflow Advisory for:
- Central Coast including Bella Coola River and tributaries, Kingcome River, Owikeno/Rivers Inlet and surrounding areas
- Vancouver Island
- Lower Mainland, including Metro Vancouver, North Shore Mountains, Fraser Valley tributaries.
- Sunshine Coast, Howe Sound and Sea-to-Sky including the Lillooet River
A major weather pattern change occurred last weekend, switching from extended, extremely dry weather to ongoing storm systems along coastal BC. Recent storms resulted in relatively light to moderate precipitation totals with cooler temperatures; river responses have thus far been subdued. Automated Snow Weather Stations in the mountains have accumulated 20 to 70 mm of snow water equivalent so far this week.
This stormy pattern continues through the weekend. Rainfall for Thursday and Friday is unlikely to cause major impacts to rivers and creeks. However, a stronger system from Saturday evening through Sunday has the potential to significantly increase flows for the Central Coast, Vancouver Island and South Coast. Forecasted two-day precipitation totals for Saturday/Sunday on the Central Coast range from 80 to 140 mm, 100 to 200 mm for West Vancouver Island, 20- 60 mm for East Vancouver Island, and 60-100 mm for the Lower Mainland, with higher totals possible. Temperatures may be warm enough during this storm to be a rain-on-snow event, adding additional water into rivers from snowmelt. Rivers are expected to rise rapidly on the weekend and peak between Sunday or Monday, depending on rainfall timing and watershed size.
Conditions are expected to be relatively cooler and drier after the weekend storm, with freezing levels dropping to 1,000 m or lower. The outlook in the long range shows the potential for a strong atmospheric river for the following weekend (November 4-6). The Canadian Global Ministry of Forests weather model is currently predicting very large rainfall totals for this event; however, there is still a large amount of uncertainty for this event this far in advance.
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.