River Forecast Centre is continuing to update its high streamflow advisories and flood watches throughout coastal B.C., and part of the Interior.
The majority of coastal B.C. remains under a high streamflow advisory, along with the Upper Fraser region, while the central coast is under a flood watch.
A news release from the Water Ministry warned coastal B.C. is experiencing a “prolonged series of rain events, leading to high streamflows and flood watches.” Additional rain is in the forecast until Friday (March 20), with the heaviest amounts of rain expected for the south coast.
The ministry warns that current high streamflow advisories for the south coast could escalate through the week, while avalanche risk is also high due to warmer temperatures, precipitation and winds.
Avalanche Canada is advising backcountry users to stay out of avalanche terrain throughout the week.
Rainfall rates have started to ease and rivers have begun to recede.
However, more rain is expected in the forecast with peak flows most likely Thursday into Friday, or larger for larger systems.
Vancouver Island river conditions
On Vancouver Island, the River Forecast Centre has downgraded a previous flood watch for northern and western Vancouver Island to a high streamflow advisory. The high streamflow advisory was maintained for the rest of the Island. The latest advisory was issued Tuesday (March 17) at 11:30.
An atmospheric river first hit the region on Sunday (March 15), which was followed by low temperatures and freezing levels that led to widespread snowfall. Temperatures and freezing levels then increased on Monday, with the heaviest rainfall on northern Vancouver Island.
The atmospheric river then shifted south.
The River Forecast Centre says rivers began to rise rapidly on Monday, with high flows such as:
• Simpson Creek near Koprino Harbour reached approximately 80 cubic metres per second on March 16 at 4 p.m. – between a 10-year and 20-year flow
• Pugh Creek near Nahwitti Lake reached 84.1 cubic metres per second on March 16 at 3:55 p.m. – a 10-year flow
• Klaskish River near Klaskino Inlet reached 150 cubic metres per second on March 16 at 4:35 p.m. – a 5-year flow
• San Josef River below Sharp Creek reached 101 cubic metres per second on March 16 at 6:05 p.m.
South coast
The River Forecast Centre says the multi-day atmospheric river is continuing to impact the south coast. An updated advisory from Monday at 4 p.m. is maintaining the high streamflow advisory for the North Shore mountains, Metro Vancouver tributaries, Howe Sound, the Sea-to-Sky corridor including Squamish and Pemberton, the Sunshine Coast and the Lower Fraser Tributaries and the Fraser Valley.
Beginning Tuesday, the atmospheric river is expected to shift south bringing “multiple pulses” of rainfall to the south coast through to Friday.
Freezing levels are expected to rise and with warming temperatures, there is potential for snowmelt runoff.
Some rivers in the south coast rose briefly due to snowfall on Sunday, but “further and more widespread rises” are expected later in the week as rainfall intensifies and freezing levels increase.
The forecast centre says widespread flooding is not currently expected in the short-term.
North and central coast
The River Forecast Centre upgraded a previous high streamflow advisory to a flood watch on Sunday for the central coast, while maintaining the high streamflow for the north coast.
The flood watch includes tributaries and smaller streams around Bella Coola, Rivers Inlet and other coastal communities. The high streamflow advisory includes tributaries along the outer coast and inland areas, including Prince Rupert, Kitimat, Terrace and surrounding areas.
The atmospheric river first hit the regions on Sunday, with “relatively cool” temperatures and lower freezing levels, which led to snow at higher elevations and limiting runoff in the beginning.
Through Sunday night and into Monday, freezing levels rose and precipitation transitioned into rain.
Precipitation totals from Sunday to Wednesday are forecast in the range of 100 to 200 millimetres.
The increasing rainfall intensity and rising freezing levels was expected to increase runoff.
Upper Fraser
The River Forecast Centre issued a high streamflow advisory for the Upper Fraser on Sunday, which included the Robson Valley and tributaries in the Prince George region.
Rivers and streams in the region are expected to begin rising Tuesday.