Flood worries grow in B.C. again as another atmospheric river on doorstep
B.C. and Washington state are bracing for more soaking rains with yet another atmospheric river this weekend, elevating the flood risk again, especially in areas hit hard by the previous event just days ago
A new atmospheric river pushing into the West Coast this weekend could exacerbate flooding issues in areas already hard hit by recent heavy rains.
Areas that experienced flooding issues by this past week’s precipitation will see more heavy rainfall, potentially worsening the situation once more with additional washouts and landslides, as well as a landslide risk.
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There could be road closures once again, along with possible ferry delays and cancellations due to gusty winds through Monday.
Here’s a look at how this weekend’s atmospheric river differs from the one that hit just a few days ago.
B.C.’s forecast holds additional hefty rainfall totals
The heaviest rainfall will arrive late Sunday into early Tuesday as a fresh atmospheric river arrives on the West Coast. Expected to impact as a Category 4 or AR-4, this type of atmospheric river is known as a pineapple express because it transports a rich reserve of moisture straight from the tropics into the West Coast.
The pineapple express tends to produce higher freezing levels than typical atmospheric rivers. Higher rainfall totals are shifting farther north compared to the previous atmospheric river.
Forecasters anticipate that this event will reach an AR-4 on the scale used to measure the intensity and impacts of atmospheric rivers, meaning that the event’s hazardous impacts could outweigh any benefits offered by the additional precipitation.
High-impact weather event with additional flooding is likely. Additional road closures are possible due to washouts, landslides, and water inundation. As well, gusty winds could bring power outages and there are likely to be travel and ferry delays.
Comparing the two atmospheric rivers
Aside from transporting more moisture into the coastline, this latest event will differ from the atmospheric river we experienced this past week.
Dangerous rainfall totals: We can expect an additional 80-100+ mm of rain throughout the Fraser Valley and Coast Mountains through Monday. The highest amounts across lower elevations are forecast for the northeast sections of Metro Vancouver. Locally, 200 mm is possible in the North Shore Mountains and western Vancouver Island.
Waterways are already swollen from this week’s rains. This much rain in a short period of time could exacerbate both the flooding and landslide risk in vulnerable areas.
Stronger dynamics: Enhanced lift in the atmosphere could provide an opportunity for thunder within the heaviest rainfall on Sunday night into Monday. Don’t be surprised if you hear some rumbles across southern Vancouver Island and the Lower Mainland after heading to bed.
Rivers and streams are already running high and the ground is saturated, increasing the risk of flooding with those conditions in place.
Damaging wind threat: Unlike last week’s event, strong wind gusts are in the forecast this weekend.
A deeper low is across northwestern B.C., increasing wind speeds as the low approaches Haida Gwaii Sunday evening. Southeasterly gales develop in the Georgia Strait and offshore Greater Victoria Sunday night, increasing the power outage threat for exposed coastal sections and the Gulf Islands. soils are saturated, increasing the risk of falling trees.
As the cold front slowly slides down the coast and the low lifts north of the region, strong winds continue and push inland towards the Fraser Valley through Monday afternoon and evening, becoming southwesterly up to 90 km/h.
Strong, southwesterly winds up to 80 km/h are forecast for Greater Victoria through Monday afternoon, increasing the threat of wind-related impacts.
And as the low lifts into Alberta, damaging winds are possible through the southern Interior, as well, with gusts up to 80 km/h possible.
Higher freezing levels: Coastal mountains will be higher than 2500 m, locally more than 3000 metres. High alpine snowmelt and instability are certain.
Temperatures at sea level will approach 15°C on Monday afternoon for Victoria and the Lower Mainland.
This will lead to high alpine snowmelt and a destabilizing of the snowpack, which could trigger avalanches across the region.
Stay with The Weather Network for all the latest on conditions across B.C.
Thumbnail courtesy of Abbotsford Police Department/@AbbyPoliceDept/X.