Additional 100-200 mm: Flood dangers increase in B.C. as rain totals add up
An ongoing, strong atmospheric river still has the potential to bring another 100-200 mm of rainfall to parts of B.C. this week, resulting in more flood alerts and keeping the threat of avalanches high
An unseasonable atmospheric river event is impacting British Columbia. It is bringing torrential rainfall, rising freezing levels and rapid snowmelt, leading to a significant risk of flooding and avalanches.
By the end of Tuesday, we will be approximately halfway through the atmospheric river event for the B.C. coast. An additional 75-100+ mm of rain is forecast for the Lower Mainland, with higher totals for the eastern Fraser and North Shore Mountain communities.
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A further 100-200 mm of rain is forecast for western Vancouver Island.
Expect extensive water pooling on roads and washouts may occur, so there could be road closures and difficult travel with the rainfall.
Pineapple express continues through much of this week, more flood alerts issued
The B.C. River Forecast Centre maintains a flood watch for:
Northern and western Vancouver Island
Central Coast
Meanwhile, high streamflow advisories are in effect for the South and North Coast, and the Upper Fraser.
Rainfall totals from Sunday, March 15 to Monday, March 16
Vancouver airport: 32.1 mm
West Vancouver: 49.6 mm
Abbotsford: 40.4 mm
Victoria: 14.5 mm
100-200+ mm of intense rainfall is forecast through the work week.
Rising freezing levels and rain-on-snow runoff are likely at mid-elevations, rapidly increasing flow rates.
A pineapple express is an atmospheric river that originates near Hawaii. This deep, rich plume of tropical moisture can fuel heavy rainfall and rising freezing levels across southwestern B.C.
There has been lots of lower-elevation snow in elevations 400-1200 metres over the past week, increasing run-off with snowmelt.
Given its strength and predicted longevity, forecasters anticipate this pineapple express event to rank an AR3 or AR4 along the immediate coastline, which means this type of event is often hazardous with river flooding impacts possible. Some areas could see the atmospheric river endure in two waves and persist for more than 72 hours.
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Some remote locations on western Vancouver Island and the North Shore Mountains will be subjected to up to 100 straight hours of rainfall this week. That’s more than four days of consecutive rainfall, highlighting the risk of flooding and rapid snowmelt.
This surge of moisture tracking northeast directly from Hawaii is fuelling heavy rainfall, which will continue for much of this week.
In addition to the heavy rainfall, we’ll also see freezing levels spike to more than 2000 metres on Monday, a rise that will last through the week before falling on Friday.
As a result, alpine rain is expected over the course of the week, leading to the elevated avalanche danger.
The high avalanche danger will likely persist on Wednesday. The start of March featured cooler weather with significant alpine snow, which has begun to melt this week.
The combination of heavy rainfall and snowmelt will likely elevate flood alerts throughout the region during the days ahead.
Pay close attention to forecasts and alerts for your area in the coming days.
Stay with The Weather Network for all the latest on conditions across B.C.