Tuesday, January 11, 2022, 11:25 AM — Heavy rain is set to hit BC once again this week, with a powerful atmospheric river threatening significant storm totals that could cause widespread flooding.
As cold air and icy conditions break along the southern coast of British Columbia this week, warming conditions and the familiar Pacific breeze will come at their cost. Another powerful atmospheric river is set to initiate several rounds of deluge beginning Thursday, prompting widespread warnings. Melting snowflakes, rising freezing levels and weakening infrastructure from catastrophic November atmospheric rivers will all once again threaten severe flooding across the region. By the time this atmospheric river subsides at the end of the week, some areas may see 100-200 mm of rainfall. Rain warnings and special weather details are available, as well as a high current flow advisory. More information on timing and effects to keep an eye on below.
This week: Rains, warm temperatures increase flood risk in lower mainland
Precipitation warnings and special weather details are already in place across BC’s Lower Mainland, including Metro Vancouver and Vancouver Island, Howe Sound and the Sunshine Coast, with the return of Pacific air to the region as temperatures rise in several rounds. It rains. Localized flooding and high stream levels are of major concern.
The BC River Forecast Center has also issued a high streamflow advisory, saying that areas that experienced flooding in November may be more vulnerable to flooding once again due to erosion and high baseflow conditions.
“The public is advised to stay away from fast flowing rivers and potentially unstable river banks,” the advisory said.
According to emergency management BC officials, sandbuffs will be provided throughout the area.
A strong south-westerly current will develop on Tuesday and as a result an atmospheric river will affect the south coast. Heavy rain from the first system will continue till Tuesday morning, then reduce in the afternoon. Heavy rain will redevelop as other systems arrive on Tuesday night and several times from Wednesday.
The heaviest rainfall is likely to fall at favorable, overcast locations near Coast Mountains. The heaviest rain will occur on Wednesday afternoon and evening, which will continue till Thursday morning. This particular atmospheric river can be as strong as Category 3.
As of Thursday, 100-200 mm of rain is expected for West Vancouver Island and Metro Vancouver, and 75-125 mm for the lower mainland.
This last and strongest system will be closely watched to bring the heaviest rain to the region.
“It is going to rain in the Lower Mainland for 72 hours in a row,” warned The Weather Network’s meteorologist Tyler Hamilton.
While the amount of rain in this period is not unprecedented, other factors at play can cause some “catastrophe”, Hamilton says.
Rivers are expected to rise on Tuesday and peak on Wednesday or Thursday. Also, the freezing level will rise between 1500-2000 meters, leading to rapid snowfall and flooding.
While January in Vancouver is generally known as a wet month, with an average of 160 mm of rain, this week alone can bring up to 100 mm to the region.
Residents are being urged to clear the base of the hold from snow, and to ensure that appropriate emergency supplies are on hand.
In addition, an extended break from significant snow and ice is expected for the next few weeks. However, winter is not over – cooler than seasonal temperatures are expected to return towards the end of the month and dominate through February.
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