'Relatively strong punch': Up to 100 mm of rain expected to fall in B.C.'s Lower Mainland in next atmospheric river

The third atmospheric river in less than a week is expected to hit southern B.C. Tuesday, Environment Canada is warning, with strong winds and more flooding possible.

The region has already endured two atmospheric rivers in recent days, though officials have warned the third could be the worst yet.

Environment Canada has issued a special weather statement ahead of the heavy rain, which is expected to arrive Tuesday and last through Wednesday. Between 50 to 100 millimetres is predicted to fall in parts of the Lower Mainland and winds gusting up to 60 km/h are also expected.

Some areas on Vancouver Island could see as much as 200 millimetres fall, however. 

Environment Canada's warning preparedness meteorologist Armel Castellan said in an update Monday that Tuesday's storm "will deliver a relatively strong punch," with rainfall similar to what was recorded over the weekend. As well, freezing levels on the mountains are expected to rise even more.

"It's not just a rain event, it's not just a snow melting event, it's also a successive storm event," Castellan said.

"Even if the third storm is not as bad as it could have been in the modelling leading up to today, it will be problematic because they are coming so close back to back with the runoff and the saturated soil."

Risk of increased flooding is already an issue, with flood warnings and watches already in place. As of Monday morning, the Tulameen, Coldwater and Lower Nicola rivers were under flood warning. A flood watch was in place for the Similkameen River.

The River Forecast Centre said in a statement Sunday night that significant rainfall impacting the Fraser Valley spilled over the Cascade and Coast mountains into Interior watersheds.

"Temperatures increased during the storm event and likely contributed to snowmelt at mid‐elevations and rain‐on‐snow runoff," the centre's summary of the current flooding situation says. "Rivers have risen quickly but are not expected to reach the levels from the Nov. 13 to 15 event, although they still may cause significant flooding."

But conditions could worsen in the days ahead.

"Currently, the weather models display significant uncertainty in total precipitation for the third event for the central region," the centre's flood summary says. "The risk remains for significant flooding under the wettest weather model scenario."

Late last week, Environment Canada issued an unprecedented "red alert" for parts of the province already devastated by the storm that saturated the ground earlier this month. 

"This alert, it's really due to the vulnerabilities that are on the ground, particularly in the Fraser Valley," Castellan said last week, adding that the ground "is completely saturated."

"We hope that everybody is prepared, feeling ready, doing as much as they can in anticipation of this extraordinary set of storms that is affecting the South Coast."

With files from CTV News Vancouver's Ian Holliday and Kendra Mangione