An extraordinary amount of rain has fallen on British Columbia this fall, saturating the ground and making disasters like the one that struck the province earlier this month more likely, according to Environment and Climate Change Canada.
The situation has prompted the weather agency to issue an unprecedented red alert for parts of the province already devastated by the previous storm.
Speaking to reporters in a technical briefing Friday, warning preparedness meteorologist Armel Castellan said some weather stations - including those in Victoria, Vancouver and Abbotsford - have recorded their wettest-ever fall seasons.
This summers drought and wildfires - as well as changes on the ground caused by previous wildfire seasons - have exacerbated conditions, he added.
The landscape is completely saturated, Castellan said. Any extra moisture runs down much more easily and much quicker.
That extra moisture could come from melting snow as two more atmospheric rivers bring warm tropical air to the province over the coming days.
The addition of snowmelt to potentially heavy rain this weekend and midweek next week has prompted the B.C. River Forecast Centre to issue flood watches and high streamflow advisories across the provinces coast.
The worst-case scenario is still not super likely - for Tuesday and Wednesday being as bad as what we saw middle of the month - but it does exist, Castellan said. 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.
All of this adds up to a uniquely dangerous situation in British Columbia, which saw another atmospheric river drop 40 to 60 millimetres of rain on Thursday and is expected to see two more such storms by next Wednesday.
The red level (alert) is something new that we have not issued (before), Castellan said. In fact, probably 10, 20 years ago when I started this career, this would be something that we may not see in a given career.
He said in hindsight, he would have wanted to issue a red alert ahead of the heat dome that ended up killing nearly 600 people across B.C. over the summer.
The weather agency didnt issue such an alert at the time, something Castellan attributed to the difficulties of forecasting.
What makes the current situation unique is the obvious vulnerability of parts of the province - such as Abbotsford, Merritt and the highways connecting the Lower Mainland to the Interior - that are still recovering from the last storm.
This alert, its really due to the vulnerabilities that are on the ground, particularly in the Fraser Valley, where we have the Sumas Prairie still recovering from the previous event, Castellan said.
The Sumas Prairie is a 90-square-kilometre low-lying area in the southeast corner of the City of Abbotsford. Much of the prairie is the former Sumas Lake, which refilled with floodwater from the nearby Sumas River and the Nooksack River in the United States during the last storm.
On Thursday, the citys mayor said he expected it to take weeks for the remaining floodwater to be pumped out of the former lake.
U.S. officials have issued a flood watch for northwestern Washington State, including the Nooksack River, for the coming weekend.