Mudslides, flooding, extreme rainfall, and high winds have battered British Columbia and the Pacific Northwest over the last week.
The areas have been hit by an atmospheric river, which has been categorized as a level 5, which is the highest level on the scale. Below we’ll explain more about this weather phenomenon and explore what has happened so far.
Water vapor imagery from the #GOESEast 🛰️ is helping show a strong low pressure system swirling over the US/Canadian border this morning. This system is bringing wind gusts as high as 55-65 mph across parts of Montana, the Dakotas, and western Minnesota. pic.twitter.com/Z08o7LucJe
— NOAA Satellites (@NOAASatellites) November 17, 2021
What is an Atmospheric River?
An atmospheric river –– or a river in the sky is a narrow corridor or band of concentrated moisture in the atmosphere. Atmospheric rivers are responsible for 65% of the western United States’ extreme rain and snow events.
Atmospheric rivers aren’t always a negative event. They can replenish depleted water sources in areas such as California, where up to half of its rainfall can come from atmospheric rivers.
While around 25 to 30 hit the coast of British Columbia each year, a strong atmospheric river can carry 25 Mississippi Rivers worth of water vapor. Then, when it hits land, it can release devastating amounts of rain that can last for days and trigger events such as mudslides and floods.
Studies show climate change is making atmospheric rivers bigger and more dangerous.
What Has Happened So Far?
On Sunday, more than 20 locations across British Columbia broke daily rainfall records.
Melting snow from high levels of snowfall over the past weeks is also contributing to high levels of water. In an area east of Vancouver, water levels rose at least two feet in an hour.
So far, one person has died and thousands of people have been evacuated from their homes, many of which have been destroyed. Roads have been closed and motorists have been stranded in their vehicles, leaving many displaced. People trying to return home witnessed what appeared to be cars sinking underwater in mudslides. Schools have also been closed.
The Pacific Northwest has also been affected by the atmospheric rivers. The area had more rainfall in the first two weeks of November than they normally get in the entire month. Up to last weekend, there had been 6.83 inches of rainfall. The average for the month of November is 6.31 inches.
The National Weather Service warned that hurricane-strength winds were possible in the Pacific Northwest region and, at one point, more than 158,0000 people were without power.
Heavy rainfall can cause a lot of damage, especially when it leads to flooding. Read our guide preparing for heavy rain and flooding, so you can keep your home family safe.