Messy meteorological medley to mangle Fraser Valley travel: forecaster

Dec 22 2022, 6:51 pm

One longtime forecaster is urging drivers to avoid traveling to the Fraser Valley amid severe weather expected for the area this weekend.

“If I could tell all my friends, colleagues, and contacts to avoid the valley on Friday-Saturday, I would,” Matt MacDonald, lead forecaster with the BC Wildfire Service, said in a post shared on his social media. 

In his dire warning online, he admitted that in his 20 years of forecasting, “I’ve rarely been so concerned about a weather forecast.”

Environment and Climate Change Canada has put in effect an arctic outflow warning and winter storm watch for Central, East, and West Fraser Valley, including Chilliwack, Hope, and Abbotsford. 

The warnings are amid another major round of snow expected for the South Coast starting Thursday night. 

ECCC says the region even faces a threat of bitterly cold temperatures and strong winds. 

“An arctic front has brought in a cold airmass to the south coast. Strong outflow winds are bringing temperatures five to 10 degrees below seasonal normals resulting in wind chill values approaching minus 20 to minus 30 over the Lower Mainland,” ECCC said. 

Meanwhile, MacDonald is emphasizing the approaching weather pattern over the South Coast this Thursday night through Saturday will result in a textbook prolonged freezing rain event for the Fraser Valley. 

The expected weather is why MacDonald is begging drivers to not travel between the Coast and Interior on Friday and Saturday. 

“Following our Arctic Outflow pattern, Road Weather Information Sensors (RWIS) is reporting road surface temperatures near -15C, ie roads are frozen rock solid,” he says. 

“As a major coastal valley, the Fraser Valley holds onto Arctic air longer than most. Weather models have a well-documented weakness in eroding and flushing out the Arctic air too fast. This has the unintended result of forecasting rain as opposed to freezing rain (FZRA).”

In his post, MacDonald shared a screenshot of the ECCC Global model that showed freezing rain through the valley, “something it rarely captures due to its coarse resolution.”

Matt MacDonald/Twitter

“In this case, the GDPS is actually forecasting 30-ish hours of FZRA! With the strengthening outflow that will act to replenish and deepen the Arctic air prior to Thursday night’s warm front, this has all the makings of a very messy meteorological medley,” he explains. 

“The incoming Category 2/3 #AtmosphericRiver will deliver 50-80 mm of rain and sky rocketing freezing levels to 2,000+ metres over the South Coast. The rain falling into the icebox that is the Fraser Valley will freeze on immediate contact with the ground/roads/bridge decks/power lines/structures and create an instantaneous coating of sheer ice. 36+ hours of FZRA = very bad.

“If I could buy shares in #ICBC I would.”

ECCC is urging drivers to avoid travel if possible because the snow could impact some roads more than others and impact visibility. 

About 10 or 20 cm of snow is expected and will later change to rain. But freezing rain is possible during that transition.

Periods of freezing rain could continue into Saturday afternoon for central and eastern Fraser Valley. 

People in the region are also being warned by ECCC to prepare for unusually cold temperatures and strong winds and ensure their pets and outdoor animals have shelter. 

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