Huge storm could dump upwards of 30cm of snow onto Ontario this month

A massive snowstorm is threatening to batter large portions of Ontario with over 30 centimetres in the coming weeks, in what could prove the first significant snowfall of the season.

Or could it just be meteorologists jumping the gun?

There is currently some difference of opinion between meteorological models, but one forecast warns that a thick blanketing of snow could cause chaos in the region during the last week of November and into December.

Now, to be perfectly transparent, North American weather models are not predicting any significant snowfall for Southern Ontario in the next 14 days.

However, the European Centre for Medium-Range Weather Forecasts (ECMWF) model paints a very different picture, calling for snowfall totals as high as 27 cm in Southern Ontario, and accumulation in excess of 40 cm in parts of Cottage Country.

And there are already worrying outlooks filtering in from our neighbours to the south. The U.S. National Oceanic and Atmospheric Administration (NOAA) is sounding the alarm about a storm set to bring heavy snowfall to the Great Lakes region as early as next week.

The NOAA issued a warning on Wednesday advising the public of a “powerful storm” that is expected to “bring cold temperatures, high winds, and snow to areas east of the Rockies” in the range of November 21 to 23.

According to the NOAA, “a powerful storm system is forecast to develop east of the Rockies early next week, moving from the Central Plains northeastward to the Great Lakes.”

“The storm is forecast to intensify further as it moves northeastward across the Midwest and Great Lakes, increasing the potential for high winds across much of the eastern U.S.,” the agency warns.

The NOAA states that cold air will descend on areas downstream of the Great Lakes, bringing an increased risk of lake effect snows. However, the agency notes, “there is uncertainty in the magnitude of the cold air, which could impact precipitation type and snow totals for some locations.”

This storm is predicted to “increase the potential for lake effect snowfall in the Great Lakes,” with a map indicating the possibility for heavy snowfall for areas around all five Great Lakes, including the southern shores of Lake Erie and Lake Ontario.

But if you were to check local weather forecasts, which operate on the North American model of predicting weather events, you wouldn’t even see the faintest sign of trouble on the horizon

So, the real question is, why are we seeing such a huge discrepancy in predictions?

Trudy Kidd, a meteorologist at Environment and Climate Change Canada (ECCC) tells blogTO that “the difference between the snowfall forecast between the European and North American models likely comes down to several factors.”

“There are differences in model resolution. There are different physics in how they handle certain conditions, but even small differences in the initial conditions that are put into the model can lead to large variances in the forecast once you have a longer lead time, because those little changes or differences between various models become amplified over time.”

While many viewing these forecasts side-by-side may be left feeling very confused, Kidd explains that “a drastic divergence between what the models have” is not uncommon when tracking events two weeks away “and there are just so many factors at play.”

“Sometimes, especially when it comes to winter weather forecasting, you can even see big differences a week in advance,” Kidd continued.

“All it takes is a strong low pressure system moving slowly to really dump a lot of precipitation on an area. But if you change the speed of the low — if it moves a little faster — it’s going to bring less precipitation. If it moves a bit north, you might find yourself in more of the rain than the snow.”

However, Kidd says that “we can be pretty confident that as we move closer to the event start to that day, the weather models will converge.”

While these diverging models can be quite confusing, Kidd says the varying forecasts serve as “a good reminder that weather is extremely complex.”

“Right now, now that we’re in November and enjoying some pretty low-key weather, it just emphasizes the importance of being prepared.” She suggests staying up to date with eather updates and preparing your vehicle or emergency kits for the snowy season ahead.