If you have heard the term snow squall and always wondered what are snow squalls and why are they so bad, I will share a little about them. I live in Western Ontario, Canada beside Lake Huron, a part of the world where snow squalls are possible for almost half of the year, October to April. They are beautiful and dangerous and I have an admiration for their power. Squalls are a very different to snow squalls.
So what is a squall?
There are squalls and there are snow squalls. By definition, a squall is the rapid onset of strong winds with speeds increasing to at least 16 knots and sustained at 22 knots for more for at least a minute. this info is courtesy of the Canadian Weather Network. 16 knots is approximately 29.6 km/h (18.4 miles per hour) and 22 knots is approximately 40.7 km/h (25.3 mph), to help you visualize. It applies mainly to ocean or Great Lake environments one and this sudden burst of wind can be quite damaging and dangerous when boats are out on the open water.
So what is a snow squall?
A snow squall is a little different. It still originates from open water but has a slightly different definition. When considering what are snow squalls, you have to consider where and when they most commonly occur.
Snow squalls occur in wintertime when relatively cooler air (usually lower than -5°C) moves across an open body of water onto land. If you visualize the
relatively warmer lake water (warmed form slow heating by the sun the past summer) as steaming like a cup of coffee as that steam moves out of onto the land it cools and snow comes out of the steam or clouds. This means when the temperature and conditions are right, and the wind direction takes the air over the lake onto the land, you have the potential for colossal amounts of snow that are very localized.
They can create an impressive accumulation of snow in a short period of time. Another name for this phenomenon is Lake Effect Snow. Wikipedia has good entry with excellent radar and snow images.
With usual low pressure snow systems in the northern hemisphere, the snow clouds prevailing winds are from the West and often the snow event or snow fall is limited in its length of time by the size of that system.
With a snow squall, as long as the temperature difference between the surface of the water and the air above remains at about 13 °C or 23 °F, snow will just keep falling out of the air. We often get both as a low front carrying snow brings the winds and cold temperatures to get the ‘snow machine’ going.
This is why towns like Barrie and Kincardine in Ontario have their spectacular snowfalls in the winter. My experience is with great Lake snow squalls from Lake Huron and occasionally from Georgian Bay. It is possible to have a squalls come off the sea as is often seen around Newfoundland or the Maritimes in the winter time.
In the picture to the left, the first real snowfall of 2010 did that in less than 24 hours. It was bare ground the day before. We had a snow day next day too. This can go on for weeks some winters. Usually once the lake freezes over often by late February the snow squalls diminish a little.
So what does a snow squall look like?
If you look out of the window during the snow squall you will see either blinding sunshine with black clouds hovering nearby, or you will not be able to see your neighbor’s house. Snow squalls are responsible for ‘whiteout’ conditions when driving. This is where thick snow is blinding and you cannot see further than
the front of your vehicle. Multiple vehicle accidents become a distinct possibility. Locations that have common snow squalls will often have frequent and rapid road closures. Children may average ‘snow days’ off school in the double digits most winters.
Sometimes snow squalls can go on for days dropping feet upon feet of snow in that time. If the wind speeds start to approach 30 km/h, dangerous conditions are prolonged as snow on the ground also becomes whipped up into the air and adds to the lack of visibility. Because of the very localized nature of snow squalls, on the satellite diagram image they start to look like individual lines like the teeth on a comb coming away from the water’s edge. This means visibility can go from excellent to nonexistent in the course of a minute if you are driving across these lines parallel to the lake shore, and actually any direction. Snowdrifts usually settle across the roads and are made more severe by the wind direction and the direction of the road. The worst drifting across the roads is when the wind is perpendicular to the road direction, so north-south roads are affected more when the wind comes from the West, which is quite common.
If you are traveling to a snow belt or snow squall area in the
winter, what should you expect?
It may seem crazy to travel to a snow belt area in the wintertime, but those who enjoy winter sports such as downhill and cross-country skiing, snowmobiling and snowshoeing are attracted to visiting in the winter due to the abundant snow. If you are planning your first trip to a snow squall area, here are a few things that you should plan to do and look out for to stay out of trouble.
If they are announce that the snowplows and snow clearing equipment have been pulled from the roads by the municipalities, stay home. This happens occasionally and is an indication that the conditions are extreme. Until you have been driving down the road and the road disappears in front of you, you will not understand what an awful feeling it is. Better to be safe at home and set off a few hours later when squalls have finished. In the image we are driving into a squall, but you can still see the car in front.
Listen closely to local radio stations weather forecasts as these can sometimes give locations of the worst ‘streamers’ of snow off the lake where the snowfall will be highest. You must be willing to change your route, or cancel your day’s travel entirely, to avoid snow squalls as they worsen. The radio or internet is also a crucial source of information on local road closures as conditions deteriorate. In Ontario if you are caught driving on a closed road, there are fines and penalties and if you have an accident on that road while it is closed, you are not covered by your insurance.
Plan on lots of deep snow. Make sure you have warm clothing, boots, hats, and gloves to deal with the cold conditions and temperatures. Squalls occur in cold locations and conditions have to be below a proximately -5°C the climate in these regions, and can easily get -25°C at times.
Have an emergency kit in your vehicle for staying warm in case of an accident or being stranded in a snow drift or going off the road in whiteout conditions. Usually these include blankets, safety candles in a votive or tin, chocolates and other high-energy foods and fresh water that is not frozen. Having a shovel for dig yourself out is important, and of course you must have a brush for clearing the snow from your windshield and headlights. Many people who live in the area invest in proper snow tires for additional grip in these rugged winter conditions and many drive all-wheel or 4WD vehicles. Also, a bag of clean cat litter for a bucket of water ash is excellent traction for getting you out of an icy spot.
It’s not all bad!
This may seem extreme, but your life may depend upon this. Snowsqualls like thunderstorms and other extreme weather conditions can be wonderful when viewed from the safety of home. And the most spectacular photographs are possible of these awesome storms.
Going for a walk in deep, white, clean snow in the blinding sunshine after fresh snowfall is breathtaking. As an immigrant from the United Kingdom moving to Canada and then moving up to the snow belt region, I can appreciate the beauty, even if many of the locals do not. I hope you have enjoyed hearing about them.
All images courtesy of Skeffling Lavender Farm.