I think most people across the Prairies would agree winter doesn’t really arrive until you have snow on the ground, so for us, I use this as our measure of when winter arrives. Even narrowing it down to this still has some problems. What if, for example, it snows five cm on Oct. 22, then by Nov. 8 it has all melted and we don’t receive any more snow until Dec. 4? Did winter start on Oct. 22 or Dec. 4? I call this situation a false start to winter and I would record the winter in this example as starting on Dec. 4. Once I determined this, I went through the snowfall records for Winnipeg, Brandon, and Dauphin, and came up with the results you see here in the table.

From the table we can see all three regions of agricultural Manitoba have seen winter start in October and as late as mid-December. Winnipeg and Brandon both have an average date for snow to stick around of Nov. 14, with Dauphin being four days earlier at Nov. 10. The “usual range” is a measure of the standard deviation around the average. It indicates the range of days within which we should expect winter to begin. If winter begins before or after these dates, it’s a fairly unusual year.

Another question I often get is whether we’re going to get a lot of snow this winter, and are we going to see any major snowstorms? I often have a tough time with this question; as those of you who regularly read my articles have probably already figured out, I really like snowstorms, at least if I don’t have to go anywhere! So, I tend to be a little biased when talking about the probability of snowstorms. If we look back over previous years’ snowfall events in our three different regions, I found that large single-day snowfalls are fairly rare events. When I looked at the number of times Winnipeg, Brandon and Dauphin received more than 10 cm of snow in one day over the last 70 years, I was surprised to find out that on average, all three locations have this occur a little less than twice per winter. When we bump up the single-day snowfall to 15 cm or more, this occurs on average a little less than once per winter. If we increase the single-day snowfall to 20 cm or more, the frequency drops down to around once every five years. Finally, to show how rare really big snowstorms are in our region, if we take a look at the probability of receiving 30 cm or more in one day, we would find that this kind of event only occurs once every 30 or so years.

One thing that I need to point out is, from December to February, agricultural Manitoba, on average, receives about 50 cm of snow. So all it takes is one big storm and we’ll be at average or even above average for the winter. This is why it’s so hard to predict whether winters will be wet or dry: often it only takes one storm to make a wet winter! Another point to make about these types of statistics is that if you get a 30-cm snowfall, it doesn’t mean the chances of seeing another large snowfall that winter are any smaller.

A second question that comes up with the talk of snow is cold temperatures: just when will they move in? The answer to that is almost always tied to when the snow moves in. While we can get some cold temperatures without snow covering the ground, to get extremely cold temperatures and sustained cold temperatures we need to have snow cover.

Snow cover acts in a couple of ways to contribute to colder temperatures. First of all, it insulates the ground, trapping the ground heat and preventing it from warming up the air above it. Secondly, snow has a very high albedo — that is, it reflects a very large proportion of the sun’s energy. So instead of the sun’s energy being absorbed by the ground and then released to warm the air, it gets reflected and we don’t warm up much during the day. Finally, snow, simply put, is cold! We really notice this in the spring, but having snow on the ground at any time of the year acts like a refrigerator to keep temperatures down.

In the next issue we’ll take our annual look at weather-related gift ideas for the upcoming holiday season.

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Just look at the weather over the last couple of weeks across the Prairies. After I pointed out that it looked as if we had finally switched into a summer-like pattern, with weaker weather systems and more thunderstorms, we saw another unusually strong upper low form over the Prairies that brought copious amounts of rain to western Alberta and parts of southern Manitoba.

Before we take a look at this unique weather event, I thought we should first look at just what Environment Canada uses as criteria for rainfall watches and warnings.

First of all, according to Environment Canada’s website, it does not issue rainfall watches, so we only need to look at warning situations. If it is going to be a short-duration event, such as a thunderstorm, you need to expect upward of 50 mm of rain in one hour before a rainfall warning will be issued, at least across the Prairies. It is actually lower over the East and West Coasts. While this might not make sense at first, if you think about it, they rarely get the intense thunderstorms that inland areas of Canada receive.

If the rainfall event is expected to be a longer-term event, the criteria for a warning is when 50 mm of rain are expected within 24 hours, or 75 mm of rain are expected within 48 hours. Sometimes, due to the nature of summer storms, you can have both types of warnings going on at the same time.

Now a lot of talk recently has been about the heavy rains we’ve seen across different parts of the Prairies over the last several years. The heavy rainfalls across western Alberta resulted in flooding that came near, or even far exceeded, the record flooding of 2005 in these areas. The 2005 flood was a one-in-100-year flood, and now only a few years later the region is seeing another one-in-100-year flood. In fact, at the Elbow River near Bragg Creek, the peak flow during the 2005 flood was 308 cubic metres per second. During this year’s flood the flow rate hit an astonishing 513 cubic metres per second before it stopped reporting.

Here in southern Manitoba, the same system that brought all of the rain to Alberta brought two rounds of heavy rain over the weekend. Slow-moving thunderstorms on Friday night into early Saturday morning brought upward of 75 to 150 mm of rain in the Reston area, according to Environment Canada. Unofficially, some localized heavy downpours were experienced, with amounts as high as 212 mm reported near Portage la Prairie. Check out the table for some of the larger rainfall totals for the weekend across southern and central Manitoba.

So why all the heavy rain? Well, it is summer, and we’ve seen and will continue to see heavy rainfall events. It’s the nature of our summer weather. Why do we seem to be seeing so many heavy rainfall events lately? It could simply be the general pattern or cycle we are in, but personally, I believe it is tied indirectly to global warming. A warmer atmosphere can hold more moisture. That moisture will eventually have to fall out of the atmosphere. When it does, it will fall out in large amounts.

People will argue against this by saying we have seen rainfall events as big, if not bigger, in the past when there was no global warming, and they are right. However, when these events occurred they tended to be isolated and very infrequent in nature. What we see now are much more widespread events occurring much more frequently.

I think simply chalking these events up to regular weather and continuing on as usual is the wrong way to go. To be successful going forward we need to start realizing that not only will we have to cope with dry periods, but we will also have to deal with heavy rainfall events. Just how we can deal with both of these successfully is the $1-million, or rather, $1-billion question.

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It doesn’t look as though we’ll see cold air move in behind this system, as the West Coast ridge of high pressure weakens, allowing our flow to become more westerly. Temperatures should moderate over the week, with high temperatures by the weekend climbing to around the -8 C range.

Central regions might see a little light snow on Saturday as a weak trough moves through, otherwise it looks like nice, quiet winter weather. A much stronger system is expected to move through central regions late on Monday and into Tuesday. This system will likely bring five to 10 cm of snow to extreme northern regions, with only a few flurries over southern areas. Winds ahead of this system will become fairly strong from the south. These south winds will bring in mild air and we could see temperatures pushing the 0 C mark on Tuesday.

Colder air will start moving back in behind this system as Arctic high pressure begins to sag southward again. We could see some more light snow late next week as a system develops to our south along the edge of the Arctic high, but confidence in this is not that high.

Usual temperature range for this period: Highs, -19 to -4 C; lows, -32 to -12 C.

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Overall the weather models were correct in forecasting what has been called a hybrid Colorado low. In fact, they did an amazing job at predicting the storm over a week in advance. What the weather models had a harder time predicting was exactly where most of the snow was going to fall. Right up to the middle of the storm, the weather models were sticking to their guns and predicting that the majority of the snow would fall over the Red River Valley, with estimates running upwards of 40 to 50 centimetres. While the models ended up being right on the money for the amount of heaviest snow, they were a little too far south and east. If you look at this week’s weather map you can see areas north and northwest of Portage la Prairie received the greatest amount of snow.

Overall, nearly all regions saw at least 15 cm of snow from this storm system, with a large portion of our region seeing over 20 cm. The highest totals from the storm were recorded north of Swan River, in the Mafeking region, where upward of 60 to 80 cm of snow was reported.

There were a couple of unusual things about this storm system. The first was a lack of really cold air for the storm system to work with. Usually, this strong of a storm at this time of the year will tap into cold air over northern Canada. While the storm is occurring, temperatures may not get that cold, but the days following a large storm like this will usually see very cold temperatures move in. Back in November 1986, in the days following the Nov. 8 snowstorm, temperatures across southern and central Manitoba bottomed out in the mid -20 C range, with some record-low temperatures recorded. In the days following this year’s storm, temperatures did cool off, but it took a bit of time and we only saw a couple of nights with lows approaching -20 C in some areas.

In reality, it was the lack of any significant cold air that kept this storm as just that: a storm, not a blizzard. If there was more cold air available for this storm, I believe things would have been much worse and we would have likely seen record amounts of snow over a much larger region. This brings me to the second unusual thing about this storm: just how much snow did fall, given the fact that all the typical weather elements didn’t really come together to make this a really big snow-producing storm?

I’ve done some number crunching on winter snowfall across southern Manitoba and I thought I would share these with you as it will help to put this snowstorm into some kind of context.

Looking at Winnipeg’s snowfall data from the years 1873 to 1991 I calculated the probability of how many snowfall events will occur over an average winter. A snowfall event is any day or days where snowfall is recorded. If snow falls on one day, it would be a snowfall event; if snow falls on two or three consecutive days, that would also be seen as a snowfall event. In a typical winter, the Winnipeg region can pretty much expect to have a minimum of 10 snowfall events. On average, this region can expect to see around 28 snow events during a winter; the record number of snow events is 38, which occurred back in the 1930s.

How much snow would this region typically expect to see during any of these snowfall events? Not surprisingly, for the majority of these events, we only receive one centimetre or less. This tells us that most of our snow comes from just a couple of big or heavy snow events each winter — and when you think about it, that’s what usually happens. The chance of seeing 10 cm of snow during a snow event is about 10 per cent. This means in a typical winter we would see this amount of snow fall about three times. If we bump up the amount of snow to 20 cm, the probability drops down to only around two per cent. This means we would typically see a 20-cm snow event about once every two years. A 30-cm snow event has a probability of around 0.5 per cent, which converts into seeing this much snow fall about once every seven years. Finally, the probability of receiving 40 cm of snow during a snowfall event is only 0.1 per cent, which converts into once every 35 years.

From this we can see that for some regions, this snowstorm was not that unusual, while for others it was the type of snow event one might see only a couple of times in a lifetime.

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In a forecast issued Oct. 17, the U.S.-based firm said slightly colder-than-normal weather with near-normal snow is predicted for most of the Prairie region, which was the warmest spot last winter.

Southern Ontario and Quebec should have a return of winter with near-normal temperatures and snow, especially during January and February.

Atlantic Canada and the Maritime provinces will be one exception to colder weather, but long-range forecasters expect major winter storms to affect the region.

The AccuWeather forecast for Saskatchewan and Manitoba said that following a very dry fall, drier-than-normal weather will persist through December. That should change during January and February as some quick-hitting storms may have an impact.

“For Regina and Winnipeg, I think we are going to see an increase in Alberta Clipper systems, especially the second half of winter, which should bring quick shots of snowfall to both those cities during that time,” senior meteorologist Brett Anderson said in the forecast.

It said that while Alberta Clipper systems are fast moving and do not have much moisture associated with them, a moderate amount of snow is predicted for this winter. Regina, Saskatoon and Winnipeg are expected to have near-normal snowfall this winter.

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Most of southeastern Manitoba saw a significant dump of wet snow late last week and while it caused a major headache for many, the moisture was more than welcome. Snow fell in most areas east of the Red River over a two-day period and by the time all was said and done, some pretty impressive totals were recorded. Table 1 is a list of some of the amounts recorded by Environment Canada.

Farther west, most of the precipitation came down as rain or a mix of rain and snow, with little snowfall accumulating. Looking at satellite images on the Saturday following this storm system, you could easily see all the snow that fell over eastern regions. Another swath of snow fell in south-central Manitoba, running from near Portage south-southeastward, toward the U.S. border. This band of snow was likely the result of the influence of Lake Manitoba. The heavy snow that fell just to the east of Lake Winnipeg was also probably the result of moisture coming off Lake Winnipeg. You could see in the same satellite image that the moisture and heat coming off Lake Winnipeg resulted in rain falling to the immediate south and east of the lake, as no snow was on the ground in these regions, while there was snow on the ground along the west side of the lake.

Whenever we get an early dump of snow the talk seems to quickly shift to how this is a sign of the winter to come. I’m not sure why this is, but I thought I’d check into this mindset, to see if early snowfalls are harbingers of snowy winters.

When I started to look back at the weather records for early snowfall, I noticed there were no large-scale October snowfall events. That is, either western Manitoba received snow, or eastern Manitoba did. I could not find one occurrence where both regions received snow at the same time in October.

Looking at western regions, using Brandon’s weather data, I found that greater than 10 centimetres of snow have fallen on at least 15 occasions going back 100 years. The last couple of times were as recent as 2009 and 2005. During both of those winters Brandon recorded average amounts of snow (Brandon’s average snowfall from October to March is 103 cm). Further back in Brandon’s weather history, one year in particular had what can only be described as the worst October on record — that is, unless you love snow. In 1959, western regions of Manitoba saw not just one day with greater than 10 cm of snow during October, but a remarkable four days! In total, in October 1959, Brandon recorded an astounding 90 cm of snow, or nearly a whole winter’s total. Interestingly, during the rest of that winter, Brandon only recorded a further 76 cm, bringing the winter total to 166 cm, well short of the record-setting year of 1903-04 when 241.3 cm of snow fell.

Farther east, using Winnipeg’s weather data, we find this area has also seen at least 15 significant October snowfalls over the last 100 or so years. The last one occurred in 2003, when 15 cm of snow fell on Oct. 27. The winter following saw near-average amounts of snow (“average” is about 113 cm for Winnipeg). What was interesting about Winnipeg’s data, compared to Brandon’s, was that nearly all of Winnipeg’s significant October snowfalls occurred during the last few days of the month, while in Brandon, there were several significant snowfalls earlier in the month. That said, there was one year that had a significant early-October snowfall: 1950, when 12.7 cm of snow fell on Oct. 2. I checked the following winter and found only 102 cm of snow fell, which is below average and way below the record winter snow for Winnipeg, 250.9 cm in 1955-56.

Overall, significant October snowfalls in southern Manitoba, while not a regular occurrence, are not that unusual either. Also, there does not appear to be any correlation between early snowfalls and snowy winters. So, for those of you who saw some of this early snow, it will melt away, if it hasn’t already — and it’s not yet time to hit the panic button about the winter to come.

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Eastern regions saw some of this precipitation last week when a Colorado low brought upwards of 10-20 centimetres of snow. Farther west, an Alberta clipper-type system brought some much-needed snow over the weekend. By Wednesday this week, a strong Colorado low looks to bring a very heavy dump of snow to our southern neighbours, so it doesn’t look like winter is over yet!

This active weather pattern looks to continue as the models show another area of low pressure moving through southern Manitoba on Friday, which will likely bring a few centimetres of snow with it. This will be followed by some cooler conditions over the weekend as our winds become northerly behind the departing low.

The weather models then show another strong storm system moving in from Alberta early next week. Currently they show this system moving through central regions, which would mean most of the snow will fall in the northern parts of agricultural Manitoba. Southern regions will still see some snow, but amounts will not be that great. While temperatures will moderate a little bit ahead of this low, cooler air will move in behind it.

Yet another area of low pressure is forecast to move through around the middle of next week. This low does not look to be that strong, so not much in the way of snow is expected. A fifth area of low pressure is expected to develop later next week, but this one is forecasted to take a much more northerly route. This would result in a return to milder conditions by next weekend.

Usual temperature range for this period: Highs, -13 to +1 C; lows, -26 to -9 C.

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Before we look at some of these big snowfalls, let’s examine why we can experience such heavy snowfalls in the spring. During our spring, Arctic regions are still covered in snow and ice and cold temperatures are usually still in place. Farther south, the snow has all melted and warm, moist air begins to build. These are the two ingredients we need for big storms to develop. Every so often these two features combine during April to produce snow instead of rain and as we’ll see below, these spring snowstorms can bring a lot of snow.

I wish I had the time to check out the weather records for every location in agricultural Manitoba, but unfortunately I don’t. So as usual, I have broken down the records into my main three areas: Dauphin, Brandon and Winnipeg. For this study, I only looked at snowfall and did not take into account any combination of rainfall and wet snow, as this would mostly have been recorded as “rainfall” at any of the Environment Canada stations.

Let’s begin by looking at Winnipeg. Being situated near the eastern side of the province, it is located close to the main storm track for late-season Colorado lows. This being said, Winnipeg has recorded some of the greatest snowstorm totals in the month of April. The two largest snowstorms over the past 135 years have occurred within the last decade. Both of these storms occur red early in the month, with the 1997 storm recording 48 cm of snow between April 4 and 6 and nearly the same amount (46 cm) fell between April 1 and 4 of 1999. The third-worst spring snowstorm occurred way back in 1872, when on April 12-13, Winnipeg received just over 38 cm of snow. The fourth-largest spring snowfall, interestingly enough, also occurred fairly recently, in 1996, when Winnipeg saw 35 cm of snow fall between April 19 and 25. I’m not sure what was going on, weather-wise, during the 1990s but there sure were some really miserable Aprils!

HIGHER ELEVATIONS

Now, on to Brandon. Being farther west, Brandon does not see as many severe spring snowstorms. First of all, it is farther away from the main storm track, and secondly, springtime temperatures tend to be a little warmer out west due to higher elevations and less snow cover. This means April snowstorms will tend to mix with rain, which will reduce the total snowfall amount. That said, the largest springtime snowstorm I was able to find occurred back on April 26, 1961, when a whopping 47 cm of snow fell in just one day! The next-largest spring snowstorm occurred on April 26-27 in 1984, when the Brandon region saw 37 cm of snow. The third-largest springtime snowstorm in this region happened back on April 5-6 in 1937, when almost 26 cm of snow fell.

To round out our records is the city of Dauphin. While the Dauphin region has a tendency to see really large fall snowstorms, Dauphin’s higher elevation seems to work against it for springtime storms. This makes sense, because as warm air streams northward in the spring, the higher elevation in this region helps to mix the warmer air down to the surface, which keeps any precipitation in the liquid state longer, which means less snow.

That said, the biggest spring snowstorm ever recorded in Dauphin occurred between April 26-28 in 1984, when 32 cm of snow fell. The second-largest snowstorm was April 19-21 in 1967 when 26 cm of snow fell. This was the same year Winnipeg saw a one-day dump of 21 cm on May 1 (since it was only a couple of days after I was born, I am constantly reminded of it – maybe that’s why I’m such a weather geek!). Coming in tied for second was the snowstorm of April 26-27, 1961 when the Dauphin region saw another 26 cm of snowfall. The fourth-largest snowstorm in the Dauphin region was only slightly smaller, but occurred in the same decade as the first two. On April 27 and 28, 1966, about 25 cm of snow fell. For this region the 1960s really seemed to have some bad spring weather!

So, as the stats point out, some of the largest snowstorms to hit our part of the world have occurred in April. Will we see a repeat this year? I really hope not, but as the weather goes, you just never know. So let’s keep our fingers crossed that April ends up bringing us perfect weather and that all this talk of flooding doesn’t materialize.

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This low looks to be a little weaker and will take a more northerly route. Central regions will see light snow or even some showers with this system, while southern regions will see a mix of sun and clouds with only a slight chance of light snow or showers. Temperatures over southern regions should be fairly mild, with highs making it into the low single digits.

Once this system pushes by, weak high pressure will work in to start the weekend. Temperatures will cool down a little, but it is not looking like things will get too cold. All eyes then turn toward a possible storm system for late in the weekend and into early next week. The weather models show a strong Colorado low developing and slowly pushing northeast. This low, should it develop, will have the potential to bring significant amounts of precipitation to southern Manitoba, North Dakota and Minnesota. A lot can change in regard to this system, but it will definitely need watching.

Cool high pressure is then forecast to drop southward behind this storm, bringing a return to more winter-like temperatures for the middle part of next week. Looking even further ahead, the weather models hint at another strong storm system developing to our southwest late next week.

Highs:-8 to +4 C.Lows: –23 to -5 C.

Probability of precipitation falling as rain: 15 per cent.

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A weak Colorado low which brought a second shot of snow to southern and eastern regions of Manitoba last weekend looks like it might be followed up by another Colorado low starting sometime on Wednesday. Currently the models are showing this system being stronger and slower moving than the previous one. This means there is the potential for significant snow accumulations across portions of agricultural Manitoba, with the heaviest amounts likely in the east. Winds also look like they could become a problem across all areas with this system creating blowing snow and possibly near-blizzard conditions, especially late Wednesday and into Thursday.

Once this low finally pulls out on Friday, we will see some cooler air move in, but the models are not pointing toward a strong cold air outbreak. Confidences in the weather models beyond this period are not very good right now, as they are changing their forecasts almost daily. The latest model run shows another chance of snow for our region early next week as weak low pressure passes by. Hopefully the models are correct with their temperature outlooks as they continue to keep the really cold air well to our north.

Usual temperature range for this period: Highs: –14 to 0 C.Lows:-25 to -8 C.

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