A Comparison of Two Historic Winter Storms in Autumn: Alberta and Manitoba

It's been a very active and early start to the winter season in the Prairies, as two significant winter storms broke records and impacted millions of people before Thanksgiving Monday. In the end of September, Waterton Lakes National Park and adjacent areas of Montana were blanketed under a metre or more of snow, and on Thanksgiving long weekend, a powerful Colorado Low wreaked havoc across southern Manitoba as heavy, wet snow and blizzard conditions lashed parts of the province. Here, we quickly review the characteristics of each storm, before comparing the two. 

Southwest Alberta, September 27-30

A multi-day event resulted from a stalled upper low over the NW US, which led to the superimposition of several potent lifting mechanisms over southwest Alberta. The storm would tap moisture from the east and cold Arctic air from the north, piling it all into the terrain beneath the northeast quadrant of the upper low. A depth of 95cm was reported in Waterton Townsite on Sunday evening at 850PM, with 95cm also being recorded the following morning despite nearly 10cm of additional accumulation in the overnight - which was suggestive of the ongoing effects of compaction. Therefore, total snowfall accumulations likely exceeded 100cm in Waterton Park and on the immediately adjacent plains to the east - where at least one other report of 92cm depth was received WNW of Cardston. Even greater amounts were reported south of the border. Click this link to see my discussion breaking down the forecast for this event.

Snow blankets Waterton Townsite.

95cm depth as of 850PM Sunday. 

Graphic from the NWS showing snow totals. Areas with 4 feet of accumulation may have occurred along the US border in the hills SW of Cardston.

Heavy snow also occurred elsewhere across southern Alberta, with Calgary breaking its all-time daily September record on the 29th, with 24.6cm of snow. As Weatherlogics' chief scientist Scott Kehler pointed out, this was the second year in a row in which all-time daily records for a given month were broken in Calgary - as the the all-time daily record for October in the city was also broken last year (2018), when the city was walloped by 32.8cm on the 2nd day of the month.

The southern foothills and front range of the Rockies were particularly hard hit, but very heavy totals fell toward Lethbridge as well. 

Aspen trees in full summer foliage bending under the weight of the snow.

The heavy snow had major impacts to travel in southern Alberta, with numerous vehicles sliding into ditches on Sunday in particular. A few minor power outages were reported, and impacts to ranching and the fall harvest where it was still ongoing were also significant.

An H3 almost being swallowed by snow drifts in the ditch along Highway 22 west of Nanton, where many vehicles slid into the ditch.

Beautiful scenes in low light near Chain Lakes, where over 80cm fell, and was sculpted into large, dune-like drifts. 

Not a day for a picnic at Chain Lakes.

For me personally, it was the heaviest single snowfall I've encountered, and it was fun to document the amazing scenes I found around the townsite. Click here to see some reactions of some of the few folks left in town, here to see me wade through really deep snow, and here for a recap of the storm.

Waist-deep in snow reporting.

Southern Manitoba, October 10-12

A powerful Colorado Low with textbook mid-latitude cyclone structure would rapidly deepen as it moved north-northeastward up a baroclinic zone out of the US Heartland, before undergoing occlusion in NW Minnesota and nearly stalling out while bringing most impactful weather of its life cycle to southern Manitoba. A retired ECCC meteorologist wrote this excellent blog on the storm, which goes into even greater depth than I will here regarding specifics and impacts of the storm. As well, here is a link to my post regarding the forecast for the storm.

Whiteout conditions were common on Friday in parts of southern Manitoba.

Heavy, wet, wind-driven snow fell across southern parts of the province, with Winnipeg picking up a storm total of 34cm in what would become the greatest October snowstorm in the city's history - and the worst winter storm since the blizzard of April 1997. Elsewhere, a report of 74cm was picked up in Carberry via social media, and as Rob pointed out in his blog, a CoCoRaHS observer south of Morden reported 90cm. The snow largely had SLRs less than 10:1, which was a main contributing factor to the scale of damage that resulted from the storm. The storm was also accompanied by strong winds, with gusts of 100km/h being picked up at Oakpoint, and 94km/h at Portage La Prairie. Significant drifting occurred in areas of the far south, where the combination of terrain-enhanced snowfall totals and strong winds could transport maximum amounts of snow.

Elevated terrain features along the Manitoba Escarpment have enough relief to influence patterns of precipitation.

A portion of a summary of the storm from ECCC.

As expected, the storm had numerous significant impacts, with widespread damage to trees and power infrastructure. The City of Winnipeg said roughly 30000 of its trees were damaged, where a falling tree branch also injured two people - one of those critically. At one point, upwards of 50000 customers were without power, with the entire city of Portage going dark for a period of time, as nearly 3000 hydro poles and several more transmission towers went down across southern Manitoba. Most highways - including the Trans-Canada between Winnipeg and Brandon - were closed during the worst of the storm on Friday and Saturday, barring the travel of thousands of residents on Thanksgiving weekend. The city of Portage opened the Herman Prior Center as an emergency shelter to travelers in need of lodging, as highways were closed and hotels were full. Delays and cancellations to flights at Winnipeg Airport also occurred, with one plane becoming stuck on a taxiway in the heavy snow - which impacted the western suburbs of the city more heavily than those on the east side.

The Manitoba Hydro outage map was lit up like this for a long period of time.

A common scene around southern Manitoba.

Longer stretches of downed hydro poles on the west side of Portage than I've ever seen from any tornadic or straight-line winds.

Adding insult to injury, the storm also came a time when southern Manitoba was already excessively wet, prompting officials to open the Red River Floodway to divert water around the city of Winnipeg for the first time in fall in the city's history.

Courtesy Agriculture Manitoba, this map reveals how wet it has been this warm season - with much of this only coming during the first part of fall.

Winter storm chasing requires that one finds reliable shelter, such as a hotel, as close to the intersection of a major population center and severe weather as possible, and then hunkering down there for the duration of the storm. It also requires topping up with gas and carrying emergency survival gear in the event that the power goes out at your hotel or you get stranded. The power did go out at my hotel - as well as in the rest of the city, which made things quite interesting for a time. Things really ramped up on Friday night, with power flashes lighting up the skies amid raging blizzard conditions for several hours. Even the road from town to my hotel near the highway became quite exciting later in the evening. At one point while filming a camera hit, a wind gust came up and knocked my camera over. See that moment here. 

A screenshot of the moment my camera was going down. Nooooooo....

Comparing the Two Storms

Both storms were well-forecast and communicated by the weather enterprise, with model guidance having a pretty good handle on the outcome of both. In the case of Waterton, both NWP and pattern recognition gave fairly high confidence for the potential of significant snowfall totals in southwest Alberta. Similarly, there was a fairly high confidence that record-breaking snowfall accompanied by strong winds would occur in part of southern Manitoba. In both cases, the effects of stalling both prolonged lift and maximized impacts. 

Despite southwest Alberta having much greater snowfall totals, impacts overall were much less for a number of reasons - even with trees in leaf in both locations. The liquid equivalent in the precipitation accumulation bullseyes were likely similar between the two storms, meaning the snow-to-liquid ratios were vastly different - and this had major implications on the degree of impact that the storms had. SLRs near 10 or 15:1 in the higher elevation, colder Alberta storm meant cooler profiles, which translated to both greater snowfall totals and lesser impact to trees and powerlines. The snow was drier and less sticky, which tended to sluff off trees and powerlines in the wind - unlike in Manitoba.

Wind was also more of a factor in Manitoba, as the stronger dynamics of the potent, occluding Colorado Low resulted in much more powerful winds at the surface that alone could be sufficient at breaking tree limbs leading to power outages in the absence of excessive snow loads. Indeed, when combined with strong winds, the concrete-like snow clinging to high-tension powerlines likely increased tensile forces to the point that large, steel transmission towers failed and buckled over.

Heavy, wet snow weighs down the lines.

The tension of the lines under snow load accompanied by strong winds caused hydro poles to snap.

A crumpled transmission tower in Portage.

That can't be a quick fix! High-tension lines are draped right down in the lake.

Of course, the population of the hardest-hit areas of southwest Alberta pales in comparison to that of the hardest hit areas of southern Manitoba, which alone would reduce impacts. Less urban areas also means less trees in urban areas would likely impact the power grid overall. Trees in general are few and far between in the high and dry environment of Chinook country along the eastern slopes.

And finally, the time of year is also likely a factor in the severity and degree of impact of these storms. Not only are trees still in leaf, making them more vulnerable to the effects of wind and snow loading, but profiles overall are warmer - meaning the sticky, damaging type of snow is likely to be more common. Zonal temperature contrasts also become much greater in the fall, which can lead to much stronger dynamics of weather systems and resulting surface winds. More precipitable water also exists in the warmer columns of fall when compared with winter, when availability to sources of rich moisture is also greater than in winter. Combine the effects of stronger dynamics of weather systems and greater moisture availability, and all you need is a stalled system to create major problems.

As climate changes, more weather extremes are expected. In western Canada, many have asked "what happened to climate change?" in response to these early winter-like events, but these types of events might be the exact types of scenarios we might begin to expect more of going forward as the climate destabilizes. After all, a warmer Arctic (and Beaufort Sea in particular at the moment) could disrupt upper air patterns and leading to blocking and/or the displacement of Arctic air to more southern latitudes, where it can influence the nature and intensity of the very types systems we have been observing.