The most significant spring blizzard in decades is bearing down on southern Manitoba, but there’s nuance in the details. What follows is the best interpretation of the upcoming weather we can discern as of the time of writing. The forecast for this system may change on short notice, so be sure to keep alert of any updated forecasts or warnings from official sources.
A complex storm system will bring a major spring blizzard to southern Manitoba beginning later today. While the broad strokes of this system have been quite clear for several days now — a testament to improvements in medium-range weather modelling over the past decade — there are many nuances to this system that will add layers of complexity to the forecast.
A pair of low pressure systems have merged overnight and now exist as a single potent low centred over western Nebraska and Colorado. This system is supported by two distinct features: an upper low over Iowa and a digging upper trough over Utah and Colorado. These two upper features and their evolution will guide the development of this system over the next 36 hours.
As this system pushes eastwards today, it will split into two surface lows: one that lifts northwards through the Dakotas through the day, and another that lingers in Colorado for a while longer before ejecting northeastwards into Minnesota. The northern low will be supported by the upper low, while the southern low will move along with the upper trough and strong frontal wave.
The first wave of snow will move into southern Manitoba this evening, supported by the northern low pressure system. This snow will likely be quite heavy with snowfall rates reaching as high as 3–5 cm/hr. This first shot of snow will lift from North Dakota into SE Saskatchewan and SW Manitoba, then spread eastwards across the Red River Valley and into NW Ontario. By the end of Wednesday, it’s likely that 20–40 cm of snow will have fallen over the southwestern corner of the province and the western escarpment/Riding Mountains, and 10–20 cm of snow in the Red River Valley and southeast corner of the province.
As the day progresses on Wednesday, the precipitation lifts northwards as the northerly surface low stalls out near the MB/ND/MN borders. It looks quite likely that this system’s dry slot will spread into southern Manitoba, bringing an end to most of the snow over the Red River Valley and southeastern Manitoba. If this happens, the region would see a reprieve from the snow later Wednesday through the night, but with a decent chance of [freezing] drizzle or few flurries through that period. The snow will continue elsewhere in Manitoba, albeit comparatively lightly with general accumulations overnight of 5–10 cm. Terrain features will continue to see enhanced accumulations with 10–20 cm possible, particularly closer to Lake Manitoba and the Riding Mountains.
On Thursday, the Colorado Low will become dominant in NW Ontario, producing heavy snow that will spread westwards across the Interlake into western Manitoba through the day. Light to moderate snow will spread back through the Red River Valley for Thursday. The stalled surface low in Manitoba will collapse as the Ontario low strengthens, and the strongest winds will shift eastwards into the Red River Valley with sustained northerlies of 50–60 km/h. Close to 5 more centimetres of snow is likely for Winnipeg on Thursday.
The snow will begin to ease on Thursday night, then clear out of the region through Friday.
Regarding the wind and blowing snow, the stalling of the low near the MB/ND/MN border and timing of the NW Ontario low takeover will result in full-fledged blizzard conditions being most likely in SE Saskatchewan into SW Manitoba. Lighter winds are likely in the Red River Valley, and the peak forecast winds for this system have subdued slightly. That said, especially in the first wave, white-out conditions will be possible in heavy snow.
So, by the time the snow tapers off on Friday, it still look likely that 30 to 50 cm of snow will fall widespread across southern Manitoba. It will be a fairly persistent event from areas in SE Saskatchewan through southwest and western Manitoba as well across the Interlake. It looks like the situation in the Red River Valley will be different though, with multiple waves of snow. Winnipeg and area will likely see a wave of very heavy snow on Wednesday morning taper off later in the day with as much as 15–25 cm possible. Snow will likely ease for the city Wednesday evening/overnight with a chance of [freezing] drizzle. The wind will pick up on Thursday as more snow moves back into the region; the Winnipeg area will likely could see as much as 5–10 cm of snow.
Lighter amounts will fall to the south, but a heavier band of snow the north will give 10+ centimetres to the Interlake and other parts of central Manitoba.
The snow, wind, and blowing snow will begin to ease Thursday night, with conditions continuing to improve on Friday. For Winnipeg, this means that about half of the expected snow will likely fall on Wednesday alone, with the other half or so coming over the following 24–36 hours as a separate wave of snow. It will still amount to quite a bit, but it won’t be the 3-day raging blizzard like it looked like it could be even a day ago.
Temperatures will hover just above freezing today and tomorrow, then fall below freezing on Thursday.
Long Range Outlook
Cooler temperatures will stick around for the weekend with sub-freezing highs and seasonably cool lows. It should be a relatively quiet period for several days after this event, giving plenty of time to clean up after this storm.
Today’s seasonal daytime high in Winnipeg is 9 °C while the seasonal overnight low is -3 °C.