As we mentioned on Wednesday, a big cool-down is underway across Southern Manitoba. While we knew earlier that it was going to get cold[1], it’s beginning to become clear that it’s going to get quite a bit colder than that. Just how cold? Winnipeg might see daytime highs in the near future not seen since last January.
Friday
⇓ -13°C / -17°C
Cloudy with sunny breaks; chance of flurries
Saturday
-16°C / -26°C
Mainly cloudy with some flurries
Sunday
-21°C / -28°C
A few clouds
Today will be the coolest day in a little over a week as temperatures will slide towards –13°C by the end of the day. Skies will start out cloudy then gradually become more mixed through the day. With favourable temperature profiles, some patchy non-accumulating light snow is possible. Winds will be out of the northwest at around 15–20km/h. Temperatures will drop to near –17°C tonight.
Daytime highs will drop on Saturday to just –16 or –15°C with mixed skies. Some flurries or light snow is expected as a system slides from Saskatchewan into North Dakota, but amounts aren’t expected to be much more than a skiff at most. Temperatures will drop into the mid-minus 20’s on Saturday night.
Sunday will be a downright cold day a few clouds around. Highs will sit near –20°C through the Red River Valley and winds will be light. Expect lows dipping close to –30°C on Sunday night.
Cold Start to Next Week
The GDPS forecast shows Southern Manitoba embedded in a deep cold trough on Monday afternoon.
Next week will begin with a substantial trough of cold air positioned over Southern Manitoba that will bring daytime highs in the mid-minus 20’s through the first half of the week. There may be a mid-week warm-up, but a return to colder weather would follow quickly behind. No big storms are on the horizon, so in general expect cold, dry weather to persist through the next week.
On Wednesday’s post, we surmised that daytime highs would generally be near –20°C. ↩
After a prolonged period of temperatures some 10 to 20°C above normal, Winnipeg & the Red River Valley is set for a rude awakening after Christmas as Arctic air plunges southwards and brings below normal temperatures to the region.
This graph of the daily average temperature compared to normal illustrates the dramatic warmth Winnipeg has seen in December.
The crash to colder temperatures will be exceptionally jarring considering the abnormal warmth we’ve seen through much of December. Leading up to Christmas, mild weather will persist as an incoming low pressure system helps extend the stay of the warm air that’s been so common the past few weeks. As the system passes on Christmas Eve, though, a major pattern change is set to take place as our fairly weak is absorbed into the rather major East Coast “Santa Bomb” which in itself will induce a shift to the gradual re-establishment of the Polar Vortex over Hudson Bay.[1]
Christmas Eve
Wednesday
-3°C / -6°C
Cloudy with evening flurries
Today will be a pleasantly mild day with highs near –3°C through the Red River Valley and winds developing out of the south to around 20–30km/h. Skies will remain mainly cloudy in advance of the incoming low pressure system with some flurry activity finally pushing into the Red River Valley by late in the afternoon and reaching Winnipeg by evening. Little is expected as far as accumulations go; the main accumulating snowfall will remain north of the Trans-Canada corridor through the Parkland and Interlake regions eastwards into Ontario where around 2–4cm are expected.
Temperatures will drop to around –6°C tonight with winds shifting to the west-northwest at around 20km/h.
Freezing drizzle will once again be possible overnight into Christmas morning as saturated low-levels are left behind the departing low pressure system. Steep low-level lapse rates and only a relatively light wind from the NW may result in another batch of road-slicking freezing drizzle. Due to its nature, freezing drizzle requires a fairly delicate balance of factors to exist, so there will be unavoidable uncertainty until later tonight, but keep in mind that it is a distinct possibility.
Christmas Day
Thursday
⇒ -5°C / -12°C
Mainly cloudy with scattered flurries
Christmas Day will be a mixed bag in Winnipeg. Temperatures will remain above-seasonal, but the push of cold air will already have begun. As a result, temperatures will likely remain steady near –5°C as any potential daytime heating is offset by the cooler air moving in. Freezing drizzle is possible through the morning hours, while flurries are more likely through the afternoon.[2] Skies will remain mainly cloudy, although a brief glimpse of sunshine is possible.
Temperatures will head down to the –12°C mark or so overnight with a continued chance for flurries and gradually diminishing cloud.
Boxing Day
Friday
⇓ -16°C / -24°C
Mixed skies with a chance of flurries
Boxing day will be when the real surge of Arctic air begins pushing in. Expect mixed skies with a chance of flurries through much of the day. Temperatures will drop through the day to around –16°C by evening. Skies should clear out overnight as the Arctic ridge begins moving in and temperatures drop to around –24°C. This will be the coldest overnight low we’ve had since November 30th into December 1st when the temperature dipped to –27.1°C. Given that the normal overnight low for this time of year is –22°C, that’s not too bad.
Cold Pattern Persists
The cold weather will be here to stay for a while as a persistent northwesterly flow develops over the province thanks to gradually establishing polar vortex over Hudson Bay.
The NAEFS 8–14 day temperature outlook is foreacsting a good chance of below-normal temperatures for Southern Manitoba.
In the end, it means a relatively dry pattern with daytime highs generally in the –15 to –20°C range.[3] This pattern looks to continue at least until late next week, so dig out those real winter clothes again and get the block heater ready, winter’s on its way back.
$.bigfoot()
The persistent vortex over Hudson Bay – for all intents and purposes a “polar vortex” – is a regular occurance over Hudson Bay in the winter months and is the most common cause for prolonged cold weather in Southern Mantioba. ↩
If things end up just a tad cooler, the freezing drizzle risk could be just a chance of flurries; if things end up a tad warmer, the freezing drizzle risk could persist through much of the day. ↩
Warm weather will stick around until Christmas, a nice break for the holidays.
Mild conditions are expected in southern Manitoba on Monday
Monday
Monday
0°C / -4°C
Light snow
Today will be very mild, but with some snow. A low pressure system off to the south will generate some light snow in southern Manitoba during the day, with accumulations of generally around 2cm expected. Given the mild temperatures, most snow should melt quickly off treated roads, making for mostly wet, as opposed to slippery, conditions.
Tuesday
Tuesday
-1°C / -8°C
Light snow
More light snow is expected on Tuesday as the system to the south remains in place. Accumulations of around 2cm will once again be possible. Temperatures will remain mild though, making for a decent day.
Wednesday
Wednesday
-3°C / -10°C
Mainly cloudy with chance of flurries
A slight chance of flurries will linger on Wednesday, but any additional accumulations should be small. A breezy south wind will develop, keeping temperatures mild.
Long Range
Conditions should remain mild until Christmas, but after that a major pattern change is coming. Models suggest that our first major arctic blast in several weeks will move in on Boxing Day. That might have many folks doing their post-Christmas shopping online, as opposed to venturing out into an unfamiliar chill.
The NAEFS is predicting below-normal temperatures in the 8-14 day time period.
Snow Squalls Paralyze Several Japanese Prefectures
This week’s Elsewhere in Weather News focuses on western side of the Japanese islands of Hokkaido and Honshu which have seen significant amounts of snow from a snowstorm that hit midweek.
An area of low pressure which was moving northeast along Japan’s west coast quickly deepened to a 949mb low and whipped Japanese islands with winds of 60 to 100km/h. These winds, combined with widespread amounts of 20-30mm of rain ahead of the system. By the time the low reached the northern islands of Japan, strong northwesterlies kicked in over Japan’s main island of Honshu. Cold Siberian air infiltrated in over the Sea of Japan behind the low which stalled out, creating prime conditions that would sustain the development of snow squalls for a long period of time.
IR Satellite image of the mature low pressure system over northern Japan with circled area showing snow squalls forming over the Sea of Japan.
Snow squalls occur when cold air moves over a warm body of water, creating an unstable temperature profile. With the instability in place, snow squalls were able to from over the Sea of Japan and make their way to the western side of Honshu. Orography – the effect that terrain has in creating localized impacts on the weather – also played a role in providing additional lift which resulted in higher accumulations. The storm prompted blizzard warnings to be issued across 11 prefectures in western Honshu and Hokkaido.
These are the areas that saw the highest snowfall amounts recorded – accumulations generally ranged from 50cm to 120cm, but locally higher amounts were recorded near Niigata, Japan, up to 200cm. The storm caused 19 fatalities and forced cancellations of 600 flights across Japan.
Mountainous terrain located to the southeast of Niigata enhanced the snowfall amounts in the region.Last week, another storm of similar strength brought significant snow to parts of Honshu as well as the northern island of Hokkaido. The forecast looks to favour more snow squalls as a similar setup to what was seen this past week – a strong low will be located near the northern island of Hokkaido and will draw in more cold Siberian air over the Sea of Japan.
