Cool Weekend Ahead

Arctic air will keep temperatures cool through the weekend with daytime highs some 5-7°C below normal. Scattered flurries will be common through the weekend, while a significant lake-effect snowfall event will impact portions of the Whiteshell and Eastern Manitoba.

850mb Temperatures Valid Saturday Morning

850mb temperatures valid Saturday morning. A deep pool of Arctic air will flood across the Prairies this weekend.

As the low that brought rain to Southern Manitoba the past few days pushes northwards into Hudson Bay, it will intensify quite considerably1 and induce a strong northwesterly flow over the Canadian Prairies. This cold air will likely produce isolated scattered flurries, however the largest effect will be strong lake-effect snow bands, primarily from the basins of Lake Winnipeg. These lake-effect bands will mainly effect the Bisset region and slowly push northwards towards Berens River as the winds back slightly to westerly through the weekend. Substantial amounts of snow are possible with these bands, with the potential for anywhere from 15-30cm of snow possible in areas that see a band have a particularly long residence time over them.

Daytime highs over the next few days will sit within a degree or two of 0°C, with overnight lows near -6 or -7°C. No significant improvement in temperatures is expected until potentially early next week as a low pressure system moves through the Central Prairies and brings ever so slightly warmer air back to the region.


  1. It’s currently forecast to deepen from a 982mb low this morning to a 967mb low tomorrow morning. 

Cooler Air Pushing Southeast Across Southern Manitoba

The powerful low pressure system that has brought rain to Winnipeg over the past couple days and is bringing 10-20cm of snow to portions of Northern Manitoba has pushed north and east of the Red River Valley, setting the stage for cooler air to filter into the region.

700mb Temperatures for Thursday Morning

NAM forecast of 700mb heights & temperatures valid Thursday morning.

The Red River Valley will be moving into a strong northwesterly flow aloft that will advect cooler air into the region. While earlier in the week, models were projecting a very potent arctic blast, things have become a little more pleasant due to a more significant amplification of the upper-level pattern. The net result of this is a cut-off upper low over the central Prairies that will, in effect, block the coldest air from being able to push southwards. This will give us more cloud than sun with daytime highs near 5 or 6°C through the rest of the work week.

The upper low begins to push eastwards for the weekend, allowing slightly cooler temperatures to the area for the weekend, with highs near 0°C, and a chance of some light snow. Accumulations will be light-to-none throughout the RRV, however a few cm may pile up in the Interlake region.

More Active Weather

More active weather is in store for this week with multiple chances for precipitation. The question is whether that precipitation will be solid or liquid.

Low pressure system passing to the south-east on Thursday

A low pressure system is currently expected to pass to our south-east on Thursday, generating minimal impacts in Manitoba

The weather to start the week will be fine, with temperatures generally in the high single digits on Monday and perhaps a few double-digit readings here and there. There will be increasing cloudiness during the day as a weather system approaches. This system will begin to spread rain over Southern Manitoba on Monday night with precipitation persisting into the day on Tuesday. Highs on Tuesday will remain very similar to Monday, but the rain will make it a considerably more miserable day. Total accumulations from this system will generally range from 5 to 15mm. As Tuesday’s system departs our region on Wednesday, cooler air will sweep in from the west making for a chilly and windy middle of the week. Temperatures on Wednesday will be in the mid single digits with a gusty west wind.

There has been much talk about the weather for later this week. Some models have been showing a significant Colorado Low system hitting portions of Manitoba on Thursday and Friday. However, other models show little or no precipitation for us later this week. At this point the consensus seems to be that it is unlikely Southern Manitoba will be getting a major blizzard later this week. Most models depict a moderate strength low system sliding past us through Minnesota and up into North-Western Ontario, perhaps bringing a few flurries or rain showers to Southern Manitoba, but not a major winter storm. Some models still show a fairly deep low pressure system to our east over Northern Minnesota and North-Western Ontario later this week, but it looks like it will be sufficiently far away to prevent us from seeing its main impacts. So at this point it appears unlikely that we’ll be seeing any significant amount of the white stuff later this week. However, expecting the unexpected as always a good saying to live by in the weather business.

Elsewhere in Weather News: October 20th, 2012

Severe Weather Outbreak in Dixie Alley

This past Wednesday evening a severe weather outbreak comprised of severe winds and strong tornadoes occurred in the southern United States, causing damage to rural areas of Northern Mississippi. This was brought on by the same system we experienced over the past couple of days. The polar jet stream along with a strong low level jet overhead and plenty of moisture from the Gulf of Mexico combined to create conditions ripe for tornadoes in Dixie Alley.

Trough

500mb heights/temperatures with trough (arrow) and circled area where the tornado outbreak occurred. (Source: Twisterdata)

The strongest, a half-mile tornado, rated EF-3 by the National Weather Service, touched down near Jackson Mississippi and caused quite a bit of damage, tearing up large trees and wrecking mobile houses. As the tornado trekked for 26 kilometers, nine people taking cover inside mobile houses were injured but thankfully no fatalities occurred during this event. As the night wore on, more tornadoes touched down in Mississippi and Arkansas, doing damage to rural homes and cutting off power to residents.

Tornado damage

Tornado damage in Leake County, MS. (Source: WLBT)

A few colder days will follow the trough this weekend and a return flow will set up, bringing warm and humid weather back to the region. Weather models are showing another large trough will likely develop late next week, bringing the potential for more dynamic weather. Of course, it is not uncommon to have severe weather in the southern US during the spring and fall, when the polar jet is in the vicinity.

Elsewhere in the world the weather has remained relatively calm, except for this unusual tornado in France.

Video of the tornado in Marseille, France. (Taner Ozdil)

Tornadoes in France are not rare but are not a common sight in October.