Heavy snow to avoid southern Manitoba


Precipitation depiction from Friday to Monday evening

For once, it seems like southern Manitoba will catch a break! A Clipper is set to impact parts of Westman tonight into tomorrow and then track towards the Interlakes region of Manitoba. This should provide a quick burst of heavy snow north of the Trans-Canada Highway. Anywhere from 10-20cm and locally higher could be seen, however major population centers like Winnipeg, Portage La Prairie and Brandon should be avoided. Dauphin and Gimli should see a lot of snow by Saturday evening.


500mb relative vorticity for Sunday night

A more "potent" system have forecasters reaching for all the models to be able to forecast for this! The infamous Colorado Low. For the most part, models aren't great a predicting the exact track of these infamous Low pressure systems, but since the track will determine which areas will see the most snow, it is quite important. An important feature of Colorado Lows is that a shortwave trough develops on the lee-side (east side) of the Rocky Mountains. Above is a depiction of 500mb shortwave with its associated upper-Low. Below is the surface Low pressure associated with the trough. The surface Low pressure is the important one to note here since that will dictate where your strongest surface winds will be. However, keeping an eye on the shortwave is critical for the positioning of the surface Low.

Resulting surface Low pressure on Monday morning

While this is only the NAM 12km model depiction of these pressure centers, the model's trends are similar and don't show much discrepancies, therefore increasing forecast confidence. It seems that this system will follow a typical Colorado-Low track and form in Nebraska and move northeast from there. This would bring the main precipitation axis in North Dakota/South Dakota/Minnesota.

Mean Sea Level Pressure by Sunday night for North America

If we zoom out for a moment, we can see that this makes sense. High pressure builds in Alberta and moves towards Manitoba on Sunday. Since winds move from areas of high pressure to areas of lower pressure, strong winds are often associated with Colorado Lows on the northwest corner of the surface Low. Coincidentally (not really), the area of strongest expected winds is where our 500mb vorticity center is being depicted. Below is a forecast model trend for the GFS (American) model showing where the surface Low should end up. Obviously, this would bring minimal precipitation to southern Manitoba, but a track north, say near Sioux Falls, SD or Watertown, SD would mean much higher snowfall totals for southern Manitoba.

GFS model trend for surface Low depiction on Sunday night

In the meantime, there are winter storm watches for parts of Westman for tomorrow's Clipper. Our current thought is that major cities on and south of the Trans-Canada highway should see minimal snowfall from either of these systems.


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Below are the Environment Canada watches:

Watches

10:17 AM CST Friday 01 February 2019 Winter storm watch in effect for (areas in yellow)


A slow-moving disturbance will spread heavy snow into western Manitoba on Saturday. Up to 30 cm of snow is possible before it tapers off on Saturday evening. Snow will spread into western Manitoba on Friday night and intensify Saturday morning. The heaviest snowfall will occur on Saturday. Snowfall warnings or winter storm warnings may be issued later today. Rapidly accumulating snow could make travel difficult over some locations. Visibility may be suddenly reduced at times in heavy snow. For information on emergency plans and kits go to http://www.getprepared.gc.ca/