Light Snow Then A Return To Cold

Winnipeg seems to have found itself in the firm grip of winter as below-seasonal temperatures dominate the forecast. A low pressure system passing to our south today will bring snow and a slight moderation to our temperatures to near-normal values, but we’ll quickly drop back to well below-normal temperatures.

Storm-total liquid-equivalent precipitation accumulation

Liquid-equivalent (how much water there would be if you melted the snow) precipitation accumulation valid 18Z today.

A weak upper trough will swing through Southern Manitoba today, embedded within a strong northwesterly flow. While temperatures have warmed some 10-15°C aloft over the entirety of the Red River Valley, it looks like the surface warm front will halt part-way between Winnipeg and the U.S. border. Areas south of the warm front (probably areas south of Morris) will be able to tap into a southerly or even southwesterly flow, allowing temperatures to warm possibly as high as -5°C. Unfortunately for areas over the Northern Red River Valley, the warm front will likely remain well to our south, keeping our winds out of the southeast and slowly backing to northwesterly as the system passes by. These wind directions all favour the reinforcement of cold air as they tap into the colder air ahead and north of the low instead of the warmer air south of the low. That means that while there will be a slight increase in temperature from the advection (bringing in) of warm air aloft, a significant portion of the warming taking place over the Northern Red River Valley will be due to heat directed towards the surface from the clouds associated with this low. Highs north of the warm front will sit in the -12 to -15°C range.

Snow associated with this system pushed in overnight and will continue through the morning before tapering off around lunch time. Heaviest accumulations will lay north of the warm front with lighter accumulations south of the warm front. North of the warm front, including here in Winnipeg, we’ll see a total of 6-8cm of light, fluffy snow, while south of the warm front (the Southern Red River Valley) will probably only see a total of 2-4cm. There’s a slight chance that a few lingering flurries will hang on through the afternoon, but accumulations with those would be minimal should they happen.

Temperatures will drop down to around -25°C tonight as the clouds begin to break up and cold air filters southwards again in a northerly flow behind the low. Temperatures struggle to climb above -20°C tomorrow as we find ourselves deep in the cold air once again, some 8-10°C below normal for this time of year.

There are hints that temperatures may begin to moderate on Friday into the weekend, climbing as high as -9°C on Saturday, as a weak south/southwesterly flow develops. I’ll bite my tongue for now as models can sometimes be overly enthusiastic on moving the cold air out of the Red River Valley, but it does look like it’s at least a possibility. If that flow does develop, it’s likely we’ll see another batch of snow late this week as the warmer air pushes in. Until then, keep the long johns handy and be sure to check back in the comments below or follow along on Twitter for updates as the week progresses!

First Major Snowfall For Southern Manitoba

Residents of Southern Saskatchewan and Manitoba are getting the snow shovels out today after an Alberta clipper brought significant snowfall to many areas in those regions.  Across southern Manitoba, many highways were closed due to the event.


Snow falls in the Osborne Village area of Winnipeg on Thursday night.  Photo ©2010 Brad Vrolijk, taken on an iPhone with Instagram.

While the low pressure system that brought snow to Southern Manitoba yesterday through last night has moved out, lake-effect snow flurries continue to affect some areas of the Red River Valley.Environment Canada has issued special weather statements outlining the amount of snow many areas received.  Across west-central Manitoba, along the Trans-Canada Highway, and through much of the Red River Valley, snowfall accumulations as of Friday morning are in the 10-20cm range:

Selected storm total snowfall amounts

Dauphin                             17 cm
Gilbert Plains                      20 cm
Brandon                             10 cm
Roblin                              12 cm
Rivers                              11 cm
Winnipeg                            10 cm
Oakbank                             10 cm
Pinawa                              12 cm
Grand Rapids                        14 cm
Wilson creek                        18 cm
Wasagaming                          15 cm
Fisher Branch                       12 cm
Portage la Prairie                  10 cm
Beauséjour                          12 cm
Morden                               5 cm

While the storm has moved out, gusty northwest winds have moved in.  Temperatures should drop into the low (high?) teens, about the −10 to −12 degree C range, by this afternoon with an arctic air mass moving in behind the clipper.  This cold air is also producing lake effect snow.

 
 

This is resulting in narrow bands of flurries through small segments of the Red River Valley.  Winnipeg has seen fairly continuous flurries through Friday morning, and has already had another 2-3cm of accumulation from them.  They should move out of the Winnipeg area this afternoon as the winds become more northerly, however travellers should be aware for the potential of heavy snow along the Trans-Canada Highway to the west and east of Winnipeg.
We will see temperatures plummet tonight to below −20 degrees, bringing us our first true winter night of the season.  Things should warm up a bit for Sunday, when there’s a good chance that more snow will push into Southern Manitoba as a system heads east-northeast out of Montana.  

 
12Z GEM-REG 48H Output (valid 12Z Sunday Morning), 3hr QPF & MSLP 

Current indications are that this system could deliver another 4-8cm of snow, however the exact amounts will be a lot clearer once the system is closer to us and more developed.

One last note, is that the wind chill this afternoon will be about −24; well below the actual temperature, so be sure to throw on an extra layer of clothing and a scarf to keep warm if you need to be out and about.
That’s all for now!  Stay warm and drive safe.