Winter Storm Moving In

The remainder of the week will be defined by a significant storm system moving through much of central North America. This system has two main areas of snow: one through the Great Lakes associated with a powerful surface low and it’s fronts and a second one that will impact us associated with the system’s upper low moving into the region. Snow and blowing snow will be replaced by bitterly cold Arctic air moving in for the weekend that will entrench itself into Southern Manitoba for the first frigid winter blast of the year.

Tuesday Night

Tuesday Night

-14°C
Periods of snow. 2-5cm accumulation.

The snow has already started flying through much of the Red River Valley and will continue to do so through much of the overnight period. There may be breaks here and there, but for the most part mainly snowy conditions are expected with a total of 2-5cm of snow piling up before the main system moves in tomorrow morning. The winds will increase to 30 gust 50km/h fairly early this evening, and there may be local areas of blowing snow giving reduced visibility. The early start to the snowfall will ensure that highway conditions will already be in a somewhat deteriorated state by morning. We’ll see temperatures drop to around -14°C tonight.

Wednesday & Wednesday Night

Update: Environment Canada has issued a snowfall warning for the Red River Valley and SE Manitoba.
Wednesday

→ -14°C / -16°C
Snow. 10-20cm by Thursday morning.

Snow will persist through to Thursday morning and will be very fluffy which will help it pile up relatively quickly We’ll likely see 5–10cm on Wednesday with another 5–10cm Wednesday night, bringing a total to somewhere between 10–20cm for the City of Winnipeg by Thursday morning.

In addition to the snow, moderate northerly winds will develop, increasing to around 30km/h with gusts to around 50–60km/h. These winds would usually not be too much of a concern, but with such fluffy snow falling, blowing snow will likely be a concern for anyone planning to do highway travelling. With winds out of the north, visibilities on Highway 75 will likely be restricted mostly by the falling snow, but any west-east highways will likely have significant drifting and blowing snow. Of particular concern will be the Trans-Canada Highway from Winnipeg to Portage la Prairie; ever battered by blowing snow, travel conditions along that stretch will likely deteriorate fairly quickly through this morning. The winds may not be strong enough to result in closure of the highway (although I wouldn’t rule it out), but they will certainly make travel more difficult.

Forecast storm-total snowfall amounts for Southern Manitoba.
Forecast storm-total snowfall amounts for Southern Manitoba.

The snow will begin to taper off late Wednesday night, perhaps into Thursday morning, with many areas in Southern Manitoba seeing close to 15–25cm of new snow. Although the significant snowfall will be done for Thursday, the wind will be another story.

Thursday

Thursday

→ -16°C / -22°C
Flurries; blowing snow in open areas.

Most of the snow will have tapered off by tomorrow morning, but we’ll still see widespread light flurry activity today which may end up adding another 2cm of snow or so to the totals for any areas that see more prolonged activity. The bigger news will be the northwesterly winds, 30–40km/h that will be blowing through the valley bringing in cold, Arctic air.

As the low pressure system moves off to our east, a bitterly cold Arctic high will begin building into the region. The colder air pushing in will prevent our temperature from rising much on Thursday and will give a pretty nasty bite to the wind. Wind chill values will sit in the –25 to –30 range, making it one of the first truly cold days of the year. In addition, some low-level instability caused by the cold air advection will combine with the northwesterly winds and fresh, fluffy snow to continue producing blowing snow through the Red River Valley in most open areas. With northwesterly winds, most highways will be affected by drifting or blowing snow.

The clouds will begin to break up overnight with some continued scattered flurry activity as we drop to a low of around –22°C.

Friday

Friday

→ -21°C / -25°C
Partly cloudy, slight chance of light flurries. Cold.

The sun will begin to peek out on Friday after what seems like forever of being cloudy. Unfortunately, that seeing that big bright ball in the sky is thanks to the Arctic high settling over the region, which means we’ll also be bitterly cold. Our daytime high won’t really recover from Thursday night’s low and we’ll just be heading down, down, down for the weekend. The winds will also be lighter ending any blowing snow concerns. We may end up seeing some flakes of snow out of whatever clouds are around, but they won’t produce any accumulations.

Skies will clear completely on Friday night as we drop to around –26°C for an overnight low.

The Weekend Ahead

Cold.

Very cold.

As the Arctic ridge really entrenches itself over the province, we’ll likely see our first overnight lows dropping below –30°C this weekend, perhaps even into the mid-minus–30’s. We’ll end off the weekend/start the new week with a chance of some snow as a system dives down through the province. At this point it doesn’t look like a very significant system.

A Mild Day Before The Deep Freeze

Southern Manitoba will see a beautiful afternoon today with plenty of sunshine and highs approaching 0°C in southwest sections of the Red River Valley. This afternoon/evening would be a great time to get out and enjoy the warm weather; a cold front sweeping southwards is going to bring a drastic change on Thursday.

500mb Wind Prognosis

+42 Hour 500mb Winds & Height forecast valid 12Z 09 February, 2012 from the GEM-REG Model

A strengthening upper ridge over the western portion of the continent will organize itself and amplify significantly today and tomorrow. By Thursday morning, it will stretch from Nevada northwards all the way to the Arctic Sea shoreline of the Yukon Territory. As a response, long-wave troughing will be enhanced over the central portions of the continent. Practically, this means that large-scale troughing will be induced in the arctic vortex and rotate around it.

In winter time, long-wave troughs are often associated with cold temperatures and incoming surface ridges of high pressure.

As this long-wave trough rotates from the Kivalliq region of Nunavut through Southern Manitoba, arctic air will be allowed to spill southwards. With this particular upper trough and associated cold front, there appears to be a significant push of cold air: temperatures on Thursday will only recover a degree or two from our overnight low of around -12°C, and temperatures will plummet on Thursday night. Currently, it looks like most areas in the Red River Valley will see overnight lows between -28°C and -32°C on Thursday night, with the colder temperatures east of the Red River and the warmer temperatures west of the Red River courtesy some light downslope winds over the escarpment. Like the previous cold front, very little precipitation is expected with it’s passage.

The normal daytime high for Winnipeg right now is -10°C. The normal overnight low is -20°C.

We’ll be under the influence of this bitterly cold air for a couple days before some warmer air advects into our region from the north again and we return to more seasonal values for Sunday and the start of the new week.