Don’t let the bits of sun and relatively warm temperatures fool you; tonight is going to be downright awful.
A complex double-barreled low pressure system (a term used when two separate lows are moving together as one entity) is moving out of Saskatchewan and Montana into Southern Manitoba this morning. This system has brought a mix of precipitation into Southern Manitoba this morning, including freezing rain over western areas and heavy snow in the Interlake. Numerous warnings have been issued across the region for weather happening now or expected to happen this evening.
The risk of freezing rain will persist through much of Southern Manitoba for an hour or two longer before temperatures will be warm enough that any precipitation will simply fall as rain. Even though little precipitation has fallen over the Red River Valley this morning, Manitoba Highways is reporting that many sections of Highway 75 and Highway 1 heading west of Winnipeg are partly iced cover due to the slight melt and re-freeze yesterday afternoon. As temperatures will just barely get over 0°C today, there may be portions of highways that are still quite slippery throughout the day.
Perhaps the biggest impact from this storm will occur tonight over the Red River Valley. As the low passes to the east, cold air will plummet down the backside of the system through the RRV.
24hr Accumulated QPF valid 12Z Saturday March 12, from the 00Z run of the GEM-LAM REG Model
As the system passes, an intense band of wrap-around precipitation will move into the RRV, bringing heavy snow to Winnipeg by 6 or 7PM tonight. Along with this heavy snow, this system will bring significant winds as well.
Surface Winds valid 06Z Saturday March 12, from the 06Z run of the GEM-LAM REG Model
Sustained winds of 50-60 km/h with gusts potentially as high as 90 km/h will blast cold air into the RRV, which will plummet the temperature from 0°C or +1°C down to approximately -14°C or -15°C over the span of a few hours. This will rapidly freeze any standing water which will very likely create extremely slick roads tonight. And last but not least, these winds, combined with the heavy snow, will very likely produce blizzard conditions through a good portion of the night.
The weather conditions will deteriorate extremely quickly this evening to become a significant winter storm. Anyone who has plans to travel in the Red River Valley tonight should keep updated on warnings, forecasts (or for a smartphone), the RADAR, and highway conditions to be able to make safe, educated travel plans. Good satellite imagery to track this system can be found here at the U of M.