A system tracking across the Rockies into Alberta will slide quickly across the Prairies, brining increasing cloudiness to Winnipeg and the RRV Saturday afternoon with a slight chance of showers in the evening. For more info, read on!
12Z 21 October GEM-REG 3 hour precipitation accumulation valid at 00Z Sunday (Saturday Evening)
Overnight a low pressure system will track across the Central Prairies towards Manitoba with a developing N-S trough intensifying as it moves eastwards. As it enters The Pas and Norway House areas on Saturday, Winnipeg and the RRV will see increasing clouds and a strengthening southerly wind to 30-40 km/h. As the trough swings through Winnipeg in the late afternoon and early evening, we’ll see a slight chance of a shower or two. The bulk of the precipitation should stay north of the city, closer to the low, where there is more significant lift. All models bring the edge of the rain close to Winnipeg, though, so it certainly isn’t out of the question for us to end up getting 2-4 mm out of an hour or two of rain. It seems most likely, though, that late afternoon and the evening will be overcast with a scattered shower or two.
After this system passes through, we’ll enter a stagnant pattern for a couple days with daytime highs just below 10°C and overnight lows slightly below 0°C.
Ensemble Mean 500mb θe
The next chance for significant weather looks to be next Tuesday night / Wednesday morning as a rather sharp 500mb cold trough swings across the province. This will present us with a slight chance of flurries overnight, but shouldn’t amount to too much. More on that next week.
Have a great weekend and enjoy these crisp fall days!
A low-pressure system approaching Manitoba will rapidly develop this evening as it enters the province, bringing one of the most substantial widespread rainfalls of the last several months. The largest amounts will lie along a narrow axis called the deformation zone which makes these events hard to predict: a slight change in the track of the low can cause shifts in the placement of the deformation zone. So where will Winnipeg lie? What can other areas of the Red River Valley expect? Click through to find out!
12hr. Rainfall from the GEM Regional Model, valid 00Z Wednesday Evening
This system is slowly built into Southern Alberta through the night last night, and is now beginning to quickly move eastwards across the Prairies. Currently, the system is fairly weak, giving only light showers to many areas across Southern SK/AB, however a shortwave ejecting onto the Prairies from the Canadian Rockies will slidealong the US/Canada border this evening and overnight and will be able to tap into warmer air aloft over the Eastern Prairies and a pool of extremely cool, Arctic air over the Northwestern Prairies.
The combination of a powerful shortwave with access to these two air masses will result in a rapidly deepening low pressure system. Currently, the low sits just east of Regina and has a central pressure of about 100.8kPa. By mid-morning Tuesday, the low will sit over the Southern Red River Valley with a central pressure of 99.5kPa, which is a significant drop in pressure over 12-18 hours.
Rain will push into SW Manitoba by this evening, with a few scattered showers across the Red River Valley before midnight. Rain will intensify and build across the RRV into SE Manitoba overnight as the system really starts tapping into some of the cooler air across the Northern Prairies. The deformation zone will become quite apparent by tomorrow morning, which will make the precipitation forecasts easier, but right now it’s looking like it will set up just over or the southeast of Winnipeg.
So! What does this all mean?
Rain will push into Winnipeg and areas south overnight and be quite intense at times. Widespread amounts through these areas will likely be 5-10mm overnight, with the chance of some higher amounts over the Western Escarpment. Tomorrow will be quite an active weather day, with continuous rain for much of the RRV and strong winds with gusts as high as 70-80km/h from the north. These strong winds will likely cause some localized erosion on the lee beaches of the lakes which are still dealing with high water levels.
Areas south of Winnipeg will see an additional 15-25mm of rain tomorrow with few areas getting as much as 30mm, as will the Whiteshell. Winnipeg itself, however, will be trickier. If the deformation zone sets up to the southeast of us, we’ll likely only get perhaps 5-10mm. If we end up under it, or it moves to our NW, we could see substantial amounts of rain. Right now, the likely scenario is 10-15mm, with the potential for amounts as high as 30mm.
The system will clear out by Wednesday and we’ll be left with daytime highs in the mid to high teens for Wed/Thursday as we sit in cooler air behind the cold front associated with the system. By the end of the week, another upper ridge begins to build into the Prairies which will push sunshine and warm temperatures back into Southern Manitoba. Currently, it looks like we’ll see highs in the mid-20’s by week’s end.
So enjoy that (most of) you’ll be at work tomorrow during our kind of miserable day, and we’ll all enjoy the sunshine and warm temperatures in another taste of summer this weekend!