Severe thunderstorms will be possible across much of Southern Manitoba today as a rare late-season setup develops through the day today.
Today
26°C / 15°C
Mostly cloudy; thunderstorms likely late in the afternoon into the evening.
A low pressure system will be pushing it’s way out of North Dakota into SW Manitoba through the day today, bringing with it a push of warm air that will lift a warm front northwards into the extreme southern portions of the province by late this afternoon. Plenty of cloud will stream into the province ahead of this system which will result in us having a mostly cloudy day with our high temperature climbing somewhere near 25°C.
This system will develop a fairly potent severe weather setup, especially for this time of year. A deep layer of moisture will build over the Southern Manitoba through the day with dew points climbing to around 18°C and extending through the boundary layer. Steep mid-level lapse rates will develop with falling 500mb heights, contributing to a large amount of instability ready to be realized should an appropriate trigger develop. 500mb winds are forecast to increase to nearly 50kt by late afternoon which when coupled with a developing low-level jet, contributes to anywhere from 40–60kt of bulk shear in place tomorrow evening/night. There’s plenty of moisture, instability and shear.
So how about that trigger? Things will remain capped through most of the province through the day thanks in no small part to the cloud cover that will inhibit much of our potential heating. Thunderstorms will likely develop in SE Saskatchewan or SW Manitoba mid-to-late afternoon as the cold front associated with this system pushes eastwards and is strengthen by an incoming upper-level disturbance. Over the SW portion of the province, the storms will likely be surface-based which will be a very important distinction. With the strong shear profiles in place, surface-based storms in SW Manitoba will have the potential to become tornadic due to a relatively strong southeasterly inflow wind. Any residents of SW Manitoba should stay alert for watches and warnings that may be issued with this storm system.
The storms that develop along the cold front will likely quickly grow upscale and develop into a squall line pushing eastwards. As it moves towards the Red River Valley the storms will become elevated as surface temperatures cool and a very strong low-level jet develops. This jet will sustain these storms as they push eastwards over the rest of the province through the evening.
Elevated thunderstorms present very little tornado risk. Thunderstorms today will have the potential of producing heavy rain, very large hail and damaging winds, all afternoon and evening.
After the storms push through (and I won’t rule out that we’ll see the umpteenth split around Winnipeg this year), we’ll see clouds break up as we drop to around 15°C.
Thursday and Friday
20°C / 9°C
Mix of sun and cloud; chance of scattered showers.
We’ll see things cloud back up early on Thursday as another cold front pushes through. There will be a chance of some scattered showers behind the cold front in some lingering instability as we climb to a high of around 20°C. Winds will be a little breezy out of the northwest to around 20–30km/h. Things will clear up for the most part on Thursday night, although there will likely be a narrow band of stratus cloud coming off of Lake Manitoba overnight. Where that cloud will end up depends entirely on the exact wind direction, but suffice to say it’ll likely end up somewhere in the Western Red River Valley.
17°C / 4°C
Mainly sunny.
Friday will be a cool and sunny day. Temperatures will only climb to around 16 or 17°C and colder Arctic air slumps southwards over the Prairies. We may see a few clouds in the afternoon, but not anything significant. Temperatures continue to cool aloft through the overnight period with 850mb temperatures dropping to nearly 2–3°C on Friday night. This should translate to an overnight low dipping into the low single digits, likely to around 3 or 4°C.
The weekend looks fairly quiet with sunny skies and temperatures rebounding back towards the mid–20’s by the start of next week.
