Tag: Thunderstorms

Severe Thunderstorms Possible in Late-Season Setup

Brad Leave a comment

Severe thunderstorms will be possible across much of Southern Manitoba today as a rare late-season setup develops through the day today.

Severe thunderstorm outlook for Wednesday afternoon through Wednesday night.

Severe thunderstorm outlook valid Wednesday afternoon through Wednesday night.

Today

Wednesday

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

Thursday

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.

Friday

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.

Warm Weather Gives Way to Cool Weekend

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Well above-seasonal temperatures will wash over Southern Manitoba today as a powerful low pressure system in the Arctic drags a swath of very warm air eastwards across the Prairies. It won’t be meant to last, though, as a strong ridge of high pressure builds in behind a cold front that pushes through on Saturday, bringing cool Arctic air with it for the weekend.

Friday

25°C / 15°C
Mainly sunny.
Saturday

22°C / 4°C
Cloudy with a good chance of showers or thundershowers, then clearing through the afternoon.
Sunday

19°C / 6°C
Mainly sunny and cool.

We’ll see a breezy wind out of the southwest today as temperatures climb into the mid–20’s thanks to a warm front that pushed through overnight. We might see a little bit of cloud, but for the most part skies should be mainly sunny. Still in the warm sector of this system, we’ll only drop to the mid-teens tonight with some increasing cloudiness towards Saturday morning as the cold front approaches.

Saturday morning will bring a fairly decent chance for some scattered shower activity as the cold front pushes into the Red River Valley from the north. There may be a few thundershowers as well but no significant or widespread thunderstorm activity is expected. Gusty northerly winds will move in behind the cold front – which should be through much of the Red River Valley by midday – with clouds scattering out to a mix or partly cloudy skies. The temperature should be able to climb a degree or two above the 20°C mark, however cold air advection will limit our high very close to that mark.

Skies will clear overnight as we drop down to a very chilly 4°C or so. Areas outside the city of Winnipeg may even see temperatures dip a little cooler than that. We may end up seeing the first frost of the year in some places on Saturday night but I don’t expect a widespread frost to occur.

Sunday will be a sunny but very cool day as the ridge of high pressure dominates the weather pattern over Southern Manitoba. We’ll see temperatures climb to only around 17 or 18°C by late afternoon but at least the winds should be relatively light, picking up out of the south later in the day to only around 15–20km/h. We’ll see an overnight low of around 7°C on Sunday night with clear skies.

An Oasis on the Horizon?

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After weeks of dry weather, some rain is finally on the way. However, for those desperately wanting rain, the water works may only come after the rain has ended.

A Low Pressure System will Spread Rain Over the Northern Plains on Monday

Monday

Monday

Mainly cloudy. Chance of showers.
23°C / 14°C

Today will see rain over some parts of Southern Manitoba as a powerful upper low approaches the region. This system will tap significant moisture over the Northern Plains, generating an area of moderate to heavy rainfall over the Dakotas. The core of this rain will slide mainly south through North Dakota and Minnesota, however the northern fringe of it may clip areas along the International Border up into south-eastern Manitoba. In these border regions rainfall amounts will be very hard to predict in advance, but a reasonable estimate would be for 5 to 15mm for the entire day. Actual amounts could be slightly higher or lower than this depending on the track of the system. In the rest of Southern Manitoba, little to no rain is expected. There will be a constant threat of showers today and tonight, but most areas including Winnipeg, should see very little if any rain. Other than the rain it will be a cloudy, but mild day, with light winds.

Tuesday and Wednesday

Tuesday

Mix of Sun and Cloud. Chance of Showers or Thundershowers.
27°C / 10°C
Wednesday

Mainly Sunny
21°C / 6°C

Tuesday should be a fairly nice day in Southern Manitoba. Skies will be a mixture of sun and cloud with temperatures in the mid to upper twenties. Late in the day a cold front will come through, likely triggering some showers and thunderstorms. These storms are not expected to be severe.

Not surprisingly, Wednesday will be a cooler day as colder air moves in behind that cold front. High temperatures will be in the low twenties with gusty north-westerly winds. Some fair weather cumulus clouds may develop during the day, but otherwise it will be mainly sunny.

Long Range

The long range outlook is a bit ambiguous at this point. It appears that we’ll probably see conditions begin to warm up around the weekend, only to be knocked back down by another cold front later on the weekend or into next week. This sort of up and down pattern makes forecasting fairly tough, so rather than making any sort of grand prediction I’ll just suggest that we’re in for a variable pattern with some warm weather interspersed with cooler periods.

Weekend to Bring A Break From The Heat

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Slightly cooler weather will move in this weekend behind a low pressure system forecast to move through tonight and tomorrow. In addition to the cooler temperatures, this system will bring a chance of rain and thunderstorms to the Red River Valley.

Tonight & Tomorrow

Friday

27°C / 18°C
Increasingly cloudy; risk of a thunderstorm late in the afternoon into the evening. Humid.

We’ll see gradually increasing cloud today as the surface trough associated with a low pressure system pushing into the northern Interlake approaches. There may be some ongoing thunderstorm activity along the trough this morning as it pushes through SW Manitoba and that threat will move eastwards into the Red River Valley by the late afternoon or early evening. A southerly wind ahead of the trough coupled with a capping inversion will draw moisture northwards once again and trap it near the surface, making for another hot, sticky day here in Winnipeg. Our high temperature will only climb to around 27 or 28°C, though, thanks to the increasing cloudiness through the day. That hot, humid weather will bring the threat for thunderstorms – potentially severe – late in the afternoon into the evening hours. At this point, it seems like somewhere between 8PM and 11PM seems like the most likely time for seeing any potential storm activity. After that we’ll see our temperature drop to around 18°C under a partly cloudy sky.

Saturday

25°C / 12°C
Becoming cloudy, good chance of showers or thundershowers. Humid again.

Saturday will be another humid day as we remain in the moist air mass ahead of the cold front. We’ll see a fairly good chance of showers or thundershowers beginning later in the morning and through the afternoon. Skies will start off as a mix of sun and cloud but should become fairly cloudy in the afternoon as things become more unstable with the approaching cold front. We’ll see a high of around 25°C which will mark the last day in our hot, muggy air mass. The threat for showers or thunderstorms will persist until the cold front passes.

500mb Winds for Saturday Afternoon

500mb winds forecast by the NAM show an intense upper-level low pushing into Southern Manitoba which may be the catalyst for showers and thunderstorms on Saturday afternoon and evening.

The cold front will push through overnight, bringing northwesterly winds that will clear out much of the moisture and drop us to a comparatively cool 12°C for an overnight low with clearing skies.

Sunday & Holiday Monday

Sunday

23°C / 8°C
Sunny. Cooler and much less humid.
Monday

25°C / 13°C
Sunny and warm.

Sunday and Labour Day Monday look absolutely beautiful. Sunday will be slightly cool with a high of only around 23°C and lead into a chilly night with a low dropping into the single digits bottoming out around 8°C. The heat starts to return on Monday with sunny skies continuing as we climb to a mild 25°C.

The Trend Next Week

Looking further into the week, it looks fairly nice overall as the upper ridge begins rebounding back northwards into the Prairies. Highs will push back into the upper 20’s with humidity staying fairly low until late in the week. Things look fairly dry through the first half of the week, with a few weak disturbances bringing the threat for isolated-to-scattered thunderstorms late in the week. For the most part, though, it looks to be a beautiful, warm week. Summer may be late, but it doesn’t look like it’s going anywhere soon!