Unsettled Ride Towards Summer Temperatures

Winnipeg is set to see summer-like heat slowly build into the region over the coming week, however the unsettled weather brought about by the zonal flow that’s been in place over the past several days will continue doing its thing for another few days yet before more stable conditions build into Manitoba.

Today will be a similar day to yesterday with daytime highs in the low 20’s through the Red River Valley and fairly light winds. Dew point values are expected to climb to around 16 or 17°C today, which when combined with a bit of daytime heating will provide some fuel for scattered thunderstorm mid-day through the afternoon. Applying the MIST principles:

• Moisture: As mentioned, dew point values are expected to rise to around 16 or 17°C thanks to some pooling along a weak trough through the region coupled with an easterly to southeasterly flow tapping into higher dew points to the southeast.
• Instability: Moderate mid-level instability will be in place thanks to a shortwave moving through the region. CAPE values, driven largely by the favourable thermodynamics in place, will be in the 1000–1500 J/kg range.
• Shear: Bulk shear of 25–35 kt will be marginally supportive of organized thunderstorms. Directional profiles will be somewhat anomalous, with easterly low-level winds backing to the northwest/west thanks to the approach of an inverted trough. End result is that, particularly through western Manitoba, storm motion will likely be quite slow, making rainfall accumulations a potential hazard with today’s storms.
• Trigger: This may be the weakest aspect of today’s storms. A very weak frontal trough will be in place, alongside a weak upper-level shortwave and impinging inverted trough. Lack of any strong focus will likely be biggest inhibitor to widespread storm organization and will diminish the severe storm potential for the day.

With those factors taken into account, we’ll likely see scattered thunderstorms across much of Southern Manitoba today, however the threat for severe thunderstorms will be quite low with just an isolated marginal severe storm risk. The exception to the rule will be in the southwest portion of the province closer to the inverted trough. Shear profiles have strongly backed surface winds with a backing profile, making slow-moving storms more likely there. With adequate bulk shear to support & ventilate the storms, heavy rainfall is a heightened risk in that area due to slower storm motion.

That said, we’ll see mixed skies today alongside our chance for thunderstorms. Expect the storms to taper off this evening as we head to a low near 13°C.

Thursday will be off to an unsettled start as another disturbance rolls through the region and brings a chance for showers or thunderstorms through the morning hours. After that, we should see some clearing skies as the temperature heads on its way to a high in the mid–20’s. Expect clear skies Thursday night with a low near 14 or 15°C.

Friday looks gorgeous with sunny skies and a high near 27°C. Mainly clear skies should prevail Friday night with a low 12°C.

A Look Ahead to the Weekend

The weekend is looking like a bit of a mixed bag. The warmth will continue to build into the Prairies, particularly in the Western Prairies as the upper ridge begins building in. Here, Saturday looks potentially wet with the possibility of a low pressure system riding down the upper ridge through Southern Manitoba which would bring another batch of rain to the region. Sunday looks nice by all accounts with a fair amount of sun and highs climbing into the upper 20’s!

This week will start out with near seasonal temperatures, but somewhat unsettled conditions. Temperatures will be in the mid twenties, but there will be a frequent risk of rain or thunderstorms.

Monday

Today will start out rainy as upper disturbance produces precipitation over much of southern Manitoba. The rain should clear out of most of the province by the afternoon, except perhaps far eastern sections, leading to a breezy, but relatively pleasant evening. Wind will be north-west at 30 km/h gusting to 60 km/h.

Tuesday

Tuesday will be a mixture of sun and cloud with risk of thunderstorms during the afternoon and evening. Daytime heating will generate an unstable atmosphere across southern Manitoba, prompting storms to develop by the afternoon. These storms should be generally non-severe, although an occasionally severe storm with hail to nickel size may be possible.

Wednesday

It appears that Wednesday will be mainly cloudy with a risk of thunderstorms once again. Unlike Tuesday, storms are Wednesday should be almost exclusively non-severe due to very weak wind shear. There may be issues with heavy rain however, as storms will be slow-moving.

Long Range

The long range forecast looks general near seasonal for southern Manitoba. We will generally remain under the primary upper jet stream, meaning frequent chances for storms and/or precipitation.

Showers and thunderstorms will once again make their return to Winnipeg & the Red River Valley for the next few days…with a catch. Despite the unsettled weather, it might end up actually being fairly pleasant this weekend for the most part!

Today will be a bit of a mixed bag with some cloudy periods and a high near 21°C. Winds will pick out out of the south to around 30km/h or so through the day.

The first of two systems that will be affecting Winnipeg & the Red River Valley today will be a convective complex lifting northeastwards out of North Dakota. It will spread cloud and a chance through southeastern Manitoba, with just a slight chance of some midday showers in Winnipeg.

The second system that will bring a risk of showers or thunderstorms to Winnipeg is a trough of low pressure that will move into our region tonight from Saskatchewan. There still exists quite a bit of uncertainty as to whether or not any precipitation will push into the Red River Valley tonight; in general, confidence is much higher over eastern Saskatchewan and southwestern Manitoba, where a significant threat for severe thunderstorms exists today.

The most likely outcome at this point is that much of the convection heading towards the Red River Valley will either taper off or dive south into North Dakota where a severe convective event called a bow echo seems probable. There is a slight chance that we’ll see some thunderstorm activity in the Red River Valley overnight, but it doesn’t appear that it would be severe.

Saturday looks like a fairly pleasant day with mixed skies about and a high near 22 or 23°C. There will be a chance for showers late in the day into the evening hours, but in general the activity isn’t expected to be very widespread over the Red River Valley. The temperature looks to drop into the low teens on Saturday night.

The threat for thunderstorms returns to the Red River Valley on Sunday afternoon as another disturbance moves through the region. Temperatures will once again top out in the low 20’s with overnight lows dropping into the low teens.

Father’s Day Forecast Update

Father’s Day

25°C / 15°C

Mainly sunny

Weather will be generally pleasant for Southern Manitoba this Father’s Day with generally sunny skies and high temperatures in the mid-20’s with fairly light winds. This is excellent news for the Manitoba Marathon; today will be a far nicer day to run than last year’s less than pleasant weather. The only exception will be in areas along a line from Swan River east-southeastwards across the Interlake towards Berens River where some pop-up showers and thunderstorms are possible this afternoon.

An more organized thunderstorm threat will develop through the day, however, beginning early-to-mid-afternoon in Saskatchewan and then progressing eastwards through southwest Manitoba this evening and through the Red River Valley overnight. Thunderstorms are expected to develop in the Regina area southwards towards the American border; these storms will be developing in an area with marginal energetics, however very favourable shear profiles will likely result in scattered thunderstorms with isolated supercell thunderstorms. As they track eastwards, a southerly low-level jet will intensify, supporting upscale growth of the convective complex as it heads into the evening.

I expect that early in the evening, the thunderstorms will have developed into a line of showers and thunderstorms heading eastwards into Southern Manitoba. In general, the severe threat in Manitoba is expected to be minimal, except for areas near the U.S. border. There is a chance that as the storms push eastwards, supported by a 50-60kt westerly jet at 500mb and running just north of a warm front in North Dakota, that the storms develop bowing segments. Bowing segments are when the thunderstorms produce strong winds that, quite literally, push part of the storm forward, making a ) shape on RADAR imagery.

Primarily for that reason, I’ve carried a slight risk for the overnight period along the US border into the Red River Valley; I’m generally expecting the worst weather to dive into North Dakota fairly early, but there’s a slight chance some of the winds end up remaining on the Manitoba side. For the remainder of the general area through southwest Manitoba into the Red River Valley, non-severe nocturnal thunderstorms are possible through the evening/overnight period.