Tag: Thunderstorms

Warm With A Chance of Thunderstorms, Then Turning Drier

Brad Leave a comment

The weather returns to slightly warmer than normal summer fare for Winnipeg to start the week with highs in the upper 20’s and mild lows. It will also be relatively dry, with the only significant chance for rain coming on Monday night as a cold front slowly moves through the Red River Valley.

Today will be a warm and windy day in Winnipeg as breezy southerlies bring summer heat and slightly muggy conditions to the Red River Valley. Skies will become mixed fairly early in the morning as the south-to-southeasterly winds ramp up to 30-40 km/h. These gusty southerly winds will bring mild temperatures into the region, pushing daytime highs just short of 30°C. In addition to the warmth, these winds will maintain the slightly humid conditions in place with dew points remaining in the 16-18°C range. Closer to the cold front — primarily over the southwestern corner of the province but also possibly into the western Red River Valley — moisture will pool and dew points will likely rise into the low 20’s, making for quite a muggy day in those areas.

A potent low pressure system over western Saskatchewan will spread gusty southerly winds across the Red River Valley on Monday afternoon.

By evening, a cold front will be pushing eastwards into the Red River Valley, bringing with it a chance of showers or thunderstorms to much of southern Manitoba.

Going over the MIST ingredients:

  • Moisture: Dew points will climb generally into the mid-teens, but elevated moisture is expected near the cold front as moderate southerly winds enhance moisture pooling ahead of the front. Moisture is also expected to be moderately deep, extending to roughly 850 mb.
  • Instability: Moderate mid-level lapse rates on the order of 7-8°C/km will combine with the low-level moisture to produce MLCAPE values of 1500-2000 J/kg.
  • Shear: Shear will be somewhat lacking with only 25-30 kt of 0-6 km bulk shear; this is fairly low and may be the real limiting factor in any thunderstorm activity that may develop.
  • Trigger: A pronounced cold frontal trough moving eastwards will provide the focus for any convective development.

Overall it seems that there will be enough energy available for severe thunderstorms, but the lack of shear will throw a wrench into the certainty of a large-scale severe weather outbreak.

The highest risk for severe weather in southern Manitoba will be over the southwestern corner where scattered thunderstorms first fire up along the cold front. These storms will have the potential to produce significant hail and strong winds. While an isolated tornado is possible, it won’t be an elevated threat with today’s thunderstorms. As the cold front moves eastwards through the evening and spreads the thunderstorm threat into the Red River Valley, the threat shifts towards favouring strong winds. Temperatures will bottom out overnight around 18-19°C with the winds tapering off.

This simulated RADAR image from the 3km NAM model shows a forecast of thunderstorms for the Red River Valley on Monday evening.

The weather then settles for Tuesday and Wednesday as a broad ridge of high pressure builds into the Prairies. Skies will clear and remain mainly sunny for much of Tuesday and Wednesday as temperatures climb to highs near 27°C both days. It will remain slightly humid with dew points remaining in the mid-teens through the middle of the week. With that humidity remaining in the region, it will keep overnight lows in the mid-teens as well.

Long Range

Gradual upper-level ridging will build into the Prairies late this week and into early next week, bringing continued mild weather and low probabilities of rain. The odd system may slide across southern Manitoba from the northwest, returning temperatures back to seasonal alongside a chance of showers. Overall, though, it appears Winnipeg and the Red River Valley will be entering into a fairly dry pattern.

Winnipeg’s seasonal daytime high is currently 26°C while the seasonal overnight low is 13°C.

Warm with Risks of Thunderstorms

Brad 3 Comments

The second half of the work week will bring warm weather to Winnipeg with several chances for showers or thunderstorms.

Winnipeg will see a slight chance of a thunderstorm today as a weak disturbance rolls through the region. While this morning will bring some sunshine, conditions will cloud up midday with a chance of showers or thunderstorms throughout the afternoon. It will be relatively mild despite the cloudier afternoon conditions, though, with daytime highs reaching around 25°C. Winds will pick up out of the south this morning to around 30 gusting 50 km/h. Expect skies to clear out this evening as winds taper off and temperatures head to a low near 15°C.

Thursday will bring mainly sunny skies and warm temperatures as daytime highs climb to 29 or 30°C. Winds will be fairly light, making for a wonderful summer day. A disturbance moving through on Thursday evening will spread cloud into southern Manitoba and bring a chance of showers or thunderstorms overnight into early Friday morning. Temperatures will dip to a low near 17°C.

Despite the chances for rain today through Friday afternoon, some models manage to keep it outside Winnipeg.

Friday will be another warm day with highs around 29°C. An incoming low pressure system will begin spreading cloud into the region midday. By late-afternoon, skies should cloud up completely and yet another chance for showers or thunderstorms move into the region for Friday evening and overnight. Temperatures will dip to a low near 18°C.

Despite several chances for rain, overall there are no strong signals that it will affect a widespread area. As we show in the image above, some forecast models produce essentially no rainfall for Winnipeg. The one thing that can be said with some confidence? Areas closer to the international border have a higher chance of seeing something.

Long Range

The weather this weekend will largely be shaped by a low-moving low pressure system that will track across the province from northwest to southeast. Saturday will bring a chance of showers with risk of a thunderstorm to Winnipeg, which will then looks to transition into a chance of showers overnight into Sunday. High temperatures will likely be slightly below normal with highs in the lower 20’s, but overnight lows will be near-seasonal at around 13 or 14°C.

Winnipeg’s seasonal daytime high is currently 26°C while the seasonal overnight low is 13°C.

Generally Mixed Weather Ahead

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Winnipeg will see a little bit of everything over the next few days as warm and humid conditions are replaced by a northwest wind that ushers in slightly cooler and much drier air. Winnipeg will also see several chances for thunderstorms this week.

This morning will start off cloudy with the chance of a thunderstorm for Winnipeg & much of the Red River Valley as elevated convection that developed overnight moves through the region. Behind the morning convection, temperatures will climb to a high near 28 or 29°C with winds of 15-25 km/h out of the northwest. It’ll get rather humid this morning with dew points climbing up to around the 18°C mark before drier air works in from the northwest for the afternoon. Skies will break up somewhat for the afternoon and then clear out in the late afternoon or evening. Temperatures will head to a low near 14°C under clear skies tonight.

Slightly cooler weather will be in place over Southern Manitoba on Tuesday

A ridge of high pressure will move across the province on Tuesday, bringing slightly cooler temperatures and mainly sunny skies for Winnipeg. A disturbance moving through North Dakota may spread cloud cover across the southern Red River Valley, but there’s still a bit of uncertainty about that. Temperatures will be just a touch below-seasonal for the latter half of June with a high near 25°C, but winds will be light, so it’ll feel like a pretty nice summer day. Temperatures will dip to a low near 13°C on Tuesday night under clear skies.

Wednesday will bring the next chance for thunderstorms to the province as a warm front moves in. It’s expected that elevated convection will from ahead of the warm front on Tuesday night in Saskatchewan, and then spread across southwest Manitoba overnight and into the Red River Valley on Wednesday morning.

The general consensus is that thunderstorm activity that develops on Tuesday night will move across the Red River Valley on Wednesday.

In these situations, there’s almost always a significant amount of uncertainty, so we’ll definitely be keeping an eye on how things develop. The end result will be a “cloudy with sunny breaks” kind of day with a high near 25°C once again. Winds will be fairly light. Skies will clear by evening & temperatures will be on the way to a low near 15°C.

Long Range

The remainder of the week looks continue the pattern. Temperatures will edge up a few degrees for Thursday and Friday, but it appears that things will turn increasingly unsettled Thursday night into Friday morning, and Friday night into Saturday.

Extended forecasts hint that we may see a stretch of warm, dry weather beginning Sunday, but that’s been advertised more than once this summer and vanished like dust in the wind, so we’ll hold off on promising that.

So…pleasant overall, but still no sign of that big hot, dry summer stretch.

Winnipeg’s seasonal daytime high is currently 26°C while the seasonal overnight low is 13°C.

Severe Thunderstorm Threat Leads Into Beautiful Weekend

Brad Leave a comment

The threat for severe thunderstorms exists today across the Red River Valley as a cold front pushing in from the northwest clashes with a hot and increasingly humid air mass. Once the cold front moves through, conditions will settle with a fantastic weekend ahead.

Today will see temperatures soaring across the Red River Valley as a southerly wind strengthening to 30 gusting 50 km/h brings in hot, humid conditions. Temperatures will climb to a high near 30 or 31°C in Winnipeg and the Red River Valley today with a comfortable morning quickly turning muggy as dew points climb up to the 19-20°C mark by late afternoon. The heat and humidity together will combine to make it feel more like the mid- to upper-thirties, so be sure to minimize prolonged exposure to the heat and stay hydrated.

A cold front will push southeastwards across the Red River Valley this afternoon. This is the estimated location of the frontal wave at 7PM tonight.

A cold front will slump through the Red River Valley late this afternoon, and as it does so there will be the threat for severe thunderstorms. With MLCAPE1 values climbing up to 2000 J/kg and 45-50 kt of deep shear2, the potential for explosive thunderstorm development exists. The biggest questions that need to be answered are:3

  1. Does nocturnal convection develop Thursday night, producing more cloud cover and delaying heating over the Red River Valley and/or eat up some of the instability over the region?
  2. What exactly is the expected strength of the capping inversion and will it be strong enough to prevent any thunderstorms from developing?

The first question we’ll know the answer to by the time you read this. If there is some thunderstorm activity overnight, it doesn’t necessarily rule out thunderstorms later today, just makes it more dependent on the clouds clearing out in time to get enough heating. The second question is much more difficult to answer, and we’ll just have to see how things go. If there happens to be an intermediate sounding available from Winnipeg later today, that should give a much better idea of how much of a thunderstorm threat there is.

As shown in yesterday’s Day 2 Thunderstorm Outlook, ECCC is forecasting a threat of severe thunderstorms over the region today.

That said, if thunderstorms do develop, which I think is likely, they will be bad. All hazards will be possible with these storms: large hail, damaging winds, torrential rainfall, and tornadoes. Rain may be the least of the concerns as the storms will be moving fairly quickly to the southeast at around 40 km/h. Tornadoes will be a threat with these storms, so make sure you stay aware of any severe thunderstorm or tornado watches and/or warnings issued by Environment Canada. The best chance for thunderstorms will be between 6PM and 11PM.

Rest of the Weekend

One the cold front passes, winds will switch around to the northwest and Winnipeg will be set for a great weekend. Saturday will see a high near 25°C with a bit of morning cloud clearing out for the afternoon. The humidity will flush out through the day, making for quite a comfortable afternoon. Temperatures will drop to a low near 12°C on Saturday night. Sunday will bring partly cloudy skies to the region with temperatures climbing back up to a high near 28°C with southerly winds increasing to 20-30 km/h. A disturbance looks set to move through on Sunday night which would bring the chance for some showers or thunderstorms and a return of the humid conditions for Monday. Expect a mild low near just 18°C on Sunday night.

Long Range

The beginning of next week looks hot and humid once again, but then temperatures return to near-seasonal values. It looks like there will be occasional chances for showers or thunderstorms through the week.

Winnipeg’s seasonal daytime high is currently 26°C while the seasonal overnight low is 13°C.

  1. MLCAPE stands for “Mixed Layer” CAPE and is an estimate of the amount of energy a thunderstorm has to work with. ↩
  2. Deep shear refers to how the winds change with height between the surface and 6km up. Under 20 kt would be considered very low, while in excess of 50 kt is extremely high. ↩
  3. And to note, I’m writing this late Thursday evening… ↩