Stormy Start to the Long Weekend

The August long weekend will be off to a stormy start today as the threat of severe thunderstorms bears down on the Interlake, Red River Valley and Whiteshell this afternoon.

Tornado near Lake Diefenbaker

One of a couple of tornadoes that the incoming system spawned in Saskatchewan yesterday. Photo by @TheMrsCogs.

A very powerful low pressure, responsible for at least two tornadoes in Saskatchewan yesterday, will move into Southern Manitoba today and push a cold front across the province through the day. Very strong dynamics will accompany this system, a stark contrast from the last few systems which have had comparatively strong thermodynamics instead. Despite the lack of strong thermodynamic parameters that are often looked at when diagnosing severe thunderstorm potential, such as CAPE, EHI or LIs, the strong dynamics will present a significant severe weather threat over south-central and southeast Manitoba.

Dynamics are physical, kinematic properties of the atmosphere, such as jets, shear and lift. Thermodynamics are thermal/energetic properties of the atmosphere such as temperatures, humidity and instability.

A band of showers will push into the western Red River Valley early in the afternoon ahead of the upper low. As the afternoon progresses, the upper low will begin to deepen and enhance the destabilization over the Red River Valley. By mid-to-late afternoon, despite the cool temperatures and cloudy skies, there should be rapid development of storms along the cold front. Tornadoes are unlikely, although not impossible, here in Southern Manitoba; that threat should be relegated to the Dakotas where even greater dynamics and substantially better thermodynamics are present. If any tornadoes do form tomorrow, it’s likely that they will be of the short-lived variety and relatively weak. The greatest threat from today’s storm will be extremely heavy rain giving rapid accumulations of 1-2” (25-50mm) given precipitable water values of 40-50mm and large, damaging hail given the cool temperatures aloft.

Thunderstorm Outlook

Day 1 thunderstorm outlook valid 18Z today through 12Z tomorrow morning.

The storms will exit the province overnight, and we’ll have a brief reprieve from precipitation. On Saturday, some showers will wrap down into the RRV on the back side of this system. Amounts will vary across the region, but in general less than 5mm is expected. Temperatures will struggle to climb to even 20°C; daytime highs of only 18 or 19°C are expected. Winds will be breezy from the NW.

This system will clear out Saturday night before nicer weather builds back in. The second half of the long weekend will see increasingly sunny skies and daytime highs near 25°C.

Warm, Unsettled Weather Continues

Warm weather will continue to dominate Southern Manitoba as we climb into the high 20’s almost every day this week. We’ll continue to see active weather as multiple systems move through the province over the second half of this week.

500mb Wind Field Valid Friday Night

Forecast 500mb wind field with heights depicting powerful upper low entering Southern Manitoba on Friday evening.

July ended up being a very hot month for Winnipeg, with 14 days of the month with daytime highs over 30°C. The month ended with an average temperature (highs and lows both considered) just over 22°C, which is about 2.5°C above the normal average temperature of 19°C. July marked the 13th consecutive month that Winnipeg has seen above-normal temperatures.

July marked the 13th consecutive month that Winnipeg has seen above-normal temperatures.

We’ll see a chance of afternoon thunderstorms across most areas of Southern Manitoba as a weak disturbance rounds the cold trough left behind yesterday’s system that brought a thunderstorm threat to Southern Manitoba. Chances for thunderstorms will be significantly higher through SW MB northwards through the Parkland region while the Red River Valley will see just a chance of thundershowers in the evening as the upper feature passes by. Daytime highs will be near 28°C through the Red River Valley with an overnight low tonight near a comfortable 15°C.

We’ll see a reprieve on Thursday, with no precipitation expected and a high near 28°C again. A powerful upper low will begin pushing across the Western Prairies bringing rain and cooler temperatures tommorow and will be the main weather-maker on Friday for us. Showers and thunderstorms will push into Western Manitoba on Thursday night and slide eastwards across the province through the day on Friday. It’s likey that we’ll see little precipitation on Friday as most of it pushes through the Interlake, however there’s a good chance of showers overnight on the backside of this system. We’ll see a daytime high of 24°C on Friday and a considerably cooler high near 20°C on Saturday.

Conditions will rapidly rebound through the end of the weekend as sunny skies return and temperatures shoot back up to 30°C.

July to End on a Hot Note

July looks to end hot as temperatures remain near thirty degrees for the first two days of the week.

Temperatures will be in the upper twenties or near thirty in Southern Manitoba on Monday

Temperatures will be in the upper twenties or near thirty in Southern Manitoba on Monday

The month of July will end just as it started, very warm. Temperatures on Monday will be in the upper twenties in Southern Manitoba. On Tuesday highs are expected to be around thirty degrees in all of Southern Manitoba. There will be a risk of thunderstorms Tuesday, with Western Manitoba having the greatest chance of seeing a storm.

The first couple days of August are expected to remain hot as well. Highs on Wednesday and Thursday should once again be up near 30C. At this point models are hinting at the potential for a thunderstorm outbreak later this week across parts of the Prairies provinces. At this point it is too early to say how Manitoba might be affected by this upcoming weather system, but it is something to watch.

Pleasant Start to the Weekend

After a few days that threatened storms for the Red River Valley, we’re heading out the other side with most communities seeing little to no rain. Steinbach is a notable exception, with over 100mm of rain falling1 through a rather unusual rainfall event early Wednesday morning which produced significant overland flooding2.

24hr. Precipitation Totals valid Sunday Evening

24 hour accumulated precipitation from Friday Saturday evening to Sunday evening.

A pleasant start to the weekend is ahead, with no chance of showers until Saturday evening and overnight. Today we’ll see mainly sunny skies as our temperatures rebound from yesterday’s system up to a high near 26°C. The overnight low tonight will be around 15°C. Warmer air pushing in aloft will allow temperatures to climb higher on Saturday and Sunday, with daytime highs close to 30°C expected. Humidity will remain relatively low for Saturday, however things may get a little uncomfortable on Sunday as dewpoints begin to climb closer to the 20°C mark.

On Saturday a disturbance entering the province will generate some showers and thunderstorms over SW Manitoba through the late morning and afternoon hours. The (thunder)showers will spread eastwards through the evening and overnight, however it’s currently looking like the bulk of precipitation will occur through the Interlake. The northern half of the Red River Valley looks to have a decent chance of seeing some sort of precipitation, however the odds look very slim that the southern half will see anything.

We’ll see increasing cloud Sunday afternoon as the back side of this system prepares to swing through Sunday night. As it does, there will again be a chance of showers for Winnipeg and, as it looks now, the eastern RRV. We’ll be sure to provide updates in the comments as this system approaches.

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