Weather Forecasts, Facts and News for Winnipeg & Southern Manitoba
Author: Brad
Brad lives in Winnipeg with his wife and two children and is the founder of A Weather Moment. He has loved weather from a very young age and has followed that passion through his life so far. He received a B.Sc. in Earth Sciences with Specialization in Atmospheric Sciences and is currently employed in the field of meteorology. You can find the author as WeatherInThePeg on Mastodon.
Temperatures will be returning to more summer-like values through the second half of this week thanks to an upper-level ridge that will push out the cold air drawn southwards behind this past weekend’s big storm and allow more heat to begin building into the region.
The coming two days will be gorgeous with plenty of sunshine, light winds and warm temperatures. Today will see daytime highs near 26 or 27°C while Thursday will bring highs a degree or two warmer. Overnight lows both nights will be near 12°C. The most significant weather feature will be the significant amounts of smoke that will be pushing into the region sourced from wildfires raging in the northwestern United States. At this point, it seems like it should mainly be aloft and not pose much of an air quality issue.
The NAM is showing large values of CAPE (energy) and shear on Friday afternoon which suggests the potential for severe thunderstorms.
Friday will see a low pressure system moving through the region, bringing warmer temperatures alongside a thunderstorm threat. The major question mark, at this point, appears to be whether or not any smoke in the region inhibits temperatures from climbing high enough to trigger thunderstorms or not. That said, it looks like the potential will be in place for severe thunderstorms with over 3000 J/kg of CAPE expected and over 50 kt of bulk shear in place.
We’ll be taking a closer look at the severe thunderstorm potential on Friday morning in the next blog post, but for now, just keep aware that the threat for severe weather may return to the Red River Valley on Friday.
Other than the storm potential, daytime highs should sit near 30°C with mixed skies. There’s also a reasonable chance that it will be quite humid, making it feel more like the upper 30’s.
Heading through the weekend, it looks like Winnipeg & the Red River Valley will see highs near 30°C with plenty of sunshine, making up for the miserable weather during the last weekend. Other than the blip on Friday, there’s plenty of warm, dry and sunny weather ahead, so enjoy!
A wild rollercoaster of weather conditions begins today as a fairly potent weather system develops today, rocketing temperatures close to the 30°C mark before things take a turn for the worse as a stormy transition sends daytime highs struggling into the low teens by the end of the weekend.
Friday: Another Beautiful Summer Day, Stormy End?
Today will be a gorgeous day as warm air surging northwards ahead of a developing low pressure system in the Northern Plains of the United States. Temperatures will climb into the upper 20’s this afternoon under fairly sunny skies. Some cloud cover will start working into the region in the afternoon alongside a slight chance of showers as a weak mid-level disturbance rolls through. In the evening, a low-level jet (LLJ) begins to intensify as the low pressure system deepens and brings more lift into the region, spreading more cloud into the region.
The RDPS is showing a warm front at 850mb just north of Winnipeg near midnight tonight. The LLJ is represented by the blue arrows and will be the trigger for thunderstorm activity tonight.
A round of thunderstorms is possible tonight along the nose of the LLJ. The risk is somewhat conditional, dependent exactly how how much moisture is advected northwards within the LLJ. Assuming enough moisture is present to realize the instability, we head to MIST:
Moisture: This will be the most uncertain aspect of tonight’s thunderstorm potential. Dewpoints at 850mb are forecast to be around 10°C, which should be enough to realize the elevated instability, however it’s a farily narrow ribbon, and if amounts are lacking a bit, convective initiation will struggle.
Instability: Fairly strong instability aloft will be present. Models suggest mid-level (700 – 500mb) lapse rates of 7–8°C/km this evening, which would be considered quite strong. If the expected moisture builds into the region, MUCAPE values of around 1000 J/kg should be realized.
Shear: The overall shear looks great, with widespread bulk shear values of 40–50kt expected over the Red River Valley this evening. The high bulk shear values are produced through a combination of strong velocity shear through the vertical coupled with large, looping hodographs indicative of favourable directional shear.
Trigger: Isentropic ascent of the LLJ as it overruns a warm front draped west-to-east along the international border coupled with falling heights ahead of the incoming upper-level low should provide a strong enough trigger to initiate convective activity.
All this combined means that there’s a fairly good chance of some thunderstorm activity through the Red River Valley this evening. It likely won’t be severe; I think the higher threat for severe storms activity will be more in southwestern Manitoba where things will initiate earlier and rooted closer to the warm front. That said, it certainly can’t be ruled out that there may be a rouge severe thunderstorm cell through the evening into the first half of the overnight period. Expect a low temperature near 17°C.
Mixed Bag On Saturday
There remains some uncertainty as to how Saturday will play out, but it seems quite probable that we’ll see some shower or thunderstorm activity through the day. There may be a few sunny breaks, but it should be cloudier than not through much of the day. If any rain manages to hold off until later in day, marginally severe thunderstorms could be possible in the Red River Valley, however it would be dependent on how much heating occurs (read: how sunny it manages to be). Even with decent heating shear looks marginal which will provide a barrier to significant thunderstorm development.
This comes with a caveat, however, as the forecast will be dependant on the timing of the cold frontal passage. With current best indications, there will be a slight risk of severe thunderstorms to the east of the Red River Valley on Saturday afternoon, however if the front slows down a little, that threat could shift westwards into the Red River Valley. We’ll take a closer look at it in an update tonight or tomorrow morning.
That said, temperatures will top out around 25°C with fairly light winds.
Saturday night will see the Red River Valley on the back side of the low and behind the cold front; colder air will begin pushing in alongside strengthening northerly winds. Expect a low near 13°C.
Miserable Sunday
Sunday will be a miserable day by any standard. Very cold air over the region—850mb temperatures are forecast to be a chilly 0–2°C—will keep our daytime highs to just the low teens. Very strong northerly winds will be in place over the region; sustained winds will likely reach 50–60km/h with gusts reaching as high as 80km/h or so. On top of all that, wrap-around precipitation will work it’s way across the Red River Valley, bringing more rain and/or showers to the region.
The NAM is forecasting 850mb temperatures of 0-2°C and very strong northerly winds over the Red River Vallye on Sunday. Miserable.
To top it off, with lake temperatures near 21°C and 850mb temperatures forecast to be near 0°C, lake-effect or lake-enhanced rain/drizzle is probable in the lee of the lakes, persisting possibly into Monday morning.
The low temperature on Sunday night will be around 6 or 7°C.
Hopeful in the Long Range
The good news is that the long-range forecast looks good. Rather quickly behind the passage of this low, a broad upper-level ridge is forecast to begin building back into the Prairies. This will bring significantly warmer weather back to the region. Considering it’s still August and we’re talking about daytime highs in the low teens, a quick bounce back into the mid- to upper–20’s for daytime highs will be much appreciated.
Benign weather will continue over the Red River Valley for the next few days as a weak ridge of high pressure remains entrenched over the region until Friday. Heading into the weekend, however, it looks like rain may be possible as a low pressure system moves into the region through the day.
There isn’t a whole lot to say regarding the coming days, so I’ll keep this post fairly brief! The weather for today and tomorrow will be largely dictated by a weak ridge of high pressure over the region that’s more a result of larger low pressure systems to our west and east than being particularly potent in and of itself.
Today will see temperatures climb to around 23°C with breezy winds building out of the north to 30–40km/h thanks to a low pressure system passing to our east. The day will start overcast with some mid- to high-level cloud that will gradually clear out through the day. Winds will taper off this evening as low temperatures head to around 9°C.
Thursday will be mainly sunny day with light winds and a high near 25°C. Expect a low near 13°C on Thursday night.
The GDPS is showing a low pressure system moving through Southern Manitboa on Friday night capable of bringing some rain to the Red River Valley.
Friday will see increasing cloudiness, particularly in the afternoon as a low pressure system begins working into the region. Temperatures will climb to around 25°C. Friday night will likely bring some rain, although specifics are still quite fuzzy. Temperatures will dip back down to around 13°C again.
Mixed Weekend
This weekend looks mixed at this point, with slightly cooler, cloudier weather on Saturday with a chance of showers and sunnier conditions on Sunday. There’s quite a bit of uncertainty with Friday night/Saturday’s low pressure system, so it’s a bit early to make much in the way of concrete forecasts. High temperatures will likely be in the low 20’s with a chance of warmer weather returning for the beginning of next week.
The heat wave across Southern Manitoba will continue through today and tomorrow as even more warmth and humidity build into the region. Significantly cooler air will move into the area on Sunday, behind a cold front passage on Saturday that will bring another round of potentially severe weather to the province.
Friday: Hot With Increasing Humidity
Today will be a hot day with increasing humidity as a deep southerly flow develops ahead of a deepening low pressure system ejecting northeastwards out of Montana. Temperatures will climb into the low 30’s with high temperatures reaching around 32 or 33°C this afternoon. Winds will also pick up out of the south to around 40km/h with gustiness on top of that. The humidity will be less than some days of late, but still fairly moderate with dew point values in the 18–20°C range. This will make it feel more like more like 37–40.
Some afternoon clouds will be about associated with the low pressure system lifting NE out of Montana. No precipitation is expected, though.[1] We’ll have a very mild low temperature tonight of 21 or 22°C.
Cold Front Brings Severe Weather Threat for Saturday
Saturday’s weather story will be dominated by a cold front pushing eastwards across the Red River Valley. The southerly winds combined with pooling ahead of the cold front will make for very humid conditions with dew point values climbing to 23–24°C. With a high temperature near 33°C, it will feel more like the low 40’s and make for very uncomfortable conditions. As the cold front pushes eastwards, showers and/or thunderstorms are quite likely.
A moderate risk of severe thunderstorms exists through much of the Interlake, Red River Valley, and Whiteshell regions of Southern Manitoba on Saturday.
There are two possible outcomes for Saturday’s setup:
Nocturnal advection develops in the Northern Plains of the United States and pushes northeastwards. Scattered showers and thunderstorms persist over the Red River Valley through much of the day before clearing out with the cold front.
No or very little precipitation develops Friday night, leaving things dry and sunnier for Saturday. Severe thunderstorms would then be possible in the afternoon along the cold front.
At this point, it appears as if option 2 is the more plausible one. As always, looking at the MIST principles of thunderstorm development:
Moisture: Abundant. A deep layer of dew points ≥ 20°C will be in place over the Red River Valley, resulting in tremendous amounts of fuel for thunderstorms.
Instability: High. While the environment will be capped much of the day, significant instability will be in place through the mid- and upper-levels of the atmosphere. Steep mid-level lapse rates coupled with the high surface moisture will produce SBCAPE values in excess of 4000 J/kg and MLCAPE values of 3000–4000 J/kg.
Shear: More than enough. In general, a 40kt jet at 500mb over the region will combine with surface winds out of the south at 10–15kt to create around 25–35kt of 0–6km bulk shear. Hodographs show strong curvature, indicating likely supercell storm mode.
Trigger: The strong cold front pushing eastwards will provide focus for convection. While the capping inversion will hold surface-based convection back, the forcing from the frontal feature should be sufficient to initiate convection. 35–40kt southwesterly low-level jet may combine with steep mid-level lapse rates to produce elevated convection.
Given the extreme instability in place over the region (even elevated convection would have 1500+ J/kg of energy to work with), severe thunderstorms would be possible with either mode of convection. With the extremely high dew points in place, any thunderstorms that develop will be capable of torrential rainfall. Strong winds and large hail will be significant threats with any thunderstorms that develop. The threat of tornadoes cannot be ignored either; with strongly curved hodographs and such enormous amounts of energy, any supercell thunderstorms that develop would be capable of producing a tornado. The highest probability would be relatively close to the low pressure centre where the surface winds will be backed slightly more.
Saturday Severe Weather Update
Everything appears to be on track regarding today’s severe weather potential. There is a moderate risk of severe thunderstorms through much of the Red River Valley, Interlake and areas eastwards to the Ontario border. This includes large swaths of popular beaches & cottage country.
AWM Day 1 Convective Outlook for August 15, 2015
For the most part, all the expected conditions continue to pan out. Some elevated convection has developed overnight, however it doesn’t look like it will inhibit surface heating through the Red River Valley very much today. Very warm daytime highs in the low 30’s combined with dewpoint values in the 22-24°C range will combine to produce MLCAPE values of 2000-2500 J/kg and SBCAPE values exceeding 3000 J/kg. Combined with over 30 kt of 0-6km bulk shear and looping hodographs, there is sufficient energetics, dynamics and shear vectors to support strong supercell thunderstorms. Throughout the entire slight risk region, there will be a risk for large hail, strong winds and torrential downpours. Further north, in the moderate risk area, surface winds will be backed slightly more as the surface low pressure system continues moving northeastwards. Additionally, areas slightly further north will be closer to the upper-level jet and see enhanced 0-6km shear values. As such, any thunderstorms that develop in this region will pose a tornado threat, with the possibility of the production of a significant tornado today.
A strong cap in place will keep surface-based convection from triggering until late in the day as a trough pushes eastwards into the Red River Valley. Discrete supercell thunderstorms will likely develop between 4 and 6PM and then push east-northeastwards. As the line of thunderstorms pushes eastwards, upscale growth is likely as the system evolves into an MCS capable of all modes of severe weather.
Sunday will bring partly cloudy skies on the back-side of the low as it departs Manitoba. Significantly cooler weather will be in place with daytime highs of just 23°C expected. There may be a slight chance of some light, isolated showers, but the threat looks minimal at this point. Temperatures will dip to around 12°C on Sunday night.
Next Week? Quick Rebound
Taking a quick peek at next week, it appears that the cool down will be short-lived as significantly warmer air begins pushing back into the region mid-week. Alongside the warmer temperatures will come the potential for more unsettled, stormy weather.
A few showers may drift towards the Red River Valley from the NW this morning, however they should dissipate before it reaches our region. ↩
