We’ll see more summer-like weather this week in Winnipeg and across the Red River Valley as it continues to feel more like July than the beginning of September.
A shortwave trough (white dashed line) will pass through southern Manitoba on Monday, bringing clouds and a risk of thunderstorms.
Monday
Today will start out mainly cloudy as a potent upper disturbance moves through southern Manitoba. This disturbance may trigger some thunderstorms early on Monday morning, some of which could impact Winnipeg and the Red River Valley. Once the disturbance moves through, skies should clear, likely at some point in the afternoon. Temperatures will be in the mid to upper twenties with the wind becoming westerly due to the passage of this system.
Tuesday
Tuesday will be a nice day, as temperatures climb into the upper twenties under mainly sunny skies. Winds will be relatively light and from the south. No precipitation is expected on Tuesday, although some storms may develop overnight into Wednesday.
Wednesday
Like Monday, we may see some morning thunderstorms on Wednesday. A strong push of moisture from the south may help to trigger these storms. Should storms develop, they could be severe, but this forecast is still a few days away, so it could change. Besides the risk of storms, Wednesday will be hot and humid, with temperatures near 30C and breezy south winds.
Long Range
The long range forecast shows us cooling down after this week. Once a strong system passes through on Thursday temperatures will drop down to more seasonal values near 20C. Enjoy this little blast of heat while it lasts, it could be one of our last warm spells this year!
Yet another tropical disturbance has developed over the Atlantic this week thanks to another mid-level wave traversing off the coast of Africa westwards over the Atlantic. It’s currently impacting the Dominican Republic and is forecast to head west-northwest towards the southeastern United States.
Erika, which formed near the Cape Verde Islands, was centered near the southwest corner of the Dominican Republic as of Friday night bearing sustained winds of 75km/h and a rather unimpressive pressure of 1000mb. The tropical disturbance has struggled mightily at getting even somewhat organized over ocean waters; dry air and strong shear were both contributing factors to this. Erika is expected to continue experiencing problems organizing in the near future due to the strong wind shear in place, as well as a new concern – the rugged islands of Hispaniola.
IR satellite image of Erika on Friday night. Erika looks rather disorganized due to relatively strong shear present, but could still bring heavy rainfall to some Caribbean Islands. (Source: NHC)
The heavy rains that accompany this tropical disturbance are not to be underestimated, however. Heavy rainfall in the order of 100mm to 150mm, as high as 250mm locally, is expected to fall across both the Dominican Republic and its neighbouring country, Haiti. There have already been 20 confirmed deaths associated with Erika from the island of Dominica (located in the Lesser Antilles), and three dozen more residents are still missing. In consequence, this tropical storm has been the deadliest natural disaster for the country since 1979.
The future of Erika remains uncertain at this point. Most models show Erika as weakening over the Caribbean islands (due to the shear/terrain problems discussed), then emerging over waters off of the western coast of Florida as a weak tropical storm. Overall, it’s unlikely that Erika will become anything more than a tropical storm that is just a rain-maker for southeast US.
In other news, it had been the year of the hurricane in the Eastern Pacific near the Hawaiian Islands. Several hurricanes have brushed by Hawaii already this year – an unusual occurrence. Yet another is on its way in the coming week. Hurricane Ignacio (category one) is expected to pass close to Hawaii. What remains to be seen is how close – Hawaii can at least expect high surf and heavy rainfall from the outer bands of Ignacio on Monday, but there is still some uncertainty on strength of the winds which depends on how close Ignacio comes. Another hurricane in the Eastern Pacific is churning; Jimena, is a high-end category four but is not expected to have any impact to land in the near future.
Notably warm and humid weather in place over Southern Manitoba today will bring a threat for severe thunderstorm activity across the region as a shortwave trundles through. An upper-level ridge will then begin to rebound back into the Southern Prairies in response to a digging trough off the western coast of North America, bringing even warmer air into the region thanks to the resultant southwesterly flow aloft that will develop.
Friday: Thunderstorms Possible Midday
A weak mid-level shortwave trundling across the region will bring a risk of thunderstorms to Winnipeg & the Red River Valley today[1] as warm and humid weather meets the colder air associated with the shortwave. As always, using our MIST principles:
Moisture: Adequate. Moderate moisture will be in place both at the surface and through the lower levels of the atmosphere as deep-layer moisture continues to build into the region.
Instability: Favourable. With both thunderstorm possibilities, both elevated and surface-based, enough instability will be in place. Surface-based convection would have greater potential to be severe, however it will rely on strong surface heating with mainly sunny skies until the shortwave arrives, which could be in question depending on what sort of nocturnal convection develops.[2] If it does end up cloudy, strong mid-level lapse rates associated with the shortwave should be enough to sustain showers or thunderstorms as it heads eastwards. All said, storms should have around 1000–2000J/kg of CAPE to work with, depending on their exact timing and where they’re based.
Shear looks quite good with around 35kt of 0–6km bulk shear and gently looping hodographs. Low-level winds are weak enough that tornado activity doesn’t look like a particular threat, but the directional shear is favourable for the organization of supercell thunderstorms.
Trigger: The shortwave moving through coupled with a weak surface trough will provide the convergence and trigger for convective initiation.
A slight risk of severe thunderstorms exists in the Red River Valley and southeastern Manitoba today.
All things considered, it’s likely that we’ll see some activity at some point today. The primary threats with today’s thunderstorms will be large hail and strong winds. Storm motions will generally be towards the southeast. Later in the day, a more organized heavy rainfall threat may develop with any storms still ongoing.
Those things aside, it will be quite a nice day. Temperatures will climb to around 28 or 29°C with a few clouds through the day. The humidity will begin to be more noticeable as dewpoints climb into the high teens by the afternoon ahead of the weak surface trough/low moving through. Winds will remain light.
Things clear out tonight with the humidity remaining in place and temperatures dipping down to about 17°C.
Hot & Humid Weekend Ahead
Temperatures will soar this weekend as warmer air moves into the region and sends daytime highs to 30°C or higher. Saturday will be a sunny day with a high around 30°C and dewpoint values in the high teens or low twenties making it feel more like the upper 30’s. Winds will be light. Expect a low near the 20°C mark on Saturday night.
This weekend could see provincial (pictured above) or federal responses to the heat and humidity over the region.
Sunday will see the daytime high climb even higher, most likely towards the 32 or 33°C mark as breezy southerly winds develop ahead of a developing low pressure trough. The humidity will remain in place with dewpoints in the high teens or low 20’s, making it feel more like the upper 30’s. There’s a slight chance we may see humidex values hit 40 on Sunday, which is Environment Canada’s criteria for a heat warning. That said, both Saturday and Sunday will likely qualify for the Province of Manitoba’s Heat Advisory and Response Pre-Alert which requires a humidex of 37 or higher.
There appears to be a slight chance late Sunday night or early Monday morning for some showers or thunderstorms to move through the area, but it looks very conditional at this point and it’s far to early to say much about it. We’ll put an update here early Sunday afternoon regarding the precipitation potential for Sunday night. Temperatures will likely only drop to around 19°C on Sunday night, however.
Long Term: Slight Cool-Down to Start Next Week
Looking ahead, it seems like we’ll see a slight cool-down next week as a frontal boundary stalls out over the region and brings a chance for multiple bouts of unsettled weather through the first half of the week. We’ll have more details about that bright and early Monday morning!
Exactly when depends on the timing which will be affected by how much and what type of elevated convection developed with this feature overnight in Saskatchewan. ↩
If the nocturnal convection is in the right spot or strong enough, our sunshine could be replaced by cloud cover instead, dramatically limiting surface heating. ↩
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!
