After a week of summer-like weather, conditions will return to reality. More fall-like temperatures are expected this week along with some rain.
Cool conditions will dominate our weather on Monday
Monday
Monday
12°C / 8°C
Mainly cloudy
Today will be mainly cloudy with a chance of an isolated shower or drizzle. Low-level moisture under a strong ridge of high pressure will be responsible for the cloud. We may see some clearing late in the day, but that won’t change the day’s expected temperatures. High temperatures today will be in the low teens, with a light easterly to south-easterly wind.
Tuesday
Tuesday
16°C / 10°C
Mainly cloudy
Tuesday will remain on the cool side, with temperatures in the low to mid teens. Despite the fact that these temperatures may seem cool, especially compared to last week, they are actually near normal for this time of year. Our next chance for rain will begin on Tuesday night as a compact, but intense, low pressure system spreads rain over southern Manitoba.
Wednesday
Wednesday
18°C / 8°C
Periods of rain
The aforementioned low pressure system will be the dominant weather feature on Wednesday. It is expected to bring light to moderate rainfall to southern Manitoba for most of Wednesday. It is too early to predict how much rain will fall, but at this point 5-10 mm looks most probable.
Long Range
The long range forecast looks very fall-like. Current modelling suggests we will see normal to below-normal weather as we move into October. That means temperatures in the low teens, plus or minus a few degrees.
Temperatures will remain well above normal for two more days before seasonal air begins pushing back into the province through the weekend as a cold front gradually progresses southeastwards. A chance for showers returns to southern Manitoba on Sunday as a disturbance developing in North Dakota causes the cold front to stall out over our area.
Friday
28°C / 16°C
Fog patches in the morning, then hot and humid
Saturday
26°C / 12°C
Chance of morning fog, then mainly sunny and warm
Sunday
⇘ 10°C / 6°C
Cloudy with rain likely
First the good news: after we burn off a little fog that developed overnight, today will be another beautiful, summer-like day with highs in the upper 20’s and surprisingly humid conditions for late September. Strong southerly winds at 40–50km/h with gusts as high as 70km/h will be tapping into a pool of moisture in the Northern Plains and drawing it northwards. Dewpoint values will sit near 17–19°C through much of the southern portions of the province.
Today will bring abnormally high late-September humidity to Southern Mantioba.
Yesterday I erroneously tweeted that our dewpoint of 17.6°C broke the previous record of 16.8°C set in 2008 and that it had been the latest on record[1] such high humidity had been seen in Winnipeg. Rob’s Obs did a little digging and found that the actual record is still held by October 8, 1997 when the dewpoint climbed to 18.6°C. Whoops. I apologize for missing that.
That being said, today will give that record a run for its money; multiple models forecast our dewpoint to climb to 19°C, which if it happens would be the latest 19°C dewpoint on record.
Saturday will be a beautiful day in Winnipeg with a high in the mid–20’s and more comfortable humidity as a cold front gradually approaching begins flushing out some of the moisture in the region. There’s a chance of fog again in the morning and we may see a few clouds around, but the bulk of the day should be mainly sunny. Winds don’t look to be an issue.
This simulated RADAR image from the NAM shows a band of rain stretching across Southern Mantioba on Sunday afternoon.
Things change on Sunday as the cold front that was approaching on Saturday stalls out as a disturbance in North Dakota develops. A band of rain is expected to develop along the stalled out front, spreading from SW Manitoba eastwards through the afternoon until a band of rain stretches across the whole province. Temperatures will start off cool and only drop from there as the rain cools things off a little further and northerly winds at 20–30km/h continue to tap cooler air and bring it into the region. The rain should taper off late in the evening here in Winnipeg with anywhere from 5–15mm falling depending on the exact timing and speed of the system. Temperatures will dip down to around 6°C.
Unsettled Week Ahead Leading to A Cold Snap
Long-range forecasts don’t look particularly great. The first couple days of the week look seasonal temperature-wise. A series of Colorado Lows look to develop mid-to-late week which will bring a chance for showers, but more significantly, begin drawing down much cooler air from the Arctic. The end of the week looks like it will end with an Arctic outbreak bringing another shot of below-normal temperatures and brisk northwesterly winds.
Records for seasonal dewpoint values go start in 1953. ↩
Wednesday will be a brief reprieve from the showery weather before a fairly potent low pressure system spreads more rain & thunderstorm activity across Southern Manitoba tonight into tomorrow morning and brings dreary weather for Thursday with strong northwesterly winds.
Wednesday
23°C / 13°C
A few sunny breaks; rain overnight.
Thursday
19°C / 6°C
Rain and drizzle tapering off mid-day. Risk of a thunderstorm. Windy.
Friday
19°C / 5°C
Mainly sunny.
Today will be a fairly pleasant day with mostly cloudy skies and a high near 23°C or so. There’s a slight chance of an isolated shower or three through the Red River Valley, including Winnipeg, but for now it looks like the activity should mainly remain to our west over southern Saskatchewan and southwest Manitoba.
Tonight, an inverted trough extending NW from a low pressure system moving through the Dakotas will spread rain with the risk of thunderstorms eastwards into the Red River Valley. Rain will likely start sometime after 1AM and persist until mid-morning Thursday. The temperature will dip to around 13°C.
The Canadian RDPS is one of the models rather bullish on higher precipitation amounts Wednesday night.
Rainfall totals for tonight are still uncertain; the general agreement is for between 10–20mm, however if substantial elevated convection develops as much as local amounts of 40–50mm may be possible. The low end of precipitation forecasts produce only around 5mm of rain.
I feel fairly comfortable with 10–20mm of rain tonight, but we’ll reassess the elevated convection potential later today and update if necessary. We’ll try and have an update fairly early this afternoon.
Unpleasant Thursday
Thursday will be quite an unpleasant day as Winnipeg moves onto the back side of the low pressure system lifting northeastwards into Ontario. The bulk of the rain should taper off mid-day, but brisk northwesterly winds building to 30–40km/h will accompany cloudy skies and a high struggling to climb into the upper teens. It’s also fairly likely drizzle will persist after the main area of rain moves out, making for a generally dreary day.
Skies will clear out for the evening, although there may be some cloudy periods through the first half of the night with some cloud moving off of Lake Manitoba, and temperatures will drop to a chilly 5 or 6°C.
Fall-Like Friday
Friday will be fairly pleasant, albeit cool, with mainly sunny skies and a high near 19 or 20°C. Winds will be fairly light through the day.
Friday night should bring clear skies and a low near 5 or 6°C.
A Look Ahead to the Weekend
The upcoming weekend is looking fairly good with unpleasant weather staying to our north. It’s looking like plenty of sun is in store with daytime highs in the ballpark of the seasonal 21°C mark and overnight lows moderating by the end of the weekend.
A major low pressure system developing in the United States and forecast to lift northwards into the Eastern Prairies through the weekend will bring generally unsettled weather ahead of a more cohesive area of precipitation that will move through on Saturday night.
Friday
22°C / 15°C
Mostly cloudy with a chance of scattered showers
Saturday
19°C / 15°C
Mostly cloudy
Sunday
23°C / 15°C
Rain ending in the morning; sunny breaks with a risk of strong-to-severe thunderstorms thereafter
Perhaps the single most important thing to keep in mind with today’s forecast is the fact that weather models have little consensus on what’s going to happen over the next few days other than the fact that there will be a large low pressure system that will impact an area somewhere between the Rocky Mountains and the Great Lakes.
That being said, it looks like the next several days will bring mixed weather to Winnipeg. Today will see a chance for scattered shower activity as a weak shortwave rolls across the Red River Valley, but nothing nearly as bad as what hit the city last night, where up to 80mm of rain fell in a rapid deluge through portions of the city that resulted in wide-spread flooding through the hardest hit areas.
Temperatures will climb to around 21 or 22°C this afternoon with a light wind out of the north. Tonight will be mainly cloudy with fairly light winds and a low near 15°C.
Saturday: The Low Approaches
Tomorrow will see mainly cloudy skies with a high of just 19 or 20°C. Winds will pick up out of the northeast to 30-40km/h as the main low pressure system for the weekend strengthens and lifts northwards through the Dakotas. By supper time, rain with the chance for embedded thunderstorms will spread through North Dakota into Southern Manitoba, reaching Winnipeg later in the evening.
The RDPS is forecasting an intense convective complex with substantial rainfall amounts on Saturday night. Who knows if it’s correct.
The rest of Saturday night will be quite rainy with 10-20mm of rain likely across most of Southern Manitoba with localized amounts in excess of 30-40mm due to embedded convection in the precipitation shield. Some models, such as the RDPS pictured above, want to produce upwards of 50-75mm of rain, although at this point that’s likely overdone and a symptom of what’s known as “convective feedback” in the model, something that ends up causing the model to produce too much precipitation when there is widespread convection occurring. Temperatures will drop to around 15°C again with winds out of the northeast at around 30km/h.
More Unsettled Weather on Sunday
The weather on Sunday will likely improve as the low pressure system lifts through the Red River Valley and pushes off to our northeast. Rain will taper off in the morning and Winnipeg will be left under mostly cloudy skies in what’s known as the “dry slot” — the area behind the cold front located between the frontal precipitation and wrap-around precipitation denoted by descending dry air aloft. The high will climb to around 22°C with some strong northeasterly winds becoming light in the afternoon.
Significant instability associated with the low pressure system will be in place, and even with temperatures climbing only into the low 20’s, it will be enough when coupled with the significant moisture in place to present a risk for strong-to-severe thunderstorms. We’ll have more information in the comments on Sunday.
Things will begin to clear out on Sunday night as the temperature drops to around 13°C.
Into next week looks fairly benign with temperatures gradually returning towards normal by week’s end. There will be a couple cool nights in the coming week with overnight lows dipping into the single-digits.
We’ll be keeping an eye on this system as it develops; slight alterations in the track of the system could dramatically impact forecasts, so if any changes are needed we’ll note them below in the comments. All in all it will be a mediocre weekend followed by an improving week.
