The first week of fall[1] will start off with weather that will seemingly put this summer to shame. Very warm weather is on the way with potentially record-breaking highs across Southern Manitoba on Thursday!
Wednesday
25°C / 14°C
Cloudy; clearing for a sunny afternoon
Thursday
31°C / 16°C
Mainly sunny; increasing humidity
Friday
30°C / 16°C
Mainly sunny & hot
A prominent upper-level ridge in place over the Prairies has pushed the polar jet stream far northwards and allowed warm air to spread into the Southern Prairies from the United States. As a result, significantly warmer than normal temperatures will continue through the remainder of the week in Winnipeg.
Today will start off fairly cloudy thanks to some stratus cloud that spread northwards ahead of a dissipating trough of low pressure. The cloud should clear out for the afternoon and we’ll see temperatures climb to around 24 or 25°C. The temperature will dip to around 14°C tonight under mainly clear skies.
Thursday and Friday will both bring highs just at or over the 30°C mark under mainly sunny skies. South to southeasterly winds will begin tapping into some moisture from the Central Plains of the US and we’ll see the humidity gradually rise for the latter half of the week. Dewpoint values will climb into the mid-to-upper teens, which when combined with highs near 30°C, it will feel more like the mid-to-upper 30’s. The overnight lows both nights will be in the mid-teens.
Record-Breaking Potential
We have a slight chance of breaking daily record high temperatures on both Thursday and Friday. For Thursday, September 25th the daily record high temperature is 31.1°C set in 1950. For Friday, September 26th the daily record high temperature is 31.7°C set in 1957. Both days will see temperatures climbing to or just above the 30°C mark, and if maximum heating is realized, we may get the bump we need to break one of these records!
Date
High Temperature (2014)
Record High
September 25
27.7°C
31.1°C (1950)
September 26
30°C (Forecast)
31.7°C (1952)
Cooler Weekend
The weekend is looking great, despite a cool-down that’s in store. Daytime highs will dip around 5°C or so for the weekend with both days seeing highs in the mid–20’s. Fortunately this still puts us around 8°C above normal for the time of year, so there will be little to complain about. We’ll likely see a bit more cloud that we do through the second half of the week, but all in all it will be a gorgeous weekend!
…sort of. Meteorological fall started at the beginning of September, but fall as most people consider it began on September 22nd after the autumnal equinox. ↩
Southern Manitoba is set to bathe in summer-time warmth as temperatures soar well above normal.
A broad upper-level trough developing over the Rocky Mountains will combine with a strengthened sub-tropical ridge over the southeastern United States to produce a southerly flow that will bring substantially warmer air to our region. As well as the warmer temperatures, humidity will become more noticeable heading into the weekend as higher dew point temperatures are advected northwards into the region. With the warmer weather will also come the potential for some shower or thunderstorm activity across much of Southern Manitoba.
Friday
25°C / 16°C
Mainly sunny. A little breezy.
Saturday
30°C / 17°C
Cloudy periods with a slight chance of showers or thundershowers. Windy and warm.
Sunday
24°C / 14°C
Chance of a morning shower or thunderstorm.
Friday
Today will be a very pleasant day. Under a mainly sunny sky, the temperature will climb to near 25°C as a southerly wind at 20-30km/h provides just enough of a breeze to keep things comfortable. The humidity will be more prominent than it’s been so far this year, but it will still be quite comfortable with dew point values climbing to around 15°C.
Heading into the night, temperatures will drop to about 16°C with variable cloudiness through the overnight hours with a slight chance of some shower .
Saturday
Tomorrow will start with a fair amount of mid-level instability riding ahead a warm front pushing eastwards. This will present itself with a slight risk for showers or thunderstorms through the early morning. Afterwards, we’ll see cloudy periods with fairly windy conditions with a southerly wind at around 30-40km/h. Very warm air will work in aloft, driving our daytime high up to 29 or 30°C. In addition to the warmer air, the southerly winds will also advect more humid air northward with the dew point climbing towards 17 or 18°C which will start to make it feel a little sticky outside.
Temperatures of 30°C or greater (dark green) are expected across much of Manitoba on Saturday.
As everything heats up, there will be a potential for thunderstorms, but there will be little in the way of a threat for severe storms. If we quickly look at the ingredients required for thunderstorms:
Moisture: Dew points will climb into the mid-to-upper teens, through a suitably deep layer, and be supportive of storm generation. The dew points are on the low side for the atmospheric thermal profile which will result in relatively high-based storms.
Instability: Deep instability will be present. Mid-levels are fairly unstable, and low-levels will destabilize fairly dramatically by mid-afternoon thanks to intense surface heating driving temperatures towards 30°C.
Shear: This is where things fall apart. While the low-level winds will provide favourable inflow into the storm bases, winds will be very slack through the mid-levels. This will dramatically impact the ability for storms to organize and will limit their potential growth.
Trigger: Triggers for storm generation look fairly weak. The synoptic triggers look to remain outside our region; the warm front will be in Central Manitoba, the cold front will be hanging back through Central Saskatchewan and the main warm sector trough also will trail back into southeastern Saskatchewan. The intense surface heating will likely produce many mesoscale triggers, especially along significant terrain such as the western escarpment of the Red River Valley and the Riding Mountains.
As a result, we’ll see the potential through much of Southern Manitoba for thunderstorms, however they’ll likely be short-lived, high based storms whose main threat will be strong winds or large hail.
It’s likely that rain with embedded thunderstorms will develop in North Dakota on Saturday night and lift northeastwards into Southern Manitoba, bringing the risk of rain and thunderstorms to somewhere in Southern Manitoba through the overnight period into Sunday morning. The areas that will see the risk will depend highly on exactly where the precipitation develops in North Dakota.
Temperatures will remain quite mild Saturday night with the overnight low bottoming out at only around 17°C.
Sunday
Sunday will be the most organized day for precipitation of the weekend. The system bringing the warmer air to the province will push off to the East through the day, dragging a cold front across the province. Widespread showers and thundershowers will be associated with the cold front as it pushes eastwards, and as a result showery weather is likely. It’s a little early for too much detail, but it seems like the chance for precipitation will start around mid-to-late morning and taper off by late afternoon.
The temperature will climb to around 23 or 24°C before the cold front swings through. Things will clear up by Sunday evening and we’ll see a beautiful night with a low near 14°C.
Next week looks to continue the warmth with highs in the mid-20’s, but by mid-week it looks like unsettled weather will return to Southern Manitoba and bring multiple days with chances for showers or thunderstorms. It seems like we’ll lock into seasonal to above seasonal temperatures, so get out and enjoy the summer weather that we’ve all waited so long to see!
After another stretch of below-normal temperatures, some truly summer-like weather is finally on the way.
Winnipeg will be under the influence of a ridge of high pressure that will keep us dry through the remainder of the week. A developing flow from the Gulf of Mexico looks poised to set up Southern Mantioba for a quick shift into summer-like weather for the end of the week.
Wednesday
15°C / 6°C
Mixed skies with a clearing trend.
Thursday
23°C / 12°C
Mainly sunny.
Friday
26°C / 14°C
Mainly sunny.
Today will bring mixed skies to Winnipeg and the Red River Valley as the system cloud associated with the low that moved through on Monday and Tuesday begins exiting the province. Cloud will likely persist through the afternoon as some fair weather cumulus develop as we warm up to our high near 15°C. Skies will clear tonight as the temperature drops. The temperature will drop to around 6°C tonight.
Tomorrow will bring mainly sunny skies, relatively light winds and a high temperature returning to a seasonal to slightly above seasonal 22 or 23°C. Things will be calm and mainly clear Thursday night with temperatures dropping to near 12°C.
Friday will mark the shift towards decidedly more summer-like weather. Under mainly sunny skies, warmer air pushing into the region will push our daytime high towards around 26°C. In addition to the warmer weather, we should also see the first days of the year that could potentially be considered “humid.” For a quick summary of the relationship between dew point and how humid it feels, and why relative humidity is a poor choice, check out the brief primer at the bottom of this post.
There’s uncertainty in exactly how humid it will get here in Southern Manitoba. Some weather models, such as the Canadian GDPS[1] are pushing dew point values as high as 20°C in the Red River Valley, but values that high are likely overdone thanks to the delayed start to the growing season due to the abnormally cold spring. It’s likely we see dew points climb into the mid-teens at least, though, so it’s fairly safe to expect that we’ll be seeing our first real shot of summer heading into the weekend.
Unsettled Weekend
There’s still a lot of uncertainty associated with the large amplitude upper-level pattern that’s expected to develop this weekend, so in general vagueries…
As the NAM shows, a broad flow from the Gulf of Mexico all the way to Southern Manitoba will be established by Saturday morning.
It’s going to be quite warm on Saturday. Daytime highs in the upper 20’s seem quite likely as well as dew points climbing into the mid-to-upper teens, although as mentioned above, there’s some uncertainty to exactly how high the dew points will get. Sunday will also be warm with highs in the mid-20’s.
Thunderstorms, potentially severe, will be possible both days, although exactly when and where is far too uncertain at the moment. It seems entirely possible that the thunderstorm activity will be constrained to the evening/overnight periods when elevated thunderstorms can develop, although late afternoon severe storms cannot be ruled out at this point. For both days the best chance for thunderstorms appears to be over Parkland Manitoba, SW Manitoba and into SE Saskatchewan and Montana/North Dakota. Here in the Red River Valley, nocturnal elevated activity looks like the most plausible scenario.
We’ll be taking a closer look at the thunderstorm and severe weather potential in Friday’s post. Until then, enjoy the imminent summer weather!
A Quick Lesson on Dew Points
Perhaps the most convenient way to quantify how humid it is outside is to look at the dew point temperature. The dew point is the temperature where water evaporates into the air at the same rate that it condenses out of the air; to put that in simpler terms, if the air comes in contact with something cooler than the dew point, water will condense out of it. Think of it as the temperature your cold glass of your favorite hot weather beverage needs to be to “sweat”.
The higher the dew point temperature is, the more water is in the air. This is an important distinction from relative humidity. Air has a quirky trait that allows it to hold more water the warmer it is. This means that air at -5°C cannot hold as much water as air at 25°C. This makes relative humidity ambiguous since it is a measure of how much water is in the air versus how much water the air can hold, or “how full the glass is.”
So a relative humdity of 100% at -5°C has less water in the air than a day where the temperature is 10°C with a relative humidity of 35% because the dew point in the first case is -5°C, while in the second case, despite the relative humidity of only 35%, the dew point is around -4.8°C.
As the dew point climbs, your perception of it being humid increases as well. In general, once the dew point rises to around 15 or 16°C, you’ll begin to notice that it feels humid. By 18 or 19°C it can begin to be uncomfortable. By the time the dew point climbs into the low-to-mid 20’s, as long as there’s sunshine, it can be extremely sticky feeling outside. Dew points in excess of 25°C are dangerous and can pose extreme health risks.
A textbook frontal passage is in store for the Red River Valley over the next few days as an incoming warm front brings a chance of flurries and another mild day before the cold front slumps through the region at week’s end, bringing another windy chance for snow.
Wednesday
-10°C / ⇑ -3°C
Cloudy, light flurries starting midday.
Thursday
+4°C / -7°C
Warm with mixed skies. Windy with flurries overnight.
Friday
-6°C / -20°C
Chance of early morning flurries, otherwise mainly sunny.
We’re off to a cold start this morning, but temperatures will soar today as a strong warm front pushes across the Red River Valley. Southerly winds will pick up through the day to around 30-40km/h by mid-afternoon. There will be a chance of flurries beginning midday and lasting through the early evening. No significant accumulations are expected and thanks the warming temperatures and recent melting, blowing snow should be minimal. Temperatures will climb to around -10°C by evening but continue rising through the overnight period to nearly -2°C by Thursday morning.
Mild air is set to push into Southern Manitoba again on Thursday.
Thursday will be another beautiful day very reminiscent of Monday this week. Winnipeg will see relatively light winds and mixed skies as the temperature climbs all the way to 4°C. Similar to Monday, there will probably be significant variation across the city with some places climbing several degrees higher to 7-8°C.
Things will take a less pleasant turn on Thursday night when a cold front slices through Southern Manitoba. Gusty winds out of the northwest to 40km/h will accompany some flurry activity that will spread into the Red River Valley from north to south through the mid-to-late evening hours. The wind and any straggling flurries should taper off early Friday morning.
Friday sees an Arctic ridge of high pressure building into Manitoba bringing cooler temperatures with it. In Winnipeg, temperatures will be some 10°C cooler than Thursday with a daytime high only near -7 or -6°C under mainly sunny skies.. Winds will remain light and the temperature will drop close to -20°C on Friday night.
Cool Weekend Ahead
Temperatures will remain well below normal through the weekend in the Red River Valley. Saturday’s high looks to be near -15°C under mainly sunny skies while Sunday sees the coldest axis of air shifting off to the east, allowing temperatures to climb to the low minus single digits with a few cloudy periods.
In the southwest corner of the province, flurries will be possible numerous times over the next 5 days as the main frontal zone sets up across the region and weak disturbances ripple along it.
