Highlights
- Conditions producing heat and humidity over Saskatchewan and Manitoba to depart
- Alberta to see a cooling pattern before returning to mid-twenty degree weather next week
- Uncertainty between models over whether Saskatchewan and Manitoba will see rain and unsettled weather
Summary
Last week’s forecast did well considering the unusually blocking pattern that developed. An area of low pressure did develop as expected over the west-central U.S. It tried to push northwards and eastwards but was kept mostly in place by a strong ridge of high pressure over the central and eastern Prairies.
The models were a bit off on how long it would take this blocking pattern to break down and on the final placement of the low. Originally, it looked like the low would lift northwestwards towards central Saskatchewan and parts of Alberta. This didn’t pan out. Instead the low lifted northwards and impacted much of eastern Saskatchewan and parts of western Manitoba.
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Prairie forecast: Summer holds on
Once again, the weather models did a good job with the last forecast. It correctly predicted the cool weather pattern…
To start this forecast period, we’re seeing the blocking pattern breaking down as the eastern Prairie low finally drifts off east. It will take with it the heat and unusually high humidity that brought mid-summer conditions to much of southern Manitoba and Saskatchewan.
Currently there’s a departing area of low pressure over Ontario and another area of low pressure off the B.C. coast. In between, there’s un upper ridge of high pressure centered over Alberta.
The weather models show the upper ridge slowly expanding across the Prairies over this forecast period. At the same time, several areas of low pressure will try to push in around the perimeter of this ridge.
The first low is the one off the B.C. coast, which is forecasted to drift northeastwards over the ridge and into the high Arctic to mostly miss the Prairies. A second, disorganized area of low pressure is forecasted to develop over the central U.S. early in the forecast period and then to try to lift northwards. Just like the last forecast, there is a fair bit of uncertainty on how far north it can push and how much moisture will lift northwards late this week and over the weekend.
Early next week, models show a strong area of low pressure coming in off the Pacific, but another building ridge of high pressure over the Prairies should shunt this system to the north. This will keep most of the Prairies in an overall warm early fall or late summer pattern.
Alberta
Sunny skies and above-seasonable temperatures are expected across Alberta during most of this forecast period thanks to a persistent upper ridge of high pressure. Expect daytime highs in the 23 to 28 C range over the rest of this week and into the early par of the weekend before slightly cooler air works in.
This cooler air is thanks to an area of low pressure that’s forecasted to push in off the Pacific into the central part of B.C. This will lead to a flattening of the upper ridge as the low pushes eastwards and gets deflected northwards over the ridge. Expected daytime highs to cool towards the 20 C mark over the weekend with overnight lows falling to a comfortable 10 to 12 C.
Early next week, another area of low pressure is forecast to push in from the Pacific over northern B.C. This low will help develop a weak upper ridge over the province, which will bring more sunshine and warm temperatures. Daytime highs should push back into the mid-twenties.
Saskatchewan and Manitoba
The blocking pattern that kept sending waves of energy and moisture northwards has finally broken down. The main area of low pressure is moving into the northwestern Ontario. Behind this low, upper-level ridging will be trying to build in from the west. At the same time, a disorganized area of low pressure will be lifting north-northeastwards out of the central U.S.
Exactly how these two features will play out is unclear at this point. One weather model is keeping most of the moisture south of these regions, while a second model shows the low pushing further north and bringing several days of unsettled weather.
It looks like the southern regions of both provinces will see more sun than clouds from late Wednesday through to Saturday. The best chances of showers looks to be late on Friday and through the day Saturday, but as I pointed out, confidence in this is low.
Weak upper-level ridging will try to build eastwards across the Prairies early next week. This should bring a return of sunny skies and above-seasonable temperatures. The one sticking point is that as the ridging pushes eastwards, a weak disturbance may move through around Tuesday. This may trigger a few showers or thundershowers.
