Slightly Cool Weather Continues

A persistent low-pressure centre over Hudson Bay will continue to bring cool nights and mild, but not hot, summer days to Winnipeg as it blocks the jet stream from pushing northwards into the southern Prairies.


23°C / 13°C
Partly cloudy with a slight chance of late-day showers.

22°C / 12°C
Partly cloudy with a tiny chance of late-day showers.

22°C / 10°C
Partly cloudy.

The next few days will see very little variation as cooler air ever so slowly slumps southwards into the Southern Prairies. We’ll see a chance of late-day showers in the Red River Valley today and tomorrow, however the chance is pretty minuscule and by no means will the showers be widespread. Temperatures will climb into the low 20’s for highs and start around 13°C for overnight lows and drop towards the 10°C mark by the end of the week. By friday the chance for showers drops off and we’ll likely just see a few clouds in the afternoon.

No Heat on the Horizon

Looking ahead to the long-range it doesn’t appear we’ll see any hot summer weather headed our way for the next 7–10 days. The low that’s keeping us cool is going to stick around for a couple days before backing up to the west, grabbing another batch of cool Arctic air and then diving southwards towards Southern Manitoba…at least, that’s how it looks now. It seems somewhat reasonable as most models have locked into a fairly consistent west-coast ridge and mid-continental toughing pattern for the next while.

Personally, I love the warm but not hot days and cool nights, although given our long-delayed spring, I’m not going to complain if nature can throw another blast of hot and humid weather our way again.

Sunny Weekend Ahead

Sunny weather will dominate the Red River Valley as a ridge of high pressure moves into Manitoba. Temperatures will be below-normal through the next 3 days as we remain entrenched in a cooler air mass originating from the north while the jet stream remains locked up in the United States.


20°C / 7°C
Mainly sunny.

22°C / 11°C
Mainly sunny.

24°C / 13°C
Mainly sunny.

Temperatures will slowly climb back towards the mid-20’s by the end of the weekend, while overnight lows will start at an extremely unseasonably cool 7 or 8°C and warm to around 13°C by Sunday night. Skies will be mainly sunny the next several days with no precipitation in sight.

A Chance to Dry Off

We’ll see sunny skies through the rest of the week and a chance to dry off after as much as 100mm of rain fell over Southern Manitoba over the weekend. The heavy rain caused a few problems of the weekend, mainly constrained to rapidly rising streams and rivers (which rose as much as a meter) and significant overland flooding. Thornhill, MB was particularly hard hit with enhanced rainfall occurring from the upslope enhancement of the western Red River Valley escarpment under northeast winds. It has been reported that 200mm or greater fell in the region, but with such sharp contrast to how much fell in nearby Morden (89mm) and CoCoRaHS reports totalling 2–3” (~ 50–80mm), it has to be considered an extremely localized event. Nonetheless, areas very close to the western escarpment were hit very hard by this rainfall event.

All that to say it was a very wet weekend that was easily the biggest rainfall event of the year. Some notable rainfall totals:

City/Town Rainfall (mm)
Deerwood 101
Morden 89
Somerset 81
Winkler 77
Manitou 76
Sprague 73
Letellier 71
Killarney 69
Carman (Ag.) 68
Altona 67
Boissevain 62
Carman (EC) 58
Gretna 58
Deloraine 55
Emerson 55
Morris 54
St. Pierre 52
Kleefeld 46
Treherne 41
Pilot Mound 40

Winnipeg 18–24 (Official)
29–34 (Unofficial)
Portage la Prairie 18
Brandon 16

It’s easy to see that the heaviest rainfalls fell in the SW Red River Valley, with lesser amounts east of the Red River and rapidly diminishing amounts near the Trans-Canada Highway. Fortunately, no rainfall is in the forecast for this coming week, which should provide the opportunity for things to dry off and a chance to get out there and cut your grass which, if it’s anything like mine, decided to grow about 4” over the past few days.


20°C / 3°C
Mainly sunny & breezy.

17°C / 4°C
Mainly Sunny

19°C / 9°C
Mainly Sunny

We’ll see mainly sunny skies the next few days as a large surface ridge pushes through the province. High temperatures will be restricted into the mid-to-upper teens as cooler air aloft dominates along with a northeasterly wind that will keep cooler, dryer air feeding into southern Manitoba. Winds will still be a factor today as they increase to around 30–40km/h once we warm up a little bit. Winds will be a lesser issue on Thursday as the surface ridge lies right on top of us and the light winds slowly shift to southeasterly as we enter the return flow on the back-side of the ridge. For Friday, winds will likely pick up late in the day or overnight as the surface pressure gradient tightens up over southern Manitoba again as a low pressure system pushes into eastern Montana/the western Dakotas. Before then, though, the winds will likely be quite calm. Our high on Friday will push back towards the 20°C mark, but likely stop just short of it.

The return flow also looks to be tapping into a bit of moisture in the Central Plains which will begin increasing our dew points heading into the weekend. For us, it will just mean the assurance that we’ll stay much warmer at night (closer to 10°C than 5°C), but for further west in Eastern Saskatchewan it looks like the moistening air may provide fuel for the first organized thunderstorm events of the year.

The Weekend

The weekend looks to be fairly benign at this point over Southern Manitoba. It looks like the atmosphere is setting up into a weak blocking pattern once again with a large upper low spinning over the B.C. Interior and Alberta with upper ridging over the Eastern Prairies. There may be a few shortwaves that ride up the ridge, but at this point it looks like if any shower activity were to push into Southern Manitoba, it would be constrained close to the Saskatchewan border. At this point, I’m comfortable saying that we’ll probably see a mix of sun and cloud with highs in the low 20’s here in the RRV this weekend, with more showery, stormier weather confined mainly to our neighbours in Saskatchewan.

Gradual Warm-Up on The Way!

Omega Block over Eastern North America

500mb heights/winds on Friday night depicting the Omega Block over Eastern North America.

Southern Manitoba has been under the grip of below-normal temperatures yet again over the past couple days, but a shift in the storm track will allow warmer air to build into the region. A large omega block, pictured above demonstrating it’s namesake (the wind flowing around the blocking pattern looks like the greek letter omega: Ω), will inhibit eastwards motion of the large-scale pattern, so the big question is: when exactly is it going to warm up? Fortunately, it’s not going to take too long.

Large-Scale Pattern Shift

Typically when blocking patterns set up, weather remains rather stagnant for a lengthy period of time: the rain stays in more or less the same place (it’s forecast to rain for most of the next 6-7 days in eastern portions of Iowa) and the sunshine remains over similar places. In extreme cases, features such as Omega Blocks can result in catastrophic flooding or droughts as similar conditions persist for weeks on end.

Fortunately, that won’t be our story. The blocking pattern is slowly decaying, but the real driver for our change in temperature will be the future of the upper trough currently over Manitoba/Northwestern Ontario. It’s simple existence is quite an anomalous feature and has only been able to maintain it’s existence by a continual reinforcement of Arctic air. Over the next few days, though, the northern storm track is going to become more active as disturbances begin to ripple through the NWT and Nunavut. These features will strengthen the upper-level winds north of 60° and cut off the reinforcing cold air.

Without this cold air injection and with the sun continually climbing higher in the sky, the cold air in our upper trough will quickly be modified out. As the northern storm track becomes more active, the flow aloft across the Northern Prairies will become more zonal as well, which will help bring warmer air into the region, although an upper ridge is forecast to build in over the Southern Prairies, keeping our winds fairly light aloft. So what does all this mean?


11°C / 0°C

14°C / 3°C

18°C / 8°C

What will be happening over the next few days, effectively, is the “bottling up” of winter once again, locking it north of a strong jet stream running through the Northern Praires/Southern Arctic. Warmer air will slowly build back into the region with temperatures returning to normal or just above normal by the end of the weekend. In addition to the warming temperatures, we’ll see nothing but sun sun sun!

Next Week

The trend looks to continue through next week, with temperatures climbing into the low 20’s and more sunshine prevailing. The next chance for any sort of precipitation looks not to be until maybe the end of the week. A warm, dry week will be good news for the flood situation in Southern Manitoba.