Uncertain Weekend Ahead

A complicated series of weather disturbances pushing across Southern Manitoba will provide a sensitive forecasting challenge as multiple batches of narrow bands of rain with sharp edges push across the Red River Valley and areas east.

This satellite shot shows the development of the next system in Colorado that will move along the existing frontal boundaries and bring more rain to Southern Manitoba.

This satellite shot from last night shows the development of the next system in Colorado that will move along the existing frontal boundaries and bring more rain to Southern Manitoba.

Friday

Friday

17°C / 9°C
Mainly cloudy. Chance of showers.

Today will bring the most disorganized batch of precipitation as a weak low pressure system pushes out of ND/MN into the Lake of the Woods area. This seemingly weak feature will be coupled with a 500mb jet streak that will advect across the Red River Valley and the Whiteshell.

The upper-level jet streak will advect over a quasi-stationary front aligned north-south over the the Red River Valley. The convergence along the front, when combined with the lift associated with the jet streak, will likely produce some isolated showers and starting midday and lasting through the evening hours. The showers will be tied very tightly to the jet, so depending on where that jet ends up exactly will dictate where the potential lies. If things shift east slightly, the showers could easily only happen over SE Manitoba (in the Sprague area) or we could even see no showers at all.

It seems fairly likely there will be some isolated to scattered showers, though. With mainly cloudy skies the temperatures will struggle to warm up and we’ll likely see a high of only – and perhaps this isn’t all that bad since it’s close to seasonal for this time of year – around 17°C. Winds won’t be much of an issue today.

We’ll see plenty of cloud tonight alongside that chance for showers in the evening with temperatures dipping to around 9 or 10°C.

Saturday

Saturday

15°C / 5°C
Cloudy. Slight chance of rain.

Saturday will be another rain event for Southern Manitoba as the upper trough that has been bringing the unsettled weather to the Prairies over the last week finally begins pushing eastwards. A low pressure will eject out of the upper trough on Friday night and rapidly lift northwards towards the Lake of the Woods and intensify. Rain will push into southeastern Manitoba on Friday night with a sharp western edge as the rain stays tightly associated with a strong upper-level jet. There’s some uncertainty on exactly where this jet is going to set up and how it will move through the day; some models keep the entirety of the rain over the SE RRV and Sprague/the Whiteshell while other models dig the upper trough a little more and pull the jet westwards, backing the rain into Winnipeg.

12hr. QPF panel from the RDPS model showing forecast rainfall accumulations through the daytime on Saturday.

12hr. QPF panel from the RDPS model showing forecast rainfall accumulations through the daytime on Saturday and the position of the low and associated fronts at day’s end. Winnipeg sits on the very edge of the main area of precipitation.

At this point, it seems like there are two rainfall scenarios for Winnipeg:

  1. The rain advects into Southern Manitoba further west than currently forecast and Winnipeg sees some rain (potentially somewhat heavy) early Saturday morning before it pulls off to our east and sits over SE Manitoba for the rest of the day.
  2. The main band of rain remains east of Winnipeg with us potentially seeing some light shower activity through the day as we get brushed by the edge of the system. Light winds and ample moisture may result in some on-and-off drizzle through the day.

While there is a chance that the main rain band may back further west and we’ll see a rainy day, I don’t think that outcome is very likely. It will be a cool, damp day with a high of only around 14 or 15°C. Clouds will clear out in the evening/overnight period as we drop to around 5°C for a low.

Sunday & Beyond

Sunday

22°C / 10°C
Mainly sunny & warming up.

Sunday will bring much more pleasant weather as we see mainly sunny skies and a high in the low–20’s. It will mark the beginning of another stretch of fairly sunny weather with well above-seasonal daytime highs. We’ll see a low of around 10°C on Sunday night with clear skies.

The start of next week will bring sunny skies and temperatures climbing into the mid–20’s, as much as 10–11°C above the seasonal daytime high of around 14–15°C for this time of year!

Showery Weather Ahead

A persistant Arctic vortex over the Eastern Arctic will continue reinforcing a westerly to northwesterly flow over the Prairies which has been bringing cooler summer weather to Southern Manitoba. Multiple disturbances are forecast to track down in the northwesterly flow which will produce a showery second half to the week.

Wednesday

22°C / 13°C
Increasing cloudiness then showers with a risk of a thunderstorm in the afternoon.
Thursday

21°C / 11°C
Cloudy with scattered showers. Windy.
Friday

22°C / 10°C
Mainly sunny.

We’ll see a fairly cloudy day today as temperatures climb to only around 22°C. A trough of low pressure will work it’s way into and through the Red River Valley bringing scattered showers with the risk of a thunderstorm through much of the day and the early evening. No severe weather is expected. Skies should clear overnight as we drop to a low of around 13°C.

On Thursday a second – more potent – system will begin working it’s way through the province. Clouds will roll in early on Thursday as an upper disturbance tracks an area of rain through the Interlake. Here in the Red River Valley we’ll likely see another round of scattered showers starting midday with the winds picking up out of the north to around 30km/h with gusts to 50 or 60km/h. Thunderstorms aren’t expected and we’ll see a high near 21°C. Things will clear out overnight as we head to a low of about 11°C.

Friday will bring more stable weather with mainly sunny skies and a high of 22°C. Winds will continue to be breezy through the morning but should begin to let up in the afternoon. Things look very pleasant through the weekend with mainly sunny skies and highs in the mid–20’s with overnight lows in the 12–13°C range.

Rainy — And Potentially Stormy — Thursday Ahead

Sunny skies will turn rather unsettled on Thursday as multiple disturbances move across Southern Manitoba.

Wednesday

Wednesday

28°C
Mainly sunny. Chance of showers near the U.S. border.
Wednesday Night

15°C
Increasing cloud. Showers beginning overnight with the risk of a thunderstorm.

We’ll see mainly sunny skies today as we spend a short amount of time in the stable air behind the cold front that passed through yesterday. That front will be sitting south of the border in North Dakota, however a very strong upper-level jet will be in place through Northern North Dakota near the Canadian border. There will be a slight chance of showers near the border thanks to the extra lift supplied by this feature.

We’ll see increasing cloudiness tonight as the upper-level jet starts pushing back northwards and the aforementioned cold front becomes a warm front and start pushing northwards again. Showers – with the risk of a thunderstorm – will develop over SW Manitoba overnight and advect eastwards into the Red River Valley before morning. No severe weather is expected.

Thursday

Thursday

24°C
Showers ending midday then cloudy with a few sunny breaks and a continued chance of showers.
Thursday Night

15°C
Showers with the risk of a thunderstorm overnight.

Thursday morning will start off rainy with the risk of a thunderstorm. Around 10–20mm of rain is possible however any higher amounts will likely be localized to any heavier patches of rain that develop. Things should taper off by midday leaving us with cloudy skies and perhaps a sunny break or two, but a chance of showers will continue through the afternoon.

Thursday night will start off cloudy then rain will push in by the late evening period as another cold front sweeps southwards from the central Prairies. Unfortunately, this area of rain will likely start off as thunderstorms over SW Manitoba.

NAM sounding valid on Thursday evening near Brandon, Manitoba.

NAM sounding valid on Thursday evening near Brandon, Manitoba.

Quickly looking at some of the convective elements in place:

  • MLCAPE values forecast to be in excess of 2000J/kg
  • 60kt 500mb jet will begin work it’s way into the region with the left exit of the jet poking into the Melita & Virden regions early in the evening.
  • A frontal boundary will be very close to the area providing convergence that can act as a trigger for storm initiation.
  • Falling heights through the upper atmosphere should help prime things for both initiation convection and to sustain anything that does manage to get going.

Low-level shear will not be favourable for the development of tornadoes, but the strong straight-line shear combined with ample moisture and relative low freezing levels will make large hail and torrential downpours a serious concern. Given the shear profile and the strength of the winds aloft, there may be a slight chance that these storms will develop strong straight-line winds. The main threat for severe weather will be over southwest and western Manitoba; at this point it looks like points from Virden to Minnedosa east to the lake then down along the shore-line to Portage face the biggest threat for severe weather, although not much would have to change to include Melita & Pilot Mound regions in there too. We’ll take a look at things a little later today and update this post with a severe thunderstorm outlook graphic if it seems applicable.

The thunderstorms will grow into an area of rain as they travel eastwards towards the Red River Valley. Here in Winnipeg we’ll still see the threat of a thunderstorm overnight, but it should mainly be rain – potentially heavy at times – amounting to about 5–10mm. If we see a thunderstorm than naturally the accumulations could be significantly more than that. The storms and rain should move out of the RRV into Northwestern Ontario overnight.

Friday

Friday

24°C / 15°C
Mainly sunny.

Mainly sunny skies will dominate on Friday as we move into a cooler, stable air mass in behind Thursday’s system. We’ll see the cooler weather persist for another day or so before hot weather begins working it’s way back into the area with temperatures looking to climb back towards 30°C on Sunday. The weekend looks gorgeous so get out there and enjoy it!

Active Pattern Developing

A more active pattern will be setting up over Southern Manitoba as a southwesterly flow aloft develops thanks to a quasi-stationary high pressure system that will set up shop over eastern North America. This will bring us multiple chances of rain and thunderstorms over the next 5 days or so.

Friday

28°C / 16°C
Showers or thunderstorms ending in the morning, then a mix of sun and clouds with the slight chance of a thunderstorm.
Saturday


30°C / 16°C
More sun than cloud. Increasing cloud then risk of showers or thunderstorms overnight.

Sunday

28°C / 16°C
Mainly sunny. Might actually not rain.

Friday

We’ll see a rainy start to the day as the remnants of Thursday night’s nocturnal convection begin to dissipate over the Red River Valley. Showers or thunderstorms will taper off through the morning, leaving us with a mix of sun and cloud by midday. Thunderstorms will redevelop along the main surface trough in Southern Manitoba in the afternoon but the complicating factor will be the positioning of the trough, which is extremely uncertain at this point.

Forecast location of the surface trough at 1PM CST from the RDPS.

Forecast location of the surface trough at 1PM CST from the RDPS.

It seems most likely that the trough will be east of Winnipeg by the time things redevelop along it, although due to that uncertainty we’re keeping a slight chance of another thunderstorm through the early afternoon in for Winnipeg. We’ll update in the comments below if it’s readily apparent that the trough will be east of town by mid-morning. We’ll see clearing skies tonight as we head to a low of around 16°C.

The Weekend

Saturday will be a hot day with relatively comfortable humidity. We’ll see temperatures climb to around the 30°C mark again across the Red River Valley under a mix of sun and cloud – although there should be more sun out there than cloud. We’ll see some increasing cloudiness in the evening as a weak upper trough pushes into the province. There will be a chance of showers or thunderstorms through the overnight period for a large swath of Southern Manitoba, although at this point the best chance looks to be from Dauphin to Brandon and then in the Red River Valley near the western escarpment.

Sunday will be a nice day where we might actually have no chance of rain! Temperatures will climb back into the high 20’s – probably close to 28°C again – under mainly sunny skies. Sunday night will be clear with a low near 16°C.

Next Week

At this point, Monday and Tuesday both look like relatively rainy, possibly stormy, days as a train of disturbances move over Southern Manitoba. There are hints that once we get past the first couple days, we’ll return to a more stable pattern, but first thing’s first; we’ll continue to have updated thoughts and details in the comments below!