Category: Forecasts

Last Day of Summer Will Be Cold, Wet and Windy

Brad Leave a comment

Far from the sunny skies and warm temperatures we’ve seen constantly over the last several months, today will be cold, wet and windy as a cold front blasts through the Red River Valley.

GEM-REG 850mb Temperatures

850mb temperatures from the GEM-REG model valid for this evening. A significant outbreak of cold air will occur over Southern Manitoba today.

A powerful cold front will push southwards through the Red River Valley today, beginning in areas north of Winnipeg early this morning, then pushing through Winnipeg mid-to-late morning and then pushing through the rest of the valley and southeast Manitoba by early this afternoon. There will be an area of showers that pushes through the central and eastern Red River Valley, with rain further east in the Whiteshell along and behind the cold front. Generally speaking, if you’ve seen showers in the past two days, you’ll likely see more today. Winnipeg will likely only see 1-2mm, however anywhere from 2-10mm are possible in the eastern Red River Valley to the Ontario border. In addition to the precipitation, strong winds will once again develop over the Red River Valley, with winds increasing out of the north to 40-50km/h with gusts to 60-70km/h immediately behind the cold front.

This system will be dragging the coldest temperatures aloft that we’ve seen this month; 850mb temperatures will drop to anywhere from -5 to -8°C. This will result in fairly significant low-to-mid-level instability, mainly through the Interlake and arcing southeastwards across the South Basin towards Sprague. This will have two main impacts:

  1. Today, associated with the passage of the cold front, there’s a chance for an isolated thundershower through the Central/Southern Interlake and the Dugald/Beausejour/Grand Beach region. They will not be very strong, however they may be able to produce small hail.
  2. As the winds at various heights in the atmosphere slowly line up, lake-effect streamers will develop this evening and overnight off of Lake Winnipeg. The location of the precipitation will be sensitive to the exact wind direction, however, in general, the regions that will be effected the most will be up in the Arborg area (from the North Basin), and then further south in the Dugald/Beausejour/Grand Beach region (from the South Basin). There will also likely be streamers in the Portage la Prairie region overnight from Lake Manitoba, however they’ll be weaker as a surface ridge approaches from the west overnight. There will only be a slight chance of isolated showers in the southern half of the Red River Valley overnight. Winnipeg will be nestled between the two bands of streamers to our west and east, however there’s a distinct chance that we could see the streamer from the South Basin move into the city overnight.

In addition to the streamers, the other significant weather tonight will be frost. Areas that clear out tonight, which will be most areas that aren’t in the lee of the lakes, will see frost with overnight lows in the -1 to -3°C range. There’s a chance that areas in SW Manitoba may see overnight lows dip as low as -5°C underneath the surface ridge.

For Saturday, here in the valley we’ll see clouds & showers from the lakes last until midday before things start to clear up in the afternoon. Temperatures will remain cool with highs only around 11°C. We’ll likely see a hard freeze tomorrow night with overnight lows in the -3 to -5°C range across most of Southern Manitoba.

On Sunday, we’ll finally see some warmer air make it’s way towards us. The models want to push temperatures as high as 18-19°C through the Red River Valley, however we often see cold air stick around a little longer than forecast. Winds are forecast to shift to the southwest, however it’s almost certain that if they don’t quite make it to SW and end up being southerly we’ll see daytime highs a few degrees cooler than that. We should see temperatures in the mid-to-upper teens last through much of next week with little significant weather on tap.

Unsettled, Cool Weather

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We’ll see showers in the Red River Valley this morning as a low pressure system slides through the Interlake and Whiteshell regions but, unfortunately, little accumulations are expected as the more significant rain will stay north and east of the Valley. More cool days are ahead as this system reinforces the colder air over the province.

Rainfall Map

A low pressure system will track SE into Ontario today, bringing with it a large area of rain, represented in blue, and showers, represented in green, to Southern Manitoba.

A low pressure system dropping southwards from Northern Manitoba has pushed an area of showers through the Interlake overnight and will bring that rain through the Whiteshell and Sprague regions today. As pictured above, the low will track far to our NE into Ontario, leaving the Red River Valley with only disorganized instability in a strong NW flow pumping cooler air southwards on the backside of this system.

Temperatures through the RRV will stay steady today at 12-13°C as strong northwesterly winds pick up as the day progresses. Winds across the valley will pick up to 50km/h with gusts as high as 70-80km/h by late this morning and remain that way through most of the afternoon before beginning to ease this evening. A chance for showers exists through the whole RRV, and models are hinting that there may be some narrow, banded areas of precipitation that develop that could result in localized amounts of 2-4mm. Areas in the southwest RRV, such as Morden, will likely see nothing more than a passing sprinkle or two today while areas closer to the South Basin will likely see showers this morning.

We’ll see cool nights ahead, with lows near 3 or 4°C for the rest of the week. Thursday and Friday will bring us a mixed sky and highs only around 14°C.

Another system will push it’s way through the area on Friday, bringing another batch of scattered showers to the RRV. No significant amounts are expected across the Red River Valley.

Frosty to Start the Week

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We’ll be in for a couple of chilly, perhaps you could even say frosty, days to start this week. Cool daytime highs and sub-zero nighttime lows are on tap.

GEM-REG 3hr. Precipitation Accumulation

Some light lake effect showers (shown in blue) are expected to develop on Monday as cold air flows over the relatively warm lakes winnipeg and manitoba.

After a rather chilly Monday morning, temperatures won’t make a dramatic recovery for the afternoon. Daytime highs on the first day of the week are expected to barely make the double digits in most areas, with highs generally in the 9-12C range expected. A breezy north wind and perhaps a couple of lake-effect showers won’t make the day any more pleasant. Tuesday night should be another cool one in Southern Manitoba. However, it appears frost will be isolated to areas around and east of the Red River Valley as some warmer air moving in from the west will keep temperatures above zero overnight in Western Manitoba. Daytime highs on Tuesday will be an improvement from Monday, though except for South-Western Manitoba where 20C values are expected, temperatures will generally remain stuck in the mid teens.

Yet another cold front will swing through overnight Tuesday into Wednesday ushering in another cool airmass to end the week. It appears high temperatures will be relegated to the teens from Wednesday through Friday. There appears to be slim odds of any significant precipitation this week, though we may at least get some measureable rain later in the week as a few strong impulses rotate through the region.

NAEFS Ensemble 8-14 day outlook

The NAEFS ensemble doesn’t give a strong indication of what type of weather we’ll see moving forward…

At this point the long range forecast looks fairly status quo. We’ll see some cooler than normal days and some warmer than normal days, but in general the pattern for the next week or two generally looks to be near normal on average. However, there will certainly be a fall feel to the air as nighttime temperatures regular drop down to the freezing mark and daytime highs stay close to the average high for mid-September of 18C.

Mainly Seasonal With A Chance of 30°C

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We’ll see fairly typical weather for this time of year across Winnipeg and the Red River Valley with a big exception being tomorrow: with southerly winds and a big upper ridge moving across the region, there’s a good chance we’ll see temperatures in the upper 20’s, perhaps even breaking 30°C on Saturday afternoon.

500mb Wind Speed

500mb wind speed from the GEM-REG for midday today depicting the upper ridge that is moving into the province.

We’ll see plenty of sunshine today as the aforementioned upper ridge begins working it’s way into our region. Temperatures will be able to climb up much higher than yesterday, where a cool air mass combined with clouds limited our temperatures. We’ll see a high near 25°C today, although it will be a bit of a climb as we dig out of a rather chilly morning.

On Saturday, the upper ridge will move across the province, bringing with it 850mb temperatures in the 17-18°C range. Winds will be out of the south, not the southwest, so we won’t see any significant downslope effect to help our temperatures out. As a result, we’ll see widespread highs near 28°C with a few locales getting as high as 29 or 30°C by the late afternoon.

A powerful cold front will dive southwards through the Red River Valley on Saturday evening which will usher cool Arctic air in from the north. 850mb temperatures will plummet to nearly 0°C for Sunday which will hold our daytime high to the mid-teens, most likely below the seasonal normal high of 18°C, under cloudy skies.

Cooler air will continue to push southwards into the beginning of next week, with 850mb temperatures dropping below 0°C on Monday and remaining over the region for much of the week. This will likely result in daytime highs in the mid-teens and overnight lows in the low single-digits for much of the week under more cloud than sun and a chance of showers on and off through the week.