Two More Nice Days

A couple more nice days are in store for the Red River Valley before a significant change in the weather occurs for the second half of the week.

850mb Temperatures valid Tuesday Morning

850mb temperatures valid Tuesday morning showing the baroclinic wave (warm and cold front) that will be tracking into Manitoba.

The Red River Valley will see a beautiful day today as temperatures climb to the 20C mark under sunny skies and light winds. A major low pressure system will begin to track across the Prairies on Tuesday, which will bring a major weather change to us, but not before we sneak one more nice day in. Temperatures will climb into the low 20’s on Tuesday with mainly sunny skies. Winds will increase out of the south to 40km/h with gusts near 60km/h in the morning, however they’ll let up in the afternoon as a weak trough passes through.

We’ll be under the influence of this major low pressure system for the second half of the week, which will bring cold, cloudy, very windy weather. We’ll have more details on what to expect bright and early on Wednesday morning. We’ll also have a complete summary of September’s weather within the next week. I hoped to have it ready for today, however circumstances have prevented me from being able to get it all together just yet.

Get out there and enjoy the nice weather while it lasts!

Last Day of Summer Will Be Cold, Wet and Windy

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.

Cool Blast Across Manitoba

A powerful low pressure system moving through the Interlake will bring significantly cooler weather to Manitoba over the next couple days. Read on to find out where the rain will be and how cool it’s going to get.

GFS Forecast for this evening

GFS 850*mb* temperature forecast for this evening. I’ve drawn on the strong high over the Western Prairies that is helping our low pressure system pull down cool Arctic air. Cold front and warm fronts have been drawn in blue and red, respectively.

As the low pressure system passes to our north today, it will drag a cold front through the Red River Valley over the course of the afternoon. Preceding this front will be an area of rain, and while a majority of the thunderstorm activity will be through the Interlake, closer to the low, there will likely be some isolated embedded thunderstorms through the Red River Valley.

Accumulations will generally be higher the further north from the international border you go; while up to 25-50mm will likely fall through the Interlake, only 2-5mm are expected over the southern RRV. Any location in the RRV that sees a thunderstorm could easily receive between 0.5 to 1” of rain. Here in Winnipeg, we’ll probably see between 5-10mm with some locally higher amounts if a thunderstorm rolls through by the end of the day.

On the backside of this system a strong northerly wind at all levels will drag down the most potent shot of cool, Arctic air we’ve seen in quite a while. While winds will be out of the south in the morning, gusty northerly winds will kick in quickly behind the cold front, with sustained speeds between 40-50km/h and gusts as high as 60-70km/h. 850mb temperatures approaching 0°C will push down into the Interlake region tonight. This will bring with it the chance for the first significant lake-effect shower event of the “fall”1 season. When looking for the generation of lake-effect showers, there’s a few things to look for:

  1. A temperature difference from the surface to 850mb of at least 13°C.
  2. Less than 60° of wind shear between the boundary layer and 700mb; preferably less than 30°.
  3. At least 100km of fetch which the air travels over open water.

Given that lake temperatures are still sitting at 22-24°C, we’ll certainly see plenty of clouds develop and move south off the lakes. Whether or not lake-effect showers develop will depend precisely on the winds, but it looks fairly favourable right now with winds forecast to be from the NW with minimal directional shear. We’ll likely see some streamers develop overnight, providing showers or drizzle to communities in lee of the lakes. Current forecasts put these narrow bands of precipitation between Portage & Winnipeg and just east of Winnipeg, but we’ll have to see what the actual wind direction ends up being as to where they’ll go. Right now it looks like there won’t be enough of a westerly component to the wind to bring them into Winnipeg.

If the surface winds end up too westerly, or the 850mb temperatures don’t cool off quite as much as forecast, then no streamers will form. It will be interesting to see what happens!

In the end, it could certainly be worse than it’s going to be. The coldest air will be over us during the overnight period, and we’ll likely have cloud cover as well which will help keep things a little warmer. By the time Thursday afternoon rolls around, the cold air will already be exiting the region, so we won’t end up dealing with temperatures quite as cool as many other areas across the Prairies will.


  1. It’s not fall yet! 

First Major Snowfall For Southern Manitoba

Residents of Southern Saskatchewan and Manitoba are getting the snow shovels out today after an Alberta clipper brought significant snowfall to many areas in those regions.  Across southern Manitoba, many highways were closed due to the event.


Snow falls in the Osborne Village area of Winnipeg on Thursday night.  Photo ©2010 Brad Vrolijk, taken on an iPhone with Instagram.

While the low pressure system that brought snow to Southern Manitoba yesterday through last night has moved out, lake-effect snow flurries continue to affect some areas of the Red River Valley.Environment Canada has issued special weather statements outlining the amount of snow many areas received.  Across west-central Manitoba, along the Trans-Canada Highway, and through much of the Red River Valley, snowfall accumulations as of Friday morning are in the 10-20cm range:

Selected storm total snowfall amounts

Dauphin                             17 cm
Gilbert Plains                      20 cm
Brandon                             10 cm
Roblin                              12 cm
Rivers                              11 cm
Winnipeg                            10 cm
Oakbank                             10 cm
Pinawa                              12 cm
Grand Rapids                        14 cm
Wilson creek                        18 cm
Wasagaming                          15 cm
Fisher Branch                       12 cm
Portage la Prairie                  10 cm
Beauséjour                          12 cm
Morden                               5 cm

While the storm has moved out, gusty northwest winds have moved in.  Temperatures should drop into the low (high?) teens, about the −10 to −12 degree C range, by this afternoon with an arctic air mass moving in behind the clipper.  This cold air is also producing lake effect snow.

 
 

This is resulting in narrow bands of flurries through small segments of the Red River Valley.  Winnipeg has seen fairly continuous flurries through Friday morning, and has already had another 2-3cm of accumulation from them.  They should move out of the Winnipeg area this afternoon as the winds become more northerly, however travellers should be aware for the potential of heavy snow along the Trans-Canada Highway to the west and east of Winnipeg.
We will see temperatures plummet tonight to below −20 degrees, bringing us our first true winter night of the season.  Things should warm up a bit for Sunday, when there’s a good chance that more snow will push into Southern Manitoba as a system heads east-northeast out of Montana.  

 
12Z GEM-REG 48H Output (valid 12Z Sunday Morning), 3hr QPF & MSLP 

Current indications are that this system could deliver another 4-8cm of snow, however the exact amounts will be a lot clearer once the system is closer to us and more developed.

One last note, is that the wind chill this afternoon will be about −24; well below the actual temperature, so be sure to throw on an extra layer of clothing and a scarf to keep warm if you need to be out and about.
That’s all for now!  Stay warm and drive safe.