Monday, December 01, 2008

Alberta clipper system approaching MB

A strong Alberta clipper system is moving across northern SK today ushering in a gusty southwest flow of very mild Pacific air over southern AB and southern SK. Temperatures have soared into the mid teens over southern AB with several record highs established for December 1st.  This warm airmass will be moving towards southern MB over the next 24 hours, but the bulk of the mild air will be bypassing to the south of Winnipeg into the Dakotas overnight. Even so, gusty south winds tonight of 40-60 km/h will bring rising temperatures overnight to the Red River valley, with temperatures expected to climb towards the freezing mark by daybreak. In fact, there's a chance we may get above zero (+1 to +3C) for a brief period early Tuesday morning as our winds shift into the west and tap some of the retreating mild airmass over southern SK. Regardless, the mild temperatures will be short lived as strong northwest winds develop behind the clipper system Tuesday, and bring increasingly colder air through the day. So watch for temperatures to fall Tuesday, especially in the afternoon and evening as those northwest winds pick up. 

As for precipitation with this system,  it looks like Winnipeg may get a period of snow tonight with a risk of freezing rain or ice pellets overnight as the warm front approaches. The bulk of the snow should remain north of Winnipeg through the Interlake and central MB, but we could see a couple of cm tonight. If any freezing precipitation develops, the best chance will be between 10 pm and 4 am, but amounts should be light. Nonetheless, road conditions could be on the slick side Tuesday morning as this system moves through with some mixed precipitation and near freezing temperatures. Look for windy and colder conditions by Tuesday afternoon with occasional flurries giving a dusting to 2 cm over Winnipeg and the Red River valley.                   



  1. I see that Environment Canada has finally switched their radars over to "snow " mode as they had it in "rain" mode all last month.
    Rob what would happen if they left it in "rain" mode all winter.
    Will the radar not be able to pick up the snow as well???

  2. I hate to be the bearer of bad news, but it looks like this "mild winter" is about to come to an abrupt end. The models I have been watching for the past three months have been grossly underestimating low temperatures. Quite commonly 5 to 10 degree off of the actual, but to the BAD news....

    They are currently showing (bearing in mind the underestimation of temperatures here) lows of -31 for late next week. This under a very strong 1052mb high pressure cell. Considering how much these temperatures have been wrong, I interpret this as a -35 to -40 low temperature in actual terms. Of course it is still a long way out, but a very unwelcome sight indeed.

    Along with this cold air comes the likelihood of a green Christmas in some parts of Manitoba. This kind of cold will not support more than snow grains for precipitation, thus preventing heavy snowfall. Areas in the South-East, like Steinbach only have 4 to 5cm on the ground. I assume some areas have little to nothing.

    So much for the good weather....

  3. Daniel..

    That's right.. the snow setting is at a lower radar angle and is scaled to pick up echoes at a lower intensity that the rain setting would otherwise miss.

    By the way, temperatures have gone above freezing just to the west of Winnipeg early this morning as winds shift into the west. Looks like Winnipeg and the RRV should get up to +1 or +2C this morning before the cold front moves through, shifting winds into the NW and dropping temperatures to -10C by the drive home.

  4. Hope you enjoyed that +1C this morning.. we may not be seeing temperatures like that for a long while! Temperatures starting to drop now as those northwest winds kick in..

  5. We have been really short-changed by these clippers so far. Ever since the pattern changed their warm sectors have either missed us or occluded out. All we needed was 1 day of about 4/5 C with strong winds to eat away most of the snow... and we couldn't get it! This reverses the trend somewhat of recent Novembers where we were easily getting warm temps. In past winters we even had warm windy days in January even with 30 cm of snow on the ground.

    Now we will see how cold it gets. With minimal to no snow cover.. we will not drop to -40 C. We would need an extensive and deep snow cover in place coupled with a very cold air mass (850 MB temps < -35 C)