Sunday, 10 November 2013

Temperatures to Plummet

     An arctic front will be passing through the RRV this morning, ushering in the coldest air of the season so far. This can be seen in the forecast model image from the NAM weather model below:

Forecast map for this afternoon at 925 mb (colours=temperature, wind barbs=wind, black lines=equal heights)
     Some flurries will be possible this morning, albeit very little accumulations are expected. In fact, we have already seen some of this flurry activity around 8 am. Temperatures will not rise much this morning, if at all, and will plummet this afternoon behind this front. Temperatures may be as low as -8°C or so by supper. In addition, winds will be on the increase later this morning and be out of the northwest at 30 to 40 km/h by early afternoon.

     It will be a cold night tonight as we drop to the high to mid minus teens. Tomorrow will be downright chilly for this time of year, being some 7 to 9 degrees below normal. Highs around -7°C to -9°C are expected. Another cold night tomorrow night with lows in the mid minus teens.

     It could be worse however. Given how cold the airmass that is moving in is, if we had snow on the ground we would be talking about lows in the minus 20's. Thankfully we don't have a snow pack on the ground. The effect of a snow pack on the ground is significant. In Saskatoon, which seems to already be in full winter, saw a low around -22°C this morning, and is expected to be just as cold tomorrow. Highs in the mid minus teens are expected there today. Snow has been on the ground there for several days now.

     Temperatures rebound on Tuesday back to more normal values, with a high around -1 to -2°C expected. Generally seasonal to above seasonal temperatures are expected through the remainder of the week. No major snowstorms expected this week.

     Here's a collection of webcam images from the Prairie's biggest cities this morning, just to compare how winter has been progressing so far. As you can see, we've been fairly lucky in Winnipeg so far.

REGINA:
SOURCE

SASKATOON:
SOURCE

CALGARY:
SOURCE





EDMONTON:
SOURCE

Publié par à l'adresse

9 comments:

  1. Walter DickensNovember 10, 2013 5:04 pm

    JJ,
    I read that the reason that without snow cover it isn't as cold is because the heat from the ground rises and warms thing up. And that with snow cover the snow prevents the heat from rising. Is this information correct?

    Thanks,
    Walter

    ReplyDelete
    Replies
    1. jjcwpgNovember 10, 2013 7:14 pm

      There's 2 main reasons why it is typically (or quite frankly almost always) colder when a snow pack is present:
      1- The snow cover acts like an insulator and prevents a good chunk of the warmth from the ground from escaping into the atmosphere.
      2- Snow is a very good reflector because it is white. As a result, it reflects a very large portion of solar radiation back into space, and that energy therefore cannot be used to heat the atmosphere.

      Delete
  2. jjcwpgNovember 10, 2013 7:28 pm

    Speaking of snow, looks like we got lucky once again today. A decent band of snow formed right after the front passed through the city this morning and we got away with just a few snowflakes. I wonder how much longer this luck will continue...

    And by the way, the daytime high this afternoon was just -15°C in Saskatoon today.

    Unfortunately the warmer weather I was seeing last week for the second half of November is still in question. The next week or two look variable, periods of warmth and periods of cool, but no major and prolonged warmups I'm sad to say.

    ReplyDelete
  3. jjcwpgNovember 11, 2013 9:11 am

    Incredible! Lows in the -30's in a couple parts of Saskatchewan this morning along with wind chill values near -40! Here's some lows:

    Spiritwood -33.5°C (west of Prince Albert) (Normal low -11°C)
    Nipawin -32.4°C (east of Prince Albert) (Normal low -12°C)
    Meadow Lake -31.2°C (Normal low -11°C)
    Southend -30.0°C (Normal low -13°C)
    Key Lake -28.7°C (Normal low -14°C)
    Melfort -28.5°C (Normal low -12°C)

    In Manitoba:
    Swan River -23.4°C
    However, Roblin has dropped to -28°C as of 8 am.

    To put in perspective, Winnipeg's earliest -30°C reading was November 19 with a low of -33.9°C in 1896.

    ReplyDelete
  4. jjcwpgNovember 11, 2013 10:53 am

    Tough temperature forecast for Wednesday. Models are not agreeing. Very warm air aloft is expected to move in, but surface temperatures are in question. NAM and GFS keep Winnipeg cool in low single digits, but something to keep in mind is that those models are fooled right now into thinking there's snow on the ground (however only a couple cm). GEM is much warmer with a high of 7°C. However, cloud cover is another factor to consider.
    Personally I'm leaning towards something around the lines of the GEM, mainly due to the magnitude of the warmth aloft expected to move in. I also like the west/southwesterly winds. We'll see...

    ReplyDelete
  5. jjcwpgNovember 11, 2013 12:30 pm

    Looks like we'll be seeing some flurries off Lake Manitoba over the next couple hours as winds shift to more west/northwesterly.

    ReplyDelete
  6. FrankNovember 11, 2013 5:16 pm

    I noticed today that the GEM model indicates a snowstorm mid saterday-mid sunday with 16 CM...

    ReplyDelete
  7. AnonymousNovember 11, 2013 6:11 pm

    Yeah I have seen this as well.

    JJ, what are your thoughts regarding the indications of a snowfall of 15CM or so From the GEM model for the weekend?

    ReplyDelete
  8. jjcwpgNovember 12, 2013 7:37 am

    Talked briefly about it in my new post.

    ReplyDelete

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