Sunday, 11 August 2013

Thick Soupy Fog Envelops the RRV

     Calm to light winds combined with lots of surface moisture from last night's rainfall have allowed for a fairly thick fog to envelop the Red River Valley this morning. Here's a visible satellite image from this morning at 8:45 am showing the fog areas in parts of southern Manitoba.

     Winnipeg airport reported visibility as low as 200 metres. You couldn't see anything in the Winnipeg webcams this morning:

     The fog will slowly ''burn off'' through the morning as the sun manages to warm the surface, allowing relative humidity to drop. When this occurs, the water droplets in the fog evaporate. Often times the fog dissipates at the surface first, leaving a layer of stratus just above the ground that will also dissipate shortly after. Fog is usually thinner at the edges (seen on satellite), therefore this is where it usually dissipates first.


  1. At my house in St boniface the visibility was down to 150 meters!

  2. Great blog! Between you, Rob's Blog, and A Weather Moment, Winnipeg seems to produce some of the best weather-related blogs in the country. I've been looking through some of your old posts for stats on the mean temperature deviations each month, but I noticed that you started including this info consistently from June 2012 onward. I've got April 2012 from your site also. I just need May 2012, and everything back from March 2012 to July 2011 (when that 15-month above normal stretch first started). If you already have that info on hand for those 10 months, I'd really appreciate it, but don't go out of your way - it's just for my own personal curiosity. :)

    1. Welcome to my blog Anon; I'm glad to hear you find it useful :)

      As for the stats you needed.. here's the mean temperature deviations from the *1981-2010 normal* for that entire stretch of warmer than normal temperatures:

      May 2011 -0.5°C (estimated due to missing data)
      Jun 2011 +0.2°C
      Jul 2011 +1.6°C
      Aug 2011 +1.6°C
      Sep 2011 +1.3°C
      Oct 2011 +3.2°C
      Nov 2011 +2.6°C
      Dec 2011 +5.4°C
      Jan 2012 +5.6°C
      Feb 2012 +3.4°C
      Mar 2012 +8.0°C
      Apr 2012 +1.4°C
      May 2012 +0.8°C
      Jun 2012 +0.9°C
      Jul 2012 +2.7°C
      Aug 2012 +0.6°C
      Sep 2012 -0.3°C

      Note that I didn't start using the 1981-2010 normals in my monthly summaries until October 2012, explaining why the deviations given in the monthly summaries prior to Oct 2012 don't match with the ones I have given above.

    2. Thanks! Just to confirm, September 2012 was actually a colder than average month when compared to 1981-2010 normals then? 'Cause it's +0.3 based on the older comparison and I just want to make sure. Thanks a lot. :)

    3. Yes September 2012 was 0.3 degrees colder than the 1981-2010 normal but 0.3 degrees warmer than the 1971-2000 normal.

    4. Anonymous,
      you might also want to check out Mike's blog @ or .ca, forget.

  3. JJ, are you convinced that we'll see 30C temps by Saturday?


    1. It certainly does look warmer by the end of the week.. as the ridge to our west is expected to strengthen and the polar vortex finally retreats to the northeast... all allowing warmer air to move in. We most certainly may get a few days of highs in the high 20's to near 30°C. Based on what I'm seeing so far, it doesn't look like a major heat wave though.

      HOPEFULLY this warmup actually does pan out or else this summer is just hopeless!

  4. Models have really ramped up the heat for the weekend in today's update. Based on current indications, highs would easily exceed 30°C with the potential for highs in the 32 to 34°C range... But it's still too early to put too much confidence on that.

    1. Would say humidity will be a big factor? I'm guessing not, usually when it's hot in August is's a dry heat.

    2. Fantastic blog! A think that this blog is the best one in the country for weather! I live just south of the city in La salle. I used to comment on robs blog but I don't any more becuase I hate having to wait a whole day for my comment to be approved.

    3. I stopped commenting on robs blog for the same reason. By putting comment moderation in he gives the idiots who troll his blog just what they want, attention.

    4. Humidity levels do look to increase as well, especially by the weekend.

  5. Some chilly lows from this morning, courtesy of Manitoba Agriculture:

    Eriksdale 2.5°C
    Dugald 3°C
    Marchand 3°C
    St Pierre Jolys 3°C
    Steinbach 4°C
    St. Adolphe 4°C
    Altona 5°C

    Got down to 5 or 6°C at Winnipeg airport, 7.0°C here in south St Vital and 11°C at The Forks.

    1. Thats freezing!

    2. Considering in a couple of days It will be well over 30!

  6. Hi JJ, Do you know why the forks is always much warmer then the airport at night? Might it have something to do with the two rivers meeting? Thanks so much.

    1. It's the 'urban heat island' effect. The darker surfaces of the downtown area (concrete, asphalt, etc..) absorb more heat during the day than in areas where there is more vegetation. That heat is released at night keeping temperatures warmer. If you're interested, here's a good video talking about this effect:

  7. Saturday is looking like a scorcher right now. Highs of 33 or 34°C along with humidex values in the high 30's and approaching 40 are likely under the current forecasts.