Tuesday, September 22, 2009

Fall arrives.. but summer hangs on through the end of the week

Fall officially arrived today at 4:18 pm CDT, but you wouldn't have known it as sunny warm weather prevailed over southern Manitoba today. And the fine late summer weather will continue the rest of the week with sunny skies and temperatures in the mid 20s.. some 10 degrees above normal for the end of September. Changes are coming though by this weekend as an intensifying storm system moves across Manitoba and drags colder air into the Prairies by Sunday along with some rainshowers. More typical fall like weather is expected to close out the last few days of September, which should finish as the warmest on record in Winnipeg, as well as over much of the Prairies.


  1. Fall is barreling our way, with this weekend being a noticeable transition period. Models are showing temperatures in the low twenties for Thunder Bay this week...contrast that with the chance of heavy wet snow on Monday in the same place!

    Some places might sneak up to 30C one more time this year over SW MB on Thursday. With 850mb temps expected to be near 18C, we should get high twenties, with the odd thirty possible.

  2. GFS and ECMWF are really developing that low next Sunday into Monday as it moves into NW Ontario. Some very cold air and strong winds coming in behind it Sunday night into Monday with single digit highs possible Monday if the GFS is right.. as well as the possibility of .. yikes.. snowflurries. Hopefully GFS is overdoing things as it's prone to do sometimes.. but sooner or later, you know a change is going to come!

  3. Should be plenty of 30 degree temps over Alberta and western SK Wednesday with 850 temps of 22-26C moving in. Look for highs of 30C in Saskatoon, 33C in Calgary, with 35C likely in a few places like Drumheller.

    As Scott mentioned, that heat spreads east into southern MB Thursday, with some 30C temps possible mainly west of the RRV.

  4. Yes Rob!

    You are right about that cold front on Sunday night!

    It looks like it will have some serious BITE to it!!!!

  5. GFS has backed off a bit on the intensity of the low moving east of us Sunday into Monday, but all models are in line for showing windy and much cooler air coming in Sunday into Monday, with temperatures likely in the 10-15C range for highs those days, as well as the possibility of a widespread frost/freeze over southern MB Tuesday morning (29th). Our temperatures then moderate for the last couple of days of September before hints of another cool down for the first few days of October. (GFS even showing the possibility of an early season snowstorm through southern AB/southwest SK/Montana by October 1st.. but again, it's a day 8 forecast from a model that likes to overdevelop things in the long range. Still something to watch..)

  6. Beauty day out there with temperatures climbing rapidly with sunshine and a favourable southwest breeze boosting temperatures up to 26C today in Winnipeg. That will make the 17th 25C day of the month.. a new record for September. I think we'll see a couple more 25C days Thursday and Friday (current forecast high of 24C seems a tad low for Thursday) before the big change Sunday. Enjoy it while you can!

  7. WHOA!

    I cannot believe how warm this September has been so far!!

    Did you see the forecast high for Edmonton for today and then compare it to the high forecasts for next week????

    Take at look at the WEATHER NETWORKS high forecast high for Edmonton for next week....

  8. +2C for a high for Sep 30th?! Yikes.. I guess they're using the extreme GFS outlook. That's the cold air coming in for Sep 30-Oct 1 that the GFS is showing will fuel that snowstorm over Montana.. Again, a possibly overdone solution, but bears watching..

  9. Coincidence or cause and effect.

    The timing of our first Major Atlantic hurricane into Canada at the end of August and the end of our cold weather.

    Was the Tropical system the major event needed to drag that cold wet producing parked system out of the north west?

    Now we have another forecast of significant cooling coincident with a major new system deluging Georgia with 500mm (half a metre of rain according to the Sports pages today)

    Are these codependent or just distant cousins.

  10. Typically in the first couple of weeks in October we see several overcast days in a row as cool NW winds move over the lakes. With the lakes being 6 (?) degrees above normal for this time of year, how could this effect change?

  11. Open lake waters in the fall help provide moisture input during cold outbreaks, creating considerable cloud cover and localized lake effect precipitation. Warmer than normal lake temperatures increases the risk of heavy lake effect events off larger lakes.. in the form of rainshowers early in the season, or snowsqualls once the air gets cold enough in October. The effect of warmer lake waters however would be short lived, as any spell of below normal temperatures will quickly cool off lake waters to normal values.

    Speaking of lake effect, there's a good possibility of off lake steamers off the MB lakes Sunday night into Monday with -2 to -5C air at 850 mb moving over 20C lake waters. That's getting into extreme instability capable of heavy lake effect precipitation, but wind shear may weaken streamers.