It looks like the fine summer-like weather we've enjoyed through much of August will close out the month this weekend with another round of summer-like warmth, especially over SE MB. But as if on queue, a sharp cold front will move across southern MB late Sunday or Monday bringing in much cooler and wetter weather just as the calendar flips to September. The details..
An upper ridge will build over southern MB on Saturday giving us a fine start to the Labour day weekend. Saturday will see plenty of sunshine across southern MB with temperatures in the mid to upper 20s along with increasing southerly winds. This upper ridge is forecast to build over Ontario over the long weekend, while cooler unsettled weather moves in over the western Prairies. The dividing line between these two airmasses will set up right through southern MB on Sunday along a cold front that is expected to drop southward across the Interlake and stall from southwest MB through Winnipeg into the Pinawa area. There will be a dramatic temperature difference across this front with summerlike temperatures of 27-30C to the south and east, and more fall-like temperatures of 20C to the north and west along with clouds and a chance of showers. Current forecasts for Winnipeg call for a high of 30C on Sunday, but I'm a little skeptical we'll get that high with that Interlake front so close to us (major bust potential Sunday because of this front). I think areas south and east of Winnipeg will have a better chance of seeing 30 degree temperatures on Sunday (including the Whiteshell, Lake of the Woods and the southern Red River valley), while places like Grand Beach through Gimli to the Riding Mtns will be considerably cooler on Sunday (highs only near 20C).
For holiday Monday, models indicate this cold front will sweep through southern MB, bringing in cooler weather for all areas but the extreme southeast along with a good chance of rain, possibly heavy in parts of southwest MB into the Interlake. All in all, looks like the best bet for a warm dry long weekend will be toward the SE corner of the province (e.g. Whiteshell, Lake of the Woods and southern Red River valley), while cooler and wetter weather moves in by Sunday to areas further north and west (especially SW MB through the Interlake). As always.. stay tuned…the forecast for this long weekend will be a tricky one.