The forecast for today is clear and cold. Considering that the original plan to go/no-go the Saturday 1 PM Pacific start is for that call to be made this afternoon. That would seem to indicate that the match is going forward as planned.
Even though the Olympic Stadium has a roof, its fragile state is always challenged when the weather man calls for snow. Though, a threshold of 3 cm of snow accumulation has been set as acceptable by the Parc Olympique, the organization managing the Olympic Stadium among other structures.
But, the forecast for Saturday is for snow and a decent amount of snow.
Cloudy with snow showers early and steady snow likely later in the day. High 32F. Winds N at 10 to 20 mph. Chance of snow 70%. 3 to 5 inches of snow expected.
And if you look exactly at when that snow is expected to be heaviest it is just the hours before the match is scheduled. It looks as if right now the call will have to be made off of gut/instinct rather than actual snow accumulations.
The match was already moved from Stade Saputo and has sold more tickets than there are seats in the primary stadium for the Montreal Impact. If they need to reschedule it would be for Sunday, which is supposed to be cold and dry, which would give the heaters that work the roof time to deal with the snow and not endanger fans.
You may want to keep your Sunday a bit free.