Will skies be clear over southern Ontario Monday night?
Cloudy skies during the evening are likely to begin clearing before morning, as moisture moves southeastward from southern Ontario overnight (illustrated below for early Tuesday).

Will skies be clear over southern Ontario Sunday night?
Partly clear skies are expected over most regions, except for more cloudiness likely over southwestern regions, due to increasing mid-level moisture over those regions (illustrated below for Sunday night on 700 mb moisture chart) and except for some high thin clouds that may occasionally appear, due to increasing jetstream-level moisture (illustrated below for early Monday).

Will skies be clear over southern Ontario Saturday night?
Clearing skies are expected after midnight, but fog is likely to form in the regions where the sky clears.

Will skies be clear over southern Ontario Friday night?
Mostly cloudy skies are likely over most regions, except for partly cloudy skies over southwestern regions, where mid-level moisture is forecast to be less extensive than other regions (illustrated below for late evening).

Will skies be clear over southern Ontario Wednesday night?

Clear skies are expected, except for some cirrus cloud that may appear over most regions, due to jetstream-level moisture which is forecast to move southeastward over southern Ontario especially after midnight (illustrated below for early Thursday) and due to jetstream winds over southern Ontario.

Will skies be clear over southern Ontario Tuesday night?
Clear skies are expected, but some thin, high jetstream-level cirrus may appear over some regions due to a strong jetstream which is forecast to be over southern Ontario overnight (illustrated below).

Will skies be clear over southern Ontario Monday night?

Clear skies are likely during the evening over most regions and then increasing cloudiness is expected after midnight over most regions due to increasing moisture (illustrated below for early Tuesday) spreading southward over southern Ontario after midnight.

Extra: related to the Aldebaran graze event: updated moisture forecast charts are shown for Monday morning's updated GFS model (although similar to NAM model output shown in the images above):