Will skies be clear over southern Ontario Sunday night?

Clear skies are forecast.

Also:

Will skies be clear over Earlton, ON during the Aldebaran lunar graze occultation event http://www.lunar-occultations.com/iota/bstar/0710zc692.htm Tuesday morning (time, approx. UTC 08:30)?

Skies may be clearing by occultation time. Forecast models predict a region of moisture at 700 mb level (generally causing mid-level cloudiness) to be moving southward from the Earlton area around 09 UTC but more widespread moisture at the 850 mb level over the area. While humidity generally <70% doesn't mean widespread cloud, upward motion (such as ahead of a warm front) can cause it to be widespread cloudiness, while strongly descending air (such as following a strong cold front) can mean dissipating cloud. In this case, a cold front is forecast to move southward over Earlton overnight Monday night and be near Toronto by sunrise Tuesday but strong subsidence is not forecast following the front. The moisture which is forecast to be over Earlton could dissipate by occultation time, but may remain as a scattered or broken layer of clouds that doesn't dissipate until either dry air moves over it and mixes with the moisture to reduce the relative humidity and cause the clouds to dissipate, or else waits until vertical mixing and convection begins after sunrise to help mix the moisture out and cause dissipating clouds.

In this case for 09  UTC Tuesday, the nearby presence of lots of moisture implies a significant risk of cloudiness (possibly broken overcast or just scattered clouds) until several hours after sunrise. But, it could also be read as clearing skies, and possibly even mostly clear skies, by occultation time.

Below are forecast charts for moisture at 850 and 700 hPa levels from GFS model and latest NAM model.

Saturday night: clear skies

Will skies be clear over southern Ontario Friday night?
Clear skies are expected, except for thin, high jetstream-level clouds that may appear occasionally due to the position of the jetstream over southern Ontario overnight (illustrated below for late evening).

Will skies be clear over southern Ontario Thursday night?

Cloudy skies during the evening are likely to begin clearing after midnight and by morning twilight when most of the moisture following Thursday evening’s cold front moves southward from southern Ontario (illustrated below for early Friday).

Will skies be clear over southern Ontario Wednesday night?
Mostly clear skies are likely, except for some clouds at low, middle and high levels that are likely to appear, especially over southwestern regions, due to moisture which is forecast to gradually increase over southwestern Ontario overnight (illustrated below for late evening).

Will skies be clear over southern Ontario Tuesday night?
Clear skies are expected, except for some high jetstream-level clouds that may appear over some locations, and except for some low clouds that may appear occasionally, caused by increasing low-level moisture over southern Ontario overnight (illustrated below for early Wednesday).

Will skies be clear over southern Ontario Monday night? Mostly clear skies are expected, except for some clouds that may appear occasionally over regions north of Lake Erie during the evening and especially over the Niagara peninsula, caused by low-level moisture gradually moving eastward from southern Ontario overnight (illustrated below for late evening).