Will skies be clear Monday evening over southern Ontario?

 It looks like the early sunset may allow several hours of mostly clear skies over many parts of southern Ontario before mid-level cloudiness increases ahead of a low pressure trough moving eastward over southern Ontario during Tuesday, especially over the regions north and west of Toronto. The bright full moon and resulting few stars visible may give the appearance of a mostly clear sky, even while cloudiness increases, but increasing moisture and cloudiness will probably be apparent during early evening over southwestern Ontario and later in the evening over regions east of Toronto.

Below: forecast chart showing mid-level (500 hPa-level) moisture at UTC 03:00 (EDT 22:00 Monday evening)

It looks like clear skies are likely during early evening, followed by increasing cloudiness with bands and waves of high-level cloudiness spreading southeastward over southern Ontario. Below is an image (if the blog site allows it to get posted) showing a supporting image with forecast moisture at 700 hPa level over the central Great Lakes region at UTC 03:00 (EST 22:00) Friday evening and spreading southeastward.

Clear skies continue over southern Ontario this week as a result of a persistent block pattern, with a ridge blocked over Ontario. The upper level ridge and a surface high pressure ridge over Ontario are resulting in clear skies and the nearly stationary pattern is resulting in little change from day to day and night to night. Other features of the block pattern that strengthen the block include deep troughs over the Atlantic and Pacific coasts and a ridge over the north Atlantic. The chart below shows the 250 hPa winds clearly tracing the ridge over Ontario and trough on each side of the ridge (as well as a weak trough south of the Great Lakes).