Tomorrow night will be humid, but there are possible rains with a 60-70% chance. The reasons are practically to do with a well organized low pressure system coming from the Southwest from Southern and Eastern Ontario whilst travelling along the highway 401 corridor.
The track is understood, but it is showing signs of additionally moving in an extreme Southwest flow, but also with a distinctive Westerly tilt. I, too, have to watch this very carefully since it is rather ubiquitous. The rains may arrive later in the afternoon, especially since they will arrive in Kingston in the morning hours.
In any case, there are several implications at work here. First, it will be humid and there could be sunny breaks, which serves as a catalyst. However, sunny breaks help develop convective clouds, so we need to pay attention to that. Second, the system is quite massive on satellite and has some decent cloud top heights, which suggests embedded thunderstorms and thus copious amounts of rainfall, should they happen. Finally, this system carries a lot of moisture with it and this helps fuel the amounts of rainfall within actual clouds.
However, I believe Montreal and Ottawa will be on the edge of the whole thing, but moreso in the afternoon, so I suspect more of an overcast scenario, but there is still a chance for showers or steadier rains.
On a smaller scale, the winds will be from the East at 10-20 km/h (or higher) while temperatures will be warm and sticky at 24-26 Celsius, but feeling like 30-31 C with the humidex.
Regardless of the changes, I sincerely recommend that you all bring an umbrella. I also wouldn't be surprised if there is a little lightning here and there (kind of like yesterday's late afternoon). The more bad news with this is that it is more likely to have "possible" steadier rains in the evening-overnight hours, so this could actually be a wash-out display...that is, until I get further reports.
I've actually noticed this system since almost a week ago, but I knew it could present problems.
Trav.
