Isolated thunderstorms possible for Southern Ontario on Wednesday as a warm, moist airmass moves over the region. A warm front will move into the region Tuesday night with temperatures rising in the mid to upper 20s Wednesday with dewpoints pushing into the upper teens, yielding moderate instability and the potential for some thunderstorms over parts of South Central and Eastern Ontario away from the shores of the Great Lakes. The strongest instability looks to be just northeast of Toronto and into Eastern Ontario where isolated thunderstorms could fire off after 2pm.
Above: moisture depiction for Wednesday 2pm EDT
The severe potential looks low as vertical wind shear will be low, however stronger shear looks to be present in around the Ottawa area during afternoon time period with the lifting north of the warm front, meaning a slightly higher chance of seeing a locally severe thunderstorm. Thunderstorms are more likely for Eastern Ontario, particularly in the late afternoon and into the evening, however a conditional thunderstorm threat remains possible for southern Ontario.
By Thursday clear skies should yield temperatures closer to 30 degrees with a system moving into the region for Friday cooling temperatures slightly and bringing a few showers to Southwestern, and south central Ontario.