Heat and Humidity to Bring risk of Severe Thunderstorms to Ontario Friday

Forecast temperatures (in F) for Friday afternoon

A strong ridge is currently advecting a very warm and moist airmass into the Eastern United States and Southern Ontario. As such, temperatures are expected to soar into the low to mid 30s across a large swath of the province, with muggy dewpoints pushing into the low to mid 20s, making for an uncomfortable few days across the region. As such, intense thunderstorms will be possible for the region Friday with temperatures ranging from 30 to 35 degrees from Windsor through the GTA and into Eastern Ontario, and dew points moistening into the mid 20s in Southwestern Ontario and to the low 20s in Central Ontario. This will lead to a corridor of moderate to high instability Friday with Mixed Layer CAPE ranging from 2000-3000 J/KG across Central Ontario and up to 4000 J/Kg for areas SW of Kitchener and London.

MLCAPE depicted on Friday for S Ontario/Quebec

Wind Shear will be rather weak, with the exception of the corridor southeast of Lake Huron where Surface to 6km wind shear will be between 25 and 35 knots. Surface to 1km shear will be weak leading to a very low tornado risk. Combined with the instability in the area, this would lead to rotating updrafts and the potential for strong winds. Some small hail is also possible in stronger storms, however mid level lapse rates will not be overly impressive ranging from around 6-6.5C/km. Low level lapse rates will be higher leading to the possibility of strong wind gusts.

Possible storms depicted by latest HRRR model

Overall, the risk is conditional and coverage/intensity of the storms will be based on what happens early Friday morning. An area of convection looks to affect parts of southwestern and central Ontario from storms that fire across NW Ontario and parts of the US Midwest Thursday afternoon and evening. If the convection remains more localized and cloud cover smaller, a more robust storm risk could be in play Friday. If the convection is more widespread and lingers Friday morning, cloud cover and precipitation could lower the risk. Severe storms should be possible anywhere from Windsor to Central Ontario, with the highest risk looking to be in SW Ontario.

Thunderstorm outlook for S Ontario for Friday

Either way, always stay tuned to your local weather app and stations for updates on possible severe weather Friday and stay hydrated if you are outdoors!

Author: Lance Quackenbush (follow me on Twitter by clicking my name!)