We are watching the risk for some scattered thunderstorms to develop across portions of Southern Ontario including Eastern and Northeastern Ontario. This also includes Southern Quebec. Some of these thunderstorms may be briefly severe and pose a gusty winds and heavy rain risk.
Scattered showers and thunderstorms till develop before and along a cold front as is passes through Southern Ontario and Southern Quebec. Some of the thunderstorms may be capable of producing brief gusty winds and heavy rain. Frequent lightning and small to moderate sized hail is also likely.
Areas in yellow and marked with a '3' can expect a moderate risk for severe thunderstorms. In Ontario, this risk includes two separate areas. The first area is in Southwestern Ontario which extends from Lake St. Clair and Bayfield over to Lake Erie near Dunnville, including Chatham, Sarnia, Stratford, Brantford and London. The second region includes portions of Eastern and Northeastern Ontario as well as Southern Quebec. This region expands from Alexandria through to Calabogie and Madawaska, including South River and West Nipissing. This includes North Bay, Algonquin Park, Pembroke and Ottawa. This same region also extends into Quebec from Temiscaming through to Obedjiwan and La Tuque, including Rigaud. This includes Gatineau and Lac McLennan. The main threats in this region include heavy rain and gusty winds near or over 90km/h. Small to moderate hail is possible in Southwestern Ontario and moderate to at times large hail in Eastern Ontario/Southern Quebec. Hail sizes will mainly range from 1-2cm with local pockets of 2.5cm-3cm. Frequent lightning is possible in the strongest storms.
An isolated tornado threat may develop in Southern Quebec/Eastern Ontario although this is questionable. An isolated landspout tornado may also be possible in Southwestern Ontario, but, again, that is questionable. Because of this questionable risk, we have not included these factors to reflect the the forecast level on the map.
Areas in green and marked with a '2' can expect a low risk for severe thunderstorms. This includes a large portion of Southern Ontario and Southern Quebec. The first area extends from Amberley southeast along Highway 86 towards Wingham and Listowel over to Guelph and Hamilton. Everything south of that line, including Essex County are under this risk. The main threats are heavy rain and brief damaging winds. Small hail might be possible. The next area is through the GTA including Oakville, Mississauga and Toronto, as well as Uxbridge. This area can expect non-severe thunderstorms which may include sub-severe storms with heavy rain, brief gusty winds and small hail. Further east, north of Lake Ontario, from Lindsay and Coborug over towards Kingston, including Madoc, Tamworth and Belleville, as well as Prince Edward County, isolated thunderstorms may travel over the region with heavy rain and gusty winds. A sub-severe thunderstorm can't be ruled out. Further in Eastern Ontario extending from Brockville and Cornwall north wards Perth, Denbigh, Sundridge, Monetville and Temagami, isolated thunderstorms may become severe as they track over the region. The best risk of this will be between Brockville and Cornwall. Heavy rain, gusty winds and small to moderate sized hail is possible. In Northeastern Ontario, there is question whether or not a few thunderstorms, isolated severe, will develop between Kirkland Lake and Gowganda. We have highlighted this region on the map although we are not expecting much to amount from those storms, if they develop. Finally, in Southern Quebec, we have highlighted a large area where isolated to scattered thunderstorms, some severe will develop and travel. This extends from the Ontario border south of Lucky Rock through to Chapais and Lake Mistassini, including Lake Albanel. This risk also extends south towards Chute-des-Passes and Trois-Pistoles, including Saguenay. This risk then extends south towards Quebec City and Sabrevois, including everything in between. This region includes Montreal and Val-d'Or. Most places will see non-severe thunderstorms or no thunderstorms at all, although, an isolated severe storm or two may be possible.
Elsewhere, areas in blue and marked with a '1' can expect non-severe thunderstorms.