Updated: May 19, 2019
We are tracking a round of showers and thunderstorms to pass over and linger over portions of Northern and Southern Ontario lasting into Monday afternoon.
Into the evening on Saturday, a patch of light to moderate showers will spread in Northeastern Ontario. This quick moving line of showers, with some possible thunderstorms over Manitoulin Island and the Bruce Peninsula, will move out of the region and into Quebec/Central and Eastern Ontario into the early morning hours on Sunday. In Southern Ontario, scattered showers may develop across the region. Including a few possible thunderstorms, especially near Lake Ontario. Into the morning hours on Sunday, another patch of showers and thunderstorms will spread back into Northeastern Ontario. The rain will start as light to moderate showers before changing over to some moderate to heavy showers in the afternoon. Across Southern Ontario, scattered showers and thunderstorms may develop in the region into the early afternoon. Some of these thunderstorms may be strong to severe. Into the late afternoon hours, moderate to heavy showers including possibly strong to isolated severe thunderstorms will continue across Northeastern Ontario extending into Central and Eastern Ontario. Possible severe thunderstorm cells will continue development and track through portions of Southern Ontario. As this patch of showers and thunderstorms continues east into Quebec and Eastern Ontario, portions of Northeastern Ontario may see a break in the activity. Into the evening hours, another round of showers and thunderstorms, some severe, will spread across Southern Ontario including portions of Northeastern Ontario. Into the overnight hours extending into Monday morning, scattered light showers will be possible across Southern and Northeastern Ontario with a chance at 1-3" of snow across portions of Northeastern Ontario, extending in a line from Wawa and Pukaskwa Park towards Cochrane and Smooth Rock Falls. Finally, in the afternoon and evening, the province will clear out.
Blue or '1':
Areas in the blue or marked with a '1' can expect less than 15mm of rain. This includes the northern shore of Lake Superior such as Thunder Bay and Nipigon. This area also extends north into portions of Far Northern Ontario. This includes Attawapiskat, Fort Albany, Moosonee, Hearst, Carmat and Cochrane. Many places will see trace amounts.
Green or '2':
Areas in the green or marked with a '2' can expect between 10 and 30mm of rain. This includes a thin portion of Northeastern Ontario extending from Lake Superior and Pukaskwa Park inland to include Peterbell, Timmins and Kirkland Lake. Most places should see near or above 15mm in this range. This area also includes ALL of Southern Ontario in a line south of Tobermory, Rosseau, Huntsville, Barry's Bay, and Arnprior. Due to thunderstorms, some severe, rainfall totals will likely reach between 20 and 30mm for most of the region with many places seeing totals as high as or over 50mm due to thunderstorms.
Yellow or '3':
Areas in the yellow or marked with a '3' can expect between 20 and 40mm of rain. This includes a large portion of Northeastern Ontario such as Wawa, Foleyet, Temiskaming Shores, Temagami, North Bay, Sudbury, Manitoulin Island, Espanola, Parry Sound, Algonquin Park and much of Renfrew County. Areas near Parry Sound, Huntsville and Tobermory may see between 20-30mm with higher confidence of a chance at seeing 40mm from system rain, therefore, the increase from the green or level 2 option. Most places should see between this range although we can't rule out local totals surpassing 50mm due to thunderstorms.
Orange or '4':
Areas in the orange or marked with a '4' can expect between 25 and 50mm of rain. This includes a small portion of Northeastern Ontario east of Lake Superior. This includes Sault Ste. Marie, Chapleau, Ruel, Elliot Lake, and Agawa Bay. Most places should see between this range although we can't rule out totals surpassing 75mm due to thunderstorms.
*Disclaimer: thunderstorms may significantly increase rainfall totals than what is described in this forecast.
We will be closely watching the severe thunderstorm threat across Southern Ontario on Sunday.
The forecast for thunderstorms can be found here: https://www.weatherwatch.space/post/isolated-severe-thunderstorms-possible-in-southern-ontario