Regional Impacts
Today
NB/NS/PEI: Chance of scattered thunderstorms over the central Maritimes this afternoon with small hail, strong wind gusts, and heavy downpours.
LAB: Chance of scattered thunderstorms over eastern Labrador today with strong wind gusts and locally heavy downpours.
NL: Slight chance of an embedded thundershower over southwestern Newfoundland this afternoon.
Tonight
NL: Slight chance of an embedded thundershower over southwestern Newfoundland tonight into tomorrow morning.
NB/NS/PEI/LAB: None.
Tomorrow
NL/LAB: Chance for scattered thunderstorms across Newfoundland and parts of Labrador tomorrow with locally heavy downpours.
NB/NS/PEI: None.
Convective Discussion…
This morning, an upper trough extends from a low over the Labrador Sea back through northern Quebec and into Hudson Bay. South of this feature, a shortwave is moving into northern New Brunswick which will spin up a surface low by this afternoon. These will be the main drivers for convection in Atlantic Canada today. Over southeastern Labrador, clear skies this morning will pave the way for instability to increase to near 750 J/kg MLCAPE by early this afternoon, however a lack of effective shear (10 to 20 kts) over the region will likely keep any storms from becoming organized. Thus heavy downpours and some strong wind gusts are the main hazards here today. In the Maritimes, the surface low over New Brunswick will pull a cold front across the province this afternoon. Better dynamics will be in play here, with a good low level jet forecast to set up as well as a 500 mb jet moving across New England and into Nova Scotia, leading to effective shear of 30 to 40 knots by this afternoon. PWATs of 32.5 mm have been observed at the 12Z Yarmouth sounding this morning, which could build to near 40 mm over the area of interest today. Given enough clearing this morning, instability is forecast to increase upwards of 1000 J/kg. While thunderstorms are expected to fire across most of the Maritimes today, the best chance for severe storms will be in eastern New Brunswick and PEI in the warm sector closer to the low centre. One of the limiting factors for Nova Scotia will be the timing of the cold front moving through as well as some drier air present over the region.
Tonight, the low over New Brunswick will move out over the Gulf of St. Lawrence before moving through the Strait of Belle Isle tomorrow. Some elevated thundershowers will be possible around the low tonight and into tomorrow morning as it pushes into western Newfoundland. Some heavy downpours will be possible tomorrow as the cold front crosses the province but mainly cloudy conditions will keep the instability from building , this should keep rainfall rates around 10 to 20 mm per hour in the strongest cells.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Forecaster: Copp