Convective Discussion
· A frontal disturbance over Quebec/New England may bring isolated/non-severe thunderstorms to northernmost areas of the Maritimes later today
· A cold front over Labrador may trigger thundershowers over southeastern portions this afternoon
· Scattered thundershowers are continuing over the Gulf Stream mainly south of the Scotian Slope waters
· Elsewhere, a quasi-stationary ridge will inhibit significant convection.
Technical Discussion
High pressure system prevails over southern Maritimes and Newfoundland. A frontal disturbance west of the region is triggering elevated thunderstorms (eastern Ontario and Western Quebec this morning). The thermal ridge associated with this feature will slowly advance towards northern NB later today with K indices suggesting isolated thunderstorms becoming likely especially during the tonight period. Precipitable water estimates from this morning sounding are already in the 30-40mm range in the risk area, and 40-50mm near the thermal ridge resulting in a potential for bouts of heavy showers, especially tonight.
The cold front over Labrador is generating some instability with towering cumulus tops extending well above the freezing level, but with limited penetration into the glaciation levels. However, the combination of mediumsurface heating - extra lift provided by the mountainous areas - and the active front could generate a small cumulonimbus capable of giving brief heavier showers and wind gusts to 70km/h. Behind the cold front, westerly gusts of around 80km/h are likely to persist.
For slope waters, clusters of convection mainly south of forecast waters will continue. Scattered thundershowers are expected.
Regional Impacts
Northwestern New Brunswick: Isolated thunderstorms possible during the late afternoon and evening. Brief heavier showers are possible.
Labrador: Slight risk of a thunderstorms possible during the afternoon and early evening. Brief heavier showers and wind gusts to 70km/h are possible. Very windy in the westerlies behind the cold front with gusts to 80 km/h.
Slope waters of the Scotian Shelf and Southern Grand Banks: Scattered thundershowers with no severe impacts expected.
Jean-Marc