Convective discussion:
Non-severe thunderstorms possible for Labrador, western New Brunswick, and most southern offshore waters. Severe is likely near Geroges Bank, where squall warnings are in effect.
Currently there is a trough extending over southwestern forecast waters, which currently have SSTs above 26 C. This is giving CAPEs near 2500-3000 J/kg, and wind gusts in excess of 40 kts are likely. PWAT is in the 50 mm range. But 0-6 km Shear is low, near 20 kts. So these are multicells organised along the weak trough moving though. While SST’s drop gradually farther east, there are still SSTs near 20 C for southernmost parts of Laurentian Fan and the Grand Banks
For western New Brunswick the main limiting factor is moisture. PWAT is near 20 mm, at 850 mb dew points are near or less than 8 C, and surface dew points are less than 16 C. While there is a strong upper jet over the province, it is not well placed for any significant lift. There is a weak trough over the southern part of the province, and some low level moisture is advecting in from southern Maine. Conditions are clear with come Cu setting up. Based on this there is a chance for isolated thundershowers this afternoon and ending this evening, with the highest chance in the south.
For Labrador there is a QS low near Ungava bay with a trough extending south crossing western areas moving towards the coast, giving weak lift enhanced a bit near the trough. A slowly approaching deep thermal trough from the west will help destabilise things, and the aforementioned upper jet is over southernmost Labrador. The left exist is a bit too far east, but may enhance things along the border range in the south, and maybe south of Lake Melville near the coast. Limiting factors are again low PWAT amounts near 20 mm, and low dew points. Excpect non severe thundershowers with some moderate wind gusts. With freezing levels generally below 8500 feet, small hail is possible.
Regional Impacts:
Labrador: non-severe thundershowers are expected this afternoon into this evening. These’s a chance of near severe cells near the southern border of Labrador.
Western New Brunswick: slight chance of thundershowers this afternoon.
Slope waters extending to south of the Avalon Peninsula: For western slope waters just south of the main discussion area, squalls are likely for western areas. Elsewhere non-severe embedded thundershowers are expected.
Doug Mercer