Convective Discussion:
The focus for surface-based convection will be over eastern Newfoundland this afternoon…
A convergence line at the surface currently advancing over central parts of the island will be the main forcing mechanism. The airmass ahead of the line is moisture limited (dewpoint values below 10 and precip. Water around 15mm), however modifying the Stephenville sounding for a worst-case scenario (20,9) gives surface-based CAPE in the order of 400-450 J/kg. This would be enough for isolated thunderstorms to form. The freezing level is down to 7 000 ft, and the distribution of the area of CAPE above it indicates the possibility of hail - the size of pellets. The storm motion for any isolated cells that form would be eastward at 40 km/h, these fast moving storm would limit the amount of rain produced over a locality, and finally the gust potential is 70 km/h.
For offshore waters, isolated thunderstorms are possible over the southern Grand Banks, upper support include a 100+ kt southwesterly jet, PVA and cold air advection along a surface front.
Regional Impacts:
Newfoundland and Labrador: Isolated non-severe thunderstorms over eastern areas.
Prince Edward Island: No thunderstorms expected.
Nova Scotia: No thunderstorms expected.
New Brunswick: No thunderstorms expected.
Jean-Marc Couturier