Atlantic Canada Weather Blog: Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today: 1. Thundershowers are possible along an advancing trof line in eastern Labrador. 2. Additionally thunderstorms are possible in central Nfld (vicinity Gander). Only hazards here are 5-10mm of rain. 3. The weather with the greater dynamics at play is over the Maritimes, with thunderstorms approaching severe limits later today across parts of SE NB, central PEI and northern and central mainland Nova Scotia. Please see the detailed yellow area on the graphic for all counties included. Hazards here include wind risk, hail, and near 25mm of rainfall in the most organized cells.

Tonight: Remnants of storms expected to advect across CB and nearby waters. Should not be surface based convection after sunset.

Tomorrow: No thunderstorms forecast. Not enough lift, no defined trigger.

Saturday: Weak non-severe cells are possible to pop up on a weak trof line across the northern tier of NB. Elsewhere, no activity forecast.

Convective Discussion

Today is a High Shear day. The upper dynamics across the Maritimes include a 110 kt WSW-ly jet at 250, with a strong jet core of 140 positioned over northern Ontario. Effective shear values are over 40kts, with 0-6k values over 60 in places. This may prove to be too much shear for the small amount of sfc based CAPE at play, however – if it isn’t overwhelmed, it is the correct recipe and orientation for supporting supercell development. The main hazards if this can develop would be 2cm hail and downdrafts near 90 km/h. Dewpoints this morning are holding strong under mainly clear skies still at 13 to 14C. Upstream Pwats are in the 22 to 30 range off morning soundings. A quieter Friday is forecast, and a weak trof line is the only possible trigger for a few unorganized single cells on Saturday.

Thunderstorm Outlook for Today