Convective Discussion
There is a chance of thundershowers over most of Atlantic Canada today. Throughout the region there is cold air aloft and freezing levels are 10,000 feet or less due to the existence of a large upper trough. In addition there is a shortwave just west of the Maritimes at 12Z this morning. There is also a cold trough at 500 mb just west of the Maritimes as indicated by 12Z soundings. There is plenty of sunshine throughout the region for the convective temperature to be reached this afternoon. The southern Maritimes is also in the left exit region of a 250 mb Jet.
Over NS and southeastern NB, shear values are forecast to be unidirectional from the southwest and near 30 knots in the 0-6km layer. CAPE values are forecast to be near 1000 J/kg over these areas. These are the areas highlighted in yellow, where there is a chance of severe thunderstorms today with strong wind gusts and possible hail. The lapse rates are steep between 850 and 700 mb over these areas contributing to strong buoyancy and also of potential for significant DCAPE giving strong wind gusts. The low freezing levels will contribute to the risk of small to medium sized hail.
Elsewhere, CAPE’s and shear are less, so thundershowers that form should not be severe.
Regional Impacts
Maritimes…Thundershowers, heavy downpours, hail and strong wind gusts are possible today. Severe thunderstorm watches may be issued for portions of the area denoted in yellow.
Newfoundland and Labrador…Risk of thundershowers for Newfoundland today or tonight. Risk of thundershowers for central/eastern Labrador.
Steve
