Regional Impacts
Labrador: Isolated non-severe thundershowers this afternoon. Locally heavy downpours and small hail will be the main threats.
Nova Scotia: Isolated non-severe thundershowers this afternoon mainly along the spine and towards the Atlantic coast this afternoon. Locally heavy downpours and moderate wind gusts will be the main threats.
Convective Discussion
An upper level low over the Labrador Sea with a trough extending southwestward into southeastern Labrador and the Lower North Shore Quebec will initiate some convection this afternoon and evening. There is some slight cooling aloft with orographic lift to aid in thunderstorm development. Southeastern Labrador could see CAPE values of around 400 J/kg with precipitable water around 20 mm. 0-6km shear is however quite low so cells that do develop could give some brief heavy downpours but would not last long. With freezing levels of around 7000ft, small hail is possible. TCUs in showers are expected further west into western Labrador throughout the day where some slight warming aloft is expected to cap and further development.
A second trough extends from the Avalon Peninsula towards the Atlantic coast of Nova Scotia this morning. Some initiation is possible behind the trough given the daytime heating in clearing skies with the possible help of a sea breeze along the spine of Nova Scotia. The upper dynamics are not as favourable, however, with a warm nose at 700 mb to overcome and drier air moving in behind the trough. If cells initiate they should move in a west/northwest direction toward the Atlantic coast and fizzle by the evening. Precipitable water is in the mid 20s and some moderate mainly uni-directional 0-6km wind shear near 40KT could keep cells that initiate going with some locally heavy downpours and moderate wind gusts possible. As this trough continues further south into the Maritime slope waters, the warmer surface temperatures as well as any convective cloud top cooling could initiate overnight convection for tomorrow morning. CAPE values in excess of 1000 J/kg and moderate 0-6km shear will help in organization of a possible organized line over East Scotian Slope and Laurentian Fan.
Thunderstorm Outlook for Day 1
Thunderstorm Outlook for Day 2
Instability associated with a cold pool dropping in from Hudson Bay and low pressure over Labrador could initiate some convection over central Labrador and into northern Newfoundland tomorrow. A short-wave trough will be moving into the Maritimes from southern Quebec tomorrow which could have some embedded convection associated with it as it tracks across southern New Brunswick into Nova Scotia overnight into Monday morning.
