Regional Impacts
NL… Some strong thunderstorms possible in parts of northern and central Newfoundland today. Main hazards are torrential downpours of 20 to 30 mm/h and strong wind gusts of 50 to 80 km/h.
NB… Some isolated thunderstorms possible over extreme northern New Brunswick this afternoon. Heavy rainfall of 10 to 20 mm/h possible.
NS/PEI… None
Convective Discussion
Two areas of interest exist today, the first being triggered by a weakening shortwave currently near the Strait of Belle Isle, the second being triggered by a broad upper trough over central Quebec, extending down into New England. The shortwave moving into western Newfoundland already has a history of lightning activity, with this expected to continue as it moves across northern Newfoundland today. MLCAPE is expected to build today in central Newfoundland as clear skies will allow surface temperatures to climb ahead of the approaching feature. In addition, decent dynamics (30 to 40 kts of bulk shear) will aid in sustaining some organized convection today across this region. This shortwave is forecast to weaken slightly as it traverses east across northern Newfoundland, however PWAT values of 40 to 45 mm may produce some torrential downpours of 20 to 30 mm per hour. Some strong wind gusts of 50 to 80 km/h are also possible in convection here today.
The second feature being monitored will approach western Labrador and parts of northern New Brunswick later this afternoon. Although MLCAPE values are forecast to climb above 500 J/kg, weaker bulk shear (15 to 25 kts) keeps the risk for any organized thunderstorms low. Low level cloud cover this morning is also expected to limit the available CAPE in northern New Brunswick, as such the risk for thunderstorms is lower here than in western Labrador, where clear skies are allowing CAPE to better build. The broad nature of this upper trough should keep the risk for any severe weather near nil due to the lack of shear and cold air advection. Nonetheless, some brief heavy downpours of 10 to 20 mm/h are possible in any thunderstorms here today.
Tomorrow, this upper trough will move into central New Brunswick. Again, bulk shear values remain quite low (10 to 20 kts), however PWAT values are expected to climb upwards of 45 mm by tomorrow afternoon over the southwestern Maritimes. Torrential rainfall rates of 15 to 25 mm/h will be the main hazard here in any thunderstorms that do develop here.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Copp