Regional Impacts
NS/NB/PEI… Some scattered thunderstorms possible over the central Maritimes today. Heavy downpours of 20 to 30 mm/h possible.
NL… Some isolated thundershowers possible today and tonight. Heavy downpours of 10 to 20 mm/h possible.
Convective Discussion
A broad upper trough will be the main focus for convection today across Atlantic Canada. A few isolated thundershowers are possible over parts of Newfoundland and Labrador this afternoon, however the main focus will be in the central Maritimes, where a few weak embedded shortwaves slightly increase the potential for some organized thunderstorms to develop today. 49.4 mm of PWAT was measured at the 12Z Yarmouth sounding this morning, with this number forecast to reach 50 to 55 mm across portions of western and central Nova Scotia, southeastern New Brunswick, and PEI this afternoon. Due to the high amount of low level cloud cover over the region, convection will rely heavily on upper level forcing today. There is a 500 mb jet over the area of interest, however it is quite weak, so convection may initially struggle to become organized until the 250 mb jet begins to intensify off the coast of Nova Scotia later this afternoon. With 20 to 30 kts of bulk shear today, the severe risk is low and storms are not expected to be long lived, however any thunderstorms that develop will have the potential to produce torrential downpours of 15 to 25 mm/h due to the high PWAT over the area.
As the upper trough moves east tonight, the risks exists for some embedded thundershowers over western Newfoundland overnight. Heavy downpours of 10 to 20 mm/h will be possible here, maybe higher over areas with topographic enhancement.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Copp