Regional Impacts
PEI.. Risk of thunderstorms tomorrow.
NB.. Risk of thunderstorms overnight, risk of severe thunderstorms for tomorrow.
NS.. Risk of thunderstorms overnight and tomorrow, heavy rainfall rates possible.
Newfoundland.. Risk of thunderstorms later tomorrow.
Labrador.. No thunderstorms expected.
Convective Discussion
Moisture will gradually increase across the region over the next 24 hours as a low-pressure system and associated deep upper trough, extending well into the eastern United States, slowly approach the Maritimes.
A plume of exceptionally high precipitable water is forecast to skim the Atlantic coast of Nova Scotia tomorrow morning before moving across eastern Nova Scotia early in the day and potentially affecting eastern Newfoundland later in the afternoon. Very heavy rainfall rates are possible within this plume, with rates likely exceeding 30 mm/h at times. While the plume may linger near the coast for much of the day, it is currently expected to only briefly affect any given location, limiting storm-total rainfall amounts.
Across New Brunswick, moisture levels will be somewhat lower than over eastern Nova Scotia. However, stronger instability is expected to develop ahead of the surface trough and approaching upper-level disturbance. Surface-based CAPE values are forecast to exceed 1000 J/kg, while deep-layer shear is expected to exceed 40 kt, supporting a risk of severe thunderstorms.
The shear profile appears relatively straight, favouring fast-moving thunderstorms and supercells. Storm motion is expected to be generally toward the northeast at approximately 50 km/h, allowing for both left- and right-moving supercells. These storms may produce small hail, strong wind gusts, and locally intense rainfall. Although rainfall rates could be high, the rapid storm motion should limit most rainfall totals to around 25 mm.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Mel Lemmon