Regional Impacts
Labrador… Risk of thunderstorms today and tomorrow, with heavy downpours and some gusty winds possible.
Newfoundland… Risk of thunderstorms across eastern Newfoundland today, with some heavier downpours and frequent lightning possible.
PEI… Slight risk of thunderstorms today.
Nova Scotia… Slight risk of thunderstorms today, mainly across eastern areas.
New Brunswick… Risk of isolated thunderstorms, mainly over northwestern sections late in the day.
Convective Discussion
The region currently remains under a somewhat anomalous pattern characterized by weak blocking. Most of the Maritimes lie between a trough extending from the Great Lakes northward into Labrador and a slow-moving low-pressure system approaching the Avalon Peninsula. This pattern is resulting in generally weak steering flow and a continued focus for convective development across portions of the region.
Across Labrador, conditions are expected to remain much the same as they were yesterday, although vertical motion may be slightly weaker. CAPE values in the 500 to 1000 J/kg range, combined with moderate low-level shear, will continue to support fairly widespread convection through the afternoon and evening. Rainfall rates in the strongest storms will likely reach 15 to 20 mm/h.
The low-pressure system over the marine area south of Newfoundland has transported more moisture into eastern portions of the Maritimes than previously anticipated. This increase in moisture has raised the potential for showers and thunderstorms in areas where low-level convergence is sufficient to overcome existing convective inhibition. However, with the exception of eastern Newfoundland, the shear profile across the region is generally not supportive of severe thunderstorms. As a result, most convection is expected to be relatively weak and disorganized, with only a low risk of severe weather. Nevertheless, locally heavy downpours remain possible where thunderstorms are able to develop.
Over eastern Newfoundland, the combination of stronger forcing associated with the nearby low-pressure system and somewhat more favourable wind profiles will support more organized convection. The most likely scenario remains clusters of thunderstorms capable of producing frequent lightning and locally heavy rainfall, with rainfall rates of 15 to 25 mm/h possible in the strongest cells. Strong downdrafts and hail are not expected to be significant concerns at this time.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Mel Lemmon