Atlantic Canada Weather Blog: Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

NB… No impacts expected today. Some thunderstorms tonight and overnight bringing frequent lightning and possibly heavy downpours. Tomorrow… Some severe thunderstorms bringing heavy rain and potentially strong wind gusts.

PEI… No impacts expected today. Some thunderstorms overnight bringing lightning and possibly some heavier rainfall. Tomorrow… Thunderstorms possible with gusty winds and possibly heavy downpours.

NS… No impacts expected today. Some thunderstorms overnight over north areas, bringing lightning and possibly some heavier rainfall. Tomorrow… Thunderstorms possible with gusty winds and possibly heavy downpours for central and eastern regions.

NFLD… No Impacts today… Tomorrow… A chance of thunderstorms over western parts of the island tomorrow with some heavier rain possible.

Convective Discussion

For the most part, thunderstorm activity will remain upstream over Quebec and Ontario today, as a low-pressure system and its associated cold front gradually move eastward. An area of high pressure to the southwest will likely help suppress thunderstorms over the Atlantic region until the unstable airmass reaches the Maritimes tonight.

We will continue to see low-level moisture advection ahead of the approaching cold front today and overnight, with dew point temperatures likely reaching the low 20s in some areas by tomorrow. The combination of this warm, moist airmass and the surface low-pressure system will be sufficient to generate CAPE values around 2000 J/kg. With precipitable water values near 50 mm, rainfall rates in thunderstorms are likely to be very high. Additionally, strong downdraft potential exists, and it is possible that some supercell storms could develop, leading to potentially damaging wind gusts.

The timing of the cold front’s passage may prove critical; if it arrives earlier than expected, the threat of severe weather may shift somewhat eastward. Thunderstorm development over Quebec today will give us a general idea of what to expect tomorrow for New Brunswick. However, as is often the case, these systems do not always unfold as predicted, and timing may shift. Keep an eye out for alerts, not just for tomorrow but also overnight, as the system approaches.

Thunderstorm Outlook for Today