Atlantic Canada Weather Outlooks

Monday, August 11, 2025

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Newfoundland and Labrador… Some isolated thunderstorms over Labrador today and tomorrow, strong wind gusts and heavy downpours possible.

NB… No impacts expected.

NS… No impacts expected.

PEI… No impacts expected.

Convective Discussion

Labrador will experience the bulk of convective activity over the next two days, with the potential for severe thunderstorms, including discrete supercells. Atmospheric dynamics are generally favourable, with deep-layer wind shear between 40–50 knots and 0–3 km shear values of 30–40 knots. Moderate CAPE values will also contribute to storm development, with some areas exceeding 1000 J/kg.

For the most part, the shear is predominantly linear, and triggering mechanisms will be somewhat limited. Troughing and surface convergence are expected to be subtle, and differential heating may play an ongoing role. Clear skies will enhance solar insolation, further aiding destabilization.

If severe storms develop, it is unlikely that any single community will be directly affected unless an organized mesoscale convective system (MCS) forms, producing a more continuous gust front. We will monitor satellite and lightning detection closely as the day progresses.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Mel Lemmon

Sunday, August 10, 2025

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts…

Today

NB/NL/Labrador: Scattered non-severe thundershowers.

NS/PEI: None

Tonight

NB/NS/PEI/NL/Labrador: None

Monday

Labrador: Scattered non-severe thundershowers.

NB/NS/PEI/NL: None

Convective Discussion

A weak trough over northern New Brunswick may trigger scattered thundershowers this afternoon. CAPE values near 1000 J/kg are expected but the effective shear is low at less than 20 knots. Gusty winds and downpours in the moistening airmass are possible in the non-severe cells. Weak troughing over Newfoundland and Labrador may produce scattered thundershowers this afternoon. CAPE values of 500 J/kg or less should limit any weather to non-severe. On Monday, a cold front sweeping across Labrador will give scattered thundershowers. Again, CAPE values of 500 J/kg or less should limit any weather to non-severe.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Saturday, August 9, 2025

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

LAB: Risk of isolated thunderstorms giving locally heavy downpours and strong wind gusts.

NB: Risk of isolated thundershowers.

NS/PEI/NL: No thunderstorms forecast.

Tonight:

LAB: Risk of isolated thunderstorms.

NS/NB/PEI/NL: No thunderstorms forecast.

Tomorrow:

LAB: Risk of isolated thunderstorms giving locally heavy downpours and strong wind gusts.

NB/NL: Risk of an isolated thundershower.

NS/PEI: No thunderstorms forecast.

Convective Discussion

A ridge of high pressure is slowly sinking southeastward into the southern Maritime waters today and a trough moves eastward into northern Quebec and across northern Labrador. Ahead and along the trough, scattered showers and risk of thundershowers are expected, mainly across southern to central Labrador where CAPE values could exceed 500 J/kg. Shear is generally weak to moderate, so expecting single to multicell potential with brief winds gusts and with precipitable water in of 35 mm, so locally heavy downpours are also possible. Weak troughing also reaches northwestern New Brunswick, where there is a slight risk of showers or thundershowers in the afternoon but conditions are still fairly dry and with some residual smoke aloft, this may cap convection.

Tomorrow, troughing lingers over Newfoundland while another trough quickly moves across central northern Quebec, affecting southwestern Labrador by the evening. With moderate shear or 30 kts and high precipitable water reaching 40 mm, there is more potential for organization into lines into western Labrador but timing may be too late for any severe potential to maintain in the evening. Some isolated showers with a small risk of a thundershower is possible over the higher terrain in northern New Brunswick and Newfoundland but again the lingering smoke aloft could cap convection.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Roberta McArthur

Friday, August 8, 2025

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

No thunderstorms forecast.

Tonight:

No thunderstorms forecast.

Tomorrow:

LAB: Risk of isolated thundershowers giving locally heavy downpours and strong wind gusts.

NB: Risk of isolated thunderstorms.

NS/PEI/NL: No thunderstorms forecast.

Convective Discussion

A ridge of high pressure continues to dominate Atlantic Canada today, supressing convective potential. Widespread smoke aloft from fires out west also will work to inhibit potential. A trough of low pressure over James Bay with a warm front that extends eastward across Ungava Bay and extreme northern Labrador may kick off some TCUs this afternoon but primarily north of Nain.

The ridge of high pressure will eventually sink southeastward into the southern Maritime waters tomorrow and the trough moves eastward into northern Quebec and across northern Labrador tomorrow. Ahead and along the trough, scattered showers and risk of thundershowers are expected, mainly across southern to central Labrador where CAPE values could exceed 500 J/kg. Westerly straight-line shear is weak to moderate, so expecting single to multicell potential with brief winds gusts and with precipitable water in of 35 mm, so locally heavy downpours are also possible. Weak troughing also reaches northwestern New Brunswick, where a slight risk of showers or thundershowers in the afternoon. Some residual smoke aloft will likely still be around which could cap convection.

Thunderstorm Outlook for Today