Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Labrador… low chance of a weak thunderstorm.

NS, PEI, NB, NFLD… no thunderstorms expected.

Convective Discussion

We are looking at a relatively dry and stable airmass for the next two days across most of the region. A low pressure system over Labrador, combined with some convergence and daytime heating, may be sufficient to produce a few lightning strikes. However, CAPE is very weak and shear is minimal, so there is no risk of significant impacts from thunderstorms.

By Wednesday, a low pressure system moving across Quebec will help bring more substantial low-level moisture into the region. There is a slight chance that severe thunderstorms could develop over New Brunswick, but with the event still three days away, there remains too much uncertainty to quantify the potential impacts. It is also possible that elevated convection could impact Nova Scotia and southern Newfoundland during this period with heavy rainfall. Tomorrow's guidance should provide a clearer outlook.

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Mel Lemmon

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

NS/NL: Isolated embedded thundershowers giving strong wind gusts and heavy rainfall.

NB/PEI/LAB: None

Tonight

NL/LAB: Slight risk of an embedded thundershower.

NB/NS/PEI : None

Tomorrow

None

Convective Discussion

A low pressure system is tracking from the Gaspe Peninsula slowly northeastward to lie over Anticosti this evening then into south-central Labrador by tomorrow morning. Organized convection this morning had been primarily along the cold front across the southern Maritime waters south of Nova Scotia, but an isolated embedded thunderstorm is still possible today in the northern Gulf of St. Lawrence and southern Newfoundland today. With high precipitable water and upslope flow, heavy rainfall is expected across southern Newfoundland and the Lower North Shore of Quebec today. Closer to the low center is also an area where there could be sufficient lift to breach the warm 500 mb cap and support isolated strikes, furthering potential rainfall amounts. The cold front has produced strong wind gusts over Nova Scotia and the Maritimes waters thanks to a strong 850mb LLJ.

For tonight there is a risk of isolated thundershowers continuing east the low centre across southeastern Labrador, and along the cold front as it moves into the Grand Banks. The low centre slowly fills as it drifts northeastward tomorrow and eventually out into the Labrador Sea tomorrow evening. For tomorrow, there is a slight risk of a strike along the trowal axis east of the low centre as it moves into the Labrador Sea. Meanwhile, a ridge of high pressure moves into the Maritimes tomorrow afternoon.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

LAB: chance of isolated thundershowers over eastern sections giving brief strong wind gusts.

NB: chance of embedded thunderstorms late evening over western sections.

NS/PEI/NL: None

Tonight

NS/NB/PEI: chance of embedded thunderstorms giving heavy rainfall and strong wind gusts.

Tomorrow

NS/NL/LAB: chance of embedded thunderstorms giving heavy rainfall and strong wind gusts.

NB/PEI: None

Convective Discussion

The stalled upper low over Labrador over the last few days is finally starting to track northward and weaken today. There is a weak shortwave currently over central Labrador, moving towards the east, and this is the trigger for thundershowers today. There is potential effective shear of 30-40kt and MLCAPE of 250J/kg, but with low moisture, some cells may organize and provide brief strong wind gusts.

While a ridge dominates the Maritimes and Newfoundland during the day, a low pressure system currently over the Great Lakes will deepen as it tracks towards the Maritimes tonight. Rain ahead with the warm front should reach New Brunswick this evening, while convective showers with the cold front will move across the Gulf of Maine and towards western New Brunswick and Nova Scotia close to midnight. This system is quite active this morning along the warm front, aided by strong dynamical forcing. Overall dynamics and thermodynamics are expected to be reduced as the system reaches the Maritimes. However, there is an increasing 60kt 850mb LLJ tonight ahead of the cold front in Nova Scotia and the southern Maritime waters. This along with possible mid-level cooling aloft may help embedded thunderstorms persist as the front continues eastward overnight, reaching eastern Nova Scotia by mid-morning. Regardless if lightning does persists, strong southerly winds and increasing precipitable water (40-50 mm) will allow for heavy rainfall rates and strong wind gusts with the frontal passage.

For tomorrow, the low centre is expected move from northern New Brunswick towards the northeast, reaching Anticosti by tomorrow evening. The cold front continues to advance, reaching Newfoundland by mid-morning. Embedded thunderstorms are still possible with heavy rain across southern Newfoundland.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

Nfld: Chance of scattered non-severe thunderstorms near St. Anthony, and the Avalon.

Labrador: chance of isolated thundershowers in area marked in grey.

Tonight

No thunderstorms forecast in Atlantic Canada.

Tomorrow

Labrador: chance of isolated non-severe thundershowers over eastern sections.

Western Nova Scotia/Gulf of Maine: chance of scattered embedded thunderstorms along an advancing front very late in the day (near midnight into Sunday).

Convective Discussion

There is now dry air in place across the Maritime provinces. This will inhibit any organized convection today. Cu fields are expected to develop by noon, but will struggle to lift past even 700mb. NB is observing sfc dewpoints of just 8 this morning. A thermal ridge is located off to the west over New England.

Nfld is a bit of a different story synoptically. The remnants of a front is still effecting the Avalon and Grand Banks with a thunderstorm chance. And another hang-back trof is acting as a second trigger across southern Labrador and over the tip of the Northern Peninsula. These storms are not expected to reach warning criteria or approach severe limits today.

Weekend Setup: Day 2 brings in a more substantial organized TS risk very late in the day/overnight approaching the Maritimes from the west. Rainfall amounts look to be 25-40mm at this point for some areas of the Maritimes. The frontal passage is overnight Saturday into Sunday morning. This prog is only valid from the noon to midnight time period. Development is shown as grey in the Gulf of Maine.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Tirone. 3:18:01 Jul 17 2026

60   FPCN11 CWHX 171354 FORECASTS FOR NOVA SCOTIA ISSUED   13:54:57 Jul 17 2

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

NB/NS/PEI/NL: Risk of thunderstorms giving brief strong winds gusts, small hail and locally heavy downpours. Risk of higher gusts for southwestern New Brunswick and western Nova Scotia this evening.

Lab: Slight risk of a thundershower giving small hail.

Tonight

NL: Slight risk of a thundershower.

NB/PEI/NS/LAB: None

Tomorrow

None

Convective Discussion

An upper low over Labrador will remain stationary today while a quick moving shortwave trough will move from Quebec towards central Maine then southern New Brunswick and Nova Scotia late this afternoon and towards southern Newfoundland by the evening. There is the possibility of pop-up convection ahead of the trough this afternoon where much of the Maritimes is clear this morning, allowing convective temperatures to be reached, especially across PEI, eastern Nova Scotia and southwestern Newfoundland once clouds clear early this afternoon. With relatively dry dew points over the Maritimes under a westerly flow, precipitable water of 15 to 20 mm and relatively weak CAPE (500J/kg), thunderstorms that develop are expected to be non-severe.  However, with the trough, dynamics are most favoured in the exit region of a strong 250mb jet moving into southwestern New Brunswick and western Nova Scotia. This area may also see a slight increase in precipitable water and CAPE values in this area may exceed 750 J/kg and effective shear increasing to 50 kts based off Maniwaki and Gray 12Z soundings. Organization is possible with the main threats being strong wind gusts and small hail if a line develops. The risk of more elevated convection will continue tonight into Newfoundland. Under the low over Labrador, showers are expected with the risk of convection east of the low. CAPE is quite low but with very cold air aloft, small hail is possible.

For tomorrow, the upper low will slowly make its way eastward by the evening. Other than continued scattered showers with the upper low, the risk of convection at this time is low.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow