Convective Outlook Valid for Today , Tonight, Tomorrow, and Wednesday

Regional Impacts

 

Today

 

NB: Slight chance for isolated thundershower(s) spanning Northwestern NB. Hazards: 15-25 mm rainfall.

 

Tonight

 

NB/NS: Slight chance for isolated thunderstorm(s) spanning Southwestern NB and Western NS.

 

Tomorrow

 

NS/NB/PEI: Chance for isolated thunderstorm(s) spanning Southern NB, Mainland NS, and most of PEI. Hazards: 70 km/h wind gusts; 15-20 mm rainfall.

 

Wednesday

 

NS/PEI/NB: Likely for organized convection spanning NB, NS, and PEI. With largest risks over Eastern NB, Mainland NS, and PEI. Hazards: 70-90 km/h wind gusts; 2 cm hail; 15-25 mm rainfall.

 

NFLD/LAB: Chance for isolated thunderstorm(s) spanning Eastern Labrador and Northern Peninsula.. Hazards: 70 km/h wind gusts; 15-25 mm rainfall.

 

Convective Discussion

For today, satellite imagery and radar show a progressing warm trough through the Maritimes and Newfoundland & Labrador. As this trough progresses through the regions, there is a possibility of some clearing over northwestern NB. If this occurs, then some isolated thundershowers are possible, giving rainfall rates of 15-25mm/hr. However, looking at current upper air soundings and air quality, there is a large amount of convective inhibition (CIN) because of a large amount of stability, along with rising heights, that will need to be eroded before convection could occur. Further to this, air quality overnight was poor, which is indicative of smoke in the area. These are the biggest factors that convection will be fighting with today.

 

For tonight, there is not likely to be a significant change from today, except that there are likely to be lowering or neutral heights, which will allow some jets and vorticity to approach the western section of the Maritimes. This would allow for some elevated convection, and fairly weak from a convective aspect.

 

For tomorrow, we should see a continued breakdown of the heights and slight ridging that was found today and tonight over the Maritimes. This breakdown is likely to allow for CAPE values to approach 1,000 J/Kg with an Effective shear nearing 35 to 40KTs. This, paired with dCAPE (downdraft CAPE) values nearing 800 J/Kg, is allowing for isolated thunderstorms which could also produce wind gusts over 70km/h.

 

On Wednesday, an approaching frontal system is forecast to cross the Maritimes and primarily impact Eastern Labrador. This frontal system is possible to have a mix of CAPE values rising to near 2,000 J/Kg along with an effective shear layer approaching 50KTs, predominantly over NB/NS/PEI. These values could produce a range of hazards; with wind, rain, and hail as the primary threats, and current regional models do indicate a risk for a weak tornado. It is worth highlighting that this tornado risk is based on regional, non-convective-allowing models and could change as higher-resolution models come into scope.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Thunderstorm Outlook for Wednesday

 

 

Forecaster: Lambert

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

NS… no thunderstorms expected.

PEI… no thunderstorms expected.

NB… tomorrow, some isolated thunderstorms possible with heavy downpours.

Newfoundland and Labrador… isolated pulse storms possible, showers with small hail or graupel possible.

Convective Discussion

For today, little convective activity is expected. A few lightning strikes are possible over central Newfoundland and western Labrador. Although upper-level support is fairly benign, a cold trough at 500 hPa may support weak updraft development. No hazardous weather is expected; however, any thunderstorms that do develop could produce locally heavier rainfall rates.

For tomorrow, stronger dynamics will move across western New Brunswick, with approximately 40 knots of deep-layer shear and total precipitable water values increasing to above 35 mm. However, surface-based convection may struggle to develop due to extensive cloud cover and a lack of strong low-level forcing. Earlier in the day, some embedded convection is possible, but the main potential for hazardous weather would occur later in the day if surface-based convection can develop.

Updraft strength is expected to remain a limiting factor, and mixed-layer CAPE values may not be sufficient to support deep convection. Additional guidance and observations tomorrow should provide a clearer picture of the overall severe weather potential.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Forecaster: Mel Lemmon

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NFLD: A chance of thundershowers.

NS/NB/PEI/LAB: None.

 

Tonight

NS/NB/PEI/NFLD/LAB: None.

 

Sunday

NFLD: A chance of thundershowers.

NS/NB/PEI/LAB: None.

 

Convective Discussion

A departing low pressure system will give a chance of afternoon thundershowers across portions of Newfoundland this afternoon. MLCAPE values are expected to be 250-500 J/kg and the effective shear will be 10 to 20 knots so any thundershowers will be weak in nature. On Sunday, weak troughing over Newfoundland will give similar or weaker atmospheric conditions as today and a chance of afternoon thundershowers.  

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NS/NB/PEI: Thundershowers giving potential significant rainfall amounts.

NFLD/LAB: Scattered thundershowers.

 

Tonight

NS/NB/PEI/NFLD/LAB: None.

 

Saturday

NFLD: A chance of thundershowers.

NS/NB/PEI/LAB: None.

 

Convective Discussion

A surface low pressure system and supporting upper low will continue to slowly move across Atlantic Canada today and then depart Newfoundland on Saturday. The main area of concern today is once again over Nova Scotia, New Brunswick and Prince Edward Island where MLCAPE values are expected to be near 1000 J/kg and the effective shear will be 20 to 25 knots. The main hazards with any storms that develop will be small hail, gusty winds and locally heavy downpours. Any storms that do develop will be slow moving so any heavy downpours may lead to significant rainfall accumulations.  On Saturday, CAPE values will be 500 J/kg or less and will give a chance of thundershowers for Newfoundland.

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NS/NB/PEI/NFLD/LAB: Scattered thundershowers.

 

Tonight

NS/NB/PEI: Chance of thundershowers.

NFLD/LAB: None.

 

Friday

NS/NB/PEI/NFLD/LAB: Scattered thundershowers.

 

Convective Discussion

A trough of low pressure and supporting upper low will slowly move across Atlantic Canada today and Friday. The main area of concern today is over Nova Scotia and New Brunswick where MLCAPE values are expected to be 1000-1500 J/kg and the shear will be 20 to 30 knots. The main hazards with any storms will be small hail, gusty winds and locally heavy downpours. Any storms that do develop will be slow moving so any heavy downpours may lead to significant rainfall accumulations.  On Friday, any potential impacts are expected to less than today due to lower CAPE, shear and precipital water values.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow