Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

 

Today

NB/LAB…Isolated thundershowers giving locally heavy downpours of 10 to 15 mm/h.

NS/PEI…None

 

Tomorrow

NB…Isolated to scattered thundershowers giving locally heavy downpours of 15 to 25 mm/h.

LAB… Isolated thundershowers giving locally heavy downpours of 10 to 15 mm/h.

NS/PEI…None

 

Convective Discussion

 

An upper low is expected to slowly move across southern Quebec today then south into Maine tomorrow. Clear skies across much of Maine, New Brunswick and southern Labrador this morning will aid in increasing instability and allow for pop-up convection ahead and near the centre of this low this afternoon and again tomorrow. There is little in the way of shear but with there will be an increase in precipitable water (25 to 35 mm) by tomorrow over western New Brunswick, so some locally heavy downpours are possible in slow moving storms. MLCAPE is forecasted to be near 1000 J/kg over much of New Brunswick tomorrow, but shear remains near 15KT, so not expecting severe thunderstorms to develop beyond heavy downpours. The amount of surface heating and a warm cap near 700 mb will be the main factors if convection develops over the spine of Nova Scotia on Monday afternoon.

 

A low pressure system will develop on Monday south of the Maritime marine district and track northeastward towards eastern Newfoundland Monday night. This low may have some embedded convection, especially near and ahead of the low centre.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

 

Roberta McArthur

 

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

 

Today

NL/LAB… Isolated thundershowers with be locally heavy downpours of 10 to 20 mm/h and small hail of 1 cm or less. There is also the possibility of cold core funnels.

 

Tomorrow

NB/LAB…Isolated thundershowers giving locally heavy downpours of 10 to 20 mm/h.

 

Convective Discussion

A rather cold upper low continues eastward this morning over Newfoundland and into the Labrador Sea with a risk of some isolated thundershowers in northern and central Newfoundland and southeastern Labrador today. This area has a history of waterspouts over the Gulf of St. Lawrence and with continued cold air aloft, relatively warm surface land and water and topographic influences will aid in the potential of cold air funnels today over Newfoundland as this low continues eastward.  With MLCAPE values around 800 J/kg, and weakening strait line bulk shear of 15KT, any thundershowers that develop are unlikely to become severe. Nonetheless, some brief heavy downpours of 10 to 20 mm/h will be possible and with lower freezing levels given the cold air aloft, there is a risk of small hail.

 

Another weak low is expected to move towards western New Brunswick and Labrador from Quebec tomorrow. Daytime heating and some instability will allow for pop-up convection ahead and near the centre of this low is where the risk of thunderstorms will be. There is little shear but moderate precipitable water so some locally heavy downpours are possible.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

 

 

Roberta McArthur

 

 

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

NB/NS/PEI/NL… Slight chance for some isolated thundershowers today across central Atlantic Canada. Main hazard will be locally heavy downpours of 10 to 20 mm/h.

 

Convective Discussion…

An upper low moving northeast into the Gulf of St. Lawrence this morning brings the risk for some isolated thundershowers across central Atlantic Canada today. Convection will be focused near the center of the upper low, though better bulk shear values (40 to 50 knots) to the east, closer to the Cabot Strait, may allow for some thundershowers to develop over Cape Breton and western Newfoundland later this afternoon. MLCAPE values are quite low across the region today, less than 750 J/kg, so thundershowers are unlikely to become severe. Nonetheless, some brief heavy downpours of 10 to 20 mm/h will be possible.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Copp

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

NB… Slight chance for some isolated thundershowers this afternoon and evening. Main threat is locally heavy downpours of 10 to 20 mm/h.

NS/PEI/NL… None.

 

Convective Discussion…

An upper low currently sitting over the St. Lawrence Valley will be the main trigger for convection today. The low will slowly begin to move east this afternoon, with convection expected to fire in Maine before crossing the border as the low moves into western New Brunswick. Instability is expected to be quite limited today, with only up to 500 J/kg of MLCAPE forecast this afternoon. Modest bulk shear of 15 to 25 knots should inhibit most storms from becoming too organized, so severe weather is not expected today. Nonetheless, the upper low should be enough to fire a few weak thunderstorms later this afternoon in western New Brunswick once convective temperatures (20 C) are reached, with locally heavy downpours of 10 to 20 mm/h being the main risk.

 

This low will continue to move east tonight, to lie over Anticosti Island by tomorrow afternoon. As such, most of the convection will be centred over the Gulf of St. Lawrence tomorrow. As the low moves into the Gulf early tomorrow morning, relatively warm waters of 18 to 20 C in the area of interest, and the cold upper low, should provide enough instability and vorticity for convection. With this, there exists a slight chance for a waterspout off the Acadian coast of New Brunswick in the morning hours.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Copp

Convective Outlook Valid for Today , Tonight and Tomorrow

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tomorrow