Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Regional Impacts

New Brunswick: Scattered thundershowers beginning by early to mid afternoon, with some heavy downpours and gusty winds.

Labrador: Isolated to scattered thundershowers with some gusty winds and brief heavy showers.

 

 

Convective Discussion

 

There’s a deep upper low over northern Hudson Bay , with a deep upper trough extending southeast over western Labrador into the eastern Gulf of St. Lawrence. There is also a deep upper thermal trough west of Labrador. Weak to moderate 250 and 500 jets have Right Exits near and north of the Gaspe Peninsula and all of this is slowly moving east. There is a reasonable chance for near severe thunderstorms for New Brunswick, with a slight chance for severe. Upper dynamic support is limited to the extreme north of the province, but there is healthy shear near 40 kts, moderate PWAT around 30-35 mm,  but with no really significant amounts from the surface to 700 mb, then with some drying. The main mechanism will be daytime heating, and some extra moisture from low stratus over New Brunswick, and a surface trough from western Labrador to just northwest of New Brunswick along the St. Lawrence as a possible organising feature. The main impacts will be locally heavy downpours and some gusty winds. Significant hail is unlikely, with freezing levels near 115 to 145 hft for Caribou and Gray.

 

For Labrador TCus have started, associated with the trough over western Labrador, and some thundershowers should start soon. This and daytime heating are the triggers and organising features. PWAT is 15 mm near YYR and 30 near YWK,  And shear is near 15 kts east and 25 west. The stability will inhibit things somewhat with a weak inversion from near 800 mb upwards. All this suggests the western cells will be a bit more  intense. Maximum CAPEs should be near 250 J/kg. So the major impacts are some intense but brief showers, some gusty winds, and a slight chance for hail.

 

 

 

Thunderstorm Outlook for Day 2

For day two a deep upper ridge starts to move in, and upper  dynamic support is minimal. However weak low level troughs approach western Labrador and the western Maritimes, and there’s a chance for some thundershowers, with a bit more support for New Brunswick with higher moisture, shear, and potential moderate CAPE.

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Southern Grand Banks may see some elevated thundershowers today and overnight. No other regional impacts are expected.

 

Convective Discussion

 

An upper-level low is slowly tracking over the southern marine district and will stall over the Grand Banks today and tomorrow. Most convection associated with the low is now south of the Maritimes marine waters, however, a strong southerly push over the eastern Grand Banks and upper level jet over the area will help lift. The highest risk for embedded convection will be in the overnight hours into Friday morning, when cloud top cooling will also help to enhance the destabilisation aloft.

 

Thunderstorm Outlook for Day 1

 

 

 

Thunderstorm Outlook for Day 2

 

A large trough will approach Atlantic Canada from central/northern Quebec on Friday and a secondary trough further south over southern Quebec. At this time, the dynamics appear more favourable further west over Quebec as the air aloft over New Brunswick remains too warm and would need a good amount of surface based heating in order to break the cap. Showers are expected to move into western New Brunswick in the mid afternoon so cloudiness out ahead in the morning could be key factor for anything getting going other than showers. Low risk has been added for now.

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Eastern Nova Scotia, southeastern Newfoundland, and the southern marine district will see locally high rainfall amounts with embedded thunderstorms possible mainly over the southern marine waters as an upper level features slowly moves eastward south of Nova Scotia today.

 

Convective Discussion

 

An upper-level low south of Nova Scotia will move eastward toward the Grand Banks today and stall over the area into Friday. For today, the primary threats for embedded convection will remain offshore near and ahead of the low centre, but there could be some enhancement this afternoon over eastern parts of Nova Scotia including Cape Breton as the low drifts further east. This system had a history of dropping high rainfall amounts over parts of southwestern Nova Scotia with precipitable water values of near 40 mm were and this may be the case today over eastern portions.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

The upper-level low will stall over the southeastern Grand Banks where some embedded convection may develop in the overnight hours into Friday morning.

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Nova Scotia.. A stationary area of thunderstorm development over southwest Nova Scotia could produce locally heavy rainfall amounts of 20 to 30mm.

 

New Brunswick.. A low probability of isolated thundershowers late this afternoon or this evening.

 

Convective Discussion

 

Thunderstorm development is expected to continue ahead of and near an upper low that is slowly progressing towards the Maritimes. Most of the convection will be triggered aloft but daytime heating could contribute to increased updraft strength this afternoon. There is some indication that a quasi-stationary feature could set up possible giving heavy rainfall amounts to some parts of southwest Nova Scotia.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Isolated Thunderstorms could develop over New Brunswick. No Severe weather expected.

 

Convective Discussion

 

There is a slight potential for thunderstorms to develop over New Brunswick today. Overall cape values are low at less than generally 500 j/kg but with high dew point temperatures. The approaching trough moving from the north may provide a sufficient trigger for storms to initiate. However with weaker updrafts severe storms are unlikely.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2