Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NB/PEI/Les Iles: Isolated thunderstorms giving heavy downpours and gusts near 50 km/h

NS: Scattered thunderstorms over eastern half of the province giving localised heavy downpours, small hail and wind gusts near 70 km/h.

NL&LAB: None

 

Convective Discussion

An upper low high pressure near the Gaspe peninsula will slowly advance eastward today and tonight, at the surface there are two areas of rain associated with a couple of low pressure systems, one near Anticosti island and a second one south of the Burin peninsula. NF radar estimates for the past 12 hours suggest rainfall amounts of 20 to 40 mm with the highest amounts just off the west coast and south of the burin, however observations from autostations suggests amounts of 10 mm. There will likely be another 10-20 mm to come until tomorrow.

The focus for surface-based convection this afternoon will be over the NErn half of NB, PE, and especially Ern NS. Under a cold pool (-16) associated with the upper low, the cumulus field is already starting to grow and diurnal instability will be on the increase during the afternoon. Surface temperature of 24 or 25 will likely be plenty to bump MLCAPE values to nearly 500 J/kg / LI of -2. There are some interesting upper dynamics combining with these conditions, including 500 mb positive vorticity advection and a slightly cyclonic 80 knots upper jet branch south of NS, placing CB and Cabot strait near a right exit. The Shearwater Hodograph shows about 30 knots of effective deep layer shear. Eastern-most areas of NS mainland and Srn CB could get stronger thunderstorms that could evolve into longer-lasting linear features and produce downpours/small hail/high winds.

A high pressure system will build in from the west tonight and Monday.

 

 

Thunderstorm Outlook for Today

 

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Monday

 

 

 

 

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

 

Today

NS/PEI: Isolated embedded thunderstorms giving lightning, heavy downpours with up to 50 mm/h rates and strong wind gusts

NB: Isolated embedded thunderstorms giving lightning, heavy downpours, small hail and strong wind gusts

NL&LAB: None

 

Tonight

NS: Isolated embedded thunderstorms giving lightning, heavy downpours and strong wind gusts over Cape Breton

NL: Isolated embedded thunderstorms giving lightning and heavy downpours.

 

Sunday

NB/PEI/NS: Scattered thunderstorms giving lightning, heavy downpours, small hail and strong wind gusts.

 

 

Convective Discussion

 

A warm and moist air mass continues to spread north and eastward across the Maritimes today ahead of a trough from a quasi-stationary low over central Quebec. The trough becomes oriented northwest/southeast today as the low centre slowly shifts southeastward across the Gulf of St. Lawrence and south of Newfoundland Sunday night. A thin stream of 40-50 mm precipitable water values is being fed northward across Nova Scotia, allowing for very high rainfall rates where 50 mm/h has been seen in parts of the HRM this morning with training thunderstorms. Areas of upper level rotation have also been evident with some wind gusts reaching 60 km/h in the stronger cells. Although lightning activity has diminished, the heavier band continues slowly north and eastward today, exiting east of Cape Breton tonight and the threat of heavy rainfall continues. A increasingly heavier rain band over southeastern New Brunswick will give high rainfall rates today which will affect parts of northern Nova Scotia and Prince Edward Island this afternoon and evening.

 

With expected clearing behind the trough today over western New Brunswick, convection is possible in the afternoon and late evening. With an increase in CAPE values exceeding 1000 J/kg, lower freezing levels, and weak to moderate 0-6km shear, there is the threat for small hail, strong wind gusts and locally heavy downpours.

 

There is the risk of waterspouts tonight into Sunday morning mainly in the Northumberland Strait and southern Gulf of St. Lawrence, where the highest SST’s above 20C and cooler 850mb temps are located, along with weak to moderate deep shear.

 

On Sunday, convection is possible again for the Maritimes in the afternoon still under the influence of the upper low which will move east of Newfoundland by Monday. With cooler air aloft, CAPE values approaching 1000 J/kg and weak to moderate shear of 20-30Kt, there is the threat of pulse or multicells over central and eastern New Brunswick towards Prince Edward Island and northern Nova Scotia.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Sunday

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

 

Today

NB: Isolated thunderstorms for northwestern regions this evening bringing lightning and locally heavy downpours

NS/PEI/NL&LAB: None

 

Tonight

NB/NS/PEI: Isolated embedded thunderstorms bringing lightning and heavy downpours

NL&LAB: None

 

Saturday

NB: Isolated embedded thunderstorms bringing lightning, heavy downpours, small hail and strong wind gusts

NS/PEI: Isolated embedded thunderstorms bringing lightning and heavy downpours

NL&LAB: None

 

 

Convective Discussion

 

With a near quasi-stationary low pressure centre over central Quebec, an associated trough will slowly track through southern Quebec and into Maine and western New Brunswick today. Showers and isolated thundershowers ahead of this feature have been ongoing this morning over northwestern New Brunswick. Although more favourable dynamics remains further west over New England today, increasing precipitable water into the mid 30s and mean storm motion to the northeast with 0-6km shear of 30 KT, could make for sustained convection and locally heavy rainfall due to possible training of storms over the same area. The trough will bring showers and embedded thunderstorms slowly eastward tonight and into Saturday across the Maritimes. There is also a waterspout risk over the Gulf of St. Lawrence and southern Maritime waters Saturday into Sunday with a 10 deg temperature difference between 850mb and surface SST’s, deep convective cloud depths above 35,000ft and little directional shear.

 

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Saturday

Convective Outlook Valid for Today, Tonight, and Tomorrow

Regional Impacts

NL: Scattered non-severe thundershowers possible over much of Labrador today. Locally heavy downpours of 10-15 mm possible.

NS: None.

NB: None.

PEI: None.

 

Convective Discussion…

A ridge of high pressure dominates Atlantic Canada today, with the exception of a weak shortwave and associated 250 mb jet moving over central Labrador. This shortwave will provide just enough lift to initiate surface-based convection this afternoon across much of Labrador, however these thundershowers are expected to remain non-severe due to a lack of mid to low level shear, as well as an approaching thermal ridge. The main threats with these thundershowers will be locally heavy downpours of 10-15 mm.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Copp

Convective Outlook Valid for Today, Tonight, and Tomorrow

Regional Impacts

NL: Scattered thundershowers possible over western Newfoundland and southern Labrador today. Locally heavy downpours of 10-20 mm possible.

NS: Risk of isolated thundershower early this afternoon over the Cape Breton Highlands. Locally heavy downpours of 10-15 mm possible.

NB: None.

PEI: None.

 

Convective Discussion…

A cold upper low currently sitting over Labrador with an associated trough extending into Cabot Strait, in combination with a 150 kt 250 mb jet located over central Newfoundland, will spark some scattered thundershowers today across Labrador, western Newfoundland, and extending down into northern parts of the Cape Breton Highlands. With stronger dynamics to the east of the area of interest today, convection is expected to remain non-severe, with the main threats being locally heavy downpours of 10-20 mm. That being said, a few waterspouts have been reported this morning from Iles-de-la-Madeleine to western shores of Newfoundland. This risk will diminish by early afternoon as the mid and lower levels of the atmosphere begin to warm and the trough moves off to the east towards Banquereau.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Copp