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

RE: Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts:

 

Today

Labrador/NB/NS/PEI/Magdalen: A chance of non-severe thundershowers.

NL: Risk of rainfall rates exceeding 25mm/hr

 

Tonight

Labrador/NL: A chance of non-severe thundershowers.

NB/NS/PE/Magdalen: None.

 

Wednesday

Labrador/NL: A chance of non-severe thundershowers.

NB/NS/PE/Magdalen: None.

 

Convective Discussion:

Thunderstorms will continue to develop today ahead of a weak cold front in western most NL and adjacent waters. A narrow ribbon of moderate PWATs of 30-35 mm in conjunction with storm motion following a mean SE wind that is almost perfectly parallel to the coast line will bring a heavy rainfall threat here. MLCAPE is rather modest, at 300-500 J/Kg, however it plays well with bulk shears near 30 kts and orographic enhancements for a localized flash flooding threat.

 

Elsewhere garden variety storms will develop across Labrador associated with a broad upper trough. This feature will swing into Northern NB later in the afternoon and may provide similar non-severe storms. The same front causing storms in western NL does hang back into eastern PEI/NS, however shears of ~40-50 kts appear too high for the limited instability early in the afternoon. CAPE may become high enough to support isolated storms later in the afternoon hours in this higher shear environment  with further surface moisture convergence and additional solar insolation.

 

Tomorrow the same upper trough will continue to provide enough instability for storms to fire with daytime heating across much of Labrador. East of the Long Range mountains a surface trough will be the focus for some thunderstorms in western NL. ML CAPEs of ~300-500 J/kg will work well with moderate bulk shears of ~35 kts. Further east towards Gander shears look to be too high with the expected CAPE environment to support thunderstorms.  

 

Thunderstorm outlook for today:

 

Thunderstorm Outlook for Tonight:

 

Thunderstorm Outlook for Tomorrow: