Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts…

 

Today

NB/NS/PEI/NL/Labrador: A chance of non-severe thunderstorms with small hail.

 

Tonight

NS/NL:  A chance of a thundershower.

NB/PEI/Labrador: None

Wednesday

NB/NS/PEI/NL/Labrador: A chance of non-severe thunderstorms with small hail.

 

Convective Discussion

A trough of low pressure will move across New Brunswick this afternoon and across Nova Scotia and Newfoundland later tonight. MLCAPE values near 1000 J/kg are expected ahead of this trough but effective shear is relatively low at around 20 knots. This should limited any severe weather potential. That being said, moderate winds gusts and downpours are possible in the moist airmass ahead of the trough (precipitable water of 30-40 mm). Over Labrador, a separate trough will give scattered thundershowers with the potential for small hail and gusty winds. On Wednesday, the slow moving trough over Labrador will sweep into New Brunswick. Again non-severe thunderstorms are possible however the shear is quite high (40-50 kts) but the MLCAPE values will be 500 J/kg or less.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

NL: Risk of an embedded thundershower.

Maritimes/LAB: None

Tonight:

Slight risk of a thundershower in northwestern New Brunswick.

Tomorrow:

NB: Risk of isolated thunderstorms giving locally heavy downpours and strong wind gusts.

NS: Risk of an isolated thundershower across the spine of the province.

LAB: Risk of isolated thundershowers giving small hail and strong wind gusts.

NL: None

Convective Discussion

A lingering cold front from a low pressure system south of Greenland tracks across Newfoundland while a trough weakens over western Labrador as a ridge sits over the Maritimes. A few lightning strikes were noted in Newfoundland along the front this morning, with the risk continuing into the afternoon.

For the Maritimes today, heat and humidity builds under a ridge, but with sufficient sea breeze convergence, there will be some showers that develop across southern New Brunswick, PEI and the spine and northern Nova Scotia but no thunderstorms are expected with these showers today. 

A quick moving short-wave trough will move into Central Quebec tonight and into New Brunswick and Labrador tomorrow. There could be a lingering thunderstorm reach northwestern New Brunswick before the threat diminishes overnight. The threat of showers or thundershowers increases on Tuesday and further on Wednesday as a series of  troughs affect the region. MLCAPE values increase to 1000Jkg across New Brunswick and with increasing precipitable water and effective shear increasing to 35kt, there is the possibility of organization into multicells or lines that develop. Over Labrador, the troughing will aid in thundershowers across western Labrador and topographical lift and convergence south and east of Lake Melville could also aid in thundershowers tomorrow. As freezing levels lower across western Labrador, small hail will also be 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

Today: Chance of a TS in NB later today. Smoke may diminish this risk. Also a chance in southern Labrador. Gusty winds would be the hazard.

Tonight: No thunderstorms forecast.

Tomorrow: Central Lab and central Nfld have a marginal risk of a lightning strike or 2. Nothing severe forecast at this time.

Tuesday: Embedded multicell thunderstorms possible in NB. Main hazards would be very heavy rain and small hail. NS could see single cell structure reaching severe limits for rain along the spine region.

Convective Discussion

Wildfire smoke may act as enhanced CIN to the TS forecast for today. It’s a fine balancing act. But, if it doesn’t – multicell thunderstorms are possible in NB late in the afternoon and evening. Effective shear is over 30 kts and bases will be decently high, giving a wind gust risk. Stable for tonight with Heat conditions building into the Maritimes. Pop up showers and -TS risk further east on Monday. Tuesday looks to be ridge breakdown with rainfall being the hazard. Training systems could develop in parts of western NB and central Maine, so this is something to watch. Details will be tailored in coming shifts on rainfall amounts/rates.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Outlook for Tuesday

Forecaster: TIRONE

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today: Embedded convection along a trundling trof line from Avalon down to slope waters. No severe hazards forecast. Rain and scattered lightning expected.

Tonight: No thunderstorms forecast.

Tomorrow: Risk of thunderstorms in southern and western Labrador. Additional risk of organized convection across NB. These storms could bring gusty winds and heavy downpours.

Convective Discussion

Conditions are fairly stable behind dominant cold frontal forcing today/tonight. Ahead of the front (and near the triple point near Stephenville, NL)  activity continues. Rainfall is the biggest hazard under organized clusters. Significant mid-level smoke is entering into the Maritimes from the NW under the building ridge. This may act as enhanced CIN to the TS forecast for Sunday. But, if it doesn’t – multicell thunderstorms are possible in NB in the afternoon and evening. Effective shear is over 30 kts and bases will be decently high, giving a wind gust risk.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Saturday Night

Thunderstorm Outlook for Sunday

Forecaster: TIRONE

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

NB/PEI/NS: Risk of severe thunderstorms with torrential downpours and strong wind gusts.

NL: Risk of thunderstorms with locally heavy downpours and strong wind gusts.

LAB: Risk of an isolated thundershower.

Tonight:

NS/PEI/NL: Isolated embedded thunderstorms giving locally heavy downpours.

Tomorrow:

NL/LAB: Risk of isolated thunderstorms giving locally heavy downpours.

Martimes: None

Convective Discussion

This morning, a trough is moving through northern New Brunswick giving some heavy downpours (15-25mm/h rates), while a trailing cold front will sweep through the Maritimes and Newfoundland this afternoon and overnight. The main area of interest exists across central to southern New Brunswick, Prince Edward Island and northern Nova Scotia, where clearing of cloud is more likely along with adequate daytime heating ahead of the cold front and allow MLCAPE values to exceed 1000 J/kg. With effective shear increasing to 45 knots ahead of the front and advection of precipitable water above 50 mm, there could be an isolated supercells early in the afternoon but mainly expecting cells to organize into line segments by late afternoon over southern New Brunswick and Prince Edward Island and continue southeastward in the evening before they lose surface instability. With these ingredients, the main threats with these storm will be very strong wind gusts and torrential downpours. Isolated thunderstorms are also possible in the trough over Labrador this afternoon with brief wind gusts.

For tomorrow the cold front continues eastward across the Maritimes waters into Newfoundland while a low pressure system develops over Newfoundland into the trough in the morning and tracks into the Labrador Seas by Sunday. Isolated thunderstorms are possible along the front and in the troughing behind the low as colder air moves in aloft and behind the low over eastern Labrador and central Newfoundland.

 

Thunderstorm Outlook for TODAY

Thunderstorm Outlook for TONIGHT

Thunderstorm Outlook for TOMORROW

Roberta McArthur