Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

Nfld: chance of a thundershower near the low centre in the vicinity of Gander and Terra Nova N.P.

Labrador: chance of a thundershower along a decaying trof in western areas stemming from Quebec.

Tonight

None expected over land areas.

Tomorrow

Labrador: slight risk of thundershowers again in western sections of Labrador.

Convective Discussion

In the Maritimes, a strong ridge of high pressure is keeping clouds at bay. There is ample CIN, and the entire column is dry on this morning’s soundings. Heat warnings are in effect for many counties. No convection is forecast.

In Nfld, some embedded TS activity could occur just to the east and south of the remnant low centre today. This system is very occluded at this point; evident on satellite. This will pull away overnight tonight. In Labrador, a slight risk of a late day thundershower coming in from Quebec along a trof is possible. But severe hazards are not being forecast. Lightning is the biggest risk today and tomorrow in these remote locations. (Forest fire smoke is also a factor in vicinity of Quebec and NB in mid and upper levels.)

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Tirone.

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

LAB: Risk of a thundershower over extreme southwestern sections.

NB/PEI/NS/NL: None

Tonight

None

Tomorrow

NL: Slight risk of a thundershower.

NB/PEI/NS/LAB : None

Convective Discussion

A low pressure system across the Lower North Shore of Quebec will track eastward today weaken tonight as it moves southeastward into Newfoundland tomorrow.  A cold front associated with the low is tracking east of Cape Breton and across Newfoundland today. There has not been much convection along the front, but there is a chance for some embedded downpours, mainly across the Maritime waters. Otherwise, the other risk will be near the vicinity of the low centre in southwestern Labrador. With MLCAPE potentially reaching 500 J/kg, effective shear near 20kt and precipitable water of 35 mm, heavy downpours are likely.  For tomorrow, there may be a very weak threat of a thundershower remaining near the low centre in central/eastern Newfoundland given sufficient lift can breach the warm 700-500mb levels, but with minimal shear and still relatively high moisture, some brief heavy downpours are possible in TCUs. Meanwhile, hot and increasingly humid conditions under a ridge of high pressure will settle over the Maritimes towards the end of the week.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

NS/NB/PEI: Embedded thundershower risk giving heavy downpours.

 

NL/LAB: None.

Tonight

NB: Embedded thundershower risk giving heavy downpours.

NS/PEI/NL/LAB: None

Tomorrow

LAB: Risk of a thundershower over  extreme southwestern sections.

NB/PEI/NS/NL: None

Convective Discussion

A low pressure system currently in southern Quebec will track slowly northeastward today to lie along the Lower North Shore of Quebec tomorrow. The warm front is tracking into the Maritimes today, bringing with it additional moisture with precipitable water above 50 and dewpoints near 20C. There are pockets of heavy rainfall expected along the warm front and in the warm sector today with a small risk of elevated embedded thundershowers. Destabilization is limited given the amount of cloud cover, but parts of southeastern NB, the valley in NS and PEI have some pockets of sunshine, and could breach the warm cap aloft. Otherwise, convection this morning has been mainly just ahead of the cold front with the thermal ridge in parts of New England and near the low centre. This is where the best dynamics are located and remain for today, but it is possible some residual convection will hold as the cold front approaches northwestern New Brunswick later this evening with heavy downpours as the main threat. The cold front is expected to weaken as it tracks across the Maritimes overnight but pockets of heavy rainfall are still possible.

For tomorrow,  the low centre continues eastward along the Lower North Shore of Quebec or extreme southern Labrador with the cold front tracking across Newfoundland. Not expecting much convection will remain with the cold front, other than over the southeastern Maritime waters, but some convection may continue near the low centre.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NB/LAB: Scattered thundershowers.

NS/PEI/NFLD: None.

 

Tonight

NS: Chance of thundershowers.

NB/PEI/NFLD/LAB: None.

 

Monday

NS/NB/PEI: Embedded thundershower risk.

NFLD/LAB: None.

 

Convective Discussion

A trough stretching from western Labrador to the St. Lawrence River Valley will likely spark some non-severe thundershowers over northwestern New Brunswick and central Labrador today.  MLCAPE values are expected to be near 500 J/kg and the shear will be 20 to 30 knots. Current soundings indicate a layer of warm air above 500 mb which should keep storms from reaching severe status. The main hazards with any storms will be small hail, strong wind gusts, and locally heavy downpours. On Monday, a low developing in the trough will give a risk of embedded thundershowers across the Maritimes. Localized downpours are possible with any thundershowers that develop.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

LAB: Scattered thunderstorms possible today capable of producing small hail, strong wind gusts, and heavy downpours.

NS/Newfoundland: Chance for some elevated thundershowers today over Cape Breton and southern Newfoundland with some locally heavy downpours.

PEI/NB: None.

Tonight

LAB: Some isolated thundershowers possible overnight over northern and western Labrador.

NS/NB/PEI/Newfoundland: None.

Tomorrow

NB: Chance of some isolated thunderstorms over northwestern New Brunswick in the afternoon and evening with small hail, strong wind gusts, and locally heavy downpours.

LAB: Some scattered thundershowers possible through the day over central Labrador capable of producing some locally heavy downpours.

NS/PEI/Newfoundland: None.

 

Convective Discussion…

Two areas of interest are in play today. The first is associated with an upper low between Cape Breton and southern Newfoundland, and the second associated with an elongated trough extending from the northern Labrador Sea down into southern Quebec. Some isolated thundershowers have already been observed this morning with this first feature along the Eastern Shore of Nova Scotia. The upper low will slowly move northeast, reaching the Avalon Peninsula overnight. Due to the amount of cloud cover over this area of interest, convection is expected to remain elevated through the day as some scattered thundershowers move into southern Newfoundland. MUCAPE values of 250 to 500 J/kg are forecast, with effective shear in the 15 to 25 knot range allowing some of these thundershowers to be sustained through the day. The main risk with these cells will be heavy rainfall rates of 20 to 30 mm per hour. This low will move east over the Atlantic tonight. The second feature over Quebec and Labrador has already produced some scattered thunderstorms, which are expected to continue through the day and into this evening. MLCAPE is expected to build near or above 1000 J/kg by early this afternoon over western Labrador, in addition to some moderate jet support providing effective shear in the range of 20 to 30 knots by late this afternoon. This should allow some cells to become organized this afternoon and into this evening, with the main hazards being some heavy downpours, strong wind gusts, and small hail. This trough is moving very slowly to the northeast which could ramp up some of the rainfall totals over the area. This risk will extend overnight and into tomorrow, but without daytime heating only a few isolated non-severe thundershowers are expected overnight.

Tomorrow, the same trough will likely spark some non-severe thundershowers over central Labrador, with MLCAPE expected to be much lower (250 to 500 J/kg) due to enhanced cloud cover over the region. However, the environment over northwestern New Brunswick is expected to ramp up by the mid-afternoon as the trough moves into the St. Lawrence river valley. Clear skies during the morning and early afternoon here should allow MUCAPE values to build to 750 to 1000 J/kg. This in combination with effective shear values of 20 to 30 knots could lead to some organized thunderstorm development in the mid-afternoon over northwestern New Brunswick. However current model tephigrams indicate a layer of warm air above 500 mb which could keep storms from reaching severe status. The timing of the trough will also play a role in when convection triggers, so there is still some uncertainty here tomorrow. The main hazards with any storms that do fire will be small hail, strong wind gusts, and locally heavy downpours.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Copp