Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

Labrador: advancing trof bringing in slightly better dynamics for taller and more organized thunderstorms. Gusty winds, small hail, and brief but heavy downpours are possible. This has already started over southern sections this AM.

NB: Thunderstorms are possible in the afternoon and evening as the cap is finally able to break in this airmass (mainly tied to geography). Small hail and heavy downpours are possible.

NS: Guidance is suggesting the cap will break in the afternoon for an isolated region along the “spine” and the South Shore. Brief, heavy downpours are possible. These cells will move south over the coastline/water late in the day. They are forecast to remain isolated.

Tonight

None expected over land areas.

Tomorrow

Labrador: repeat of dynamics from Friday but less moisture to work with over western areas.

NB: Scattered thunderstorms are possible again in the afternoon and evening. Southern sections look to be more airmass, and northern areas forced by an advancing trof. Details will be added on Saturday regarding these specifics.

NS/Bay of Fundy: Numerous scattered thunderstorms are expected along the E-W spine and northern areas of NS. The main hazards will be small hail and heavy downpours for areas under the cells.

Convective Discussion

The story for the Maritimes today continues to be the high heat and humidity. Dew points this morning are reaching 21 in places. This is fuel for convective weather, if the cap can break. It seems that it will across NB this afternoon, and isolated western parts of NS (using E townships of Quebec as an upstream reference from yesterday). These cells will bring brief heavy downpours. There is less forest fire smoke present in the mid levels of the atmosphere than yesterday, but it is not zero. Storms that fire today are largely expected to be terrain driven.

In Labrador, the organization is quite a bit better for multi-cells over southern sections, forced along the advancing circulation/trof. Formation is evident already on visible satellite. These cells could produce strong wind gusts, and small hail along with frequent lightning and heavy downpours. Northern areas of Labrador are only expected to see single cell or embedded convection similar to yesterday.

Tomorrow will bring a renewed and more broad convective risk to Atlantic Canada. With the high moisture and forcings approaching from the west acting to destabilize the airmass further, multiple areas of thunderstorms are expected – tied to geographic and synoptic triggers. The exact timing and locations will be clearer tomorrow morning on water vapour imagery, but it is important to note that if any cells persistently train over one area, quite a bit of rainfall could occur in a short amount of time. Pwats are expected to be very high.

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

Labrador: slight risk of a thundershower along an elongated trof in western areas stemming from Quebec, similar to yesterday.

Tonight

None expected over land areas.

Tomorrow

Labrador: advancing trof bringing in slightly better dynamics for taller and more organized thunderstorms. Gusty winds, small hail, and brief but heavy downpours are possible.

NB: Thunderstorms are possible in the afternoon and evening as the cap is finally able to break in this airmass (mainly tied to geography). Small hail and heavy downpours are possible.

NS: Guidance is suggesting the cap will break in the afternoon for an isolated region along the “spine” and the South Shore. Heavy downpours are possible. These cells will move south over the coastline/water late in the day.

Convective Discussion

This morning, Nfld is in the overcast and drizzle regime thanks to the occluded low churning in the Atlantic to their east. Western Labrador has a chance of seeing some thundershower activity forced by the very elongated trof in Quebec.

The Maritimes are well into day 2 of their heat event under a strong and humid ridge of high pressure. Dew points are becoming tropical and are near 19 in places this AM. Thunderstorm activity is not forecast today in these stable conditions. However, tomorrow there are signals that this may start to break down. And so, TS risks are being added in some areas on Friday. MLCAPE tomorrow is 1000 in places, and 20-30kts effective shear. This will be monitored closely to see where the subtle triggers set up tomorrow.

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

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