Regional Impacts
Today
NB/LAB: Slight risk for some isolated thunderstorms over northwestern New Brunswick and western Labrador late this evening with small hail, gusty winds, and locally heavy downpours.
NL: Chance of an elevated thundershower over western Newfoundland today with some locally heavy downpours.
NS/PEI: None.
Tonight
NL/LAB: Slight risk for an elevated thundershower overnight.
NB/NS/PEI: None.
Tomorrow
LAB: Chance for some scattered thunderstorms over southeastern Labrador with small hail, gusty winds, and locally heavy downpours.
NB/NS/PEI/NL: None.
Convective Discussion…
This morning, a disorganized elongated trough extends south from the Labrador Sea into the Atlantic waters south of Nova Scotia. Scattered thunderstorms in this trough have persisted overnight as it approaches western Newfoundland and southern Labrador, with this risk expected to continue through today. These storms are likely to stay elevated due to a thermal ridge between 750 and 800 mb evident on the 12Z Stephenville sounding, but an advancing shortwave near Cape Breton within the trough should keep scattered thundershowers going through the day. Weak MUCAPE values near 500 J/kg and effective shear of 10 to 20 kts will keep anything from becoming severe today over western Newfoundland, but some brief heavy downpours are possible with PWATs near 40 mm observed this morning at Stephenville. Elsewhere, a large trough over central Quebec will continue to move east this afternoon, reaching northwestern New Brunswick and western Labrador late this evening. A large capping inversion is present around 700 mb over New Brunswick, which is likely to keep any storms from firing this afternoon ahead of the trough. Good shear is in place (30 to 40 kts effective) and some clearing of the low level cloud is evident this morning which could help bump MLCAPE values upwards of 750 J/kg but this is unlikely to erode the cap. Due to the timing of the trough, thunderstorms aren’t expected to fire until late this evening, but by that point daytime heating will begin to shut down. The risk here today is low, but if anything is able to break the cap before the trough arrives it will have the potential to produce some gusty winds, small hail, and some heavy downpours.
Tonight, an elevated thundershower or two is possible over central Newfoundland as the first trough continues to move northeast and out over the Labrador Sea by tomorrow afternoon. The second trough impacting western Labrador and northwestern New Brunswick today will bring a similar risk for some scattered thunderstorms over southeastern Labrador tomorrow as it gradually moves east. A similar environment to today in the west is expected here, with the risk of some small hail, gusty winds, and locally heavy downpours.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Forecaster: Copp