Regional Impacts
Today:
NS/NB/PEI: Risk of thunderstorms giving moderate wind and heavy downpours.
Lab: Risk of thundershowers.
NL: Nil.
Tonight:
NS/ PEI: Risk of thunderstorms giving heavy downpours.
Lab: Risk of thundershowers, mainly over higher terrain.
NB/NL: Nil
Tomorrow:
Lab: Risk of thunderstorms giving moderate wind, heavy downpours and a risk of small hail.
NL: Risk of thunderstorms along the southwest coast.
NS: Risk of a thundershower.
NB/PEI: Nil
Convective Discussion
A Low off the southwest coast of Nova Scotia is having its frontal wave sheared apart, which is allowing for a complex setup for today and into tomorrow. Looking at water vapour imagery, along with upper-air soundings, we can see that the main cold front is back towards the US Eastern Seaboard; meanwhile, the upper jets have sheared off from the low centre as the trowel wraps through Nova Scotia and New Brunswick, creating a dry slot. Along with the synoptic setup, there is vorticity advection affecting Northwest New Brunswick, and a departing ridge over Labrador, which is allowing for topography-induced troughs to develop. With this setup, we are seeing Precipitable Water values (PWAT) nearing 50mm, along with CAPE values hovering around the 500 J/kg mark. As such, going forward with this setup, it is most reasonable to use the Most Unstable CAPE (MUCAPE) values, to which we are seeing a swath of MUCAPE values between 500-1000 J/Kg around the Maritimes and Labrador.
Tonight, the disconnected frontal wave from today will progress eastward, allowing for some isolated thunderstorms to persist in the overnight hours for the Maritimes. For Labrador, there is a risk of thundershowers overnight; This drier air could allow for some thunderstorms overnight, though there is more uncertainty with this.
Tomorrow, remnants from today’s frontal wave will likely stay just to the southwest of Newfoundland, and model guidance indicates that convection will struggle to move inland. For Labrador, there is a stronger low-pressure system moving through Northern Quebec and Southern Baffin Island, which model guidance suggests a cold front could extend from Ungava Bay to Southern Quebec. The warm sector will enter Labrador with this frontal system, bringing a slight risk of hail, moderate winds, and rainfall. As this system progresses, the risks could change, as there are some timing uncertainties.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Forecaster: Lambert