Regional Impacts
NB … Strong thunderstorms possible this afternoon and into this evening with 70 to 90 km/h wind gusts, rainfall rates of 20 to 40 mm/h, and pea sized hail.
NL … Risk of some scattered thunderstorms this afternoon in western Labrador with rainfall rates of 20 to 30 mm/h and wind gusts of 60 to 80 km/h.
NS/PEI … Risk of an isolated thundershower later this evening with rainfall rates of up to 15 mm/h.
Convective Discussion …
An upper trough moving into the Maritimes brings the threat for strong thunderstorms across New Brunswick this afternoon. Good moisture advection at the surface will increase dewpoints to near 20 degrees in western New Brunswick, as such MUCAPE values are expected to climb to 1000 to 1500 J/kg this afternoon in this region. Remnant cloud from yesterdays convection over Ontario and Quebec moving through New Brunswick this morning will keep surface temperatures in the low to mid twenties, nonetheless an approaching cold front should provide ample surface lift to break any capping inversion that remains this afternoon. High shear values upwards of 50 knots will allow these storms to remain fairly organized throughout their lifespan, with a few supercells even possible. The main hazards with these storms will be strong wind gusts of up to 90 km/h, and heavy downpours of 20 to 40 mm/h. There is also a chance for some pea sized hail in some of the stronger cells. These storms are expected to die off as they approach the cooler waters of the Bay of Fundy and the Gulf of St. Lawrence later this evening, though a few lightning strikes are possible over southern Nova Scotia overnight.
In Labrador, some scattered thunderstorms are possible from Labrador City to Churchill Falls as the aforementioned upper trough approaches from the west. Thunderstorms may become organized this afternoon, as bulk shear values of 40 to 50 knots move through the region. Cape values are expected to reach 1000 J/kg this afternoon, however cloudy skies this morning may inhibit CAPE from getting this high. Thus the threat for any strong thunderstorms remains low. Any storms that do become organized may bring locally heavy rainfall of 20 to 30 mm/h and strong wind gusts of 60 to 80 km/h.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Copp