Convective Discussion
Today there are three things going on. For Labrador a combination of a surface low under a weak diffluent upper jet will give non-severe thunderstorms which may persist into this evening. For New Brunswick air-mass thundershowers are possible ahead of a slowly approaching low, with a southerly flow brining in an axis of moisture up to al least 700 mb. Finally there is a low crossing the scotia shelf and giving embedded thundershowers.
For Labrador the upper trough moving in from the west is diffluent with a weak jet on the south side. Shear is around 25-30 kts, with CAPEs possibly reaching 500 J/kg, but more likely less.
Dewponts will increase slightly this afternoon, and if they reach 16 C, the 500 CAPE may occur. Downdrafts are possible, but shouldn’t be more than 60- kph.
For western New Brunswick, surface to 700 mb dewpoints are increasing and may reach 17+ C from he surface, and good insolation is expected early this afternoon with mainly clear skies in the northwest. PWATs are healthy and between 30-40 mm. Shear is low, arguing for airmass pop-ups. The only worry is the slow speeds of the potential thundershowers, which may give 25 mm/hr.
Regional Impacts
New Brunswick: mainly a chance of non-severe thundershowers into this evening, with a chance for local downpours near or possibly exceeding 20 mm.
Labrador: a chance of non severe thundershowers, with showers up to 15-20 mm and some gusty winds.
Southern Waters: Embedded thundershowers with occasional gusty winds.
Doug Mercer