Convective discussion
A weak low/frontal feature west of Labrador will move across tonight to lie east of Labrador Tuesday morning. This system has a cold front associated with it that will drop down over the Norther Gulf tonight. This will give some thundershowers, and over western Labrador may give significant wind gusts.
Technical discussion
A weak low near the surface is just west of Labrador, with some support from a weak trough extending to mid-levels just west of a thermal ridge. This is moving through western Labrador and cooling aloft is occurring behind it. Moisture is currently marginal, but there are precipitable water amounts of 25-35 mm near the front and low. Also, an axis of 18 degree surface dew points are approaching from the southwest (south of the cold front), and should start moving into Western Labrador by late this afternoon.
Shear is strong, and there are two midlevel jets approaching western Labrador, one in the extreme southwest and the other further north. Shear values are between 45 to 70 kts. Based on the soundings and forecast afternoon temperatures, CAPEs in the 500-1000 J/kg range are expected for western Labrador, dropping to 250 over eastern Labrador.
The main threat is downdrafts, possibly reaching 90 km/h for Churchill Falls and west, followed by short intense downpours. Freezing levels of near 10,000 feet allow the possibility of small hail over the western higher terrain and the mountains, but again, moisture levels are limited.
Regional impacts
Labrador: possibly severe downdrafts Churchill Falls and west . Elsewhere isolated to scattered thundershowers.
New Brunswick/ Northern Gulf of St. Lawrence/Western Labrador Coast/ Atlantic slope waters: isolated thundershowers.
Elsewhere: none.
Doug Mercer