Convective Discussion:
A front east of an occluded low west of Labrador will move east across the Big Land. Ove the Maritimes the same front will drop south over New Brunswick this afternoon, spreading thundershowers south across the province and into Prince Edward Island. There is a possibility of significant weather, mainly downdrafts, for New Brunswick and parts of Southern Labrador, and small hail for Southern Labrador
Technical Discussion:
Currently the cold front is over the St. Lawrence River heading south, and there is another weak trough over Central New Brunswick that has triggered a few cells along and east west line. Most of the tephis over NB show a weak cap that should break sometime this afternoon with temperatures into the low 30’s, and enhancement with both the trough and front should organise things. Shear values near 50 knots over NB diminishing to about 35 over NS, should stay steady or increase. CAPEs should be healthy, in the 500 to 1000 J/kg range. Moisture is more marginal, with dewpoint values near 14-17 for NB and PEI. Also precipitable water amounts are in the 20-30 mm range, so not huge. The big risk here is for downdrafts, probably from mid-afternoon until near sunset. Midlevel cooling as the main front approaches should enhance thing sin the middle to late afternoon as well.
Labrador is similar, with CAPEs in to 500-1000 J/kg range, and shear a little lower. Over the mountains south of Lake Melville the relatively low freezing levels give a risk for hail. This may affect the Trans-Labrador Highway.
The Avalon may see isolated showers into the overnight periods
Regional Impacts:
New Brunswick: Downdrafts possibly to 90 km/h. Thundershowers.
Labrador south: Downdrafts possibly to 90 km/h. Small hail, especially over higher terrain.
Avalon Peninsula: Chance of thundershowers into the overnight period.
Elsewhere: nothing significant
Doug Mercer