Thunderstorm Outlook for Day 1
Regional Impacts
Nova Scotia, New Brunswick and Prince Edward Island, and Newfoundland: a few thundershowers with a slight risk of small hail, some gusty winds, and brief downpours.
Labrador: similar to the Maritimes, but a bit weaker.
Convective Discussion
Currently there is a broad occluded low west of Labrador with a deep cold upper trough extending south to southeast across the eastern Gulf of St. Lawrence. In addition there is a weak broad east-west trough across most of Atlantic Canada. Currently there are strikes along the deep upper trough from Gulf - Port au Port to the vicinity of Wabush. The ingredients are fairly moderate for most regions, with PWAT generally between 20-30 mm, with most of it below 700 mb, freezing levels not far from 10,000 ft, giving a possibility of small hail, and dry air above 700 mb, giving some gusty winds. Shear is a bit more variable. Over Labrador it varies from 15-25 kts, which probably will inhibit hail. For Newfoundland it increase from 15 near Stephenville to near 45 kts near St. John’s, and with some partially clear skies over the island may give some small hail and good but non-severe wind gusts as you move east. Surface dewpoints range from 8-12 for Labrador and 10-15 for Newfoundland. The CAPEs for Newfoundland should stay below 500 L’kg, and for Labrador below 250.
For the Maritimes there is little in the way of upper support except for the weak broad trough near New Brunswick. Clear skies over most of the Maritimes will give good insolation, except for New Brunswick where some cloud is moving in. For the Maritimes PWAT is similar, with dewpoints ranging from 13-16 C for New Brunswick and 15-18 for the rest of the Maritimes. The shear is between 25-35 kts, and mean layer CAPEs may exceed 500 J/kg, especially for eastern Nova Scotia. Again, freezing levels near 10,000 ft may give small hail, as seen yesterday in New Brunswick. For tonight a trough will approach from the southwest and may give some nocturnal convection.
Thunderstorm Outlook for Day 2
Roughly similar areas, with somewhat different dynamics. There will be a broad low over Maine and extending north, with a trough extending east to Newfoundland, part of which will push north twards Labrador, initiating some thundershowers. A second trough, mentioned above, will continue to move across Nova Scotia tomorrow. The freezing levels will be a bit higher tomorrow, reducing the chance for hail.
