Regional Impacts
NB, NS, and PEI: Scattered thunderstorms today and tomorrow, some of the stronger storms could produce heavy downpours 10 to 20 mm, and possibly higher.
NL: None, deeper instability limited to the west of a line from Fermont/Lab City to Lake Eon to Chevery.
Convective Discussion…
A surface and upper low over Maine will move east today, reaching the Gulf of St. Lawrence tonight. The upper low will then weaken and open up over Labrador. Moisture associated with these features will continue to produce widespread showers with embedded thundershowers with forecast guidance suggesting CAPE of 250 J/kg or less, however as the day progresses, insolation from breaks in the cloud cover and the cold temperatures aloft will increase the depth of the instability with surface-based CAPE values expected to reach 500 J/kg. Under these conditions this deeper convection will produce locally heavier showers 10-20 mm, some small hail < 1cm, and wind gusts to around 60 km/h. Generally the shear is weak, except over NS where current soundings indicate 0-6km values above 20 kt which might produce weakly organised convective cells.
A series of weak low pressure systems will extend from NY state to Atlantic Canada on Friday. Low level moisture/fog will give way to isolated thunderstorms during the day.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Friday
