Convective Discussion
There is a risk for non-severe thundershowers over northern New Brunswick late this afternoon into the evening and overnight with an approaching low pressure system over central Quebec tracking eastward today. Elsewhere no significant convection is expected with a ridge of high pressure stretching from Labrador to Nova Scotia keeping conditions dry.
Technical Discussion
The warm front in association with the low pressure system over Quebec has pushed north of New Brunswick. The ingredients necessary to initiate and maintain convection this late this afternoon over northern New Brunswick should be present. In the upper levels, there is an approaching 80KT 250mb jet and northern New Brunswick lies in the favourable left exit region. The 500mb level has increasing diffluence, slightly cooling temperatures, as well as increasing 700 and 850mb warming will help to destabilize the air mass. A trough within the warm sector is also expected to push eastward over Northern New Brunswick tonight to kick start the convection. The biggest inhibitor are the current relatively dry low levels and moist upper levels. Upstream precipital water values are in the range of 15-20mm. There is also widespread cloud cover currently from Quebec into western New Brunswick which may delay convective initiation if convective temperatures are not reached. If they do, only CAPE values maxed near 500 J/kg will be reached. Freezing levels are low so there is the risk of small hail.
Regional Impacts
New Brunswick: Showers and risk of thundershowers over northern New Brunswick beginning late this afternoon and may continue into the early overnight hours. Some local heavy downpours, gusts to 50 km/hr, and small hail (<2cm) are possible.
Nova Scotia: None
Prince Edward Island: None
Newfounland and Labrador: None
Roberta McArthur