Convective Discussion
For today, we have a broad trough extending from the Great Lakes northeastward toward central Labrador. Within this trough there are a couple of upper level features over central Quebec and central Labrador. Convective temperatures are not expected to be reached, especially given the amount of cloud cover currently in the region but there will be a decrease in temperatures aloft, leading to further instability along with the upper level features as a trigger to initiate some non-severe convection this afternoon and evening. Areas south of Labrador City to Goose Bay over southern Labrador into North Shore Quebec could see CAPE values close to 500 J/kg and with 0-6km shear values nearing 40 kts, some thunderstorms may organize further into lines or weak bow echos where locally heavy downpours and brief gusts are possible.
Meanwhile, a low pressure system south of the Great Lakes will progress northeastward over New England today. The system is then expected to intensify offshore near Cape Cod overnight into Friday morning and track over Nova Scotia Friday afternoon. This system will likely have embedded convection overnight along the warm front which will push into New Brunswick this evening and into Friday morning for Prince Edward Island and western Nova Scotia. Heavy rainfall will be the biggest threat with this system as it taps into tropical moisture streaming northward from the southern Gulf stream. Rainfall warnings have been issued for southern New Brunswick and northern Nova Scotia and will likely be extended eastward this afternoon.
Regional Impacts
Newfoundland and Labrador: Lightning, locally heavy downpours and brief gusts for parts of central and western Labrador.
Maritimes: Embedded thunderstorms will give lightning and enhanced heavy rainfall beginning late this afternoon and evening over northern New Brunswick and overnight and into Friday morning for western Nova Scotia and Prince Edward Island.
Roberta McArthur