Convective Discussion
There are a few areas of convective potential for today into tomorrow morning. A slow moving upper low currently near Sable Island will continue to track eastward and stall just east of Cape Breton by this evening. Meanwhile, a trough currently over Hudson Bay will track eastward towards central Quebec and western Labrador this evening and reach northwestern New Brunswick by tomorrow morning.
Under the upper level feature south of Nova Scotia, most of the convection should remain over eastern coastal regions of Nova Scotia, Eastern Shore, Sable and marine waters farther east this afternoon and evening near the vicinity of the low centre. Due to the slow nature of this system, some areas are expected to get locally heavy downpours. A rainfall warning is in effect for Victoria county due to upslope enhancement in easterly winds. Precipitable water values remain in the 30-35mm range looking at the Yarmouth and Sable Island morning soundings. Winds should remain quite stable over the marine waters but any convection that makes it onshore may see brief wind gusts reaching 30kts. Rain could be heavy at times over southern Newfoundland today as the low continues to drift closer but the threat of convection is low.
Areas of western Labrador will see an increasingly unstable air mass this afternoon as weak troughing moves into the area and convective temperatures are expected to be reached to initiate surface based convection, especially over areas that have cleared out of the stratus early this morning. CAPE values could reach the 500-700 J/kg range but with weak shear this morning, generally pulse type storms are expected. Into late afternoon, however, the 0-6KM shear is forecast to increase from 20 to 30KT which may allow some thunderstorms could be maintained or possibly organize into small squall lines. This along with fairy low freezing levels may produce small hail, brief heavy downpours and strong gusts. Conditions are not expected to reach severe warning criteria. The upper flow may hinder initially some of the surface based convection as well due to warming aloft as a warm front approaches the region from central Quebec. An extension of this trough will also make its way farther south toward Maine and northwestern New Brunswick by early tomorrow morning.
Regional Impacts
Nova Scotia…
Locally heavy downpours over eastern mainland Nova Scotia and Cape Breton
New Brunswick…
Isolated thunderstorms may affect northwestern New Brunswick early tomorrow morning.
Labrador…
Small hail, strong winds and locally heavy downpours are possible for western and central Labrador late this afternoon and overnight.
HAPPY CANADA DAY!
Roberta McArthur