Regional Impacts
Today:
NB: Near-severe thunderstorms possible over western and northern regions this afternoon and evening giving strong wind gusts (70 to 90 km/h), small hail and heavy downpours (20-40mm per hour rates).
NS/PEI/NL&LAB: None
Tonight:
NB: Thunderstorms possible overnight giving heavy downpours.
NL&LAB: Thunderstorms possible over southwestern Newfoundland and southwestern Labrador.
Saturday:
NB: Thunderstorms over central and southern regions this afternoon and evening giving heavy downpours.
NL: Thunderstorms over central to northern giving heavy downpours.
NS/PEI/LAB: None
Convective Discussion
An upper level trough extends from the Great Lakes northeast into the St. Lawrence River Valley with a surface low pressure developing this afternoon over central Quebec. Ahead of the trough over the Maritimes lies a warm and humid air mass with dewpoints remaining near 20C today over central to northern New Brunswick and precipitable water near 40 mm. Should there be sufficient clearing this afternoon, this may also provide additional surface based heat with temperatures into the high 20s with possible MUCAPE (upwards of 2000 J/kg) over central to northern New Brunswick. Caribou’s 12Z sounding indicates a capping inversion near 850mb but there is decent instability above. With a 40KT 700mb jet and weak to moderate deep layer shear near 25KT, multicell development will likely occur over the higher terrain in north and central Maine (already ongoing this morning) and northwestern New Brunswick this afternoon. Cells may form into more organized lines as they track northeastward this afternoon and into the overnight. Given general northeast orientation of storm movement, there is the threat training and locally heavy downpours over the same locations. With sufficient mid-level instability, downdraft wind gusts and small hail with the more intense storms are also possible.
For Saturday, the trough inches slowly southeastward. The threat for severe thunderstorm development has decreased, but areas of central and southern New Brunswick could see heavy downpours in the afternoon and evening as well as northern Newfoundland.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Saturday
Forecaster: McArthur