Regional Impacts
NB: Organized thunderstorms possible over NW NB this afternoon, 0 to 1 cm hail and locally heavy rain of 20 to 40 mm possible.
NS & PEI: Isolated thundershowers with locally heavy downpours of 10 to 15 mm.
NL: Slight chance for an embedded thundershower over southern Labrador, locally heavy downpours are the main risk.
Convective Discussion…
The main area of interest today is along the NB/Maine border. A shortwave currently over western Maine will slowly push east, which will provide ample lift for convective activity this afternoon. A 100 kt southerly 250mb jet sitting over western NB will aid in the development of organized thunderstorms, pending the clearing of low level cloud over northwestern NB. Models have been under-forecasting cloud cover here, and if things do not clear out this afternoon, thunderstorm activity will be limited. If cloud does begin to clear this afternoon, surface based CAPE values may exceed 1000 J/kg; this in combination with 20-30 kts of 0-6 km shear will support the development of organized thunderstorms. The main threats would be 0 to 1 cm hail, locally heavy downpours of 20 to 40 mm, and convective gusts up to 70 km/h. The risk here will be entirely dependant on whether or not the low level cloud clears out enough to allow surface temperatures to rise into the low to mid twenties, allowing for surface based convection to initiate.
A few lightning strikes are also possible over parts of NS and PEI today, as a 55 kt 500mb jet sits over the region. This will allow for some isolated embedded convection, with locally heavy downpours being the main threat. This risk will remain overnight before the jet begins to push east tomorrow morning.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Copp