Regional Impacts
New Brunswick, PEI, valley and northern Nova Scotia: There is a risk of severe thunderstorms today giving heavy rainfall, strong winds and small hail. Currently some storms producing heavy rain across northern NB. A few thunderstorms should form early this afternoon across the south. Scattered thunderstorms should develop later this afternoon across NS that could advect into PEI .
Southwestern Labrador: slight risk of a thundershower this afternoon and evening.
East of the Avalon: isolated elevated thundershowers.
Convective Discussion
There is a fairly decent chance in seeing some severe thunderstorms today across New Brunswick, Nova Scotia and PEI today giving heavy rain, strong winds and hail. There is a strong 250 jet placing the favourable areas in the left exit region, as well as some divergence. Divergence is also evident at 500 mb as the upper trough slowly approaches from the west, so heights will be falling a little as well. There is not as much low-level moisture as yesterday but still enough to add to the buoyant atmosphere. The 12Z KCAR tephi has a decent unstable profile, PWAT of 36 mm, a relatively low FZLVL (around 10,ooo feet) and about 35 knots of shear. The current storms affecting the northern half of NB is giving locally heavy rainfall. Modifying the sounding gives a mixed layer CAPE of around 1000. Mind you the shear will be decreasing through the day across northern NB, it will remain across southern NB, so strong storms giving wind gusts of around 80 km/h, heavy rain and hail of up to 2 cm are possible. For Nova Scotia, the issue right now in the favourable zone (valley and northern areas) is the mid level cloud cover. The 12Z YQI tephi has decent low-to-mid level lapse rates and shear of up to 35 knots. PWAT is the same as KCAR. Modifying it for a temperature of 31 degrees gives close to 1000 CAPE. So, much like NB there is a decent chance in seeing severe storms. The issue, as mentioned above is the current cloud cover. There is a back edge moving into the Gulf of Maine so I would expect cells to develop later this afternoon. Again heavy rain, strong winds and small hail are possible in the stronger storms. Some of these cells across southern NB and NS should progress into PEI later today.
A slight risk of a thundershower this afternoon and evening near Wabush/Labrador City in the vicinity of the upper low.
Thunderstorm Outlook for Day 1
Thunderstorm Outlook for Day 2
Jeremy