Regional Impacts
For Nova Scotia: there is a slight risk of a severe thunderstorm across portions of the eastern mainland into early this evening. The main threat is heavy rainfall. Some gusty winds are also possible but below warning threshold (90 km/h).
For New Brunswick: scattered thunderstorms are expected to develop this afternoon.
For Newfoundland: there is a risk of isolated elevated/nocturnal thundershowers tonight
Convective Discussion
As mentioned above, there is a slight risk of a severe thunderstorm across the eastern mainland of Nova Scotia this afternoon. Looking at the parameters (MIST): we have the moisture with dewpoint temperatures into the low 20’s and a moist tongue at 850; the instability is there with model LI’s in the minus 5 to minus 8 range; analysis from the 12Z YQI and YAW tephis show 30-40 knots of shear in the 0-6 km level; and lastly a weak trough offering up a trigger mechanism once the convective temperature is reached early this afternoon. Upper air analysis doesn’t show much at 250 mb as the main jet is well to the north of NS. There is a 40 knot jet at 500 mb, but not really an indication of at least minimal falling atmospheric heights. The upper level trough at 500/700 is well to the west and won’t be a factor until D2 as it approaches Maine and New Brunswick. One thing noted on the 12Z tephis is the warm, stable air aloft. This will be the determining factor. Modifying the 12Z soundings for temperatures of 30, and dewpoints of 22 gives about 1000 mixed-layer CAPE. The MUCAPE is way overdone and ignored. I expect TCUs to form shortly after the lunch hour with isolated-to-scattered TS not long thereafter. Once again, the stability aloft may prevent any potential cells from becoming severe (25+ mm of rain in one hour).
Scattered cells are likely to develop across northern New Brunswick this afternoon…there is a very little chance in seeing anything close to severe limits. Locally heavy downpours can be expected.
Lastly, there is a risk of elevated convection tonight across southern Newfoundland.
Thunderstorm Outlook for Day 1
Thunderstorm Outlook for Day 2
