Regional Impacts
Today
NB: Risk of marginally severe thunderstorms over northwestern New Brunswick this afternoon capable of producing heavy downpours, strong winds, and some small hail.
NS/PEI/NFLD/LAB: None.
Tonight
NS: Slight chance of elevated thundershowers over southwestern Nova Scotia before morning.
NB: Chance of a few thundershowers over northern New Brunswick with locally heavy downpours.
PEI/NFLD/LAB: None.
Tomorrow
NS: Slight chance of some isolated embedded thundershowers over mainland Nova Scotia.
NB: Slight chance of an isolated thundershower over extreme northwestern New Brunswick.
PEI/NFLD/LAB: None
Convective Discussion…
An active couple of days are in store for Atlantic Canada as a trough approaches from the west and begins to erode a ridge of high pressure over the central Maritimes. Today, the main threat area will be in parts of northwestern New Brunswick, where some marginally severe thunderstorms are possible this afternoon. Some overnight convection is lingering over the area of interest, leading to some increased cloud cover, but current satellite imagery shows clearing off to the west over southern Quebec. This should allow MLCAPE values to rise near 1000 J/kg this afternoon over the northwestern portion of New Brunswick and with effective shear near 40 knots, some marginally severe thunderstorms are possible. One limiting factor in the intensity of these storms will be relatively moderate lapse rates, but given enough clearing early this afternoon, storms should have no issues firing. Given the weaker lapse rates, hail will not be much of a concern, but some decent PWAT values near 30 to 35 mm will lead to some heavy downpours in thunderstorms. In addition, there is potential for some strong wind gusts in the downdrafts of these storms. Without the 12Z sounding out of Caribou this morning, there isn’t a good sample of the current environment over the area, but the Maniwaka sounding from 00Z last night shows a relatively unstable airmass in a highly sheared environment. In addition, model tephigrams are indicating some curvature in the low level winds over northwestern New Brunswick this afternoon leading to a non-zero tornado risk, though this risk remains very low at this time. Severe thunderstorm watches may be issued early this afternoon as confidence increases.
Tonight, the trough will continue to slowly move east, reaching southwestern Nova Scotia by morning. With some weak mid-level instability expected overnight, some elevated thundershowers are possible here, in addition to northern New Brunswick. The trough will continue to move east through the day tomorrow, extending the risk for an elevated thundershower over parts of mainland Nova Scotia. The unstable airmass behind the trough may also lead to some isolated thundershowers over extreme northwestern New Brunswick in the afternoon.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Forecaster: Copp