Regional Impacts: Today- primarily lightning in eastern Labrador and much of central Newfoundland with a secondary hazard of convective gusts to ~70 km/h in central Newfoundland. Lightning will be a hazard later this evening in western Labrador.
Tonight- Lightning for much of NB, with hail greater than 1 cm, heavy downpours and wind gusts greater than 70 km/h possible before noon in NW NB. Isolated lightning over western Labrador.
Tomorrow- scattered to isolated lightning for most of NB, PEI and NS. West to Northwest NB at greatest risk hail greater than 2cm, wind gusts ~90 km/h and heavy downpours. Much of western and central Labrador will again see lightning as a primary hazard.
Convective Discussion: Today weak vorticity advection in conjunction associated with a upper trough will yield the risk for lightning in eastern Labrador and much of central Newfoundland. As a building upper ridge advects eastward lapse rates will become less favourable for eastern Labrador later in the day. Given the lower surface dew points, profiles suggest storms that do develop over Newfoundland will be fairly high based, yielding the potential for gusty convective winds to ~70 km/h. The potential for small hail cannot be ruled out entirely with a relatively low hail growth zone, despite skinny CAPE profiles. Western Labrador will likely be subjected to some isolated storms that are currently ongoing in central Quebec as instability continues to build eastward with the upper ridge continuing to advect towards Newfoundland.
Tonight a strong LLJ of ~35-40 kts will be the focal point for elevated convection for much of NB into western Labrador. Enough instability looks to remain in NW most NB for some surface based convection to develop prior to the Friday noon hour. These storms will initially be able to work with MLCAPES of up 750 J/kg with strong linear shear profiles with bulk shears up to 40 kts ahead of an approaching cold front. This gives rise to the potential for severe weather rather early in the day on Friday, primary hazard appear to be marginally severe hail, strong gusty winds and heavier downpours given PWATs of ~30-35mm. Storm motion will be relatively quick at 30-40 kts, limiting excessive rainfall despite the high moisture being advected into the region.
Tomorrow elevated convection will continue to advect eastward with the progression of the strong LLJ, additional solar insolation should increase the amount of energy storms have to work with ahead of the cold front in western NB. Again linear shear profiles, with fast easterly storm motion gives rise for a wind hazard with gusts ~90-100 km/h. Severe hail with MLCAPES ~1000 J/Kg is also a possibility. Storm mode should primarily be linear, although there is a slight chance of a discrete supercells at the base of the cold front from central Maine to west-central NB. Here a non-zero tornado threat could exist if low level wind profiles end up being southeasterly rather than southerly. Right now confidence and probability is too low to note outside of this discussion.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
