Regional Impacts
Today
Labrador: 70-90 km/h gusts, 2-3 cm hail, risk of cold core funnels.
NS: 70-90 km/h gusts, 15-25 mm/h rainfall rates, ~1cm hail
NL/PEI : isolated to scattered thunderstorms
NB/Magdalen- QC: None
Tonight
Labrador: A chance of thunderstorms.
NB/NS/NL/Magdalen- QC: None.
Monday
Labrador: chance of thunderstorms.
NB/NS/NL/Magdalen- QC: None.
Convective Discussion
A 3-4 SD vertically stacked cold upper low continues to slowly move east across Labrador. Near the centre of the upper low, an area of minimal vertical wind shear will yield the potential for widespread cold core funnel clouds across western Labrador with plenty of vertically slacked low level vorticity. Southeastern sections of Labrador will benefit from strong potential vorticity advection from the upstream deep upper low. This in combination with steeper lapse rates, lower freezing levels, linear shear profiles of 35-45 kts and daytime instability up to 1500 J/kg of SBCAPE will yield the primary hazard of significant hail in organized convection. The steeper low level lapse rates and cooler environment also presents a strong wind gust secondary hazard. Small hail is also possible across western NL, but weaker instability through the HGZ should keep this smaller in nature despite lower freezing levels.
On going clearing ahead of a weakening cold front across NS may also result in severe weather later this afternoon. Initiation is expected to be aided by coastal convergence at the surface with a sea breeze front in addition to the weakening cold front. Higher freezing levels and instability through the hail growth zone should keep any hail small in nature, however strong wind gusts may occur with significantly developed convection. PWATs appear to be slightly higher as well across NS near 35 mm, which would also present a near severe rainfall rate threat with organized convection.
Tonight a chance of thunderstorms will be limited to the stronger dynamics near the upper low tonight as day time instability abates. Tomorrow a similar situation is expected
across south central Labrador, with any storms being dynamically driven given limited expected thermodynamics (MLCAPEs ~300-400 J/kg).
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Brennan