Convective discussion:
Scattered thunderstorms will persist today over central and eastern LAB under the influence of an upper level trough of low pressure. Scattered thunderstorms will develop early this afternoon over central and east/northeast NL in association with a surface trough and 500 mb short wave.
Technical Discussion:
Conditions look pretty good for near severe thunderstorms across portions of NL this afternoon. From 15-21 UTC there is a strong 250 jet mb with divergence over SE NL, placing the risk area above in the left exit region (which will promote ageostrophic motions). 12Z tephi from YJT shows good shear at close to 45 knots, good drying in the mid levels which would lead to possible strong wind gusts at the surface. Looking at SAT PIX there appears to be an area of PVA moving into WRN NL (associated with a somewhat decent short wave trough at 500 mb) which will move eastward and add to the potential for thunderstorms once the convective temperature is reached. 12Z surface analysis shows a surface trough near WRN NL (which should act as a trigger). Adjusting the YJT surface temperature to 27 degrees produces close to 1000 CAPE, with fairly good moisture near the surface. In addition instabilities are pretty good (LI’s of minus 4 to minus 6). All these ingredients point to the potential for severe thunderstorms, likely from the Buchans/Millertown area to regions north and east. For now near severe cells are expected, but this area will have to be monitored this afternoon and into early this evening.
Over LAB scattered TS will continue today east of the upper trough. Looking at the 12Z YYR sounding, freezing levels are pretty low, but the shear is really weak so no severe weather is expected. Small hail is almost a given under some of these cells.
Regional Impacts:
Newfoundland: Scattered afternoon/evening thunderstorms from central and east/northeast. Slight risk of severe.
Labrador: Scattered non-severe thunderstorms. Small hail likely.
Nova Scotia: nil.
Prince Edward Island: nil.
New Brunswick: nil.
Jeremy