Regional Impacts
Today
NS: Embedded thunderstorms with locally heavy downpours >25 mm/hr possible today.
NB: Isolated thunderstorms over NW NB, 70 km/h wind gusts, 1-2 cm hail, and locally heavy downpours >25 mm/hr possible this afternoon.
PEI: None.
NL: Isolated thundershowers over Labrador and western NFLD today, embedded thunderstorms with locally heavy downpours >25 mm/hr possible over the Port-Aux-Basques region this evening.
Thursday
NS: None.
NB: None.
PEI: None.
NL: Embedded thunderstorms possible over central NFLD tomorrow, with locally heavy downpours >25mm/hr possible.
Convective Discussion…
Two main areas interest for potential severe weather exist today. The first threat area is associated with a trough moving through Nova Scotia today. Within this trough we are likely to see some embedded convection, with heavy downpours being the main risk. PWAT values from the Yarmouth sounding this morning indicated 45 mm, this is forecast to build to 50-60 mm by this afternoon east of Halifax. Bulk shear values of 40-50 kts will aid in sustaining this convection today as it moves east, reaching the Port-Aux-Basques region of NFLD by this evening. Total rainfall amounts may be in the range of 30-60 mm in areas of strongest convection, with rainfall rates of >25 mm/hr possible.
The second area of interest is in NW NB, which is associated with a small vorticity centre that is forecast to track along the Gaspe Peninsula this afternoon. This vort max has already spawned a severe thunderstorm near Saguenay, QC, with some weaker echoes popping up to the south near Maine. A relatively strong 250 mb jet over NW NB should aid in the intensification of some of these southern cells as they approach the NB border this afternoon. SBCAPE values upwards of 1500 J/kg and bulk shear values of 40-50 kts in this region will allow for some of these storms to potentially become severe as they enter NB. Small hail (1-2 cm), gusty winds (70 km/h), and brief but intense downpours (>25mm/hr) will be the main threats associated with these cells.
Tomorrow, the aforementioned trough moving through NS today will bring the threat for some embedded convection with locally heavy downpours to central NFLD. PWAT values are expected to be slightly lower tomorrow, in the 40-50 mm range. The main threat will once a gain be heavy rain, with rainfall rates of >25mm/hr possible.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Copp