Regional Impacts
Today:
NL/LAB… Some isolated thunderstorms possible in parts of central and eastern Newfoundland as well as western Labrador today. Locally heavy downpours of 10 to 20 mm/h.
NB…Risk of thundershowers in western New Brunswick with 10 to 20 mm/h rates.
NS/PEI… None.
Saturday:
NB…Some thunderstorms possibly severe for northern regions with locally heavy downpours of 25 mm/h, small hail and strong wind gusts.
LAB…Scattered thunderstorms over central and southeastern regions.
NS…Embedded thunderstorms possible with locally heavy downpours of 10 to 20 mm.
Convective Discussion
For today, a shortwave trough continues eastward across Newfoundland today while a broad trough moves across Hudson Bay into Central Quebec and western Labrador this evening. MLCAPE over central Newfoundland of 500 J/kg, bulk shear of 20kt and further cooling at 500mb could see some convection maintain in the afternoon. High precipitable water near 45 mm remains over the region, so locally heavy downpours are the main risk. Some TCUs in showers are possible for the Maritimes this afternoon under a hot and humid air mass. Precipitable water is around 30 mm but mean wind is rather weak, so any convection that develops may also give locally heavy downpours. There is a risk of a thunderstorms mainly where MLCAPE could reach 1000 J/kg over northern New Brunswick with a weak trough approaching from the west. There is only a slight risk that TCUs could breach the warm 500-700mb cap currently over Nova Scotia along the Annapolis Valley with the help of some sea breeze convergence.
For tomorrow, the broad trough continues over central and eastern Labrador and southwestward into northern New Brunswick. Convection could be organized given increasing moisture under a southwest flow in the afternoon with upwards of 1200 J/kg of MLCAPE, but upper dynamics are expected to be weak to moderate with bulk shear of 20 kt. Some organization of convection is possible into multicells are possible with brief strong wind gusts, locally heavy downpours and small hail being the main threats for northern New Brunswick. A second shortwave moves into New England tonight and into the Gulf of Maine by early Saturday into southwestern Nova Scotia. There is a risk of elevated convection and locally heavy downpours for Nova Scotia and southern Maritimes waters with an increasing 40kt 850mb jet as this wave continues eastward.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Roberta McArthur