Regional Impacts
Today
NB: Risk of severe thunderstorms in the afternoon and into the evening capable of producing very strong wind gusts, dime to nickel sized hail, and heavy downpours.
NS/PEI: Chance of a thunderstorm in the evening capable of producing strong wind gusts, small hail, and heavy downpours.
NFLD: Chance of some isolated thundershowers in the early afternoon over central and eastern Newfoundland which could produce some heavy downpours.
LAB: Risk of an isolated thunderstorm reaching southwestern Labrador this evening giving small hail, strong winds and heavy downpours.
Tonight:
NB/PEI/NS: Risk of elevated thunderstorms giving heavy downpours.
Tomorrow
NB/PEI/NS/NL: Risk of near severe thunderstorms in the afternoon and into the evening capable of producing strong wind gusts, small hail hail, and heavy downpours.
LAB: Risk of isolated thunderstorms giving brief wind gusts, small hail and heavy downpours.
Convective Discussion
The active weather continues today under a hot and humid airmass. Watches and warnings were on the go early this morning from the shortwave moving across the Gulf of St. Lawrence into Newfoundland extending southwest into Nova Scotia aided by a strong upper level jet. Heavy downpours (PWTAS into the 50s) and intense lightning have been observed with the storms and they will continue southeastward across eastern Newfoundland and over the southern marine waters this afternoon.
Another area of active weather is expected for New Brunswick today. With ample energy already in place (dew points this morning 19 to 23C) giving MLCAPE possibly reaching 2000 J/kg, the trigger will be an upper jet as is crosses central Quebec this morning and into northern New Brunswick along with daytime convective temperatures expected to be reached under clear skies this morning. The 12Z Caribou sounding is not available, but looking further upstream at the Maniwaki and Chibougamau soundings, they are indicating decent 0-6km shear of 35 to 45kt and PW of 43mm. With effective shear increasing by the afternoon to near 50 kt, there is the risk for bowlines or potential supercells given some low level spin available. Freezing levels are high but dime to nickel sized hail, strong winds and very high rainfall rates are likely.
Thunderstorms may also reach into extreme southwestern Labrador today with the unstable airmass.
For tonight, thunderstorms should begin to lessen across New Brunswick with the sun setting but there could be some lingering elevated convection past midnight across the Gulf of St. Lawrence with the upper jet still in place. There is another shortwave expected to affect southern Quebec into Maine this evening and any convection may continue overnight into western Nova Scotia with the help of the upper jet over the area. Lightning and heavy downpours will be the main risks.
For tomorrow, an upper low slowly tracks eastward across central Labrador while a shortwave trough moves into Newfoundland. Widespread showers are expected to trigger across central to southern Labrador by the early afternoon, while instability, sea breeze convergence and continuing heat and humidity across the Maritimes will aid in thunderstorm development. MLCAPE could exceed 1500J/kg , and shear remains high in the morning near 40-50kt but will diminish some by the afternoon across New Brunswick. Regardless, heavy rain, small hail and strong wind gusts will be the main threats for New Brunswick, PEI and central to eastern Nova Scotia and Newfoundland.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
