Regional Impacts
Today
NB: Chance of some scattered thundershowers over western New Brunswick this afternoon with some locally heavy downpours.
Lab: Chance of some isolated thundershowers through central Labrador this afternoon.
NS/PEI/NFLD: None.
Tonight
NS/NB/PEI/NFLD/LAB : None.
Tomorrow
LAB: Risk of some marginally severe thunderstorms over southern Labrador in the afternoon with small hail, strong wind gusts, and locally heavy downpours.
NS: Risk of an elevated thundershower over southern mainland Nova Scotia through the day.
NB/PEI/NFLD: None.
Convective Discussion…
A ridge of high pressure sits over central Atlantic Canda this morning with a weak surface trough extending from central Maine up into central Quebec, just west of Labrador. This trough will be the main focus for any convection today, as it slowly begins to move east. A small but strong upper low over central Ontario will combine with a shortwave near New England and approach the trough this afternoon, which will act as the main trigger for convection. MLCAPE values over western New Brunswick are forecast to be around 500 to 750 J/kg today, with effective shear around 15 to 25 knots. One of the limiting factors however is how quickly the shortwave is advected East into New Brunswick, as well as some warm air aloft between 500 and 700 mb. This could limit the higher shear and some better thermodynamics from reaching the risk area until later this evening, which would lead to more isolated and short-lived thundershowers this afternoon. The risk for more organized storms could still increase into this evening however as the shortwave approaches, which could be capable of producing some locally heavy downpours of 10 to 20 mm per hour.
There is also a slight risk of some isolated thundershowers with a weak trough over central Labrador today which is in a similar environment to western New Brunswick, however there is a lack of moisture evident over this area which will reduce the risk of storms here today. Current surface observations show dewpoints only in the 5 to 7 degree range, with temperatures already above 20. Nonetheless, the potential for some isolated thundershowers exists which could produce some gusty winds.
Tonight, the shortwave will reach the Gulf of Maine, bringing with it the risk of an elevated thundershower over the marine areas west of Nova Scotia in the early morning hours. Into tomorrow, the shortwave will track across Nova Scotia, continuing to bring the chance for an elevated thundershower across the southern half of the mainland during the day and into the evening. Elsewhere, the upper low currently over central Ontario will sit over central Quebec by tomorrow morning with today’s surface trough now extending east from the upper low into southern Labrador. This will be the main focus for convection tomorrow, as MLCAPE values in the warm sector just south of the trough could reach 750 to 1000 J/kg by the afternoon. Slightly better moisture being advected in from the south and effective shear in the range of 20 to 30 knots should be sufficient to get some organized, marginally severe thunderstorms tomorrow afternoon. The surface trough is initially forecast to remain fairly stationary before eventually shifting south in the late afternoon/early evening. This in combination with an expected easterly storm motion could lead to some multi-cell training storms early in the day which would increase the risk of heavy rainfall for some areas. Some small hail and strong wind gusts are also possible with these storms. Luckily, the main risk area is expected to remain over unpopulated areas but could impact a few communities early in the afternoon.
Thunderstorm Outlook for Today
Thunderstorm Outlook for Tonight
Thunderstorm Outlook for Tomorrow
Forecaster: Copp