Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

NB: Risk of marginally severe thunderstorms over northwestern New Brunswick this afternoon capable of producing heavy downpours, strong winds, and some small hail.

NS/PEI/NFLD/LAB: None.

Tonight

NS: Slight chance of elevated thundershowers over southwestern Nova Scotia before morning.

NB: Chance of a few thundershowers over northern New Brunswick with locally heavy downpours.

PEI/NFLD/LAB: None.

Tomorrow

NS: Slight chance of some isolated embedded thundershowers over mainland Nova Scotia.

NB: Slight chance of an isolated thundershower over extreme northwestern New Brunswick.

PEI/NFLD/LAB: None

 

Convective Discussion…

An active couple of days are in store for Atlantic Canada as a trough approaches from the west and begins to erode a ridge of high pressure over the central Maritimes. Today, the main threat area will be in parts of northwestern New Brunswick, where some marginally severe thunderstorms are possible this afternoon. Some overnight convection is lingering over the area of interest, leading to some increased cloud cover, but current satellite imagery shows clearing off to the west over southern Quebec. This should allow MLCAPE values to rise near 1000 J/kg this afternoon over the northwestern portion of New Brunswick and with effective shear near 40 knots, some marginally severe thunderstorms are possible. One limiting factor in the intensity of these storms will be relatively moderate lapse rates, but given enough clearing early this afternoon, storms should have no issues firing. Given the weaker lapse rates, hail will not be much of a concern, but some decent PWAT values near 30 to 35 mm will lead to some heavy downpours in thunderstorms. In addition, there is potential for some strong wind gusts in the downdrafts of these storms. Without the 12Z sounding out of Caribou this morning, there isn’t a good sample of the current environment over the area, but the Maniwaka sounding from 00Z last night shows a relatively unstable airmass in a highly sheared environment. In addition, model tephigrams are indicating some curvature in the low level winds over northwestern New Brunswick this afternoon leading to a non-zero tornado risk, though this risk remains very low at this time. Severe thunderstorm watches may be issued early this afternoon as confidence increases.

Tonight, the trough will continue to slowly move east, reaching southwestern Nova Scotia by morning. With some weak mid-level instability expected overnight, some elevated thundershowers are possible here, in addition to northern New Brunswick. The trough will continue to move east through the day tomorrow, extending the risk for an elevated thundershower over parts of mainland Nova Scotia. The unstable airmass behind the trough may also lead to some isolated thundershowers over extreme northwestern New Brunswick in the afternoon.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Copp

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NB: Chance of organized thundershowers west.

NS/PEI/NFLD/LAB: None.

 

Tonight

NB: Chance of elevated thundershowers.

NB/PEI/NFLD/LAB: None.

 

Sunday

NB: Chance of organized thundershowers central and west.

NS/PEI/NFLD/LAB: None.

 

Convective Discussion

Over portions of western New Brunswick today, daytime heating combined with troughing and afternoon clearing will likely initiate surface driven convection later this afternoon and into this evening.  CAPE values of 500-1000 J/kg and shear of 40-50 knots are expected. Near severe to severe thunderstorms are possible in this environment. Elevated convection is possible tonight over portions of western and central New Brunswick associated with 850 mb thickness ridging.

On Sunday, a warm front will approach New Brunswick. Once again, CAPE values of 500-1000 J/kg and shear of 40-50 knots are expected. Near severe to severe thunderstorms are possible.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NB: Chance of thundershowers west.

NS/PEI/NFLD/LAB: None.

 

Tonight

NS/NB: Chance of embedded thundershowers.

PEI/NFLD/LAB: None.

 

Saturday

NS/NB: Chance of embedded thundershowers NS and southeast NB. Chance of organized thundershowers central and western NB.

PEI/NFLD/LAB: None.

 

Convective Discussion

There is a chance of thundershowers over extreme western New Brunswick this afternoon associated with a warm front. Limited CAPE and shear values will limit any thundershowers to weak. Embedded thundershowers are possible overnight in western Nova Scotia and southern NB.

On Saturday, embedded thundershowers are possible along the departing warm front over southeast NB and areas of Nova Scotia.  Over portions of western and central NB daytime heating combined with troughing will likely initiate surface driven convection.  CAPE values of 1000-1500 J/kg and shear of 40-50 knots are expected. Near severe to severe thunderstorms are possible in this environment.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

NS: Slight risk of an isolated thundershower over southwestern Nova Scotia this afternoon with locally heavy downpours.

NFLD: Slight risk of some isolated thundershowers today with some locally heavy downpours.

NB/PEI/LAB: None.

Tonight

NB: Risk of an isolated thundershower over northwestern New Brunswick overnight with locally heavy downpours.

NS/PEI/NFLD/LAB: None.

Tomorrow

NB: Risk of an isolated thunderstorm over western New Brunswick in the afternoon with heavy downpours and gusty winds.

NS/PEI/NFLD/LAB: None.

 

Convective Discussion…

A slightly more active end to the week is in store for Atlantic Canada as a ridge of high pressure over the region begins to erode. A few areas to watch exist today, the first associated with some weak upper troughing with a few embedded vorticity centres extending from Newfoundland down to Cape Cod. This threat area triggered a few elevated thundershowers overnight, but will remain largely offshore as the trough moves east. That being said, a few thundershowers may develop over parts of Newfoundland today and into this evening given sufficient clearing in combination with an approaching 500 mb jet currently centred over Labrador. MUCAPE values over this area should remain fairly low (less than 200 J/kg) but given the relatively high 0 to 6 km shear (35 to 45 knots), there could be just enough energy to get some isolated thundershowers to develop which may produce some locally heavy downpours.

The second area to watch will be over southwestern Nova Scotia this afternoon. The risk here is a bit lower due to a lack of forcing, however higher instability (500 to 750 J/kg MLCAPE) with 20 to 30 knots of effective shear could trigger an isolated thundershower or two if a convergence zone does set up. Anything that does fire here this afternoon will likely be short-lived but with very weak mean wind, they will remain fairly stationary which could lead to some heavy downpours of 10 to 20 mm per hour.

Tonight, a very slow moving surface trough currently over southern Quebec and extending into western Maine will approach northwestern New Brunswick. This could lead to some elevated thundershowers overnight with MUCAPE values of around 500 to 750 J/kg and effective shear of 20 to 30 knots. The timing of initiation will depend on how quickly the 500 mb jet approaches from Southern Ontario but a few strikes are possible before morning.

Tomorrow looks a bit more interesting over western New Brunswick as the aforementioned trough sets up over the area along with a better 500 mb jet setup. Current guidance indicates MLCAPE values could build to around 1000 J/kg which could lead to some marginally severe thunderstorms. There is some uncertainty in the timing of the trough however, with some guidance keeping it over Maine until later in the evening. Nonetheless, the potential does exist for some isolated thunderstorms with heavy downpours and gusty winds, especially along the Maine border.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Copp

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

Labrador: Isolated thundershowers possible over southwestern Labrador this afternoon with locally heavy downpours.

NS/NB/PEI/NFLD: None.

Tonight

NS/NB/PEI/NFLD/LAB: None

Tomorrow

NS/NB/PEI/NFLD/LAB: None.

 

Convective Discussion…

With a ridge of high pressure over the central Maritimes today, not much is expected in the way of convection. A slight risk area does exist over southwestern Labrador today, where a 500 mb jet exiting the region in conjunction with a weak shortwave may provide enough support for some isolated thundershowers this afternoon given sufficient surface heating. MUCAPE values of 250 to 500 J/kg and effective shear around 15 to 25 kts should be enough to support a few lightning strikes in the area. Although quite a bit of cloud cover is lingering over northern Quebec, some signs of clearing are evident this morning. The only other issue is a lack of low-level moisture over the area which is keeping the risk level low and as such, any storms that do initiate will likely be elevated.

High resolution guidance is hinting at some potential convective activity over the Gaspe Peninsula into northeastern New Brunswick later this afternoon. 12Z soundings in the area indicate a weak thermal trough in the mid to upper levels, however the thermal ridge remains strong and intact at 850 mb. With a lack of upper level support over this region, any storms that do fire would likely be surface-based, but with the capping at 850 surface-based initiation is unlikely. A lack of low-level moisture here in combination with daytime highs near 30 degrees also indicate that storms are unlikely to fire in this region.

Tonight and tomorrow, there is a slight risk of some elevated thundershower activity off the southwest coast of Nova Scotia associated with a weak shortwave, but no impacts are expected over land.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Copp