Convective Outlook Valid for Today , Tonight, Tomorrow, and Wednesday

Regional Impacts

Today

NS: Chance for elevated thunderstorms spanning Southwestern Nova Scotia through Central Nova Scotia. Risk for gusts of 60 to 70 km/h and rainfall of 20mm.

PEI: Chance for elevated thunderstorms spanning the province. Risk for gusts of 60 to 70 km/h and rainfall of 20mm.

NB: Chance for elevated thunderstorms in the Southeast sections of the province. Risk for gusts of 60 to 70 km/h and rainfall of 20mm. Slight chance of an Isolated thundershower over extreme Northwestern New Brunswick.

NFLD/LAB: Nil.

Tonight

NS: Chance for elevated thundershowers spanning Southwestern Nova Scotia through Central Nova Scotia. Risk for gusts of 60 to 70 km/h and rainfall of 20mm.

PEI: Chance for elevated thundershowers spanning the province. Risk for gusts of 60 to 70 km/h and rainfall of 20mm.

NB: Chance for elevated thundershowers in the Southeast sections of the province. Risk for gusts of 60 to 70 km/h and rainfall of 20mm. Slight chance of an isolated thundershower over extreme Northwestern New Brunswick.

NFLD/LAB: Nil.

Tomorrow

NS: Chance for elevated thundershowers spanning Central Nova Scotia through Cape Breton.

PEI: Chance for elevated thundershowers spanning the province in the morning.

NB: Chance for elevated thundershowers over the majority of the province.

NFLD: Chance for elevated thundershowers over the extreme Southwest and South-central regions of the province.

Lab: Nil

Wednesday

NS: Chance for isolated thunderstorms predominantly over the Central regions of the province.

PEI: Chance for isolated thunderstorms over the province.

NB: Chance for isolated thunderstorms over the interior of the province. Risks include gusts of 70-80km/h and hail near 2cm.

NFLD: Chance for elevated thundershowers over the Southern and Central regions of the province.

LAB: Nil.

 

Convective Discussion…

An approaching frontal system is progressing through the Atlantic Canada today is eroding the previously placed high pressure system throughout today and tomorrow.

Today, the main threat area will be in the Southeastern sections of New Brunswick and over most of mainland Nova Scotia where elevated thunderstorms could produce heavy downpours with rainfall possibly exceeding 20mm of rain and wind gusts of 60 to 70km/h. From ship observations there was reports of winds in excess of 60km/h. Current satellite imagery shows the approaching frontal system with embedded thunderstorms over the marine regions from overnight approaching the Nova Scotia coast. This should allow the continuation of MUCAPE to near 600 J/Kg, along with PWAT’s to remain near 30-40mm by this afternoon and progress eastward.

Tonight, as the frontal system progresses eastward bringing the elevated thunderstorms into Cape Breton and begin approaching Southern Newfoundland. Additionally, behind the frontal system there is expected to be a clearing in behind the system allowing for instability to approach New Brunswick allowing for further convection to occur. Thunderstorms in the clearing are expected to start off as surface based showers and becoming elevated overnight. This instability mixed with cloud-top cooling is expected to give rise to elevated thunderstorms.

Tomorrow, the frontal system from overnight will continue to progress eastward and begin to slow down over Cape Breton and Southern Newfoundland. In behind the frontal system tomorrow there is likely to be a narrow corridor of MUCAPE nearing 700 J/Kg with shear of 20 to 30Kt giving rise to the possibility of thundershowers from Southeast New Brunswick into Central Nova Scotia.  

Wednesday, as the frontal system has departed and began to diminish over Newfoundland the previous couple of days rainfall is expected to give rise to excess moisture that align with Jet streak approaching from the West to act as a trigger for more severe thunderstorms over the interior of NB. There remains some uncertainty with this setup as it does rely on how must moisture gets injected into the interior of New Brunswick from these next couple of days. Current computer guidance is indicating that within the interior of New Brunswick there could be a risk of thunderstorm with gusts in excess of 80 km/h and hail nearing 2 cm. This come from MUCAPE nearing 2,000 J/Kg and MLCAPE nearing 1,000 J/Kg along with relatively good shear throughout the profile.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Thunderstorm Outlook for Wednesday

Forecaster: McArthur/Lambert

 

 

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