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

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

Labrador: Isolated thundershowers over south-central Labrador this afternoon with some heavy downpours

NS/NB/PEI/NFLD: None.

Tonight

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

Tomorrow

Labrador: Isolated thundershowers over western Labrador in the afternoon with some heavy downpours

NS/NB/PEI/NFLD: None.

 

Convective Discussion…

Another quiet day is in store for Atlantic Canada as a ridge of high pressure builds in from the west. A 500 mb jet extends from northern Quebec into southwestern Nova Scotia this morning, however it is not expected to trigger any thunderstorm activity due to the approaching thermal ridge. Surface temperatures are expected to rise near 30 degrees Celsius this afternoon over much of New Brunswick and Nova Scotia, this combined with a lack of low level moisture should also help prevent any convection over the area today.

The main area to watch today will be in south-central Labrador where some isolated thundershowers could develop this afternoon, associated with some weak surface troughing and mid level cooling around the back side of an upper low over the southern Labrador Sea. The risk here however remains fairly low due to a lack of CAPE (less than 200 J/kg of mixed-layer) and fairly weak effective layer shear (10 to 20 kts), though some low level cloud cover this morning hints at just enough low level moisture to fire off a few weak thundershowers later today. The main risk with any thundershowers that do develop here today will be some brief heavy downpours of 5 to 10 mm.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Copp

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Labrador… low risk of thunderstorms over northern areas today, low risk for south-central on Tuesday.

Newfoundland… Slight risk of near shore lightning today

PEI, NB and NS… No impacts from thunderstorms expected.

Convective Discussion

A push of drier air behind a departing trough of low pressure will help settle conditions over the next couple of days. There remains a slight risk that offshore thunderstorms could affect eastern Newfoundland today, but the associated surface low and its weather are expected to move away through the day.

Over Labrador, a weak shortwave may trigger a few isolated thundershowers over higher terrain today. A similar setup could extend slightly farther south tomorrow; however, confidence in this potential remains low.

Looking ahead to the remainder of the week, conditions should remain fairly quiet as a ridge of high pressure builds across the region.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Mel Lemmon