Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Nova Scotia and Southeastern New Brunswick… Locally heavier embedded rainfall, frequent lightning possible tonight.

 

Convective Discussion

 

A vertically stacked low pressure system will gradually make its way across Nova Scotia over the next couple of days, bringing unstable air along with it.  Aloft a weak cyclonic jet ahead of the upper low could be a contributing factor to support some vertical motion over the next couple of days but otherwise the thermodynamics are not overly favourable for development of severe thunderstorms. There will be very little surface based CAPE with this system with thunderstorm imitating above 850 mb for most of the period. Most unstable CAPE in general will remain below 500 J/kg, with low to moderate deep shear. Precipitable water values will be in the 30-40mm, this coupled with potential updrafts could lead to locally heavier rainfall rates approaching 25mm/hr.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

 

Mel Lemmon

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Maritimes: Scattered thunderstorms today, with some discrete cells possibly reaching severe limits for moderate hail, and rain. (Funnel clouds are possible).

NL: Embedded thundershowers within a greater area of showers/rain.

 

Convective Discussion

 

Dynamics at play over Newfoundland today include a trough line generating instability over the island. Precip is likely to be in the rates of 5-10mm, and these cells are moving quite quickly to the north. Winds gusts locally may reach near 60 to 70 km/h. Both CAPE and Shear are much more favourable for thunderstorm development over portions of the Maritimes. In SW NS, ML CAPE of 500-800 is present, and convective trigger temps will easily be surpassed with the cloud holes that are developing this morning. In central and SE NB, MLCAPE is 760-1000 J/kg, with Effective Shear of 25-30kts in the lower levels. Lapse rates of -6 were analyzed this morning, as the upper low feature continues to destabilize this air mass. SFC dew points of 12-16 are observed as the morning fog burns off. This upper trof is very important to watch as it sweeps through the AOR this afternoon. Helicity values (similar to those near Hants county yesterday) will be present near Moncton and Shediac late this afternoon. As such, there is a *non-zero chance of a funnel cloud or non-supercell tornado* in this area. However – the chance is very low, and it is not included on the graphical depiction because of the low likelihood and low severity. Watches will be used to alert the public if required. Another advancing trough will bring a line of convection up from the south Saturday evening, over the marine areas and affecting NS’s south and Acadian shores.

 

Thunderstorm Outlook for TODAY

 

Thunderstorm Outlook for TONIGHT

 

 

Thunderstorm Outlook for SATURDAY

 

 

Forecaster: J. TIRONE/ASPC

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

NB, NS, and PEI: Scattered thunderstorms today and tomorrow, some of the stronger storms could produce heavy downpours 10 to 20 mm, and possibly higher.

NL: None, deeper instability limited to the west of a line from Fermont/Lab City to Lake Eon to Chevery.

 

Convective Discussion…

A surface and upper low over Maine will move east today, reaching the Gulf of St. Lawrence tonight. The upper low will then weaken and open up over Labrador. Moisture associated with these features will continue to produce widespread showers with embedded thundershowers with forecast guidance suggesting CAPE of 250 J/kg or less, however as the day progresses, insolation from breaks in the cloud cover and the cold temperatures aloft will increase the depth of the instability with surface-based CAPE values expected to reach 500 J/kg. Under these conditions this deeper convection will produce locally heavier showers 10-20 mm, some small hail < 1cm, and wind gusts to around 60 km/h. Generally the shear is weak, except over NS where current soundings indicate 0-6km values above 20 kt which might produce weakly organised convective cells.

 

A series of weak low pressure systems will extend from NY state to Atlantic Canada on Friday. Low level moisture/fog will give way to isolated thunderstorms during the day.

 

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

 

Thunderstorm Outlook for Friday

 

 

Convective Outlook Valid for Today, Tonight, and Tomorrow

Regional Impacts

NB, NS, and PEI: Scattered thunderstorms today and tomorrow, with locally heavy downpours up to 25 mm, possibly higher.

NL: Isolated thundershowers possible over western Labrador, locally heavy downpours up to 15 mm.

 

Convective Discussion…

An upper trough is moving through the Maritimes today, bringing the risk for some elevated convection. 0 to 6 km wind shear of 30 to 40 kts, in combination with the aforementioned trough are providing ample lift and instability today for some organized convection. Thunderstorms are expected to stay elevated, as a thermal ridge at 850 mb should prevent anything from becoming surface based, however heavy downpours up to 25 mm and potentially higher are possible. An upper low will then approach the Maritimes from the west tonight, bringing the risk for some elevated convection for parts of western New Brunswick and southwestern Nova Scotia into tomorrow morning. This upper low will continue to slowly move east tomorrow afternoon, bringing upper and mid level cooling across the Maritimes. This will allow for convection to be more surface based, with locally heavy downpours of up to 25 mm the main risk.

 

Some isolated thundershowers are possible in parts of western and central Labrador today with an upper low moving through northern Quebec. Locally heavy downpours of up to 15 mm are possible with these thundershowers.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Copp

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

NB: Scattered thunderstorms tonight and Wednesday, with locally heavy downpours possible, 15-30 mm.

NS: Scattered thunderstorms tonight and Wednesday, with locally heavy downpours possible, 15-30 mm.

PEI: Scattered thunderstorms on Wednesday afternoon, with locally heavy downpours possible, 15-30 mm.

NL: Isolated thundershowers possible over central Labrador on Wednesday afternoon.

 

Convective Discussion…

As a ridge of high pressure continues to dominate Atlantic Canada today, an approaching trough from the west will provide ample instability and wind shear for some elevated convection overnight tonight over the southwestern Maritimes. This trough will continue to push east on Wednesday, spreading the risk for elevated convection across most of the Maritime provinces. A thermal ridge at 850 mb will prevent any convection from becoming surface based, as such the main risk for these storms will be locally heavy rainfall, with 15-30 mm possible.

 

For Labrador, some isolated thundershowers are possible on Wednesday afternoon as a shortwave currently over Hudson’s Bay slowly approaches from the west. Locally heavy rainfall near 15 mm is possible with these thundershowers.

 

Thunderstorm Outlook for Today

 

 

Thunderstorm Outlook for Tonight

 

 

Thunderstorm Outlook for Wednesday

 

 

Copp