Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Today: for Labrador, isolated non-severe thunderstorms giving brief downpours with rainfall rates of 10-15mm/h.

 

Tonight: non-severe isolated thunderstorms in Labrador dissipating.

 

Thursday: for Labrador, isolated non-severe thunderstorms activity shifting to southernmost areas. Brief downpours with rainfall rates of 10-15mm/h. For Newfoundland, there is a slight risk of a thunderstorm west of a line from Gander to Terra Nova.

 

Convective Discussion: A strong upper ridge over eastern Canada will provide dry conditions for most of the region, with increasingly warmer temperatures and stable conditions.  A surface front over far northern Quebec stretches southeastward over central Labrador and is the focus for deeper instability today with localised thunderstorms and rainfall in excess of 10 mm. This activity will shift southward Friday reaching areas over higher terrain between the Churchill river valley and the lower Quebec north shore. Forecast guidance is suggesting an area of convergence west of Terra Nova park Friday afternoon with a few TCU potentially evolving into CB’s at the peak of insolation. Elsewhere no thunderstorms are expected.

 

Thunderstorm Outlook for today:

 

 

Thunderstorm Outlook for Friday:

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Today: none.

 

Tonight: none.

 

Wednesday: none.

 

Convective Discussion:

A surface trough over western NB will enable the development of showers today, however vertical growth will be limited by a capping inversion at 750 mb and prevent lightning. Outside of this region a building surface ridge will prevent convective development

for the next couple of days across Atlantic Canada. On the ridge’s northern periphery in central Labrador tomorrow some instability will be present (MLCAPES 150-200 J/KG), but high bulk shears will shunt convective growth preventing storms.

 

 

Thunderstorm Outlook for today

 

Thunderstorm outlook for Wednesday

 

 

Allen

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Local rainfall amounts of 20 mm for central sections of NF today.

 

Convective Discussion

 

This morning the low at 500mb/surface are located over Cabot strait and continue to move eastward passing east of the Avalon tonight. Ahead of these features, several curving bands of rain are detected by NF radar. Satellite shows colder cloud tops along the south coast and over central regions, but the Stephenville sounding shows that the instability is limiting vertical development to embedded ACC which could still give higher rainfall rates periodically during the day. There has not been any lightning activity detected by CLDN or GLM over the region since last night and none is anticipated for the rest of the day. The low feature will exit NF after midnight.

 

For Tuesday, the RDPS is indicating an area of potential instability west of Nain, but this activity will likely be limited to the 850-700mb level due to a mid-level inversion.. Otherwise dry conditions are expected Tuesday and Wednesday as an upper ridge builds over Atlantic Canada.  

 

*Note that National Monitoring has an open ticket on the lightning sensor at Wabush Lake. They are unable to access the equipment since yesterday (June 18)

 

Thunderstorm Outlook for Today

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Locally heavy downpours giving 15-25 mm for areas affected by thunderstorms.

 

Convective Discussion

 

After a bout of intense lightning activity overnight things are expected to be somewhat less intense today. Some thunderstorms will continue over Nova Scotia and possibly into southern New Brunswick and PEI later in the day. Updraft potential is not expected to be very high however some favourable dynamics are like to organise the convection into multicell clusters, with some upper support before the upper jet exits the region later today. Locally 15-25mm is expected, slightly less than the rainfall rates than the ~25mm/hr that we saw overnight. Some small hail is possible with the lowering freezing levels but it should well below warning level.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2

 

Mel Lemmon

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