Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Southern LAB: Scattered to frequent thunderstorms are expected this afternoon and evening giving strong wind gusts, small hail and heavy downpours.

Southern NB: Scattered thunderstorms possible later today, tonight and early Sunday morning giving heavy downpours. Isolated thunderstorms possible again Sunday afternoon/evening.

PEI: Scattered thunderstorms possible overnight tonight or early Sunday morning giving heavy downpours.

SWRN NL: Isolated thunderstorms possible Sunday morning giving heavy downpours.

NS: A very slight chance of a thunderstorm this afternoon/evening for some central locales giving heavy downpours.

 

Convective Discussion

 

The interesting area to watch today will be up in the Big Land, where a frontal trough (acting as the trigger) will give way to scattered to frequent thunderstorms this afternoon. Moisture is nothing to write home about, however the shear and instability is good. 12Z YYR sounding shows about 50 knots of westerly shear, as well as some fairly steep lapse rates in the mid-levels. That could lead to good vertical velocities and support small hail growth. Strong wind gusts of 70-80 km/h are possible. Pretty much all the activity will be confined to areas where there are no public forecasts. However, there is a possibility of a strong storm or 2 advecting towards southeastern communities later this afternoon and into this evening. The only caveat would be the enormous amount of smoke evident on visible SAT imagery. The current ongoing thunderstorm activity in the southeast will soon diminish.

 

A pre-frontal trough/short wave over the New England states will move into southwestern NB later today crossing the MRTMS tonight before weakening over southwestern NL Sunday morning. Although there is not much history of lightning, there are indications of development as the sun sets this evening leading to a nocturnal event for some areas. Locally heavy downpours are the threat if they form.

 

Lastly  a slight chance of an afternoon/evening thunderstorm Sunday for a portion of southwestern NB. Again, heavy downpours seems to be the main threat at the moment.

 

Thunderstorm Outlook for today

 

Thunderstorm Outlook for tonight/Sunday morning

 

Thunderstorm Outlook for Sunday

 

Jeremy

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

 

Today: Newfoundland and Labrador- Non-severe thunderstorms possible in southern Labrador and central-eastern Newfoundland giving rainfall rates of 10-20mm/h, strong wind gusts and lightning.

               

Tonight: Labrador- Non-severe thunderstorms for central/southern Labrador

 

Saturday: Labrador: Near-severe thunderstorms possible in Labrador giving rainfall rates of 20mm/h, strong wind gusts and lightning.

                New Brunswick: Near-severe thunderstorms possible with rainfall rates of 20mm/h and lightning Saturday evening.

                Nova Scotia: Near-severe thunderstorms possible with rainfall rates of 20mm/h and lightning Saturday evening.

 

 

Convective Discussion

 

A frontal boundary extending eastward over central Quebec into central Labrador and southeastward into northern Newfoundland is slowly sinking southwards today while a stationary ridge of high pressure over New England and the Maritimes slowly weakens. Upper dynamics are somewhat favourable over Labrador today to sustain elevated thunderstorms that develop along the boundary but with little thermodynamics changes, CAPE values of 200-500 J/kg, the main threat will be locally heavy downpours. Over Newfoundland, although there is quite a bit of smoke over the region from wildfires over Quebec, an 850 mb jet and sufficient shear may aid in thunderstorm development on a line from Gander to Terra Nova. A trough of low pressure south of Nova Scotia is also slowly moving eastward. Some embedded thunderstorms are expected for the southern slope waters.

 

For Saturday, the trough of low pressure will track southeastward over central Labrador with a cold front extending across northern Quebec. With high precipitable water rates, increasing CAPE values exceeding 1000 J/kg and moderate shear, the threat for near-severe thunderstorms increases with more organized squall lines or bow echos. Instability and moisture will also increase over the Maritimes as an upper low slowly moves into the region from New England. Precipitable water values of 40-50 mm and CAPE values exceeding 500 J/kg may lead to increased threat for thunderstorms, but the dynamics are not as favourable, so pulse type storms are more likely at this time with locally heavy downpours in the evening.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 1 Night

 

 

Thunderstorm Outlook for Day 2

 

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