Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Labrador…Risk of thundershowers this evening over western sections.

 

Convective Discussion

 

A trough moves in from central Quebec tonight into western Labrador, extending from a low pressure system over Hudson Bay. This trough is expected to bring in showers and a risk of thundershowers over central Quebec which may continue into this evening into western Labrador as the area is under the influence of moderate 0-6km shear and PWATs near 30 mm.

 

Tropical Storm Henri will soon be making landfall in New England or eastern Long Island, and weaken into a depression then a post-tropical storm on Monday. Outer rain bands well north and east of the centre with heavy rainfall possible will move over the Maritime southwestern marine district today and tomorrow.

 

 

Thunderstorm Outlook for Day 1 – August 22, 2021

 

 

Thunderstorm Outlook for Day 2 – August 23, 2021

 

Convective Outlook Valid for August 21st and 22nd

Thunderstorm Outlook for Day 1

 

Regional Impacts

None

 

Convective Discussion

With a ridge of high pressure dominating the area, there is no risk of severe thunderstorms today.  A trough moves in from the west Sunday night over western Labrador bringing a risk of thundershowers.

 

 

Thunderstorm Outlook for Day 2

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Some heavy downpours and local gusty winds with isolated thunderstorms, mainly  for New Brunswick  and southern Newfoundland. Otherwise noting significant expected for today and tomorrow.

 

Convective Discussion

 

The main area of interest is southern Newfoundland and New Brunswick. To the north there is too much shear (~40-60 kts)  and not enough moisture (PWATs 20 mm or less), combined with  a ridge building in from the west.

 

Currently there is a trough extending east over Newfoundland and southwest over the Maritimes from a developing weak low over the Gulf. The low will track over southern Newfoundland today and tonight. For New Brunswick there are currently some stable layers that will destabilise somewhat with the trough and daytime heating, combined with surface dewpoints between 18-22 and PWATs fairly healthy in the 35-55 mm range. There is little shear (~12-22 kts) arguing for airmass pop-ups. Farther north there is less upper support but more daytime heating. For both cases CAPEs on the order of 500 J/kg are possibly. The low shear and good moisture argue for airmass pop-ups with local heavy downpours and brief gusty winds.

 

For Newfoundland the stability this morning was higher, with the developing low hopefully destabilising aloft and giving some lift from convergence below. The moisture is a bit less with PWATS near 35 mm, but the dewpoints are only a couple of degrees cooler than the Maritimes. So the impacts should be similar, but possibly with the training along the trough-low-topography combination.

 

 

 

 

 

 

Thunderstorm Outlook for Day 2

 

Good news.

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

A chance for occasional heavy showers and some wind gusts for southwestern New Brunswick. Chance of isolated thundershowers for northeastern Newfoundland.

 

Convective Discussion

Basically there is a low in the Labrador Sea with a couple of troughs extending southwest into the Maritimes. Most of Atlantic Canada is under an inversion preventing any significant lift, with the exception of New Brunswick. There is a shallow inversion combined with some afternoon destabilisation. There’s also half decent moisture, with PWATs in excess of 30 mm, and dew points in excess of 20 C for southwestern New Brunswick. Afternoon surface CAPES may be around 400-800 J/kg. However, with shear being  12-25 kts for most regions, air mass pop-ups will probably be the rule for today.

 

For Newfoundland there is a chance of a thundershower or two this afternoon, if the daytime heating is high enough.

 

 

Thunderstorm Outlook for Day 2

 

 

 

 

 

Convective Outlook Valid for August 18th and 19th

Thunderstorm Outlook for Day 1

 

Regional Impacts - Risk of isolated thunderstorms over NB bringing local heavy showers of 10 -15mm.  Risk as well over interior Labrador and interior

 

Convective Discussion

As high pressure begins to move away and higher surface moisture moves in, conditions become a bit better for thunderstorm activity today.  The atmosphere becomes a bit more unstable as a jet stream tracks into the area from the north.  CAPE values of around 500 J/kg are currently expected.  However, mid level moisture is high and wind shear values are low at around 25kts so long lived storms are not currently expected.  Local heavy showers of up to 10-15 mm is possible for parts of  New Brunswick in isolated thunderstorms especially over clear skies.  Risk of isolated non severe thundershowers as well for interior Labrador and interior Newfoundland. 

 

 

Thunderstorm Outlook for Day 2