Convective Outlook Valid for August 16th and 17th

Thunderstorm Outlook for Day 1

 

Regional Impacts

Western Labrador: isolated thundershowers possible giving 5 - 10 mm.

 

Convective Discussion

Much of the area is under high pressure today  with relatively dry conditions so no thunderstorm activity is expected except over western Labrador where a trough will move into the area this afternoon possibly bringing a few thundershowers with 5-10 mm possible.  Severe thunderstorms not expected as the trough will be weakening as it moves over the area.

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

For Labrador…isolated thunderstorms possible locally 20mm possible.

For Newfoundland…Scattered thunderstorms possible with heavy downpours and gusty winds.

 

Convective Discussion

 

The focus has moved from the Maritimes to Newfoundland today with precipitable water values near 50mm and most unstable cape values ~1000 j/kg. Thunderstorm structure should be similar to what New Brunswick saw yesterday with several reports of nearly 25mm in less than an hour although unreported amounts were likely higher. There is some potential for cluster or multicell storms to form giving decent gusts, however it may be a challenge to trigger the stronger storms but it does seem that the cloud is breaking up over the island and solar insolation could increase through the afternoon.

 

 

 

 

Mel Lemmon

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

New Brunswick…Isolated or possibly organised thunderstorms with potentially heavy downpours and strong wind gusts.

 

Nova Scotia and PEI… Isolated thunderstorms with potentially heavy downpours.

 

Newfoundland and Labrador… Isolated thunderstorms with potentially heavy downpours and gusty winds for southwest Labrador.

 

Convective Discussion

We will begin to see some movement on the very warm air mass that has bee situated over the region for the last several days as a cold front slowly moved over Quebec today. A broad area of showers and thunderstorms will slowly move over New Brunswick and Labrador today, making its way over Nova Scotia and Newfoundland tonight. The dynamics for severe weather should be better today than it has been for the last few days  with about 30 knots of deep shear over New Brunswick and Labrador making the likelihood of longer lived thunderstorms much higher. Convergence should be sufficient today near the trough line to initiate thunderstorms which are already occurring in Maine and Quebec. Severe Thunderstorm watches could potentially be issued this afternoon should some deeper convection begin to form over the area.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

New Brunswick…Heavy downpours possible this afternoon and evening over eastern coastal regions.

Nova Scotia… Heavy downpours possible this afternoon and evening.

Prince Edward Island… An isolated thundershower is possible this afternoon.

Labrador… Heavy downpours possible this afternoon and evening over south/central sections.

Newfoundland…Heavy downpours are possible early this afternoon and evening over southeastern sections. An isolated thundershower is possible as well this afternoon over western sections.

 

Convective Discussion

 

A very warm and humid air mass continues over the Atlantic region today as a trough of low pressure over southern Quebec extending into New England slowly makes its way further east. A weak trough moved through overnight and is still providing some elevated convection this morning over the Gulf of St. Lawrence and eastern Maritime marine areas with heavy showers moving into the Burin Peninsula of Newfoundland. Stratus and fog over the Maritimes and western Newfoundland continues to clear this morning, making way for temperatures to rise into the low 30s for many areas this afternoon. There lacks a strong trigger as the main trough remains further west still, but some coastal convergence could provide enough lift for some single or multicellular storms to fire this afternoon. There is ample moisture with PWATs approaching 50 mm in Nova Scotia but shear remains weak and freezing levels are near 1500ft, therefore the main threat should be being lightning and heavy downpours, especially if any training occurs. Isolated thundershowers are also possible this afternoon over western Newfoundland given lift over the higher terrain, as well as in central/southern Labrador.

 

Thunderstorm Outlook for Day 1 – August 13, 2021

 

 

Thunderstorm Outlook for Day 2 – August 14, 2021

 

A sharper cold front will move into New Brunswick tomorrow afternoon. Ahead and along this front, storms are likely with the potential to be severe.

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

New Brunswick…Heavy downpours in thunderstorms, small hail late this afternoon.

Nova Scotia…Heavy downpours possible this afternoon.

PEI… Heavy downpours possible this afternoon.

Labrador…A chance of thunderstorms this afternoon.

 

Convective Discussion

 

Heavy Rain/downpours will be the story today and tomorrow as the moisture and instability are the main driving mechanisms. Overall the dynamics will remain rather weak… but due to the high moisture content , with precipatable water values near 50mm, even weaker updraft storms will produce decent rainfall amounts.  There is some early convection over southern New Brunswick but after that passes around noon convection may be suppressed until late this afternoon or early this evening. In general slow moving storms could produce locally 25mm but there is some potential for multicell clusters later today that could bring higher amounts and 2cm hail for central and northwestern New Brunswick.  We will be on the look out for local convergence over Nova Scotia along the spine which could cause some local enhancement, tomorrow this will almost definitely be the place to look.

 

The dynamics or shear is somewhat better over western Labrador today although the potential thunderstorms could be somewhat limited by convective inhibition at a multiple layers, however should stronger updrafts be present surface gusts will be more likely in the thunderstorms.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

 

Mel Lemmon