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

Convective Outlook Valid for August 17th and 18th

Thunderstorm Outlook for Day 1

 

Regional Impacts - None

 

Convective Discussion

High pressure continues to dominate much of the area today bringing unfavourable conditions for thunderstorm formation.

 

 

Thunderstorm Outlook for Day 2

Regional Impacts – Risk of thundershowers for New Brunswick, western PEI and interior Labrador.  Local heavy showers of up to 10 mm possible.

 

Convective Discussion

As the high pressure begins to move away, conditions become a bit better for thunderstorm activity.  Higher moisture levels begin to move into New Brunswick and the atmosphere becomes a bit more unstable as a jet stream tracks into the area.  CAPE values of 500 J/kg are currently expected.  Wind shear values are low at around 25kts so long lived storms are not currently expected.  Local heavy showers of up to 10 mm is possible for parts of  New Brunswick.  Risk of non severe thundershowers as well for interior Labrador.

 

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