Convective Outlook for June 22nd and June 23rd, 2021

Thunderstorm Outlook for Day 1

 

Regional Impacts:

 

Potential for isolated non severe thundershowers today over much of the Maritimes with a potential for isolated severe cells over areas that become cloud free.  Main threat is heavy local downpours but strong winds and hail are also possible

 

Convective Discussion:

 

The cold front that caused much damage last night over Quebec and Maine is now over New Brunswick.  The area is quite cloudy which helps to inhibit severe cell growth but some areas may become cloud free and will be able to reach higher temps and hence become more unstable.  Strong jet over the area with an abundance of low level moisture and the trough to help kick things off.  Cloud free areas will be watched closely.  Areas with more cloud could still see convection with lower likelihood to become severe.

 

 

 

Thunderstorm Outlook for Day 2

 

No convective activity expected for day 2 at this time.

 

 

Barrie MacKinnon

 

Convective Outlook for June 21st and June 22nd, 2021

Thunderstorm Outlook for Day 1

 

Regional Impacts:

 

Risk of isolated thunderstorms this evening over northwestern New Brunswick with possible heavy showers and strong wind gusts.

 

Convective Discussion:

 

Instability over the Maritimes is quite low as a thermal ridge sits over the area at issue time.  The thermal ridge tracks east through the day and so instability increases slightly over the area this evening.  Prog tephis only showing around 100 J/kg this evening which is quite insignificant so only a risk of isolated thundershowers is expected.  The highest threat if thundershowers develop is local heavy rainfall as low level moisture is moderate.  Strong wind gusts below warning criteria is also possible.

 

 

Thunderstorm Outlook for Day 2

 

Barrie MacKinnon

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Regional Impacts:

 

A few thunderstorms are expected in New Brunswick this afternoon and early this evening. There is a possibility they could advect into PEI, especially Prince County. There are a few thunderstorms in Anticosti marine area currently. Later today these storms could affect parts of northwestern Newfoundland.

 

Convective Discussion:

 

For New Brunswick, modifying Caribou’s 12Z tephi for the forecast high in northern NB of 23 deg gives about 300 J/kg of cape. For the forecast high of 26 deg of central NB gives 600 – 800 J/kg of cape. Shear values 0-6 km over NB are expected to be about 35 knots. Gusty winds are possible but not expected to reach warning criteria. Small hail is possible as freezing levels are near 10,000 feet. Precipitable water indicates that 25-30 mm of rain is possible. However, storms will be moving at about 25 knots, so unless training occurs, any given locality shouldn’t receive excessive rainfall.

 

The thunderstorm risk in northwestern Newfoundland is associated with a deep layer trough in a low shear environment. Convection in this area is elevated with lift from 750-850 mb. These thundershowers are not expected to have significant rain or wind with them.

 

 

 

For Monday, Isolated thunderstorms are possible over northwestern New Brunswick.

 

 

 

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Regional Impacts

For New Brunswick, scattered thunderstorms over western New Brunswick later this afternoon and into the evening. Some of these storms will likely give Heavy downpours, potential damaging wind gusts around 80 km/h, and localized hail of up to 2cm.

Western Labrador, isolated non-severe thunderstorms this afternoon.

 

Convective Discussion

A large area of Cloud&Rain has affected New Brunswick this morning but it will be shifting eastward out of the region this afternoon. Satellite imagery is showing clearing along the Lower St. Lawrence seaway and Maine during the past 1-2 hours. This bright sunshine will become key for the convective temperatures being reached over NB later on. An advancing upper cold low over western Quebec will help destabilize the environment further -  pushing Mixed layer cape values to a significant 1000 J/kg. Supported by a 30kt SWly LLJ, this very unstable environment will be capable of maintaining multi-cell clusters from Maine to Western NB. Any long-lived cells could produce Very heavy downpours, damaging winds and hail.

 

For Sunday, Isolated non-severe thunderstorms are possible over eastern Nova Scotia.

 

 

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for June 18th and June 19th

Regional Impacts

 

For Western Labrador.. isolated thunderstorms possible later today and this evening with 15 to 20 mm of rain possible, no severe weather expected.

 

Elsewhere.. No Thunderstorms expected today, however severe thunderstorms are possible for New Brunswick tomorrow. See the Day 2 outlook further below.

 

Convective Discussion

 

An upper trough is slowly progressing across Northern Ontario today with favourable conditions for severe weather to the south and east of the track. For today a weak ridge should be sufficient to hold back convection for most of the Atlantic Provinces except for Western Labrador where weaker isolated thunderstorms are possible later this afternoon and evening.  

 

Dynamics are favourable for a broad area with high values of shear moving into New Brunswick tomorrow, supercells with strong wind gusts are possible along with heavy rain. Although there is some uncertainty with the speed of the upper low which may impact the timing and location of severe occurrence.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2