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

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

A chance of thundershowers for southernmost Labrador

 

Regional Impacts

Southern border of Labrador  to just south of the Trans Labrador Highway. Local heavy showers, possible small hail, and some wind gusts.

 

Convective Discussion

A deep cold low southwest of Labrador will move east along the border this afternoon and into the evening. There’s some upper support with the cooling aloft and surface insolation this afternoon which should break the inversion near 700 mb, and give a few hundred J/kg of CAPE. Shear will be moderate at about 25 kts, and PWAT will be on the low side at about 20 mm.  Freezing levels will be around 7500 ft, giving a chance for small hail.

 

The rest of the Atlantic Provinces are in a relatively unfavourable environment, with dewpoints below 10 almost  everywhere and strong inversions over Newfoundland.

 

 

 

Thunderstorm Outlook for Day 2

A chance of thundershowers for westernmost Labrador

 

Regional Impacts

Westernmost Labrador to the Churchill reservoir. Local heavy showers and a chance for small hail.

 

Convective discussion

A low will approach from near James Bay and the warm frontal trough ahead of it will nudge into westernmost Labrador late in the day.  There is more moisture in the profile on Friday and the warm nose at the surface will give relative cooling aloft. The current forecast suggests temperatures near the trigger temperature. Impacts would be isolated heavy showers and a small chance for hail with the freezing level near 10,000 feet.

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

Non-severe thunderstorms are possible inland today across the Maritimes. Western Labrador may also see a few lightning strikes this afternoon. Moderate rain would be the main hazard with any isolated cell that develops.

 

Convective Discussion

With MUCAPE of 300J/kg and Eff Shear of 35kTs, single cell thunderstorms could develop along cold front as well as near upper low currently in Quebec. The shear aloft at 4-6k is very high (over 55kTs) so no storm is expected to be very tall or last very long. Areas that have the best moisture present today are along the Atlantic coast of Nova Scotia, but with dense fog and heavy mid cloud this may be difficult for anything surface based to be realized today.

 

 

Thunderstorm Outlook for Thursday

 

Regional Impacts

Isolated non-severe thunderstorms are forecast in the afternoon/early evening for central Labrador near Happy Valley - Goose Bay.

 

Convective Discussion

With a trigger temp of only 14C and FL of 8,000ft, these single cells will be rain makers. Near the upper low, storms will be short lived with minimal 0-6k shear present (15kTs) to sustain their life cycle. 500-700mb deltaT values of 18 suggest numerous “popcorn” cells to develop.