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.

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

Isolated non-severe thunderstorms are expected today with heavy downpours being the biggest threat for northern New Brunswick. There is also a slight risk of elevated thunderstorms this evening and overnight along the Fundy shores, Nova Scotia and parts of PEI.

 

Convective Discussion

A sweeping long wave trough will enter New Brunswick this afternoon bringing with it the ability to trigger thunderstorms. SFC based CAPE values of 500-1000J/Kg may be difficult to be fully realized with all the synoptic cloud currently present. However, there is 35kTs of 0-6k Shear today, so a storm that may develop will likely drop 25-40mm of rain in a few locations. With easterly progression, thundershowers may persist into mainland NS overnight tonight.

 

 

Thunderstorm Outlook for Wednesday

 

Regional Impacts

Isolated non-severe thunderstorms are forecast for parts of New Brunswick.

 

Convective Discussion

Much less SFC based CAPE available (200-300J/kg), as well as much more shear as low centre approaches from west – short lived single cells possible.

 

 

 

 

 

 

 

 

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

Isolated non-severe thunderstorms are expected today in parts of northern New Brunswick.

 

Convective Discussion

In a moderate southwest flow, and dew points building throughout today, there will be a few isolated non-severe thunderstorms. Pockets of heavy rain would be the biggest threat with any cell that develops. Storms will be short lived however with not much shear at play in the atmosphere.

 

 

Thunderstorm Outlook for Tuesday

 

Regional Impacts

Isolated non-severe thunderstorms are possible in Western Labrador and parts of New Brunswick.

 

Convective Discussion

Surface based CAPE (500-1000J/kg) and shear (30+kTs) are more favourable for single cell/multi cell storms to develop on Tuesday under the passage of a cold front. With PWATs of 30+mm, heavy rain is again the risk under a cell that may develop.