Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

Strong winds, especially multicells with organising features giving strong winds, are possible for south New Brunswick and parts of Nova Scotia.

 

Regional Impacts

New Brunswick and Nova Scotia: high winds and heavy downpours, possibly severe for both.

Newfoundland and Labrador: nothing significant.

Prince Edward Island: Gusty winds and local heavy rain, probably less than severe.

 

Convective Discussion

A tropical ridge south of the district and a deep trough extending southwest of Hudson Bay slanting east as you near ground level. A weak thermal ridge near NB with weak cold advection and good moisture trapped under an inversion. When the inversion breaks we expect multicells and linear features. PWATs are near 50 mm, dewpoints below the 850 layer are in the low to mid 20s, shear is about 40 kts for the threat region shown, and the winds are mainly straight line. With possible organising due to convergence and some weak troughing my cause things to persist tonight

 

 

 

Thunderstorm Outlook for Day 2

A broad weak low over the southern Maritimes and local convergence, including sea breeze fronts, may give some isolated thundershowers. Moisture is okay, and there is some moderate shear, so it may give near severe conditions in the afternoon.

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Regional Impacts

Non-severe thunderstorms for Labrador. Non–severe for part of the Maritimes, with a higher threat to western Nova Scotia and New Brunswick.

 

Convective Discussion

For the Maritimes there is plenty of moisture at least up to 850 mb, with PWATs up to 50+ mm and dewpoints above 20 C,  and a LLJ advectiing more from New England. Shear a bit on the high side over northern NB but in the 25-40 kt range for the rest of the Maritimes.  There is some PVA and upper jet support, and the upper trough farther west slanting down to the east. New Brunswick and Western Nova Scotia and PEI are mostly clear, but with Cu and TCu starting.

 

For Labrador there is a deep trough to the west and moving east, partially clearing skies in the west for good insolation, and healthy shear near 45 kts, but PWATs less than 20 mm and marginal instability. Isolated to scattered thundershowers with local heavy showers, followed by some wind gusts, and a chance of small hail with FZLVLs near 10,000 feet.

 

 

 

Thunderstorm Outlook for Day 2

Non–severe for part of the Maritimes, with a threat of severe thunderstorms for western Nova Scotia and New Brunswick. The highest threat is for heavy rainfall, followed by strong wind gusts to near warning levels.

 

 

ATL Thunderstorm Outlook for Today and Tomorrow

Thunderstorm Outlook for Day 1 – JUNE 28

 

Regional Impacts 

Severe thunderstorms possible over central and southern NB ahead of a trough line in a very hot and humid airmass. Non-severe isolated storms are also possible inland in NS along sea-breeze convergence lines. 

Convective Discussion 

With 35-40kts of 0-6k shear, sfc based CAPE of 800-1200J/kg and Pwats of 45-55mm, the hazards in NB is heavy rainfall, small hail, and gusty winds. If a few storms can bubble up ahead of the approaching front, then discrete supercells are possible on Monday afternoon. Watches and warnings may be required. This is being monitored closely from the Atlantic Storm Prediction Centre. 

Thunderstorm Outlook for Day 2 – JUNE 29

 

Regional Impacts 

Non-severe airmass driven thundershowers are possible over many areas of the Maritimes, and Labrador. The best organized convection will be in eastern NB. 

Convective Discussion 

Less daytime heating energy is available to work with than on Day 1 but still enough to get 500J/kg in pockets. Single cell storms are expected, with rain and gusty winds. 

Thunderstorm Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1 – JUNE 27th 

 

Regional Impacts 

Isolated thunderstorms are expected this afternoon and evening across central and parts of northern New Brunswick. In central NB, a cell or two could approach severe limits today for heavy rainfall of 25-40mm. A few lightning strikes are also possible along an elongated boundary in Labrador. 

 

Convective Discussion 

Today's thunderstorm risk is highly dependent on synoptic cloud location. The moisture is certainly available with >20 degree dew points. The limiting factor could be the daytime heating needed to overcome a weak cap at 700mb. If highs near 30 can be achieved, then heavy rainfall is the main hazard. Low-mid level shear values are more favourable for severe weather on Day 2 (dynamics advecting in from west). 

 

 

 

Thunderstorm Outlook for Day 2 

 

Regional Impacts 

Severe thunderstorms are possible in southern and central New Brunswick. Isolated, non-severe thunderstorms are also possible near the Cobequid pass in Nova Scotia. Hot daytime highs, and dew points remaining near 20 will facilitate this. 

 

Convective Discussion 

800-1200J/kg of sfc based CAPE can be realized, with ample sfc-midlevel moisture, 16-18 degree T diffs from 500-700mb, and 35-40kts of 0-6k shear. Pwats near 50mm make heavy rain, small hail – FL at 11,000ft – and gusty winds the main hazards. Low level helicity does not appear elevated at this time. Check back tomorrow for an updated OUTLOOK. 

 

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

Regional Impacts

Isolated thunderstorms over western Labrador this afternoon and into the evening. the main threat will be brief heavy downpours and high wind gusts.

Convective Discussion

A weak surface cold front extending through northern Quebec will advance towards Labrador this afternoon. Colder air aloft will destabilize the airmass between Shefferville and Wabush, and then around Churchill Falls late in the day. The La Grande sounding was modified with a Ts,Td combination of 23,14 which was enough to generate CAPE values of 250+ J/kg  and Lifted index of -1. The hodograph is showing unidirectional winds through the unstable column and a westerly shear / Jet of 50kt - which would be enough to sustain these isolated pulse thunderstorms a little longer, which could in turn could produce surface gusts of 35kt or more.

   

Thunderstorm Outlook for Sunday

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

Slight risk of a non-severe thunderstorm over westernmost NS this evening and after midnight.

 

Convective Discussion

Moisture associated with a weak low pressure area over the Gulf of Maine will continue to advance over the

southern Maritimes during the day. Bands of showers along with an isolated thunderstorm will be moving through

Fundy and Lurcher.

 

 

Thunderstorm Outlook for Saturday

 

For Saturday, Risk of non-severe thunderstorms over western and central Labrador.

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Nil.

 

Convective Discussion

No thunderstorms expected in the region today. Some isolated thundershowers over MRTM waters south of NS overnight tonight and into Friday morning.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2

 

Jeremy

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

No thunderstorms expected at this time. There is small chance of a lightning strike or two this afternoon over SE Labrador, GNP, and Green Bay-White Bay as the trough passes through.

 

Thunderstorm Outlook for Day 2

 

No convective activity expected for Day 2 at this time.

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

 

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.

 

 

 

 

 

 

 

 

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts:

 

Over extreme southeastern Labrador and Newfoundland (except for the southwest and southeast), there is a risk of a popup thundershower today. Small hail is possible due to the low freezing levels even though the thundershowers are expected to be weak.

 

Convective Discussion

 

A deep layer trough from the surface to 250 mb extends from eastern Labrador to western Newfoundland. The upper and mid levels are very cold (freezing levels are 4500 – 5000 feet). With daytime heating, there may be isolated popup thundershowers near and east of the trough. Shear values are low (less than 30 knots). West of the trough, the environment is strongly capped near 700 mb and the low levels are dry. Thundershowers are very unlikely west of the trough. A strong upper level jet over 100 knots exists to the south of Newfoundland. This jet is too far south to affect convection over land areas.

 

This deep layer trough is expected to move to the east of Newfoundland and Labrador tonight and Monday. No thundershowers are expected tonight and Monday over Atlantic Canada.

 

Thunderstorm Outlook for Today:

 

 

 

Thunderstorm Outlook for Monday: None expected.

 

 

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts:

 

Over southeastern Labrador and northern and central Newfoundland, there is a slight risk of a popup thundershower this afternoon and Sunday afternoon.

 

Convective Discussion

 

A slow moving deep layer trough from the surface to 250 mb extends from an upper low over Labrador to the Gulf of St. Lawrence. As this trough moves very slowly eastward, upper level temperatures will drop east of it over southern Labrador and northern and central Newfoundland. With daytime heating, there is a slight possibility of CBs topped at 30,000 to 35,000 feet in a low shear environment. West of the trough, over the Maritimes, the environment is strongly capped near 700 mb, inhibiting thunderstorm activity.

 

Similar conditions are forecast for Sunday afternoon except that the trough will be slightly farther east making the risk area slightly farther east.

 

Thunderstorm Outlook for Today:

 

 

Thunderstorm Outlook for Sunday: