Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

NB: Risk of severe thunderstorms with heavy downpours, strong wind gusts and a non-zero threat of a tornado over Madawaska and western Restigouche county.

NL: Risk of thunderstorms with locally heavy downpours and strong wind gusts.

LAB/PEI/NS: None

Tonight:

Isolated embedded thunderstorms giving locally heavy downpours.

Tomorrow:

NS/NL/LAB: Risk of thunderstorms giving locally heavy downpours.

Convective Discussion

For today, the threat of severe convection increases for northwestern New Brunswick as a low pressure system tracks northeastward over southeastern Quebec and toward Labrador by Friday. Convection has been ongoing this morning along the St. Lawrence towards northern Newfoundland while an MCV materialized ahead of the low centre over the Great Lakes. Looking at the 12Z Caribou sounding and clear skies over much of central and northern Maine and New Brunswick, should convective temperatures be reached (>31C), there is the potential for MLCAPE values of 1000-1500 J/kg, deep 45kt layer shear and further advection of high precipitable water (50 mm) from the Gulf Stream. There may a slight warming in the 500mb temperature leading to a limit in destabilization. However, lift from the approaching cold front as well as the other ingredients will aid in the potential for multicell lines or potential supercells this afternoon and evening across northern Maine and into New Brunswick. Heavy rain and strong wind gusts will be the main threats with convection that develops but there is also a slight threat of a tornado over Madawaska and western Restigouche counties where the SRH values exceed 100.

Troughing over northern Newfoundland continues eastward where some embedded thundershowers may continue into the afternoon where heavy downpours will be the main threat along with brief strong wind gusts.

For tonight into Friday, the cold front associated with the low pressure system will track across the Maritimes tonight and across Newfoundland on Friday giving embedded thunderstorms. As well, moderate to heavy rainfall is likely ahead of the low centre for central and eastern Labrador overnight and throughout Friday.

Thunderstorm Outlook for TODAY

Thunderstorm Outlook for TONIGHT

Thunderstorm Outlook for TOMORROW

 

Roberta McArthur

 

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

NB: Risk of thunderstorms giving heavy downpours and gusty winds in the late afternoon.

NS: Slight risk of a thundershower across the spine in the afternoon.

PEI/NL/LAB: None

 

Tonight:

NB: Risk of thunderstorms giving heavy downpours and gusty winds in the evening.

NL: Slight risk of an embedded thunderstorm reaching western region by early morning.

Tomorrow:

NB: Risk of severe thunderstorms with heavy downpours and strong wind gusts.

NL: Risk of thundershowers with locally heavy downpours and strong wind gusts.

LAB/PEI/NS: None

Convective Discussion

The main threat of severe convection today will lie along and ahead of a trough that will moves east to southeastward from north shore Quebec towards the Gaspe Peninsula this afternoon. Organised thunderstorms are not as likely now to reach northern New Brunswick given the timing and position of this trough, but there is still ample deep moisture and daytime heating that anything that does develop will give heavy downpours with water loaded gust potential. Mixed CAPE values are expected to exceed 1000Jkg and with effective shear reaching 35-40kt in northern New Brunswick. This trough will track across the northern Gulf of St. Lawrence and towards Newfoundland by tomorrow morning.

Over Nova Scotia, sea breeze convergence and daytime heating may be enough for a pop-up shower or thundershower across the spine if convective temperatures can be reached. Any cells that do develop will be slow moving and capable of producing localized heavy downpours as cells drift to the southeast.

For tomorrow, the threat of severe convection increases for new Brunswick as a low pressure tracks northeastward over southeastern Quebec and toward Labrador by Friday and a cold front will track into New Brunswick early evening and through the remainder of the Maritimes overnight into Friday.  High MLCAPE, deep 50kt layer shear and high precipitable water (50 mm) will aid in the potential for multicell lines or potential supercells. Meanwhile, the trough from today will impact parts of Newfoundland tomorrow, mostly off the northeast coast where sea breeze and daytime heating will aid in further lift. Heavy downpours are expected to be the main threat but with moderate deep layer shear, some organization into lines is possible.

Thunderstorm Outlook for TODAY

Thunderstorm Outlook for TONIGHT

Thunderstorm Outlook for TOMORROW

 

Roberta McArthur

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Labrador… A few thunderstorms becoming organised over eastern areas. Heavy downpours and strong wind gusts are possible.

Newfoundland… Slight risk of thunderstorms over the northwest this evening and tonight.

New Brunswick…. Slight risk of thunderstorms this afternoon.

PEI… Slight risk of thunderstorms over the west this evening.

NS… little to no impacts today.

 

Convective Discussion

The main area of interest today will be over Labrador, as an unusually high amount of moisture moves into the region, with dew point temperatures approaching 20°C in the east. An approaching surface trough, currently crossing central Labrador, combined with elevated low-level moisture, will increase the potential for thunderstorms. Mixed-layer CAPE values are expected to reach around 1500 J/kg, so rainfall rates exceeding 30 mm per hour are likely.

With the surface trough acting as an organizing feature and low-level shear values in the range of 25–30 knots, there is a chance that storms could organize into a mesoscale convective system (MCS). Overshooting tops and lightning activity should serve as good indicators of which storms are severe. Equilibrium levels for the more intense storms are expected to be around -50°C, which should help distinguish the severe cells.

This situation is expected to evolve rapidly this afternoon as solar insolation and the approaching trough initiate thunderstorm development. Alerts may be required. Strong wind gusts and small to moderate hail are also possible with the storms.

Over New Brunswick, conditions are expected to be somewhat less dramatic. While wind shear values are favorable — with over 40 knots of deep-layer shear — thunderstorms may struggle to develop due to relatively thin CAPE. The strong shear may, in fact, inhibit deep convective growth. Although a few cells capable of producing lightning may form over northern New Brunswick, it is unlikely they will evolve into long-lived, organized thunderstorms.

The situation is likely to be conducive for organised thunderstorms over New Brunswick and Nova Scotia to a lesser extent tomorrow. Over NB deep shear values should still be quite high but the potential from higher CAPE values and updraft potential will be more likely to produce severe storms.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

 

Mel Lemmon

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today: Severe thunderstorms are likely in the vicinity of Goose Bay, Labrador. There is the potential of supercells and a history of hail, wind, and rain with this front. Severe thunderstorms are also possible in the far NW corner of NB through the Edmundston valley with the same frontal passage. Gusty winds, hail, and rain are the main hazards here as well. However, some tornadic rotation is possible later this afternoon and early evening.

Tonight: Decaying thunderstorms continue for many areas in NB and Labrador. There will also be offshore convection south of NS and Nfld tonight.

Tomorrow: Risk of isolated non-severe thundershowers across much of NB, parts of western Nfld along the de-stabilized trof. Capping ridge is starting to enter the lower Maritimes – preventing widespread deep convection.

Convective Discussion

A very strong low pressure system anchored over the Kavallik region of northern Quebec is bringing a sweeping front from the Labrador Sea down to the Ohio River Valley. This broad feature is driving deep convection, with enhanced spin out ahead of it. It is has a 3-day history of impactful weather as it tracked thru much of eastern Canada. Cape values in central Lab are near 1500+ today, and Effective Helicity is heightened. Sig tor flags supercell development late day near Goose Bay. Sig tor 2 also flags the same area. NW NB is non-zero as well near 00z tonight. However, there is a CIN factor to contend with. Dewpoints of 20 need to advect further east this afternoon, and there is a lot of other cloud cover in the vicinity. Difficult to get discrete cells without a partial clearing. Svr TS watches are going to be issued for areas directly downstream of this trigger – E. Townships of Quebec, Edmundston, Goose Bay. Dynamics are weaker night 1 and day 2 across the Maritimes, with high heat building into the region for much of the week ahead. Isolated higher based windy storms are forecast for Tuesday.

Thunderstorm Outlook for TODAY

Thunderstorm Outlook for TONIGHT

Thunderstorm Outlook for TOMORROW

Forecaster: TIRONE.

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

LAB: Risk of thunderstorms late this afternoon with locally heavy downpours and strong wind gusts.

Maritimes/NL: None

Tonight:

LAB/NB: Risk near-severe embedded thunderstorms this evening giving locally heavy downpours and strong wing gusts.

PEI/NS/NL: None

Tomorrow:

LAB: Risk of near-severe thunderstorms with heavy downpours, small hail and strong wind gusts.

NB: Risk of a thunderstorms giving locally heavy downpours and strong wind gusts.

PEI /NS /NL: None

Convective Discussion

A low pressure system over James Bay this morning has a trailing cold front stretching from central Quebec into the eastern USA. Thunderstorms along and ahead of the front may reach western Labrador and northwestern New Brunswick by early evening with the threat continuing into the evening. This front will continue to stream in precipitable water into the 40-50 mm range even as far as northern Labrador over the next few days. However, some smoke notes aloft over the region may work to inhibit full daytime heating potential. The highest risk of severe thunderstorms remains over southern to central Quebec where with cooler air aloft, and a strong 850mb jet. Regardless, heavy downpours and strong wind gusts may continue into the overnight for western New Brunswick and western to central Labrador.  

Tomorrow, the front will continue to track eastward further north over Labrador. With CAPE potentially reaching 1000 and moderate effective shear reaching 35-40KT, lines may organize into lines in the afternoon ahead of the cold front over central and eastern Labrador. Behind the front, a shortwave is expected to quickly track across central Quebec and into western Labrador by the evening. With this, there could be further multicell convection with strong wind gusts being the main threat with a drier air mass.

Meanwhile further south, a slow moving low pressure system and ridge over the southern marine waters will keep the threat of convection mainly over north and western New Brunswick. Locally heavy rain and strong wind gusts would be the main threat with convection that can continue from northern Maine.

 

Thunderstorm Outlook for TODAY

Thunderstorm Outlook for TONIGHT

Thunderstorm Outlook for TOMORROW

 

Roberta McArthur