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

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

LAB: Risk of thundershowers with heavy downpours and gusty winds in northern Labrador.

NB: Slight risk of a thundershower giving a brief heavy downpour and gusty winds.

PEI/NS/NL: None

Tonight:

None

Tomorrow:

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

Maritimes/NL: None

Convective Discussion

A low pressure system is slowly moving southeastward across the Grand Banks today. There has been the odd embedded thunderstorm north of the low over the Avalon Peninsula this morning and the threat of heavy downpours continues further east, mainly affecting the northern and southeastern Grand Banks today.

A weak trough will move into northern Labrador today from northern Quebec. While upper dynamics are limited, sea breeze convergence, terrain influence and warm surface temperatures could aid in the development of thundershowers this afternoon.

Although there is a ridge over the Maritimes keeping most of the area capped for any strong convection, the convective temperatures may be realised over parts of central and western New Brunswick this afternoon with high temperatures reaching 28C. Based off the 12Z Caribou sounding and not much change expected in the mid-upper levels,  isolated showers with a slight risk of a thundershower giving a brief heavy downpour are possible.

Tomorrow, a relatively deep low pressure system will track into James Bay, with a trailing cold front stretching from central Quebec into the eastern USA. Thunderstorms along and ahead of the front may reach western Labrador by afternoon before convection diminishes in the evening.

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: isolated thunderstorms this afternoon/early evening giving some gusty winds, heavy downpours, and possibly small hail. Do not expect any cells to become severe.

NS and southeastern NL: risk of an elevated thunderstorm today and into this evening giving locally heavy downpours.

 

Tonight

Southeastern NL: continuing with the risk of an elevated thunderstorm through the overnight and into Saturday morning giving locally heavy downpours.

 

Saturday

Lab: slight risk of an afternoon thunderstorm.

 

Convective Discussion

 

A couple features of interest today: one is a frontal trough passing south of NS and the other a 500 mb trough entering NB. There has been some history of activity with both features, more notably the upper trough. The instability doesn’t appear as deep as it was yesterday when the trough was upstream in Quebec, and the feature itself is showing some signs of weakening. There should be some isolated storms in Maine that will drift across inro western NB through the afternoon giving some gusty winds, locally heavy downpours and small hail. The 12Z tephi out of caribou has pretty weak shear but the FZLVL is just above 10,000 ft so the chance for small hail seems legit.

 

The trough currently passing south of NS and approaching southeastern NF will produce some isolated thunderstorms offshore with a slight chance it could touch the Burin and southern Avalon tonight and into Saturday morning. The instability is pretty good but quite high so we shall see if anything does materialize. Locally heavy downpours would be the only threat.

 

Lastly a weak surface trough could be enough to trigger an isolated thunderstorm or 2 across parts of the Big Land on Saturday.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Jeremy