Convective Outlook Valid for Today and Tomorrow

Regional Impacts

NB: downpours and scattered lightning

NS: downpours and scattered lightning most of mainland

PEI: Isolated lightning western half

NF: None

Labrador: Isolated lightning Eagle River region

Marine waters: Scattered lightning eastern marine district into southwestern Grand Banks. Isolated lightning near Anticosti. Isolated lightning western Northumberland strait.

 

 

Convective Discussion:  Generally unstable with an upper trough over the Maritimes providing steep mid tropospheric lapse rates. Shear will be minimal today with slow storm motion initially easterly at 5-10 kts becoming southeasterly later in the afternoon into the early evening. Given slow storm motion and PWATs into the upper 20mm, the primarily hazard today will be downpours over the Maritimes. In eastern Labrador over meager instabilities of ~300 J/kg aided by a deformation zone on the western periphery of the upper trough may allow for the odd strike, however bulk shears in excess of 40 kts may prove to be too much to allow for convection to reach heights sufficient to generate lightning. Differential heating near the deformation zone may also allow for the odd strike near Anticosti island. Much of the southern/eastern Marine district remains in a moist unstable environment, with PVA from the upper trough continuing to trigger scattered thunderstorms. This region of instability is expected to slowly advect east with the upper trough, giving continued scattered convection over the next 36 hours.

 

On Canada day (tomorrow), little thunderstorm activity is expect. However storms may move into northwestern NB from eastern Quebec in the early evening hours as a cold front moves towards Atlantic Canada.

 

Thunderstorm outlook for today:

 

 

Thunderstorm outlook for tonight:

 

 

Thunderstorm outlook for Friday (Canada Day):

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Labrador: Scattered thundershowers for western and northern regions.

NB: Isolated thundershowers in the northwest.

NL/NS/PEI: None.

Slope waters: Isolated thundershowers.

 

Convective Discussion

Today: The only area with marginal excitement for a forecaster is western Labrador where there is an approaching deep layer trough from the surface to 500 mb, wind shear in the 40-50 knot range and modest instability. The only caveat would be solar insolation which will be somewhat difficult given the current cloud cover. The Maniwaki TEP profile from 12 UTC is decent for thunderstorms but realistically is too far upstream to give a good indication for western Labrador. Expect some scattered cells embedded along the frontal feature as it approaches this afternoon but non-severe in nature. Some isolated thundershowers are possible in NW NB later today as that aforementioned front approaches the St. Lawrence valley. Lastly high PWATs, Tds and a weak surface trough will give some isolated cells mainly south of the slope waters…some may trickle into the southern marine district later on.

 

Tonight: Some instability is indicated on guidance in conjunction with a surface trough and falling 500 mb heights in western NB, which may give some isolated thundershowers through the overnight and into Thursday morning. That trough south of the marine district will begin to push northward bringing some scattered thunderstorms tonight and Thursday morning.

 

Thursday afternoon: Scattered thunderstorms are likely for most of NB and convergence areas across the usual areas in NS as an upper trough of low pressure crosses the MRTMS. Cells will be very slow moving so locally heavy rainfall is possible. Scattered thunderstorms associated with the surface trough for waters south of NS and NL.

 

Thunderstorm Outlook for Today

 

Thunderstorm outlook for tonight

 

Thunderstorm outlook for Thursday

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

NB: Isolated thundershowers for southern regions

NS: None

PEI: Isolated thundershowers for western regions

NF: None

Labrador: Isolated thundershowers over southeastern regions

Marine waters: Isolated thundershowers for Laurentian Fan.

 

 

Convective Discussion:  Clearing behind an upper trough will allow for modest instability to develop this afternoon (MLCAPES ~350 J/kg), causing  isolated convection initiation over areas of enhanced differential heating. A secondary area for potential CBs also exists over southern NB into western PEI later this afternoon into the evening. Here SBCAPES of ~400 J/kg should develop with clearing early occurring early this afternoon, convection looks to be triggered by an upper trough moving eastward from Vermont, aided by a right entrance region of a 130 kt upper jet, and surface convergence that was already evident on the 12z analysis from ~CYFC to Kent County. Primary hazards would be isolated lightning, downpours should be limited by rather low PWATs ~ 20mm.

 

Tomorrow another cold front is expected to move through north-central Quebec into western Labrador triggering CBs with modest CAPES on the order of 400 J/Kg. High LCLs on the order of 1.5-2 km, unstable PBL lapse rates will present an additional hazard for some strong wind gusts outside of lightning and some small hail,  given the position of the HGZ and shear character. CBs associated with this feature further south may also move into NW most NB late tomorrow evening, but felt the risk was low enough to leave it out of the day 2 outlook at this time. Another marginal area left off the outlook tomorrow is immediately inland along the northern coast of NL, where an upper trough, coastal convergence and modest instability of 200-300 J/Kg may allow for the odd strike before a 700 mb thermal ridge moves in bringing capping issues. Again felt probability was a little too low to be included in the day 2 outlook at this time.

 

The slope waters present reasonable instability at T/td’s of 22/20, with isolated lightning becoming scattered by Wednesday evening, with a persistent LLJ.   

 

Thunderstorm outlook for today

 

Thunderstorm outlook for tonight

 

 

Thunderstorm outlook for Wednesday

 

 

Convective Outlook Valid for Today and Tomorrow

 

Regional Impacts

NB: None

NS: None

PEI: None

NF: None

Labrador: Scattered thunderstorms with strong wind gusts up to 90 km/h and hail up to 2cm.

Marine waters: Isolated thunderstorms for Laurentian Fan and southwestern Grand Banks.

 

 

Convective Discussion:  Left exit region of a 120 kt upper jet will advect eastward into western Labrador early this afternoon enhancing synoptic ascent as profiles destabilize with an advancing upper trough.

Shear character will be linear today with bulk shears on the order of 40+ kts enabling a hail threat despite thinner CAPE profiles early in the day. Should cloud cover not prevent significant daytime insolation, highs could get into the low 30s with surface dews in the mid teens, allowing for significant SBCAPES on the order of 1000+J/Kg, yielding a wind hazard given steep PBL lapse rates through much of western-central Labrador. Storm motion should be quite quick, on the order of ~35 kts from the SW, limiting a rainfall hazard.

Over the southeastern marine district, PVA from a mid tropospheric upper trough in combination with a ~30 kt LLJ  could yield the odd elevated strike today/ tonight.

 

The thermal ridge that is in place over eastern Labrador is expected move eastward tomorrow allowing for isolated convection initiation over areas of enhanced differential heating. A secondary area for potential CBs also exists over southwestern NB, where T/Td’s of ~22/12 allow for up to 400 J/Kg of SBCAPE, with minimal capping in close proximity a right entrance region of a 120kt upper jet. However American guidance is much drier with dew points stuck in the single digits, which if proven correct will limit convective development.   

 

Thunderstorm outlook for today

 

 

Thunderstorm outlook for tonight.

 

 

 

Thunderstorm outlook for Tuesday

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

NB: None.

NS: Isolated thunderstorms possible over inland areas of southwestern NS.

PEI: None

NF&Lab: None

Marine waters: Isolated embedded thunderstorms possible over the southern edge of the slope waters.

 

Convective Discussion

 

Very little, if any, convection is expected over land areas of Atlantic Canada today. Warm air aloft associated with an upper ridge over New Brunswick and Newfoundland Labrador is giving profiles too stable for thunderstorm activity to occur. There is a slight possibility of surface based convection this afternoon over inland areas of southwestern NS. However, as was the case yesterday, there is a subsidence inversion above 700 mb. Even though there is ample heat and moisture in the low levels, the cap associated with this subsidence inversion makes it difficult for thunderstorms to form. They can’t be ruled out, however.

 

Embedded thunderstorms are possible over the extreme southern slope waters associated with a persistent area of showers.

 

 

 

 

Thunderstorm Outlook for Monday morning.

 

Regional Impacts

NB: None

NS: None

PEI: None

NF&Lab: None

Marine waters: Isolated embedded thunderstorms over the slope waters.

 

Convective Discussion

 

Thunderstorm activity is not expected over land areas in Atlantic Canada overnight tonight. The profiles remain too warm aloft.

 

 

Thunderstorm Outlook for Monday afternoon and evening

 

Regional Impacts

NB: None

NS: None

PEI: None

NF&Lab: Scattered thunderstorms are possible over western Labrador

Marine waters: Isolated embedded thunderstorms remain possible over the southern edge of the slope waters.

 

Convective Discussion

 

An approaching upper trough and associated PVA across Quebec will give conditions conducive to thunderstorms in Western Labrador Monday afternoon and evening. In addition, there is a strong mid-level and upper level jet moving into the region. So any thunderstorms that form will have enough shear and upper support to keep them going. The models indicate a lot of mid-level cloud, so initiation from the sfc is unlikely.

 

Conditions remain too stable for convective activity over the Maritimes.

 

Thunderstorms remain possible over the southern slope waters.

 

 

 

Thunderstorm Outlook for Tuesday

 

Regional Impacts

NB: Scattered thunderstorms possible

NS: Scattered thunderstorms possible

PEI: Scattered thunderstorms possible

NF&Lab: None

Marine waters: Isolated embedded thunderstorms remain possible over the southern edge of the slope waters.

 

Convective Discussion

 

A cold front will track across the Maritimes Tuesday and Tuesday night possibly triggering thunderstorms.

 

 

 

Convective Outlook Valid for Today and Tomorrow

 

Thunderstorm Outlook for Today

 

Regional Impacts

NB: Isolated thunderstorms over southern areas.

NS: Isolated thunderstorms possible over inland areas of central mainland NS.

PEI: None

NF&Lab: Isolated thunderstorms over southeastern Labrador.

Marine waters: Isolated embedded thunderstorms over marine areas south of Newfoundland.

 

Convective Discussion

 

Surface based convection is possible over central areas of mainland NS and parts of southern NB as afternoon temperatures rise into the mid to high 20s. However, CAPEs over both areas are quite low as the profile is forecast to be quite warm in the 500-700 mb layer. There is very little shear over these areas of potential convection as a weak upper trough moves over NS and NB. The 500 mb winds are forecast to be in 5 to 10 knot range over NS and 20 knots over NB. So any thunderstorm cells that do form will be short lived and vertical. The threat is locally heavy downpours.

 

An area of rain and potential embedded convection south of NS and NF today will persist today and tonight as the upper trough will persist south of NS and slowly weaken. Isolated thundershowers are possible. However, lightning activity hasn’t occurred recently.

 

Surface based convection is possible over southeastern Labrador. Although CAPEs are not expected to huge, there is a lot of shear (50 to 60 knots sfc to 500mb). Also the upper 250 mb jet is over the region and is about 100 knots.  Based on this scenario, severe conditions with gusty winds and hail can’t be ruled out if thunderstorms occur. The shear may be too strong for cells to organize and may be torn apart before they can form.  There have been a few lightning strikes to the west of this region this morning.

 

 

 

 

Thunderstorm Outlook for Sunday

 

Regional Impacts

NB: None

NS: None

PEI: None

NF&Lab: None

Marine waters: Isolated embedded thunderstorms over marine areas south of Atlantic Canada.

 

Convective Discussion

 

Thunderstorms are not expected over land areas of Atlantic Canada on Sunday. Although lifted indices are forecast to be in the -2 to -4 range over parts of NS and NB, the profiles are dry and there is a subsidence inversion near 700 mb. The inversion is a result of a weak upper ridge moving in from the west.

 

Elevated convection within a band of moderate to occasionally heavy rain south of Atlantic Canada remains possible as the upper trough persists offshore and gradually weakens. Lift in this area of rain is from about 850 mb.

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

NB: None

NS: None

PEI: None

NF&Lab: Isolated thunderstorms over western Labrador possible.

Marine waters: Isolated embedded thunderstorms over marine areas south of Nova Scotia.

 

Convective Discussion

 

Surface based convection is possible over western Labrador this afternoon. Maximum unstable CAPEs are around 900 J/kg. Shear is decent, at about 30 knots and is unidirectional from the SW. The 250 mb jet over Goose Bay at 12Z was 90 knots. However, the upper jet is positioned south and east of the area where initiation is most likely to occur. The threats of thunderstorms if they occur are heavy downpours and gusty winds. Warning criteria conditions are not expected.

 

Elevated convection within a band of moderate to occasionally heavy rain south of NS is possible. Lift in this area of rain is from about 850 mb. This area of rain and embedded convection is ahead of a slow-moving upper trough. Severe conditions are not expected.

 

 

Thunderstorm Outlook for Saturday

 

Regional Impacts

NB: None

NS: Isolated thunderstorms possible over inland areas of mainland NS.

PEI: None

NF&Lab: Isolated thunderstorms over southeastern Labrador and southeastern Newfoundland possible.

Marine waters: Isolated embedded thunderstorms over marine areas south of Newfoundland.

 

Convective Discussion

 

Surface based convection is possible over inland areas of mainland NS as afternoon temperatures rise into the mid to high 20s. However, CAPEs are quite low as the profile is forecast to be quite warm in the 500-700 mb layer. There is very little shear over this area of potential convection as the aforementioned upper trough moves over NS on Saturday. The 500 mb winds are forecast to be in 5 to 10 knot range. So any thunderstorm cells that do form will be short lived and vertical. The threat is locally heavy downpours.

 

The area of rain and embedded convection south of NS today is expected to shift eastward on Saturday as the upper trough moves eastward. Isolated thundershowers over southeastern Newfoundland are possible. Severe conditions are not expected.

 

Surface based convection is possible over southeastern Labrador. Although CAPEs are not expected to huge, there will be a lot of shear (50 knots sfc to 500mb). Also the upper level jet is forecast to move over the region. Based on this scenario, severe conditions with gusty winds and hail can’t be ruled out.

 

 

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

NB: None

NS: None

PEI: None

NF&Lab: None

Marine waters: Isolated thunderstorms developing tonight over southwestern waters, then spreading northeast.

 

Convective Discussion

The main features this morning are a 500mb upper low south of New England with a southeasterly upper jet ahead of it as indicated by Yarmouth and Shearwater soundings. At the surface, a frontal boundary extend from the back of the upper low, mid-Atlantic coast of the US, to southern Quebec, and then to Labrador. Several low pressure centres are analysed along the front, but the main centre appears to be just north of the Ottawa Valley where several clusters of lightning strikes are detected . Another area with lightning activity is over the Gulf Stream, southeast of Nantucket. Over time, a push of cold air aloft currently over James Bay will catch up with the frontal band over northern Quebec and Lab, while a new upper low emerges over the Maritimes. This new system will drive a swath of very moist air over all of the Atlantic provinces which will eventually connect with the advancing frontal boundary producing some heavy rain. Isolated thunderstorms will likely occur near the upper low, and along the front.

 

 

Thunderstorm Outlook for Friday

 

Isolated thunderstorms ahead of an upper low over CB and southwestern NF, and along a frontal system advancing over Labrador.

 

 

Convective Outlook Valid for Today, Tomorrow and Friday

Regional Impacts

NB: None

NS: None

PEI: None

NF: None

Labrador: Isolated thunderstorms possible over northwestern sections later today into this evening.

Marine waters: Isolated thunderstorms for Laurentian Fan and East Scotian Slope by later today into this evening.

 

Convective Discussion: Two areas of focus for convection today. The primary area of concern will be over northwestern Labrador where surface based convection initiating in north-central Quebec will move eastward towards a QS upper ridge positioned over central Labrador. Any convection will become elevated and more isolated as it moves towards this region, as upper level dynamics become less favourable. Nevertheless an isolated strike cannot be ruled out entirely with marginal MUCAPES of ~200 J/kg. The second area of convection will be located to the east of a cut-off low over the eastern slope waters. Here convection is expected to be elevated forced by decent instability  (MUCAPES ~500 J/Kg), and a strong LLJ (~30-35 kts at 850 mb). However it should be isolated in nature given that the best synoptic ascent will be located well to the SW (near the cut-off low). Over the next two days this area of concern is expected to gradually advect west-northwest, and convection should increase in frequency from isolated to scattered as PVA becomes more aligned with the area of instability and the LLJ. Continued moisture advection to the from the subtropics will cause PWATs to rise into the mid 40s by Thursday evening, so if elevated convection does manage to make it to land, rainfall rates will become a primary hazard.

 

Thunderstorm outlook for today:

 

 

Thunderstorm outlook for tonight:

 

 

Thunderstorm outlook for Thursday:

 

 

Thunderstorm outlook for Thursday night into Friday:

 

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

NB: None

NS: None

PEI: None

NF: None

Labrador: None, isolated thunderstorms possible over northwestern sections on Wednesday.

Marine waters: Isolated Thunderstorms over southwestern Grand Banks. Isolated thunderstorms for Laurentian Fan and East Scotian Slope by Wednesday evening into Thursday.

 

Convective Discussion: Upper trough in the process of being cut-off to the south of the Maritimes as heights rise in Labrador. To the east of this feature moist unstable profiles and a moderately strong 850 mb jet can support isolated elevated convection over the southwestern Grand Banks.

As this cut-off feature retrogrades to the southwest, the instability associated with this jet structure will gradually advect westward allowing for isolated convection over Laurentian fan and the East Scotia Slope on Wednesday night into Thursday respectively. On Wednesday afternoon northwestern most Labrador has profiles that support elevated instability on the order of 300-500 J/kg however a sufficient triggering mechanism may be lacking as a warm front remains well to the east over north-central Quebec. Regardless an isolated strike cannot be ruled out, especially if this feature advects eastward faster than advertised by our current guidance.  

 

Thunderstorm outlook for today:

 

 

Thunderstorm outlook for tonight:

 

Thunderstorm outlook for Wednesday:

 

 

Thunderstorm outlook for Wednesday Night and Thursday:

 

 

TEST

Thunderstorm Outlook for Day 1

 

Regional Impacts

 

Convective Discussion

 

Thunderstorm Outlook for Day 2

Atlantic Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today, June 20^th.

 

Regional Impacts

Isolated non-severe thundershowers are possible over the Gulf waters as well as offshore over Laurentian fan. These cells are expected to be embedded in showers being driven by the upper trof. Only a few lightning strikes are forecast in the risk areas.

 

Convective Discussion

The upper low is still the dominant weather forcing for today. Not much has changed since yesterday, other than sfc temperatures cooling further in NB. As a result, the atmosphere although saturated/moisture rich in the low levels is fairly stable. Shearwater this AM is moist yet stable up to 9,000ft. Much more of a springtime fog/drizzle airmass regime than a summer severe weather day. East of CYQY, there is even thermal ridging above 700 to prevent anything further. And, back to the west, the airmass is far too dry (across Maine).

 

 

Thunderstorm Outlook for Tomorrow, June 21^st.

 

Regional Impacts

No thunderstorms expected at this time.

 

Convective Discussion

Atmosphere continues to stabilize further as upper low fills. Forecast highs quite cool across Atlantic Canada for first day of summer.

 

 

HTTP://WEATHER.GC.CA

 

END/ASPC

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

Isolated non-severe thunderstorms

 

Regional Impacts

NB: None

NS: Towering Cumulus cloud over northern regions possibly giving a brief shower

PEI: Towering Cumulus cloud possibly giving a brief shower

NF: None

Marine waters: Isolated Thunderstorms over northern Gulf of St. Lawrence today, and south coast of NF tonight.

 

Convective Discussion

Current satellite imagery is showing an Upper / Surface Low pair over Maine / NB producing extensive cloud cover and occasional rain. At the surface, a warm front extends from the low northeastward to great northern peninsula of NF. The intersection of this feature with a strong southerly low-level jet will continue to support isolated non-severe thunderstorms over the northern Gulf of St. Lawrence. A strong southern flow of moist air prevails over NF ahead of the upper low feature and it is producing pockets of heavy rain along the west coast.

The strong southerly flow has been advecting very stable air in the mid-levels which is favoring a corridor of dry air over central NS this morning. The sounding at Shearwater has a very strong inversion at a height of 3-4 km which will likely limit the amount of vertical development of the cumulus cloud. In fact, a max temperature of 24 (and dew point of 10) only renders about 200 J/kg of MUCAPE, however topographic features such as the Cobequid Mountains could potentially provide the necessary lift for an isolated tall TCU/CB.

 

 

Thunderstorm Outlook for Monday

 

No thunderstorms expected

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

New Brunswick: Scattered thunderstorms with brief heavy downpours, Hail of 2 cm, and wind gusts to 80 km/h

Nova Scotia: Numerous Strong thunderstorms with Hail of 2 cm or more, heavy downpours and wind gusts to 90 km/h

PEI: Hail 1 cm or more, heavy downpours and wind gusts 70 km/h or more

Newfoundland: Chance of a thundershower late in the day and tonight in the southwest

Labrador: Turning much colder with brief heavy showers, no thunderstorms expected

 

Convective Discussion

An upper low over Maine will advance over the Maritimes today and remain in place on Sunday. A cold trough extends southeastward from the low and will be rotating over the region today.. this will be the focus for convective initiation. Strong surface heating over NS-PEI-Ern NB will further contribute in the destabilization of the environment, and modified soundings can easily push mixed layer cape values between 500-1000 J/kg with a temperature/dewpoint combination of 25/15. This very buoyant air mass will produce CB with tops to 7 or 8 km and max overshooting tops to 12 km especially over regions along the Northumberland Strait. The early morning soundings were also indicating deep layer shear strong enough to support multi-cellular clusters with some capable of producing damaging wet macrobursts. The main threat will be large Hail, torrential downpour and damaging winds.  

 

 

Thunderstorm Outlook for Sunday

 

Slight risk of a thunderstorm over eastern Maritimes.

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

New Brunswick: Hail 1 cm or more, heavy downpours and wind gusts 70 km/h or more today and Saturday

Nova Scotia: Hail 1 cm or more, heavy downpours and wind gusts 70 km/h or more Saturday

PEI: Hail 1 cm or more, heavy downpours and wind gusts 70 km/h or more Saturday

Newfoundland: Chance of a thundershower tonight in the southwest

Labrador: Chance of a thundershowers today and Saturday

 

Convective Discussion: A cold front will track across western New Brunswick this afternoon and eastern New Brunswick on Saturday. Falling heights ahead of an approaching vorticity max is occurring this afternoon. Lots of cloud around today which may limit the severe potential over western New Brunswick. Today over western New Brunswick, PWAT values of 30-35 mm, linear shear near 30 knots and Cape of 500-1000 J/kg are expected. The CAPE is very cloud dependent and so the severe weather potential all hinges on that.  On Saturday lots of sun is expected in the noted area which will likely produce small hail, downpours and gusty winds.  PWAT values of 30-35 mm, linear shear of 20-30 knots and Cape of 500-1000 J/kg are expected.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 1 Night

 

 

Thunderstorm Outlook for Day 2

 

 

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts: Today- primarily lightning in eastern Labrador and much of central Newfoundland with a secondary hazard of convective gusts to ~70 km/h in central Newfoundland. Lightning will be a hazard later this evening in western Labrador.

 

Tonight- Lightning for much of NB, with hail greater than 1 cm, heavy downpours and wind gusts greater than 70 km/h possible before noon in NW NB. Isolated lightning over western Labrador.

 

Tomorrow- scattered to isolated lightning for most of NB, PEI and NS. West to Northwest NB at greatest risk hail greater than 2cm, wind gusts ~90 km/h and heavy downpours. Much of western and central Labrador will again see lightning as a primary hazard.

 

Convective Discussion: Today weak vorticity advection in conjunction associated with a upper trough will yield the risk for lightning in eastern  Labrador and much of central Newfoundland. As a building upper ridge advects eastward lapse rates will become less favourable for eastern Labrador later in the day. Given the lower surface dew points,  profiles suggest storms that do develop over Newfoundland will be fairly high based, yielding the potential for gusty convective winds to ~70 km/h. The potential for small hail cannot be ruled out entirely with a relatively low hail growth zone, despite skinny CAPE profiles. Western Labrador will likely be subjected to some isolated storms that are currently ongoing in central Quebec as instability continues to build eastward with the upper ridge continuing to advect towards Newfoundland.  

 

Tonight a strong LLJ of ~35-40 kts will be the focal point for elevated convection for much of NB into western Labrador. Enough instability looks to remain in NW most NB for some surface based  convection to develop prior to the Friday noon hour. These storms will initially be able to work with MLCAPES of up 750 J/kg with strong linear shear profiles with bulk shears up to 40 kts ahead of an approaching cold front. This gives rise to the potential for severe weather rather early in the day on Friday, primary hazard appear to be marginally severe hail, strong gusty winds and heavier downpours given PWATs of ~30-35mm. Storm motion will be relatively quick at 30-40 kts, limiting excessive rainfall despite the high moisture being advected into the region.

 

Tomorrow elevated convection will continue to advect eastward with the progression of the strong LLJ, additional solar insolation should increase the amount of energy storms have to work with ahead of the cold front in western NB. Again linear shear profiles, with fast easterly storm motion gives rise for a wind hazard with gusts ~90-100 km/h. Severe hail with MLCAPES ~1000 J/Kg is also a possibility. Storm mode should primarily be linear, although there is a slight chance of a discrete supercells at the base of the cold front from central Maine to west-central NB. Here a non-zero tornado threat could exist if low level wind profiles end up being southeasterly rather than southerly. Right now confidence and probability is too low to note outside of this discussion.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

New Brunswick /Labrador: Slight risk in portions this afternoon and Thursday night.

Nova Scotia/PEI/Newfoundland: Nil.

 

Convective Discussion

 

Weak surface based convection is possible this afternoon but ML cape values near 300 J/kg and wind shear near 20 kts will limit any potential to just isolated showers and a risk of non-severe thundershowers.  A risk of embedded non-severe thunderstorms late Thursday evening ahead of an approaching trough.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

 

Regional Impacts: NS/NB and Labrador: Lightning, and downpours are the hazards of concern today.

 

Convective Discussion: up to 500  J/kg of MLCAPEs will yield isolated non-severe storms in western NS/NB where clearing is anticipated to occur. Bulk shears will initially be rather low but will increase to ~ 20 kts later this afternoon, however the thermodynamics will become less favourable later in the day as a TROWAL rotates in from the NE stabilizing the atmosphere. From a jet dynamic standpoint this region is also briefly in the left exit region of a 120kt jet max early this afternoon before it advect eastward over the western marine district.  Slightly greater instability of ~500-600 J/Kg MLCAPEs in the terrain in southern Labrador will also see some isolated pulse storms with low bulk shears and slow storm motion of ~10 kts or less.  Elevated convection giving lightning over the southeastern marine district will continue along the leading edge of the upper trough today.

 

Two areas of thunderstorms possible tomorrow, primarily in the terrain along the northwestern Labrador Quebec border, and in northern NB. In Northern NB inverted V-profiles could yield some gusty winds in TCU showers, but instability is marginal once mixed for a reasonable dew point and may not yield much in the way of lightning.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

A few near-severe thunderstorms are possible over parts of NB. Isolated non-severe thunderstorms for southern Maritimes and Labrador

 

Regional Impacts

NB: Northwest..Scattered thunderstorms developing upstream and migrating over the region with downpours likely, rainfall rates could result in amounts of 30 mm or more. Any longer lasting storms have the potential to produce small hail and wind gusts in excess of 70 km/h. Likelihood of thunderstorms is minimal over the northeast.

South NB, PEI, and NS.. rain spreading throughout with isolated embedded thunderstorms producing heavy downpours, rainfall amounts through Tuesday could exceed 50 mm locally.

Lab: Slight risk of a thunderstorms between Wabush and the power line towards Sept-Isles

 

Convective Discussion

The analysis this morning is showing a couple of interesting features, the first being a rather large cold pool associated with a 500mb low over Northwestern/central Quebec, and the second is a frontal disturbance currently east of Cape Cod and advancing towards the Maritimes. Widespread showers continue to spread across southern NB and northern NS. Radar is also detecting strong echoes in northern NB and the Lower St. Lawrence, however Lightning flashes have diminished since mid-morning but will likely increase once again this afternoon as the cold pool advances towards the St. Lawrence, Bands of Towering cumulus are currently forming over the Eastern Townships of Quebec and the Saguenay. In terms of dynamics for the afternoon, there is a departing cyclonic upper jet, advancing surface/upper trop with a moderate southerly flow ahead of it. In behind the trough there is a 30 westerly LLJ punching through the Highlands of Maine. The limiting factor for significant vertical development of convective cloud is the lack of strait sunshine, in fact Satellite is showing extensive cloud cover as far west as the Beauce, including Maine (north and south).  

The most likely scenario will be for surface convection initiation to occur over the Lower St. Lawrence, Beauce and Maine north woods.. and then migrate east of the provincial/international border during the middle to late part of the afternoon. As for the mode of convection, the deep layer shear values will also be limiting (< 30kt) but using a convective temperature of 22 / dewpoint of 14 would suggest MLCAPE of 500 J/kg  with CB tops above 10 km with a possibility of some isolated tops above 12km making some of the more persistent clusters near-severe. The main threat would be torrential downpours, but hail of up to 1cm and winds of 70km/h are also likely. We will defer until early afternoon before making a final decision on a severe thunderstorm watch.

The other area of concern is related to the frontal system, a large area of cold cloud top is currently advancing over the western marine district and there are at least three fairly active convective clusters embedded in that system. The steering flow aloft is south to southwest which could help in spreading heavier rain over NS.

Over NF an upper ridge will prevail today, as indicated by the dry conditions in both soundings from Stephenville and St. John’s. Satellite imagery shows open cellular Cumuliform cloud developing over Labrador and because of the diffluent flow aloft and the cold pool to the west - a few thunderstorms are likely. Goose Bay sounding is very dry in the low levels but if surface warming is maximised then there is a good possibility of strong wind gusts due to downdraft currents.

 

Thunderstorm Outlook for Tuesday

Slight risk of a thunderstorm over western NB, and also central and western Lab

 

Convective Outlook Valid for June 12th and June 13th, 2022

Thunderstorm Outlook for Day 1

Isolated tstorms producing local downpours today for New Brunswick and parts of coastal NS with slight risk of severe thunderstorms producing heavy downpours.

 

Regional Impacts

Risk of localised heavy downpours for New Brunswick and parts of coastal Nova Scotia.

Risk of non severe thundershowers for southern Newfoundland.

 

Convective Discussion

Isolated thunderstorms a possibility today across New Brunswick and parts of coastal Nova Scotia.  Generally conditions are unfavourable for severe t-storm formation.  The area is not dynamically in a favourable location, low level max winds are only around 20 kts, precipitable water is only around 25 mm, low level Td’s are around 12C and vertical motions look to be inhibited at around 500mb.  However, some coastal convergence along eastern NB and parts of NS could push parcels above the 500mb cap which could result in local heavy downpours especially since they will be slow moving or stationary.  Also, forecasts highs are around 26 degrees.  If actual highs go a few degrees warmer, then it may be enough thermodynamic lift to get past the 500 mb cap and produce some local heavy downpours. 

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

Isolated thundershowers producing locally heavy downpours.

 

Regional Impacts

Northern NB: isolated thundershowers

 

Convective Discussion

Isolated non-severe thunderstorms are possible across northern NB this afternoon and into this evening. There is some moisture in the lower levels as evident on the 12Z CAR TEP but the dynamics are very weak today, with not much of a trigger to speak of. The forcing from the surface to 500 mb is further upstream and won’t make it this far east today. Pulse cells could give locally heavy downpours but that’s about it. OTQZ a quiet day in store for the rest of the region.

 

 

Thunderstorm Outlook for Day 2

Isolated thundershowers producing locally heavy downpours, mainly across northern and eastern NB, the spine of NS and central NL.

 

 

Jeremy

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

Scattered Thunderstorms producing locally heavy downpours.

 

Regional Impacts

Central and Southern Labrador: scattered thunderstorms giving localised 25mm

 

Convective Discussion

Upper Low over the Quebec North Shore will slowly rotate north today. Mid-level instability northeast of the system continues to produce elevated CB/ACB’s . CLDN shows the persistence of these lightning strikes over the boundary between Quebec and Labrador. These storms should reach the Trans-Labrador Hwy this afternoon but the flash rate should dimininsh.

In NB, the cloud cover extends from the low to southern NB and therefore will be a limiting factor for the vertical development of convective cloud. Temperature of 20 / Dewpoint of 12 was enough to produce SBCAPE of about 300 J/kg but the airmass dries quickly in the mid-levels as indicated by the 12z CAR sounding.

 

 

 

Thunderstorm Outlook for Saturday

 

Slight risk of non-severe thunderstorms over parts of NB