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.