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.