Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

 

Today

New Brunswick: Isolated to scattered severe thunderstorms possible giving torrential downpours (25 to 50 mm per hour rates), small hail and gusty winds in central to northern regions.

Labrador: Isolated non-severe thunderstorms possible in the afternoon giving heavy downpours and gusty winds.

 

Tonight

New Brunswick: Isolated non-severe thunderstorms giving locally heavy downpours and gusty winds.

 

Saturday

New Brunswick: Isolated severe thunderstorms possible giving locally heavy downpours and gusty winds.

Newfoundland and Labrador: Isolated non-severe thunderstorms possible giving locally heavy downpours.

 

Convective Discussion

 

An approaching trough from central Quebec combined with daytime heating will trigger convection into Labrador and New Brunswick this afternoon and evening. The air mass continues to be hot and humid (20-22C dewpoints this morning over New Brunswick and 19C into southwestern Labrador) and surface based CAPE values are expected to exceed 1500 J/kg in New Brunswick. There will be further destabilization in the upper levels as a 500 mb thermal ridge currently over the Maritimes tracks further east but there is only weak to moderate 0-6km shear of 20 to 30 kts. Therefore, there is the threat of slow moving severe pulse or multicell storms for central to northern New Brunswick with torrential downpours being the main threat with 25 to 50 mm per hour rates likely, although strong wind gusts and small hail are also possible. This could especially be a concern for areas of northwestern New Brunswick that received substantial rainfall from last week.

 

Early morning elevated thundershowers over Prince Edward Island and northern and eastern Nova Scotia may continue into early this afternoon. Upper level troughing over eastern Newfoundland will keep the environment cool and unstable but some elevated convection may persist in the waters east of Newfoundland.

 

For Saturday, the main threat of showers and thunderstorms will be over New Brunswick under a hot and humid air mass and central Labrador as the trough slowly progresses eastward. Isolated convection under an upper trough in central Newfoundland is also possible.  

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Saturday

 

Forecaster: McArthur

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

 

Today

Labrador: Isolated thunderstorms possible giving locally heavy downpours and gusty winds.

New Brunswick: Isolated thunderstorms possible giving locally heavy downpours.

 

Tonight

None.

 

Friday

Labrador: Isolated thunderstorms possible in the afternoon giving heavy downpours and gusty winds.

New Brunswick: Isolated severe thunderstorms possible giving locally heavy downpours, small hail and gusty winds.

 

Convective Discussion

 

A slow moving upper low will remain over Newfoundland today, while an approaching trough moves eastward into western Labrador this afternoon. There may be some remnant early afternoon convection under the upper low over the Avalon Peninsula and marine areas east of Newfoundland. Dynamics are more favourable over western Labrador with the approach on a trough in central Quebec giving diffluence aloft and a weak 500 mb thermal trough.  With a fairly decent temperature and dew point spread, there is the threat of convective gusts.

 

Over the Maritimes, a weak ridge of high pressure and increased warming in the mid to upper levels should cap any convection. However, convective temperatures are expected to be reached over northern Maine and western New Brunswick. With only weak to moderate wind shear over the area, there should not be much organization of cells that develop. Therefore, locally heavy downpours are the main threat with these. There is an incoming 700mb thermal ridge which should prevent convection in Nova Scotia, but some inland TCUs may develop in the sea breeze in western Nova Scotia and give some locally heavy downpours.

 

For Friday, a approaching trough from Quebec will trigger convection into Labrador and New Brunswick. With an increasingly hot and humid flow, surface based CAPE values are reaching over 1500 J/kg in New Brunswick but 0-6km shear appears to remain weak to moderate. There is the threat of severe pulse storm are possible for northwestern New Brunswick with heavy downpours being the main threat but strong wind gusts and small hail are also possible.  Some inland showers may develop again in the sea breeze in Nova Scotia.

 

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Friday

 

Forecaster: McArthur

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Today

NS and NB: Isolated severe thunderstorms possible producing torrential downpours, small hail and gusty winds.

 

Tonight

NL: Isolated thunderstorms possible giving torrential downpours.

 

Thursday

LAB: Isolated thunderstorms possible in the afternoon giving heavy downpours and gusty winds.

 

Convective Discussion

There is a risk for severe thunderstorms across a good portion of the MRTMs today as an upper trough of low pressure slowly pushes across the region. There is a leftover area of convection currently over southern NB and NS that will perhaps inhibit convection for a brief period of time, but skies are now clearing over northern NB which will allow us to reach the convective temperature before noon. Tephi analysis does show some good CAPE up to 1000 J/KG, but the shear is relatively low (roughly 25 knots of so from the surface to 500 mb). The Pwat is high (41 out of YQI and 43 at YAW). The main concern with the cells today would be their slow motion giving torrential rainfall over a fairly short period of time. Small hail and locally strong winds are also possible in the stronger storms.

 

The short wave through that brought some early morning convection to central NB and south of NS will be over a portion of NL tonight and Thursday morning, so there is a risk for isolated embedded thundershowers.

 

Lastly an approaching upper trough of low pressure will give the risk for afternoon and evening thunderstorms across western LAB on Thursday.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for tonight

 

Thunderstorm Outlook for Thursday

 

 

Jeremy

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Today:

NL: Isolated embedded thundershowers possible today giving locally heavy rainfall.

NB: Isolated thunderstorms this afternoon and evening giving some wind gusts, small hail and locally heavy rainfall.

 

Tonight:

NS: Isolated thundershowers possible overnight tonight and into Wednesday morning giving locally heavy rainfall.

 

Wednesday:

NS/NB/PEI: Scattered thunderstorms expected in the afternoon giving strong wind gusts, small hail and locally heavy rainfall.

 

Convective Discussion

 

A slow moving frontal trough of low pressure will give the risk of an elevated embedded thundershower to most of NL today. In NB, skies are clearing across the western part of the province which will allow for TCUs to develop with isolated to scattered thunderstorms expected this afternoon. 12Z KCAR tephi shows basically no wind shear (less than 20 knots), but adjusting the surface temp and Td a little gives some MLCAPE of 750 j/kg or so. Pwat is in the 30-35 range or so. Locally torrential downpours, gusty winds and small hail are possible in the stronger cells. Severe storms do not appear likely but will have to keep an eye on rainfall rates through the course of the day.

 

A weak short wave trough currently upstream over southwestern New England will cross NS tonight and Wednesday morning giving the risk for some thundershowers mainly across the southwestern mainland.

 

On Wednesday scattered thunderstorms are likely across most of the MRTMs in the vicinity of an upper trough of low pressure.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for tonight and Wednesday morning

 

Thunderstorm Outlook for Wednesday afternoon

 

Jeremy

Convective Outlook Valid for Today and Tomorrow empty test

Regional Impacts

 

Convective Discussion

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow