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

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

Isolated non-severe thunderstorms are possible this afternoon along the Atlantic coast of NS

 

Regional Impacts

Some of these thunderstorms could produce brief heavy downpours especially along the South Shore of NS.

Elsewhere across the Atlantic provinces.. no thunderstorms expected.

 

Convective Discussion

This morning at 500mb, the Upper air analysis is showing an upper trough extending from NF to NS, and a ridge building over New England / Quebec where heights have increased by 3-6 dam since last evening. Clouds and showers lingering over parts of NS this morning are now beginning to dissipate. The sea breeze circulation is getting established west of Halifax and the intersection with the prevailing light northerly flow behind the trough will become the focus for any thunderstorm initiation this afternoon. A modified surface temperature of 19-20 is enough to trigger TCU/CB with tops just under 6.5 km. The is the presence of a strong westerly upper jet with the max core of 120kt east of Sable results in deep layer sheer of 50+ knots along the coast. Any storm that forms will not persist very long over one locality.

 

 

 

 

Thunderstorm Outlook for Tuesday

No thunderstorms expected

 

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Isolated severe thunderstorms are possible this afternoon over western and central New Brunswick.

 

Regional Impacts

Slow moving thunderstorms could produce downpours and some hail, and frequent lightning.

 

Convective Discussion

Satellite imagery is showing an upper cold low over Saguenay Lac St-Jean, and a thermal trough extending along the St. Lawrence valley ahead of the advancing cold pool over which currently sits over northern Quebec/Labrador. 500mb heights have dropped between 3-6 dam over the Maritimes since last evening and the air mass is quite unstable again this morning. For this afternoon, surface-based CAPE values in excess of 600 J/kg, and sufficient mid-level lapse rates will in some case be pushing cloud tops above the equilibrium level.. Over-shooting tops to about 10-12 km are likely with the more robust storms. Some of the guidance even suggest the possibility of hail growth to about 1cm. The winds aloft have diminished since last evening upper air soundings, any of these slow moving cells could produce high rainfall amounts in successive waves. The general storm motion will be eastward at about 20 km/h.

 

 

Thunderstorm Outlook for Monday

 

Risk of a thunderstorm along the south shore of NS.

Convective Outlook valid for Today, and Tomorrow

Thunderstorm Outlook for Today, JUNE 4^th.

 

A few non-severe thunderstorms are possible today in parts of New Brunswick.

 

 

Regional Impacts

Lightning will be the only expected hazard from any cells that develop.

 

Convective Discussion

A weak trough is pushing east this morning out of Quebec and the St Lawrence valley. Pwats are around 20mm today in NB and Maine, so a sub-warning rainfall amount of 15-20mm is forecast.

 

Thunderstorm Outlook for Day 2, JUNE 5^th.

 

Widespread non-severe thunderstorms are forecast over a similar region in New Brunswick. Some more organized cells may produce wind gusts to 70km/h and approach severe limits with upwards of 25mm of rainfall. A watch may be required on Sunday.

 

 

Regional Impacts

Gusts to 70km/h are possible in central NB, as well as rainfall amounts near 25mm. Lightning will also be a hazard.

 

Convective Discussion

ML CAPE values are near 1000J/kg and 500-700mb differences at 18C. 0-6km shear across central NB is also near 30-35kts, so severe single cell storms are possible. Storm motion is slow at 5-10kts, and to the East.