Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

New Brunswick…Heavy downpours possible this afternoon and evening over eastern coastal regions.

Nova Scotia… Heavy downpours possible this afternoon and evening.

Prince Edward Island… An isolated thundershower is possible this afternoon.

Labrador… Heavy downpours possible this afternoon and evening over south/central sections.

Newfoundland…Heavy downpours are possible early this afternoon and evening over southeastern sections. An isolated thundershower is possible as well this afternoon over western sections.

 

Convective Discussion

 

A very warm and humid air mass continues over the Atlantic region today as a trough of low pressure over southern Quebec extending into New England slowly makes its way further east. A weak trough moved through overnight and is still providing some elevated convection this morning over the Gulf of St. Lawrence and eastern Maritime marine areas with heavy showers moving into the Burin Peninsula of Newfoundland. Stratus and fog over the Maritimes and western Newfoundland continues to clear this morning, making way for temperatures to rise into the low 30s for many areas this afternoon. There lacks a strong trigger as the main trough remains further west still, but some coastal convergence could provide enough lift for some single or multicellular storms to fire this afternoon. There is ample moisture with PWATs approaching 50 mm in Nova Scotia but shear remains weak and freezing levels are near 1500ft, therefore the main threat should be being lightning and heavy downpours, especially if any training occurs. Isolated thundershowers are also possible this afternoon over western Newfoundland given lift over the higher terrain, as well as in central/southern Labrador.

 

Thunderstorm Outlook for Day 1 – August 13, 2021

 

 

Thunderstorm Outlook for Day 2 – August 14, 2021

 

A sharper cold front will move into New Brunswick tomorrow afternoon. Ahead and along this front, storms are likely with the potential to be severe.

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

New Brunswick…Heavy downpours in thunderstorms, small hail late this afternoon.

Nova Scotia…Heavy downpours possible this afternoon.

PEI… Heavy downpours possible this afternoon.

Labrador…A chance of thunderstorms this afternoon.

 

Convective Discussion

 

Heavy Rain/downpours will be the story today and tomorrow as the moisture and instability are the main driving mechanisms. Overall the dynamics will remain rather weak… but due to the high moisture content , with precipatable water values near 50mm, even weaker updraft storms will produce decent rainfall amounts.  There is some early convection over southern New Brunswick but after that passes around noon convection may be suppressed until late this afternoon or early this evening. In general slow moving storms could produce locally 25mm but there is some potential for multicell clusters later today that could bring higher amounts and 2cm hail for central and northwestern New Brunswick.  We will be on the look out for local convergence over Nova Scotia along the spine which could cause some local enhancement, tomorrow this will almost definitely be the place to look.

 

The dynamics or shear is somewhat better over western Labrador today although the potential thunderstorms could be somewhat limited by convective inhibition at a multiple layers, however should stronger updrafts be present surface gusts will be more likely in the thunderstorms.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

 

Mel Lemmon

Convective Outlook for Today, and Tomorrow

Thunderstorm Outlook valid for Today – WED, Aug 11, 2021

 

Regional Impacts

Isolated severe thunderstorms are possible over western portions of Labrador today. Elsewhere, non-severe thunderstorms are possible, lasting into overnight hours for areas in NS.

 

Convective Discussion

An advancing long-wave trof will trigger thunderstorms in central and northern Quebec and into adjacent Atlantic regions. These storms will mainly be rainmakers. Shear is okay at 15-20Kts, and Pwats remain near 35-45mm. Convection into tomorrow morning across SW NS is likely to be more elevated in nature producing a lot of lightning.

 

 

 

Thunderstorm Outlook valid for Tomorrow – THURS, Aug 12, 2021

 

Regional Impacts

Isolated severe thunderstorms are possible in New Brunswick. Scattered non-severe thunderstorms are also forecast across many areas of the Maritimes.

 

Convective Discussion

An invading hot and humid tropical airmass is bringing with it a lot of potential energy. With dew points above 20C and sfc temps near 29C (or higher), large amounts of CAPE can be realized from the surface. It won’t take much as a trigger to get things going…..a shortwave impulse or even a sea breeze convergence line. There is ~25Kts  of 0-6k shear, and Pwats in the RDPS are near 55mm. Model suggested 500-700mb deltT is 19 in places tomorrow. This was realized across the Ohio valley and New York State yesterday afternoon.

 

 

Convective Outlook for Today, and Tomorrow

Thunderstorm Outlook for TODAY – Tuesday, Aug 10, 2021

 

Regional Impacts

Isolated severe thunderstorms are possible over northern NB this afternoon and into this evening.

 

Convective Discussion

The limiting factor today remains to be shear. The sfc moisture is present for good buoyancy, but any storm that develops will have minimal forward motion, and unable to slant its structure significantly. And so, the biggest hazard is heavy rainfall and a downburst gust of wind.

 

 

Thunderstorm Outlook for TOMORROW – Wednesday, Aug 11, 2021

 

Regional Impacts

Isolated severe thunderstorms are possible over western portions of Labrador. Elsewhere, non-severe thunderstorms are possible.

 

Convective Discussion

An advancing trof will trigger thunderstorms in Quebec and into adjacent Atlantic regions. Greatest hazard with these storms is heavy rainfall. Shear is slightly better at 10-20Kts, and Pwats remain near 35-45mm.

 

Convective Outlook for Today, and Tomorrow

Thunderstorm Outlook for TODAY – Monday, Aug 9, 2021

Regional Impacts

Isolated non-severe thundershowers are possible this afternoon and early evening over extreme NW New Brunswick.

 

Convective Discussion

A weak approaching boundary from Quebec may be enough to trigger just enough lift to excite a TCU or 2 this afternoon in the northern terrain. Only hazard with a cell if it can form would be lightning. With dew points of only 11, this airmass is not muggy enough to see any impactful rainfall.

 

 

 

Thunderstorm Outlook for TOMORROW – Tuesday, Aug 10, 2021

 

Regional Impacts

Isolated severe thunderstorms are possible across the northern tier of New Brunswick with heavy downpours and gusty winds being the main threats. Elsewhere, isolated non-severe cells may spark up if we get partial clearing of the cloud deck/fog/mist.

 

Convective Discussion

Shear depicted in the RDPS is enough to get multi-cell training storms, as well as profiles look elevated enough to cause gusty winds to near 90km/h. Heavy rain will be the biggest concern if a storm lacks forward motion (25-50mm/h). This thunderstorm risk will be re-assessed by the ASPC on Tues AM.