Convective Outlook for Today, and Tomorrow

Thunderstorm Outlook valid for Today – Sept 6^th, 2021.

 

Regional Impacts

Heavy rainfall and moderate winds are possible if discrete severe cells develop in NW areas of New Brunswick this afternoon. Risk of isolated non-severe thundershowers across rest of province and PEI.

 

Convective Discussion

With Pwats near 45mm in places, the greatest hazard today is heavy rain. As a large long wave trough sweeps through the region from ONT/QUE late this afternoon and evening, thunderstorms could be triggered in this unstable airmass. Mixed CAPE values are 500-1000J/kg, with 0-6k shear of near 40kTs. Storms are not expected to be widespread at this time as the timing will be slightly out of phase with the main LLJ. They are also not expected (at this issue time) to be more than marginally severe on the Canadian side of the border due to rainfall >25mm/hr, and possible gusts of 60km/h.

 

 

Thunderstorm Outlook valid for Tomorrow – Sept 7^th, 2021.

 

Regional Impacts

Non-severe embedded thundershowers forecast for many areas near the centre of the upper low.

 

Convective Discussion

This weather feature brings with it fall-like characteristics. The cool upper low aloft will be able to trigger a few lightning strikes within a general showery weather pattern. This is the last convective outlook issued by the ASPC Summer Severe Weather Support Desk for 2021.

 

 

Forecaster: TIRONE

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

No thunderstorm expected.

 

Convective Discussion

500 mb ridge over the Maritimes at 12z this morning will be east of NF Monday. Mid and High cloud spilling over the ridge today with shower activity west of the region spilling into the forecast districts tonight, precipitable water increases to 30+mm and steady rain spreads over parts of the Maritimes. There is a slight risk of an elevated thunderstorm after midnight over NW NB as the airmass moisture increases, and cloud top cooling enhances embedded TCU/ACC’s.  

 

 

Thunderstorm Outlook for Monday

Showers will linger Monday morning with perhaps the risk of a thunderstorm early in the morning. Surface-based convection will develop over Maine during the afternoon but the airmass will likely remain capped over NB, with the expected of westernmost areas which could destabilize late in the day. The approach of a vigorous shortwave from the Great Lakes, a surface cold front, and daytime heating will all contribute to this next bout of convection. Upper Jet, MLCAPE 500+ J/kg, strong shear, lower freezing levels – all point to enhanced convective conditions late on Labour Day.  

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Slight risk of a non-severe thunderstorm over the Gulf of St. Lawrence and southwest NF.

 

Convective Discussion

500 mb cold low east of Gaspe will slowly move northeast today. Under mainly cloudy conditions widespread showers are expected, and later today there may be just enough instability to produce a weak thunderstorm under the cold pool.

High pressure system will build over the Atlantic provinces Sunday.

 

Thunderstorm Outlook for today

 

Thunderstorm Outlook for Sunday

 

No thunderstorms expected

 

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Nova Scotia/New Brunswick/PEI/Newfoundland:  A risk of embedded thundershowers from the tropical moisture left over from Ida. Heavy downpours giving 30 mm in an hour are possible today and tonight.

Labrador: Nil.

 

Convective Discussion

 

A risk of embedded thundershowers as the remnants of Ida move across the region. PWAT values are near 50 mm so rainfall is a concern but we have rainfall warnings out for a broad area of Atlantic Canada. Heavy downpours giving 30 mm in an hour are possible today.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Newfoundland:  Isolated thundershowers this afternoon and evening.  Potential severe thundershowers giving downpours, gusty winds and hail in the southwest early this afternoon.

Nova Scotia: Slight risk over Cape Breton

New Brunswick/PEI/Labrador: Nil.

 

Convective Discussion

 

A weak low pressure system will approach western Newfoundland this afternoon. ML cape values near 500 J/kg are expected and wind shear near 25 kts.  This morning, convection developed over the Gulf of St. Lawrence near the Magdalen Island and then advected eastward. The earlier convection was mainly driven by upper level dynamics which weaken somewhat this afternoon as the jet slips south of Newfoundland.  Dry mid layers will allow for gusty conditions. PWAT values will be near 25 mm so rainfall is a concern. Just a risk of embedded non-severe thunderstorms over the Maritimes on Thursday.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2