Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1 – July 25^th, 2021

 

Regional Impacts

 

None during the day. Showers are moving into western New Brunswick early this afternoon. There is a slight risk for a thundershower this evening over northwestern New Brunswick and western Nova Scotia early Monday morning.

 

Convective Discussion

 

A trough over central Quebec extending southward into New England will progress eastward today while a ridge of high pressure lies over Newfoundland and Labrador today. Showers associated with the warm front will move into western New Brunswick this afternoon. Upper dynamics remain west of the Maritimes today. However, behind this area of showers, there is the possibility of convection in the warm air mass this afternoon over southern Quebec and Maine. A weak low-level jet over Maine may help to maintain convection into northwestern New Brunswick this evening. Some elevated convection is also possible overnight over the Maritimes western marine district.

 

 

 

 

Thunderstorm Outlook for Day 2 – July 26^th, 2021

 

As the warm front pushes through overnight into Monday morning, moisture is expected to increase in the warm sector. A short-wave trough is expected to track over Maine and into New Brunswick on Monday. With increasing instability and 0-6km shear near 35KT over southern New Brunswick and parts central/northern Nova Scotia, there is the possibility storms to develops with strong wind gusts along with localized heavy rain.

 

 

 

 

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1- July 24^th, 2021

 

Regional Impacts

 

New Brunswick…Isolated thundershowers are possible this afternoon with locally heavy showers and small hail.

 

Convective Discussion

 

A slow moving low pressure system over Newfoundland will slowly drift eastward today while a ridge of high pressure builds into the western Maritimes. There is little in the way of dynamics today, but with solar insolation along with some coastal convergence and cooler air aloft, there may be enough instability to kick up some isolated showers with the risk of a thundershower this afternoon mainly over eastern New Brunswick today. PWAT of 20-25 mm with freezing levels around 9500ft mean that some brief heavy downpours and very small hail are possible.

 

There will also be some showers and Newfoundland and isolated showers in Nova Scotia today.

 

 

Thunderstorm Outlook for Day 2- July 25^th, 2021

 

No thunderstorms are expected during the day tomorrow. A trough will be approaching from the west Sunday night and there is the possibility of overnight convection into the early morning hours on Monday.

Convective Outlook Valid for Today

Thunderstorm Outlook for Today

 

Regional Impacts

Scattered thunderstorms today across the Maritime provinces.  Locally heavy showers, small hail and gusty winds are likely.

 

Convective Discussion

There is very little shear but cape values of 500-1000 J/kg are expected. This will lead to short lived pulse storms giving brief downpours (PWAT 20-25 mm), small hail (freezing levels near 8000 feet) and gusty winds. 

 

Convective Outlook Valid for Today

Thunderstorm Outlook for Today

 

Regional Impacts

Isolated thunderstorms today over NB and western Labrador. Over eastern NS and southwestern NFLD, locally heavy showers are possible.  20 mm/hr or more is not out of the question.

 

Convective Discussion

A favourable left exit of a jet over weak surface troughing supported heavy rain over portions of Nova Scotia and PEI this morning. 25 mm or more in an hour was reported in the Bridgewater area. The embedded line of convection has moved east and watches are in place in areas of most concern this afternoon. The PWAT values of 35-40 mm persist in this area and that is the same airmass that gave flooding to areas of King County Nova Scotia yesterday. Southwestern Newfoundland will need to be monitored for potential significant rainfall this afternoon. Over NB and western Labrador, surface heating this afternoon will give isolated thundershowers and low freezing levels which will support small hail formation. Cape values of less than 500 J/kg and shear less than 20 knots are expected in these areas.

 

Convective Outlook Valid for Today

Thunderstorm Outlook for Today

 

Regional Impacts

Isolated thunderstorms today over NS and southern NB with locally heavy showers possible.  20 mm or more is not out of the question.

 

Convective Discussion

Dynamics are not great today for severe thunderstorms, however the risk is still there but likely low.  There is not much support in the upper level dynamics with no significant jet stream over the area and a lot of moisture at 700 mb.  A lot of cloud over most of the area will inhibit solar insolation.  Wind shear values between 20 to 30 kts will likely not be enough to help maintain long lived cells.  However, there is a lot of low level moisture over the area and a marginally unstable atmosphere (500 J/kg ) associated with a broad and nearly stationary trough over the region. Any storms have a low chance of becoming severe however they could still bring quite significant rain due to the abundance of moisture (PWAT near 35 mm) and the fact that the cells will likely be slow moving.