Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1 - Saturday

 

Regional Impacts

There is a slight risk of non-severe thunderstorms for northeastern NB, northern PEI, Iles-de-la-Madeleine, and northern Cape Breton.

Isolated thunderstorms are likely over central NF and southeastern Lab.

 

Convective Discussion

Extensive cloud cover over southern Labrador and much of the Gulf of St. Lawrence due to the presence of a mature surface low pressure system near Blanc Sablon. A couple of cold fronts trailing behind could provide enough lift for convective cloud growth over the Atlantic provinces. For the Maritimes, the convective temperature for this afternoon is about 22 degrees which might be reached in areas of eastern NB where solar insolation will be greater. T/Td of 22/10 will yield CAPE values slightly above 200 J/kg. Similar conditions are expected over central NF with the advancing airmass. While the surface temperature required for initiation is similar, the moisture content of the airmass is higher over NF – this will contribute to somewhat higher energy from the surface and mixed-layer CAPE above 300 J/kg. Brief heavier showers is the main threat.

 

 

Thunderstorm Outlook for Day 2 – Sunday

 

Some lingering daytime instability over parts of NF giving a slight risk of thunderstorm.

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Regional Impacts

Isolated thunderstorms with heavier showers throughout NS, PEI, and Les Iles-de-la-Madeleine this afternoon and this evening. This activity will continue into the night for areas adjacent to the Gulf of St. Lawrence.

 

Some daytime convection might develop over southern Lab during the afternoon – an isolated/non-severe thunderstorm.

 

There is a slight chance of a thunderstorm along with brief heavier showers over southern areas of NF tonight.

 

Convective Discussion

Frontal wave at the surface approaching Yarmouth county at 12z. The associated low will travel northeasterward and reach the Northern Peninsula of NF Saturday. The airmass around this system is fairly moist with overcast layers of cloud extending from the low levels to 7-8 km, and embedded CB’s to about 9 km. Precipitable water from the area soundings are showing values of 30-25mm. Deterministic models are suggesting synoptic rainfall of 15 to 30 mm over the region, with the EU is hinting at areas of 40-50mm. Rainfall rates of 10mm/hr reported along the Atlantic coast west of Halifax this morning would support the idea of locally higher amounts.

 

 

 

Thunderstorm Outlook for Day 2 – Saturday

 

Late day thunderstorms with heavy showers are possible especially for areas adjacent to the Gulf of St. Lawrence.

 

ATL Thunderstorm Outlook for Today and Tomorrow

Convective Outlook for Today – THURS July 29^th

 

Regional Impacts

Non-severe thundershowers are possible over offshore waters from a frontal passage. Isolated, non-severe thundershowers are also possible over eastern Labrador.

 

Convective Discussion

The main forcing for today’s weather is a sweeping trough that is well east of the Maritimes. The rest of the region is dominated by a ridge of high pressure and strongly capped at 700mb. Nova Scotia in particular is quite dry at the surface. If a cell does manage to bubble up in Labrador, it will be short lived and single cell pulse in nature.

 

 

Convective Outlook for Tomorrow – FRI July 30^th

 

Regional Impacts

Embedded non-severe thunderstorms are possible in parts of the Maritimes with a developing low pressure system. Heavy synoptic rain is the main hazard, in New Brunswick.

 

Convective Discussion

The limiting factor for any storms to develop will simply be the battle with cloud cover. If the low does not have clear slots to facilitate daytime heating, it will be difficult to create strong lift and cloud tops cold enough to cause any lightning. Nevertheless, a rainy/windy day in store for many parts of Atlantic Canada.

 

 

Convective Outlook for Day 3 – SAT July 31^st

 

Regional Impacts

The start of the long weekend does not look to be very stormy in regards to thunderstorms. No deep shear or strong CAPE is being resolved by the models at this time. No forcing of concern is expected on Saturday specifically.

 

Convective Discussion

There does not appear to be a signal for severe convective weather for PEI at this time. Check future forecasts from Environment Canada for updates.

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Scattered thundershowers are expected across portions of NL today. Some embedded TSRA possible for the far eastern Avalon associated with the frontal trough. Some surface-based cells are likely this afternoon and evening for central regions of the island if given enough solar insolation. An isolated TSRA is also possible for SERN LAB.

 

Convective Discussion

There is a chance for an isolated strong storm or 2 for central regions of Newfoundland today giving torrential downpours and gusty winds (to about 70 km/h). PWATs are in the low to mid 30’s and shear is decent at about 40 knots or so. The instability is modest at best, but CAPE of about 500 j/kg or so is possible once the sun breaks through the clouds. The likelihood of any cell becoming severe is really low.

 

Thunderstorm Outlook for Day 1

 

Jeremy

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

There is a risk of isolated severe thunderstorms for across extreme SE NB, PEI and a good chunk of NS today giving strong winds, torrential rainfall and small hail. There will also be scattered thundershowers/storms for SE LAB and NL giving heavy downpours and gusty winds.

 

Convective Discussion

There will not be a lot of time to delve into the gory details in this section today due to the current strong storms and watches in place for those resulting in an obvious time contraint. Long story short: The CAPE is high (in excess of 1000 j/kg), shear up around 40 knots, PWAT 30-40 mm, a fairly active surface trough (with history to boot for strong storms) and a moist, unstable atmosphere. Given the fact strong storms developed overnight and into this morning shows the already good dynamics at play…and add the thermodynamics could exasperate things. Currently watches are in effect for Kent County and Moncton and Southeast New Brunswick County, as well as Cumberland County-Minas Shore and Cumberland County North and Cobequid Pass of Nova Scotia. Watches will be extended further to the south and east across NS in the next half an hour or so.

 

Thunderstorm Outlook for July 27^th, 2021

 

Thunderstorm Outlook for July 28^th, 2021

 

Jeremy