Convective Outlook Valid for July 20th and July 21st

Thunderstorm Outlook for Day 1 – July 20^th, 2021

 

Regional Impacts

Scattered thunderstorms today over NFLD, PEI, NS and southeastern NB with locally heavy showers possible especially over southeastern NB.  10 to 20 mm but higher 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 the 700.  A lot of smoke and cloud over the area will inhibit solar insolation.  Wind shear values of 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 marginally unstable atmosphere ahead of a trough currently located over NB.  This trough will track southeastward through the day and will likely kick off some tstorms.  These storms have a low chance of becoming severe due to all the inhibiting ingredients mentioned above, however they could still bring down quite a bit of rain due to the abundance of moisture and the fact that the cells will likely be slow moving.  10 to 20 mm expected with higher possible.

 

 

 

 

 

Thunderstorm Outlook for Day 2 – July 21^st, 2021

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1- July 19^th, 2021

 

 

Regional Impacts

 

Nova Scotia and Prince Edward Island…Isolated risk today and this evening. Locally heavy downpours and gusty winds are possible.

 

New Brunswick…Isolated risk mainly for central regions with heavy downpours possible today and this evening.

 

Labrador…Isolated risk for southern regions near this afternoon and evening.

 

Maritime waters…Isolated thunderstorms continue today and overnight, possibly reaching southern Newfoundland early tomorrow morning.

 

Convective Discussion

 

A surface trough lies to the west extending from southern Labrador toward southern Quebec and into the New England. The main threat of organized convection remains closer to the trough north of the St. Lawrence River and extended northeast towards extreme southern Labrador today where heavy downpours and small hail is possible. The Maritimes remain in a moist southwesterly flow today ahead of this trough. Precipitation moved through the region yesterday evening and is now moving into southern Newfoundland today. Isolated thundershowers continue this morning south of Nova Scotia and may make their way inland along the Atlantic coast of Nova Scotia today bringing heavy downpours. Although most of the Maritimes remains cloudy this morning, some scattering of the cloud mainly over the Annapolis Valley and northern Nova Scotia could help the area reach their convective temperature. Dew points this morning are near 20C. There is also the aid of an 850mb low-level jet, weak 0-6km shear of near 20 kts, some cooling in the upper levels, and precipitable water values near 40 mm. Thunderstorms should be short-lived but would likely produce heavy downpours that will drift to the northeast into eastern Prince Edward Island or western Cape Breton this evening.

 

 

Thunderstorm Outlook for Day 2- July 20^th, 2021

 

This trough today will continue to slide further east tomorrow. Some enhanced risk is possible over much of New Brunswick, Nova Scotia and Prince Edward Island.

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Labrador… Today isolated non-severe thunderstorms possible. Tomorrow an increased potential for more intense thunderstorms with

gusty winds.

 

Nova Scotia… Today a chance of thunderstorms with locally heavy amounts for southwest areas late this afternoon and this evening. Tomorrow an enhanced chance of thunderstorms with locally heavy downpours and gusty  winds expected.

 

New Brunswick and PEI… Tomorrow a chance of thunderstorms with locally heavy downpours.

 

Convective Discussion

 

Overall moisture will remain high for the next couple days in a general southwest flow over the region. Surface troughing will act to enhance the chance of thunderstorms tomorrow for most of the Atlantic region. Moderate wind shear will remain as well over Nova Scotia and Labrador giving a slightly higher chance of organised convection tomorrow.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

For today limited impacts are expected with only a chance of embedded thunderstorms possible in highlighted areas.

 

For tomorrow embedded thunderstorms in a broader area of precipitation could produce locally heavy downpours across southwest Nova Scotia.

 

Convective Discussion

 

Overall today should not be overly active with a weak surface ridge building. Most of the enhanced convection is expected to remain south of the region but some remnant convection could persist over Newfoundland chance should pass though fairly early today.

 

For tomorrow surface convergence and very high precipitable water (PWAT) contents over 50mm for some areas could lead to potentially heavy downpours across western Nova Scotia.

 

Thunderstorm Outlook for Day 1

 

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

A cold front will sweep through New Brunswick this afternoon, with a fair chance for severe weather.

 

Regional Impacts

 

New Brunswick and parts of Western Nova Scotia: heavy rain, high winds, and possible hail. For the rest of the Maritimes, local heavy rain and some gusty winds.

Labrador: local heavy rain and gusty winds.

Newfoundland: nothing significant.

 

Convective Discussion

 

A deep low over western Labrador with a surface manifestation north of Gaspe has a cold front extending southwest, roughly along the St. Lawrence River. Shear near and ahead of the front is healthy at about 40-50 diminishing to 24 kts in the south of NB and NS. There is a corridor of moisture ahead of the front being advected ENE, with surface dew points near 20 C and PWATs near 30-50 mm. Finally, there’s some clearing of low level clouds out ahead, mainly southern Maine, southern New Brunswick,  and PEI and Nova Scotia. There’s little evidence for strong SRH, so straight line winds and bow echoes should be mainly the order of the day. With the PWATs higher rainfall amounts are likely, especially id there is some training. Surface CAPEs in excess of 1000 and possibly 2000 J/kg are possible, and despite freezing levels of 14,000 feet, hail is also possible with isolated supercells. Conditions should decrease late this afternoon into this evening as the main action moves into Nova scotia.

 

 

 

Thunderstorm Outlook for Day 2

 

The remnant of the system with give a chance of local heavy showers and gusty winds.