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.

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

A frontal trough with an associated vort max from WV near Yarmouth maintained a line of thunderstorms this morning, with pcpn amounts up to 30 mm observed. This feature will continue into the afternoon for Nova Scotia with gradual weakening. There may be some thundershowers later this afternoon in northwestern New Brunswick. Nothing significant is expected for Labrador nor Newfoundland.

 

Regional Impacts

Maritimes: Local heavy showers ending later today for Nova Scotia and possibly for northwestern New Brunswick, who might also see some gusty winds.

Newfoundland and Labrador: nothing significant. A strike ot two south of forecasts areas are possible.

 

Convective Discussion:

For Newfoundland and Labrador there are significant inversions, preventing any significant convection in their forecast areas.

 

There is currently a deep ridge over eastern Newfoundland and a deep low slanting down from 250 mb over Hudson Bay to near Ungava Bay at the surface.  There is also a trough over the Gulf with a couple of vort maxes, with the one near Yarmouth this morning giving some extra support for convection. Things should weaken a bit this afternoon along the trough. For New Brunswick there’s some moisture and low stratus trapped under an inversion that should erode with daytime heating this afternoon, especially in the northwest, where the shear should reach or exceed 30 kts. PWATs are healthy and around 30 mm. Impacts there are local heavy downpours and gusty winds.

 

 

 

Thunderstorm Outlook for Day 2

On Friday a deep trough extending southwest to the Great Lakes will move into our region with a healthy jet and a fair amount of moisture. Unadjusted ML CAPEs are near 500 J/kg, and with some extra heating things could get interesting.