Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Western Labrador: risk of afternoon and evening thundershowers.

Northern New Brunswick: Risk of afternoon and evening thundershowers.

 

Convective Discussion

Isolated thundershowers are expected to form over western Labrador this afternoon in association with a trough of low pressure moving into the region from Quebec. La Grande tephi shows decent shear but somewhat of a cap in the mid-upper levels. PWAT is around 36 mm. Expected non-severe cells to develop with locally heavy rainfall and gusty winds.

 

There is also the risk of a thundershower this afternoon and evening across northern New Brunswick. KCAR tephi shows 500+ CAPE but very little shear. There is also the lack of a trigger so if cells do develop they will be slow moving. PWAT is around 35 mm so heavy downpours would be the main concern. Looking at both the YQI and YAW soundings it will be quite difficult to generate CBs in NS. However local areas of convergence could generate an isolated cell.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Regional Impacts

New Brunswick and Prince Edward Island: Slow moving non-severe thunderstorms developing this afternoon, with local heavy downpours and gusty winds. Near the Bay of Chaleur a slight chance for severe wind gusts, and a possibility of 2 cm hail this afternoon.

Labrador: continuing non-severe thunderstorms, tapering off this evening, with local heavy downpours and gusty winds.

 

Convective Discussion

A deep upper low over the northern Labrador Sea has two associated troughs, on extending from the low southwest to southwest of  Labrador, with some associated PVA. And a second roughly north-south trough over the eastern Gulf of St. Lawrence, again with some PVA. For the second trough there is a deep inversion, inhibiting significant convection for Newfoundland.  For Labrador the profiles are good for CAPE maxing between 500-1000 J/kg this afternoon, and reasonable PWAT possibly exceeding 25 mm, but with shear on the low side around 15-25 kts. While freezing levels are near 9500 ft at Goose Bay, the low shear argues against a separation of updraft and downdraft, possibly inhibiting hail growth. The main impacts should be heavy downpours and some brief strong gusty winds.

 

For most of New Brunswick there will be airmass convection, with decent moisture (PWAT near 30 mm and surface dewpoints in the 17-20 C range and some low level strauts burning off), good insolation after the cloud clears, shear in the 25-35 kt range, and surface based CAPEs possibly nearing 1000 J/kg this afternoon. Freezing levels in the south are too high for hail at about 15,000 ft, but in the north they are about 11,500 ft, which given the CAPE and the shear, gives a possibility for hail. In the Bay of Chaleur a weak jet and PVA may enhance conditions enough for near severe gusty winds, and a slight chance for 2 cm hail.

 

 

 

Thunderstorm Outlook for Day 2

 

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

New Brunswick: mainly non-severe thundershowers this afternoon into this evening for most of the province. In the northwest marginal severe thundershowers with the highest threat for gusty winds and local heavy downpours.

Nova Scotia: non-severe thundershowers this into this evening and overnight for most of the province.

Labrador: non-severe thundershowers this afternoon into this evening, with a second batch possible overnight.

 

 

Convective Discussion

 

There is currently a deep upper ridge east of Labrador with a trough just west of it over Labrador. This will move east this afternoon into this evening, just west of the trough there will be a jet approaching  with the left exit region over northwestern New Brunswick by this evening. Finally there is a surface frontal  trough moving in from the northwest this afternoon and then moving across Nova Scotia tonight.  There’s also weak destabilisation aloft between a thermal ridge over Labrador and a weak thermal trough east of James Bay. We have some good insolation this afternoon and ample low level moisture, with 850 dew points 12-14 C, surface dew points in the 16-20 C range and PWAT in the 30-40+ mm range being maintained by a southwesterly flow. The shear is fairly low, around 20-25 kts currently.  

 

So mainly multi-cells getting organised eventually along the approaching frontal trough, some heavy downpours with gusty winds likely, and a low chance of hail with freezing levels in the 12,000 ft range. The chance for severe wind gusts may be enhance if a squall line or derecho forms this evening. The trough will also probably keep convection going well into the evening.

 

Thunderstorm outlook for day 1

 

 

 

 

Thunderstorm Outlook for Day 2

 

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Isolated non-severe thunderstorms may develop over eastern parts of Labrador.

 

Convective Discussion

 

For the most part today looks fairly quiet as an upper ridge progresses slowly eastward towards the region today. This building ridge will suppress most deep convection today with most of the thunderstorm activity remaining over Ontario and Quebec. A weak surface tough along with most unstable cape values 500-1000 j/kg could be sufficient to trigger some isolated thunderstorms over eastern Labrador this afternoon however no severe storms are expected.

 

For tomorrow we will begin to see the breakdown of the upper ridge, this along with increasing low level moisture could help trigger thunderstorms over western New Brunswick and western Labrador tomorrow afternoon.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Isolated non-severe thunderstorms over central and eastern NB to the Bay of Fundy, Annapolis Valley and northwestern NS, also southeastern Labrador.

 

Convective Discussion

This morning an upper trough extends over the Gulf of St. Lawrence and eastern portions of the Maritimes, with extensive cloud&rain detected on Sat and Rad. A northerly jet streak and some other upper support will maintain unstable conditions and trigger the development of isolated thunderstorms just behind the trough. Further to the west, conditions will generally begin to dry out as a ridge continues to build over Ontario and western Quebec – this is a prelude to the arrival of the next warm airmass.

Another area for potential thunderstorm development is over southeastern Labrador where a surface trough currently over the mid coast will continue to progress southward. Sat imagery is already indicating the presence of glaciated towering cloud tops over the mountains east of Goose Bay. These storms may become somewhat organised (along the trough) and present the appearance of a solid line. Winds may gust between 50 to 70 km/h ahead of these storms.

 

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2