Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Regional Impacts

 

Low risk of high based thunderstorms over the higher terrain in northern New Brunswick and western Newfoundland late this afternoon and evening. Convective downdraft gusts are the main concern should anything develop.

 

Convective Discussion

 

A very hot and slightly humid air mass continues to reside over the Maritime provinces today. A trough over southern Labrador into northern Newfoundland will slowly sink southward today and reach northeastern New Brunswick and the Gulf of St. Lawrence tonight.  Temperatures profiles over NB this morning suggest a very dry air mass but with a lot of buoyant potential.  An isolated thunderstorm cannot be ruled out, especially with the help of forcing from hills and where forest and other vegetation may provide the extra moisture and energy needed or with the help of a sea breeze convergence off the Bay of Chaleur. The forecast highs are such that the convective temperature of 37 could even be reached on its own. Given such a dry and warm profile at all levels, there may not be much in the way of precipitation but convective wind gusts could be a concern. There may be a similar situation off the higher terrain in southwestern Newfoundland.

 

 

Thunderstorm Outlook for Day 2

 

Daytime heating air mass type thunderstorms are possible mainly over Maine tomorrow afternoon but with the slight winds aloft from the west, some of these cells could reach into western New Brunswick in the evening. The risk remains very low as mixing in the low levels may inhibit development. A ridge of high pressure  sinks south into Newfoundland and Labrador tomorrow with no convective weather expected.

 

 

 

Roberta McArthur

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Slight risk of a non-severe thunderstorm over southern portions of the interior of Newfoundland later this afternoon.

 

 

Convective Discussion

 

Over Newfoundland, an area of surface based instability is expected to develop later this afternoon over unpopulated interior areas of the island. This is supported by a weak disturbance embedded in the strong northwesterly flow aloft. One condition for the destabilization to occur would be for the current cloud deck to break-up/scatter out which should happen beginning over the west coast during the early afternoon, then later over inland areas.   

Warm and dry conditions will prevail over the Maritimes today.

 

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

Hot and somewhat more humid conditions are in store for Friday across the Maritimes. Some of this (modified) airmass will try to push across Cabot Strait into southwest NF. Temperatures profiles over NB are supporting the potential for the development of an isolated thunderstorm, especially with the help of forcing from hills and  where forest and other vegetation may provide the extra moisture and energy needed.

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

isolated non-severe thunderstorm over western Labrador this afternoon.

 

Convective Discussion

Aloft this morning there is an east-west oriented ridge over the Great Lakes and the Maritimes. To the north, a frontal band extends from Labrador westward to northern Ontario and the eastern Prairies. At the surface, rain continues fall along  a warm front which is moving towards the Labrador coast and the Great Northern Peninsula of NF. Moist and somewhat unstable airmass will prevail over the rest of Labrador this afternoon and into the evening. Based on the soundings from YZV and LG4, the expected daytime high (low to mid-twenties) should be enough to produce an isolated cell, especially over southernmost areas. Very strong winds aloft may not permit much vertical development, but considering the amounts of moisture brief moderate showers are a good possibility along with winds mixing to the surface and giving gusts between 50-70 km/h.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Regional Impacts

Slight risk of a thundershower over Southeastern Labrador

 

Convective Discussion

The tail of a weak departing trough currently over the south Labrador coast could provide enough forcing for showers and a weak thundershower to develop until mid-afternoon. This region is on the southern periphery of pool of cold air aloft. Forecast guidance is suggesting a small area of surface-base CAPE in the 100-200 J/kg range, and the lighting guidance is also indicating a chance of lightning over the same area.    

 

Thunderstorm Outlook for Day 2

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Regional Impacts:

 

Labrador: a chance of thundershowers this afternoon into this evening with gusty winds (weak dry microburst)

 

Offshore waters south of  Nova Scotia and Newfoindland: embedded convection with heavy downpours.

 

Convective Discussion

A deep cold trough is moving into western Labrador with some associated PVA and a left exit region from the upper jet west of the trough. There’s also a little cold advection. Near the surface there is a capping inversion that will weaken this afternoon. The main limiter here is moisture and CAPE. PWAT is only 15 mm, dew points are pretty low, and if the upper lift is strong enough you might get 200 J/kg. There’s moderate deep layer shear as well. There’s a chance for a weak dry microburst, which will probably be the major impact. Conditions will improve overnight.

 

For the offshore waters, it’s a continuation of the rationale from yesterday, with an inverted trough as the trigger for a saturated moist adiabatic profile. Shear is moderate near the trough, but mainly less than 35 kts. So mainly rain and some gustry winds.

 

 

 

 

Thunderstorm Outlook for Day 2

 

 

There may be some convection overnight and into Tuesday morning just south of Labrador, but there’s only a slight chance of it reaching towards the Strait.