Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Slight risk of a thunderstorm giving brief moderate downpour for Valley and Central NS, PEI, and southern NB.

 

Convective Discussion

Some instability is expected this afternoon but it will manifest itself mostly in the low levels (below 3000m). Precipitable water range from 25-32 mm over southern portions of the Maritimes – hence the possibility of a brief downpour from towering clouds. Some regions have slightly higher dewpoints, and some will experience more surface heating from the sun - this greater instability could lead to the development of isolated thunderstorms.

 

Large high pressure cell over northern Quebec giving stable and dry air mass over Newfoundland and Labrador. Available energy is 0, and the precipitable water is an anemic 9mm at Stephenville.

 

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

NS/NB/PEI/NFLD: Chance of a thundershower this afternoon.

Labrador: None.

 

Convective Discussion

 

Afternoon, surface based convection is possible today. Especially in areas where offshore northeast winds give convergence with onshore sea breezes. Precipital water is 20-30 mm so local downpours are likely. Dry mid layers will allow possible wind gusts and low freezing levels of 10,000 feet may allow small hail. The cape is generally low (300-400 J/kg) and the sheer is 20-30 kts so any storm develop will be mostly pulse in variety.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

NS/NB/PEI: None

NFLD: A chance of severe wind gusts and downpours this afternoon.

Labrador: Elevated convection giving downpours.

 

Convective Discussion

 

Elevated convection giving downpours is possible in Labrador. Precipital water is 30 mm there and it is in the region of the left exit of a 100 kt jet which is giving it support. Over eastern regions of Newfoundland surface based convection will initiate this afternoon. Precipital water is 40 mm and dry mid layers will allow possible wind gusts to 80 km/hr. A high freezing level of 13,000 feet will limit possible hail size. The sheer is a relatively low 20 kts or less so storms will be mostly pulse in variety.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

There is a slight risk of an isolated severe thunderstorm or 2 across central areas of New Brunswick this afternoon into this evening giving torrential rainfall and strong winds. Small hail is also a possible in the stronger cells.

Scattered thundershowers are likely for southeastern Labrador and western Newfoundland today and into tonight. This is mostly elevated precipitation so just some heavy downpours are expected.

There is a slight risk of a thundershower this afternoon and early this evening across the valley and northern Nova Scotia.

Lastly isolated thundershowers are possible for western Labrador later today.

 

Convective Discussion

The same front that produced some severe weather in Quebec yesterday is now situated across central areas of New Brunswick (though in a somewhat weakened state). The 12Z KCAR profile does support MLCAPE of 800-1000 j/kg, PWAT around 44 mm and good shear at around 40 knots. And also good low level instability. There are 2 warm noses that could prevent things from firing. However given enough buoyant energy, a diffluent flow at 500 mb observed at 12Z and a jet streak at 250 mb placing the region in the left exit region, isolated severe storms are a possibility.

 

An upper level feature will give some scattered thundershowers to SE LAB and WRN NL but all non-severe.

 

For the valley and northern NS there is a slight risk of a thundershower this afternoon and evening…but the limiting factor will be the upstream cloud cover now entering the region and lack of any trigger. Expect mostly TCU giving locally heavy downpours.

 

An approaching upper-level trough over north-central Quebec will give some isolated non-severe cells to western LAB later today.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2

 

Jeremy

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

There is a risk of thundershowers this afternoon and evening across western and central Labrador. These could advect eastward affecting portions of the LAB coast tonight as well. Brief heavy downpours and gusty winds are possible.

There is a slight risk for a severe thunderstorm across the far northwest of NB. The main threat would be torrential rainfall…however strong wind gusts are also a possibility.

Lastly, there is a risk of isolated thundershowers this afternoon across the valley and northern NS. Torrential rainfall is the main threat.

 

Convective Discussion

The main focus today will be to see what forms upstream across southern Quebec and northern Maine. What will be a moot point today is a trigger. The KCAR tephi has ~ 25 knots of shear, PWAT of around 40 and MLCAPE of 1000-1200 j/kg. There is a moist tongue near the surface which would add to the buoyancy as the day progresses. The deep layer trough at 500 mb is further upstream at 12Z, but that should propagate eastward today, resulting in an increase in wind shear across NW NB. If cells do make it to the region, torrential downpours and gusts to 70-80 km/h would be expected. Will have to monitor the upstream development this afternoon and the evolution of movement.

 

For Labrador, where shear is 40-45 knots, and closer to the surface and upper trough, scattered cells are likely. Then only issue would be warm air aloft…however given the dynamics that would be broken fairly easily. Brief heavy downpours and gusty winds are possible with the storms.

 

There is a risk of isolated non-severe thunderstorms across the valley and northern NS this afternoon. There is very little shear (YQI and GYX showing 20 knots), but the PWAT is 40+. CAPE looks to be in the 500-1000 range. Locally torrential downpours will be the threat.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2