Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today: No thunderstorms expected with a trailing cold front departing, smoke aloft, and general building ridge conditions.

Tonight: No convective activity. Pockets of frost.

Tomorrow: Non-severe thundershowers/showers are forecast across portions of eastern and northern mainland NS in the afternoon from daytime heating. Labrador could see a few ridge-rider cells move from the NW to the SE in the day. Airmass is fairly dry and only a few mm of rain would be expected.

Sunday: Weak trof line across northern tier of NB and SE Labrador. No hazards expected other than a lightning strike or 2.

Convective Discussion

Much quieter day than yesterday expected. Cold front and Jet dynamics have pulled out of the Maritimes. Mid-levels are drying out significantly on this morning’s soundings. Sfc dewpoints in NB are struggling to reach 5 in places. Haze and smoke aloft are also further adding to stability. Saturday has low and skinny CAPE, and minimal shear (effective is only 10kts) across parts of NS – could see a spark or 2 with the tallest TCU. Single cell is the expected storm mode with not much motion. Sunday, this setup is established in northern NB and across eastern Labrador. Risk of -TS is now in the public bulletins.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Thunderstorm Outlook for Sunday (Day 3)

 

 

Forecaster: Tirone.

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today: 1. Thundershowers are possible along an advancing trof line in eastern Labrador. 2. Additionally thunderstorms are possible in central Nfld (vicinity Gander). Only hazards here are 5-10mm of rain. 3. The weather with the greater dynamics at play is over the Maritimes, with thunderstorms approaching severe limits later today across parts of SE NB, central PEI and northern and central mainland Nova Scotia. Please see the detailed yellow area on the graphic for all counties included. Hazards here include wind risk, hail, and near 25mm of rainfall in the most organized cells.

Tonight: Remnants of storms expected to advect across CB and nearby waters. Should not be surface based convection after sunset.

Tomorrow: No thunderstorms forecast. Not enough lift, no defined trigger.

Saturday: Weak non-severe cells are possible to pop up on a weak trof line across the northern tier of NB. Elsewhere, no activity forecast.

 

Convective Discussion

Today is a High Shear day. The upper dynamics across the Maritimes include a 110 kt WSW-ly jet at 250, with a strong jet core of 140 positioned over northern Ontario. Effective shear values are over 40kts, with 0-6k values over 60 in places. This may prove to be too much shear for the small amount of sfc based CAPE at play, however – if it isn’t overwhelmed, it is the correct recipe and orientation for supporting supercell development. The main hazards if this can develop would be 2cm hail and downdrafts near 90 km/h. Dewpoints this morning are holding strong under mainly clear skies still at 13 to 14C. Upstream Pwats are in the 22 to 30 range off morning soundings. A quieter Friday is forecast, and a weak trof line is the only possible trigger for a few unorganized single cells on Saturday.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Thunderstorm Outlook for Saturday (Day 3)

 

 

Forecaster: Tirone.

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

Labrador: Risk of a thundershower this afternoon with strong wind gusts and small hail.

Northern New Brunswick: slight risk of a pop-up thundershower.

Tomorrow: Risk of near-severe thunderstorms giving strong wind gusts and small hail for parts of New Brunswick, Prince Edward Island, and northern Nova Scotia. Risk of thundershowers for southeastern Labrador.

Convective Discussion

A low pressure system over northern Quebec will slowly drift eastward across northern Labrador today. Period of moderate to heavy rain associated with a trough extending from the low move across Newfoundland. Cooler air aloft behind the low along with surface heating will lead to destabilization this afternoon with the risk of some pop-up thundershowers mainly across central and western Labrador southward towards northern New Brunswick. Winds over Labrador will be increasing with the low throughout the day, but there could be enhanced wind gusts in any convection that develops but with low freezing levels there is also the possibility of small hail.

For Thursday, another trough that will be over the Great Lakes today will  make its way into Atlantic Canada by tomorrow morning. This will aid in triggering thunderstorms by early afternoon along the trough line from southeastern Labrador towards New Brunswick. For the Maritimes, mixed CAPE values are expected to reach 500 J/kg, and although the overall 0-6km layer shear is high >60kt, the effective shear into the afternoon over New Brunswick will be closer to 40 kt, and more conducive to maintaining convection or organizing into lines. The main threat will be strong wind gusts and small hail as freezing levels decrease as storms that develop are expected to move quickly and precipitable water around 25 mm.   

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

 

Roberta McArthur

 

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Maritimes: Risk of embedded TS with rainfall rates of 10 to 15 mm/h this afternoon and overnight.

Labrador: Slight risk of a thundershowers for western areas tomorrow.

Convective Discussion

A trough associated with a low pressure system over James Bay will bring a broad destabilization with cooling aloft throughout the day but MUCAPE remains minimal with at most 250 J/kg and may not break through the warmer air still remaining from 700 to 500 mb. There will be some lift near 850 mb from a 35 KT LLJ and weak effective shear to help generate a few embedded thundershowers across western New Brunswick this afternoon ahead of the main trough still over Quebec. Storm motion should keep overall precipitation lower and the system moves across the Maritimes tonight, but with precipitable water of 30 to 40 mm moving through with this system, there may still be periods of moderate to heavy rainfall.

The trough moves into Newfoundland on Wednesday with moderate rainfall possible while behind and south of the low as if tracks over northern Quebec will enable weak pop-up convection over western and central Labrador.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Roberta McArthur

 

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

Labrador: Non-severe risk of a thundershower in south-central Labrador.

Maritimes and Newfoundland: Nil

Tuesday and Tuesday night:

Maritimes: Risk of embedded TS with rainfall of 10 to 20 mm.

 

Convective Discussion

Slight risk of a thundershower today along a trough extending from central Quebec southeastward across Labrador that will move southeast and weaken by tonight. Goose Bay sounding shows a cap between 700 and 500 mb that is not likely to be breached, so mainly expecting on TCUs but the cap may be broken south of the public regions. Upper smoke from fires over central and western Canada continues to linger across Atlantic Canada, also adding to the unlikelihood of exceeding the necessary surface heating.

Tomorrow, a trough associated with a low pressure system over James Bay will bring a broad destabilization with cooling aloft throughout the day. There will likely be enough lift near 850 mb from a 35 KT LLJ to generate embedded thunderstorms across western New Brunswick and Nova Scotia by early evening and into the overnight. Moderate to heavy rain in possible across the Maritimes as higher precipitable water of 30 to 40 mm comes in from the Gulf Stream.

The trough moves into Newfoundland on Wednesday and behind and south of the low as if tracks over northern Quebec will enable pop-up convection over western Labrador.

 

Thunderstorm Outlook for TODAY

 

Thunderstorm Outlook for TONIGHT

 

Thunderstorm Outlook for TOMORROW

 

 

Roberta McArthur