Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Today

NL: Scattered thunderstorms with small hail, downpours and gusty winds

NB/NS/PEI: Isolated thunderstorms.

Labrador: None.

 

Tonight

NB/PEI/NL/NS/Labrador: None.

 

Saturday

NS:  Isolated thundershowers

NB/PEI/NL/Labrador: None

 

Convective Discussion

A weakening cold front over central New Brunswick will track southeastward to lie on a line stretching from Newfoundland to Nova Scotia tonight. There is not much shear (20 kts and linear) over the Maritimes and the ML Cape is 500-1000 J/kg. PWAT values of 35-45 mm may allow downpours if the convection initiates. With the low shear, training cells giving high rainfall potential is the most obvious threat. Over Newfoundland the shear is 20-30 kts so more organized thunderstorms are likely. Dry mid levels support wind gusts to 70 km/h. Also downpours are likely with PWAT values of 35-45 mm. Small hail is also a possibility. Tonight and Saturday little convection is expected. The front may linger over western Nova Scotia Saturday afternoon giving the risk of a thundershower.

 

Thunderstorm outlook for today

 

Thunderstorm outlook for tonight

 

Thunderstorm outlook for Saturday

 

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Today

NB/Labrador: Isolated thunderstorms.

NS/PEI/NL: None.

 

Tonight

NB/PEI/NL: Isolated thunderstorms.

NS/Labrador: None.

 

 

Friday

NB/NS/PEI/NL:  Isolated thundershowers

Labrador: None

 

 

Convective Discussion

A weakening cold front will track southeastward to lie over the St. Lawrence River tonight and over a line stretching from Newfoundland to New Brunswick on Friday. There is not much shear (20 to 30 knots and linear) and the ML Cape is 500 J/kg or less. PWAT values of 35-45 mm may allow downpours if the convection initiates. Dry mid levels support the model guidance suggested wind gusts to 70 km/h. Guidance is suggesting that hail will not be a factor.

 

Thunderstorm Outlook for today

 

 

Thunderstorm Outlook for tonight

 

 

Thunderstorm Outlook for Friday

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

NL: Rainfall rates 25-35mm/hr, wind gusts 70-80 km/h.

 

Tonight

None

 

Tuesday:

NB: isolated lightning.

 

Convective Discussion:

Significant instability exists across Newfoundland today. A 25/18.5 modified 12z RAOB from Stephenville yields a MLCAPE of 1000 J/kg, providing ample energy for storms to develop. Nevertheless effective shear of 20-25 kts should limit storm structure to the pulse variety. Moisture is quiet abundant with PWAT ranging from 35-45mm, giving a primary rainfall rate hazard this afternoon with storms that develop. Steep lapse rates from 900mb to the surface and widespread MLCAPEs in excess of 1000 J/kg present a secondary wind hazard, especially if shear ends up being locally enhanced (allowing for the odd storm to take on some super cellular characteristics).  Hail is anticipated to be small if it occurs due to a high HGZ and lower shear values.

 

Thursday:

Another upper trough moving through Ontario today will weaken and move eastward into northern NB tomorrow. Ongoing moisture advection throughout the day in southwest flow ahead of the upper trough should allow for some free lift late in the afternoon. Bulk shears of 30 to 40 kts in combination with MLCAPES up to 750 J/Kg could yield some stronger storms, however there remains some uncertainty in terms of the timing of upper trough.

 

 

Thunderstorm outlook for today:

 

Thunderstorm outlook for tonight:

 

 

Thunderstorm outlook for Thursday:

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

Labrador.. numerous strong thunderstorms expected with downpours giving rainfall rates of 20+ mm/h, wind gusts 70 to 90 km/h, and hail. Some of the storms could reach severe limits and a watch has been issued for the Churchill Valley, including the Churchill Falls townsite.

NB.. Strong thunderstorms producing downpours giving rainfall rates of 10-20 mm/hr, gusts 60-80 km/h.

NF.. risk of a non-severe thunderstorm over western sections

NS and PEI.. risk of a non-severe thunderstorm

 

Convective Discussion

A surface cold front over the St. Lawrence Valley will move across Labrador and New Brunswick this afternoon. This feature is the focus for convective activity today. Thunderstorms have already been reported in western Labrador, and the expectation is for the storms to become numerous during the afternoon. The left exit of an approaching cyclonic upper jet will support the potential for severe thunderstorms over central Labrador. Also, in the warm sector the regional model is indicating the presence of a curved, but generally longer-live cells will likely form into organized clusters/lines. Over NB where midlevel support is not as solid, MLCAPE of ~1000 J/kg and effective shear of 30-35kt could be enough to support strong thunderstorms with convective wind gusts, there is a slight chance that some of these storms could approach the supercell category.

 

Thunderstorm Outlook for Tonight

 

 

Thunderstorm Outlook for Wednesday

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Today..

Newfoundland and New Brunswick… Slight risk of thunderstorms giving locally heavy downpours.

NS, PEI and Labrador… No thunderstorms expected

 

Tomorrow..

Labrador… Severe thunderstorms possible with heavy rain and strong wind gusts.

New Brunswick… Thunderstorms could give locally heavy downpours.

NS, PEI and NFLD… Low probability of thunderstorms.

 

 

Convective Discussion

There is a low probability of thunderstorms over the Atlantic region today a slight risk over interior parts of newfoundland and western New Brunswick. There model seems to be underdoing the surface dew points so it is possible that the cap at 700 may be overcome with daytime heating and surface convergence. Overall updrafts in thunderstorms should not be very strong with surface CAPE values generally under 500 J/kg and wind shear values not overly favourable for organised convection.

 

Tomorrow dynamics will become more enhanced wind shear and an approaching cold front that also act to enhance convection, the environment should support organised convection. There is a slight risk of severe thunderstorms over Labrador with strong gusts possible in some storms, however it is possible that could cover and rain may subdue any severe thunderstorms.  Over New Brunswick the risk will be somewhat more significant than today with more moisture and a better triggering mechanism, but weak updrafts could be the limiting factor and severe thunderstorms being only a slight possibility.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2