Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Labrador.. chance of a few isolated thunderstorms later today and this evening. For tomorrow a low risk of severe thunderstorms over western areas with some potential for significant wind gusts.

 

Convective Discussion

 

After the passage of the cold front yesterday, most of the Atlantic Provinces will remain relatively quiet with respect to thunderstorm activity today and tomorrow. Most of the preferable dynamics are well north across northern Quebec, moving into western Labrador later today. Low level moisture will be the biggest limiting factor but dewpoint temperatures are expected to increase into the mid-teens tomorrow. With ample shear over 50 knots to 6 km and decent moisture it will largely be a question of timing, if daytime heating is sufficient and the weak upper ridge breaks down early enough there is some potential for severe thunderstorms later in the day. Most of the shear is straight line but there is some potential for supercells to develop, looking for long lived cells on Satellite will be helpful, should they develop.

 

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Mel Lemmon

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts…

 

Today

NB/NS/PEI/NL:  Chance of afternoon thunderstorms.

Labrador:  None.

 

Tonight

NB/NS/PEI/NL/Labrador:  None.

 

Saturday

NB/NS/PEI/NL/Labrador:  None.

Convective Discussion…

A weak trough of low pressure will track across the southern Maritimes and Newfoundland this afternoon. Embedded thunderstorms are possible over western Newfoundland this afternoon and evening. Over the Maritimes, non-severe surface based thunderstorms are possible this afternoon in the vicinity of the trough. CAPE values are 500-1000 J/kg, shear is near 20 kts and PWAT is 20-25 mm. If thunderstorms do develop, then brief downpours and gusty winds are a possibility.

 

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts…

 

Today

Labrador:  Chance of afternoon thunderstorms southeast.

NB/NS/PEI/NL:  None.

 

Tonight

NB/NS/PEI/NL/ Labrador:  None.

 

Thursday

NB/PEI/Labrador:  A chance of afternoon/evening thunderstorms.

NS/NL: None.

 

Convective Discussion…

A weak trough of low pressure tracking across Labrador will give a chance of non-severe afternoon thundershowers over sections of southeast Labrador today. On Thursday, some embedded thundershowers are possible across portions of New Brunswick and Prince Edward Island. If clearing occurs late in the day over extreme northwest New Brunswick then some surface based activity is possible. Another trough of low pressure tracking across northern Labrador will give a chance of non-severe afternoon thundershowers over sections of central and northern Labrador Thursday afternoon.

 

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

Labrador: 70-90 km/h gusts, 2-3 cm hail, risk of cold core funnels.

NS: 70-90 km/h gusts, 15-25 mm/h rainfall rates, ~1cm hail

NL/PEI : isolated to scattered thunderstorms

NB/Magdalen- QC:  None

Tonight

Labrador:  A chance of thunderstorms.

NB/NS/NL/Magdalen- QC: None.

Monday

Labrador:  chance of thunderstorms.

NB/NS/NL/Magdalen- QC: None.

 

Convective Discussion

A 3-4 SD vertically stacked cold upper low continues to slowly move east across Labrador. Near the centre of the upper low, an area of minimal vertical wind shear will yield the potential for widespread cold core funnel clouds across western Labrador with plenty of vertically slacked low level vorticity. Southeastern sections of Labrador will benefit from strong potential vorticity advection from the upstream deep upper low. This in combination with steeper lapse rates, lower freezing levels, linear shear profiles of 35-45 kts and daytime instability up to 1500 J/kg of SBCAPE will yield the primary hazard of significant hail in organized convection. The steeper low level lapse rates and cooler environment also presents a strong wind gust secondary hazard. Small hail is also possible across western NL, but weaker instability through the HGZ should keep this smaller in nature despite lower freezing levels.

 

On going clearing ahead of a weakening cold front across NS may also result in severe weather later this afternoon. Initiation is expected to be aided by coastal convergence at the surface with a sea breeze front in addition to the weakening cold front. Higher freezing levels and instability through the hail growth zone should keep any hail small in nature, however strong wind gusts may occur with significantly developed convection. PWATs appear to be slightly higher as well across NS near 35 mm, which would also present a near severe rainfall rate threat with organized convection.  

 

Tonight a chance of thunderstorms will be limited to the stronger dynamics near the upper low tonight as day time instability abates. Tomorrow a similar situation is expected

across south central Labrador, with any storms being dynamically driven given limited expected thermodynamics (MLCAPEs ~300-400 J/kg).

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Brennan

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NB/Labrador: Isolated of  thunderstorm.

NL/NS/PEI/Magdalen- QC:  None

Tonight

Labrador:  A chance of thunderstorms.

NB/NS/PEI/:  None.

Sunday

NB/NS/NL/Labrador:  isolated to scattered thunderstorms, 10-15 mm/h rainfall rates, small hail, wind gusts ~70 km/h.

Magdalen- QC: None.

 

Convective Discussion

Focus of thunderstorms today will be mainly across Labrador with potential vorticity advection ahead of a slow moving upper low centered over western QC.

Surface instability - MLCAPE is rather meager for the 30-40kts of bulk shear, but strong dynamic forcing and higher MUCAPE will likely produce elevated storms and lightning among showers.

South of this feature a cold front will gradually cross the St. Lawrence valley and move into northwestern NB later this evening giving a chance of thunderstorms.

Tonight dynamics will remain more or less status quo across Labrador, but the focus of lightning will be more confined to the upper low with less surface instability overnight.

 

Tomorrow convection will again be focused near the upper low across much of Labrador (to be centred near Churchill Falls), with some stacked low level voracity cold core funnel clouds are possible across western Labrador…

although unlike to be observed given the population density.

Further east instability will have a better opportunity to build during the day ahead of the cold front across southeast most NB, most of PEI, NS and western NL. MLCAPEs up to 750 J/kg will be sufficient in places with 35-45 kts of bulk shear to yield organized convection.

Lower PWATs (25-30mm) than what has been observed most of the summer to date on significant convective days should limit the rainfall rate hazard. On the other hand lower freezing levels and the drier air could yield small hail and gusty winds.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Brennan