Convective Outlook Valid for Today, Tonight, and Tomorrow

Regional Impacts

NL: Scattered thundershowers possible over western Newfoundland and southern Labrador today. Locally heavy downpours of 10-20 mm possible.

NS: Risk of isolated thundershower early this afternoon over the Cape Breton Highlands. Locally heavy downpours of 10-15 mm possible.

NB: None.

PEI: None.

 

Convective Discussion…

A cold upper low currently sitting over Labrador with an associated trough extending into Cabot Strait, in combination with a 150 kt 250 mb jet located over central Newfoundland, will spark some scattered thundershowers today across Labrador, western Newfoundland, and extending down into northern parts of the Cape Breton Highlands. With stronger dynamics to the east of the area of interest today, convection is expected to remain non-severe, with the main threats being locally heavy downpours of 10-20 mm. That being said, a few waterspouts have been reported this morning from Iles-de-la-Madeleine to western shores of Newfoundland. This risk will diminish by early afternoon as the mid and lower levels of the atmosphere begin to warm and the trough moves off to the east towards Banquereau.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Copp

RE: Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts:

 

Today

Labrador/NB/NS/PEI/Magdalen: A chance of non-severe thundershowers.

NL: Risk of rainfall rates exceeding 25mm/hr

 

Tonight

Labrador/NL: A chance of non-severe thundershowers.

NB/NS/PE/Magdalen: None.

 

Wednesday

Labrador/NL: A chance of non-severe thundershowers.

NB/NS/PE/Magdalen: None.

 

Convective Discussion:

Thunderstorms will continue to develop today ahead of a weak cold front in western most NL and adjacent waters. A narrow ribbon of moderate PWATs of 30-35 mm in conjunction with storm motion following a mean SE wind that is almost perfectly parallel to the coast line will bring a heavy rainfall threat here. MLCAPE is rather modest, at 300-500 J/Kg, however it plays well with bulk shears near 30 kts and orographic enhancements for a localized flash flooding threat.

 

Elsewhere garden variety storms will develop across Labrador associated with a broad upper trough. This feature will swing into Northern NB later in the afternoon and may provide similar non-severe storms. The same front causing storms in western NL does hang back into eastern PEI/NS, however shears of ~40-50 kts appear too high for the limited instability early in the afternoon. CAPE may become high enough to support isolated storms later in the afternoon hours in this higher shear environment  with further surface moisture convergence and additional solar insolation.

 

Tomorrow the same upper trough will continue to provide enough instability for storms to fire with daytime heating across much of Labrador. East of the Long Range mountains a surface trough will be the focus for some thunderstorms in western NL. ML CAPEs of ~300-500 J/kg will work well with moderate bulk shears of ~35 kts. Further east towards Gander shears look to be too high with the expected CAPE environment to support thunderstorms.  

 

Thunderstorm outlook for today:

 

Thunderstorm Outlook for Tonight:

 

Thunderstorm Outlook for Tomorrow:

 

Convective Outlook Valid for Today , Tonight and Tomorrow

 

Regional Impacts:

 

Today

Labrador/NB/NS/PEI/Magdalen: A chance of non-severe thundershowers.

NL: None

 

Tonight

Labrador/NS/NL/PEI/Magdalen: A chance of non-severe thundershowers.

NB: None.

 

Tuesday

Labrador/NL/ Magdalen: A chance of non-severe thundershowers.  

NS/PEI/NL: None

 

Convective Discussion:

The base of an upper trough will gradually move eastward today. MLCAPEs will build into the 200-500 J/Kg range by the later afternoon hours with bulk shears ~ 30 kts, however low level shear is expected to be on the low side given the lack of any significant surface feature or jets, which should limit storm organization. The most frequent lightning activity is expected to be across west-central Labrador today, where vorticity advections will be strongest aiding ascent in addition to general instability. In the Maritimes initiation will be limited until there is sufficient surface heating in combination with cooler air aloft slowing moving into the region with the upper trough.

 

Tonight into tomorrow morning thunderstorms will be focused mainly across the gulf, reaching western NL by the morning hours. In the southern Maritimes shears of ~50kts are expected to be too strong for the weak instability (200-400 J/Kg) to yield any storms. Further north/east into NL and Labrador this is not expected to be a problem with bulk shears lower in the range of 20-35 kts, which should once again yield non severe storms mainly focused near the upper trough. It is possible some an isolated storm may move into northern NB from the Gaspe late in the afternoon, however probability is to low to consider at this time.

 

Thunderstorm outlook for today:

 

Thunderstorm Outlook for Tonight:

 

Thunderstorm Outlook for Tomorrow:

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts:

 

Today

Labrador: A chance of non-severe thundershowers.

NB/NS/PEI/NL: None.

 

Tonight

Labrador: A chance of non-severe thundershowers.

NS/PEI/NL NB: None.

 

Monday

NB/PEI/Labrador: A chance of non-severe thundershowers.  

NS/NL: None

 

Convective Discussion:

Finally the warm and humid air mass has departed region.  A supportive upper trough and a weak surface trough will give a potential for thundershowers in western Labrador today and Monday. The same lingering trough set-up will give potential thundershowers over New Brunswick and western PEI on Monday. MLCAPE values near 500 J/kg are expected over Labrador today and over Labrador/New Brunswick on Monday. Shear values near 20 kts will limit the thunderstorm impacts to non-severe. Gusty winds to 60 km/h are possible.

 

Thunderstorm outlook for today:

 

Thunderstorm Outlook for Tonight:

 

Thunderstorm Outlook for Tomorrow:

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

Central NL: likely some scattered  thunderstorms giving gusty winds and locally torrential downpours this afternoon and into early this evening.

 

Sunday

Western Lab: slightest risk of an afternoon thunderstorm in the Lab City/Wabush area giving heaving downpours.

 

Convective Discussion

 

The only area to watch today is in Newfoundland where a short wave trough and surface frontal trough will be pushing through this afternoon. While some things look good for near severe storms, others look to perhaps limit them – one of those is being the very strong shear (close to 60 knots from 0-6 km at YJT)...which could be too high. There is a good moisture in the low levels with a trigger in the form of a short wave trough and associated surface cold front. The instability is nothing to write home about, so that too could act as a caveat. Skies are beginning to clear in the favourable upstream region where thunderstorms typically form then advect east-northeastward. For now expect gusty winds to 70 km/h and locally torrential downpours. The fast-moving nature of the cells should limit excessive rainfall. Although not mentioned in the graphic, small hail is also possible given the FZLVL is just above 10kft at YJT. OTWZ nil sig wx expected in the region.

 

There is the slightest risk of a thunderstorm Sunday afternoon in the Lab City and Wabush area as a large scale upper trough slowly approaches from Quebec.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Sunday

 

Jeremy