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

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NB: risk of a severe thunderstorm producing strong winds, hail and torrential rainfall this afternoon and evening.

Western Lab/PEI: scattered thunderstorms possible later today giving gusty winds, small hail and torrential downpours.

 

Tonight

Western NL/NB/PEI/western Lab: scattered thunderstorms possible giving mainly torrential downpours.

 

Saturday

Central NL: scattered thunderstorms possible in the afternoon and evening giving gusty winds, small hail and torrential downpours.

 

Convective Discussion

The main area of focus today will be across parts of NB as a short wave trough slowly approaches from the southern Quebec area. The timing of this feature will be important to maximize the full extent of day time heating. However, the dynamics later today are really good, so any storms that form and move into the region could last for a number of hours. The 12Z KCAR tephi has 2 strong warm noses above the surface, but does show close to 50 knots of mean shear from the surface to 6 km. it’s likely the Maniwaki profile further upstream would be more representative of the air mass that will be approaching NB later this afternoon. Adjusting for a surface temperature of 28-29 yields over 1000 CAPE. Much like the KCAR sounding the wind shear is high. And there is no lack of low level moisture as the Tds are in the high teens. Once the surface front/500 mb short wave makes its way in numerous thunderstorms will form in southern QB/northern ME, and will be monitored as they get close to NB. Based on current SAT imagery the timing for the potential severe storms will be later this afternoon and into the evening hours. As already mentioned, the dynamics appear good so even with the sun setting individual cells could last well into the night. Elsewhere some scattered thunderstorm possible for western Labrador and a portion of the Maritimes that is further downstream from the more buoyant atmosphere.

 

Nighttime activity is likely across western NL and a portion of the Maritimes as some of the cells that develop today maintain themselves and continue moving generally eastward (aided with cloud top cooling). The main concern would be torrential downpours at this time.

 

The same short wave could give a strong storm or 2 across central NL Saturday.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight and Saturday morning

 

Thunderstorm Outlook for Saturday

 

Jeremy

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

 

Today:

NB: Scattered thunderstorms possible this evening over southern regions giving lightning, locally heavy downpours of 10-20 mm.

NS: Scattered thunderstorms possible this evening for western regions giving lightning, locally heavy downpours of 25-50 mm, small hail and 70-90 km/h wind gusts .

NL and LAB: Scattered thunderstorms possible through Labrador and parts of central NFLD today giving lightning, 1-2 cm hail, 70km/h wind gusts, and locally heavy downpours of 20-30 mm.

 

Tonight:

NB/PEI/NS: Scattered thunderstorms possible tonight giving locally heavy downpours of 20-30 mm.

LAB: Isolated thunderstorms for eastern area giving locally heavy downpours.

 

Friday:

NB: Scattered thunderstorms giving lightning, locally heavy downpours, small hail, and strong wind gusts.

LAB: Isolated thunderstorms giving lightning, locally heavy downpours, small hail, and strong wind gusts.

 

Convective Discussion

There are a couple of different features to track of interest today. An intense short wave trough that affected southern Ontario yesterday is moving over New England today and eastward towards the Maritimes tonight. Ahead of this trough, afternoon instability will increase along with moisture over southern New Brunswick and Nova Scotia. Although the main threat of severe weather remains west over New England given the dynamics and the timing of this feature, convection could persist into the overnight hours. An approaching 30KT 850mb jet, moderate 0-6km shear, and cloud top cooling will also aid in continued risk of convection overnight, giving the risk of lightning and heavy downpours into Friday morning as the trough axis exits east of Cape Breton.

 

An upper low over northern Quebec will shift southeastward across Labrador today and out over the Labrador Sea tonight with a trough extending southward into Newfoundland. Convection occurring this morning east of the low centre will persist into this afternoon. An area of concern lies in central to southeastern Labrador (left exit of a 250mb jet, an approaching 500mb cold trough, increasing moderate shear and MLCAPE values above 1500 J/kg) such that convection that develops this afternoon with daytime heating could organize into multicell lines. Freezing levels are also lower which could increases the hail potential as well. There is also the possibility of embedded convection over Newfoundland from an area of moisture moving in from the Gulf of St. Lawrence this morning.

 

For Friday, the short wave trough exiting Cape Breton will affect portions of the marine waters south of Newfoundland. Meanwhile, the next short wave over central Quebec will be quickly tracking eastward towards New Brunswick and the Gulf of St. Lawrence by Friday night. Ahead of this trough in the afternoon, scattered thunderstorms are possible over northern New Brunswick and southwestern Labrador.

 

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Friday

Convective Outlook Valid for Today, Tonight, and Tomorrow

Regional Impacts

NS: Isolated thundershowers possible this afternoon across mainland NS, locally heavy downpours of 10-20 mm. Chance of an isolated thunderstorm over the Cape Breton Highlands early this afternoon; 1-2 cm hail, 70-90 km/h wind gusts, and locally heavy downpours of 25-50 mm.

NB: Isolated thundershowers possible today, locally heavy downpours of 10-20 mm.

PEI: Isolated thunderstorm possible over eastern PEI early this afternoon; 1-2 cm hail, 70-90 km/h wind gusts, and locally heavy downpours of 25-50 mm.

NL: Scattered thunderstorms possible through west-central NFLD today; 1-2 cm hail, 70-90 km/h wind gusts, and locally heavy downpours of 25-50 mm.

 

Convective Discussion…

A small but intense shortwave trough moving through the Maritimes this morning brings the chance for sever weather across the eastern gulf of St. Lawrence and west-central NFLD today. Models have been struggling to resolve the intensity of this trough, with some strong storms having already moved through PEI and Iles-de-la-Madeleine this morning. These storms have weakened slightly as they moved over cooler gulf waters, but may re-intensify as they approach Cape Breton and the western shores of NFLD early this afternoon. Upper dynamics will allow for sustained convection over west-central NFLD, with a 110 kt 250 mb jet over the region. Bulk shear of 30-40 kts and SBCAPE values in excess of 1000 J/kg provide an ample environment for severe weather potential with the incoming shortwave trough acting as the main trigger. These storms will move northeast into north-central NFLD by this evening. The main threats with these storms will be pea to dime size hail, strong wind gusts reaching 70-90 km/h, and locally heavy downpours of 25-30 mm per hour.

 

In addition, isolated pop-up thundershowers are possible across the Maritimes this afternoon. Due to a lack of upper support however, these storms are expected to have short life spans, with the main threat being brief heavy downpours.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Copp

Convective Outlook Valid for Today, Tonight, and Tomorrow

Regional Impacts

NS: None.

NB: A few thunderstorms possible over western and northern NB this afternoon; 1-2 cm hail, 70-90 km/h wind gusts, and locally heavy downpours of 25-50 mm.

PEI: Slight chance for an isolated thundershower over western PEI this evening, locally heavy downpours of 15 mm possible.

NL: A few thunderstorms possible between Goose Bay and Labrador City this afternoon; 1 cm hail, 70 km/h wind gusts, and locally heavy downpours of 20-40 mm.

 

Convective Discussion…

A small shortwave moving through eastern Quebec this morning will bring the risk for severe weather across parts of northwestern NB and central Labrador today. In NB, SBCAPE values are expected to climb upwards of 1500 J/kg this afternoon. This, in combination with bulk shear values of 30-40 kts will provide an ample environment for the development of severe weather. Dew points in parts of New Brunswick have been observed to be slightly higher than models have forecast this morning, as such SBCAPE values may be slightly higher than models are currently predicting. The main threat with these cells will be small hail of 1-2 cm, strong wind gusts of 70-90 km/h, and locally heavy downpours upwards of 25 mm per hour.

 

In central Labrador, SBCAPE values will be similar to those in NW NB, 1500-2000 J/kg between Labrador City and Goose Bay. Bulk shear here is slightly weaker however, in the 20-30 kt range, nonetheless a 40 kt 500 mb jet over the region will aid in sustaining organized convection this afternoon and into this evening. There is a chance these storms make it to Goose Bay by late this evening, however the main threat area is to the west of here. The hazards associated with these storms will be 1 cm hail, 70 km/h wind gusts, and locally heavy downpours of 20-40 mm.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Copp