Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NS/NB/LAB: Chance of scattered thundershowers.

PEI/NFLD: None.

 

Tonight

NB: Chance of elevated thundershowers.

NS/PEI/NFLD/LAB: None.

 

Sunday

NB/LAB: Chance of organized thundershowers central and west.

NS/NFLD: Chance of scattered thundershowers.

PEI: None.

 

Convective Discussion

Scattered thundershowers are possible across Nova Scotia, New Brunswick and extreme southeast Labrador today. CAPE values of 500 J/kg and shear near 20 knots will limited any thundershowers to non-severe. Downpours with training are the most likely event today with PWAT values near 30 mm and winds remaining light. On Sunday, the environment remains quite similar with scattered thundershowers once again possible across most of the region however over New Brunswick and southeast Labrador CAPE values will increase to near 1500 J/kg while shear will remain near 20 knots. This may produce gusty wind and downpours for those regions. Hopefully the lack of shear will keep conditions below warning criteria.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

NB/NS/PEI: Risk of showers and thunderstorms across NB in the afternoon into western NS and PEI in the late afternoon/evening giving brief wind gusts and heavy downpours. There is a chance that a cell or two could approach severe limits late this afternoon near Keji National Park and in the Annapolis Valley of Nova Scotia. This convection should be short lived based on the dynamics today. The main hazard is rain.

Labrador: Scattered thunderstorms across the region from early afternoon to the evening giving brief wind gusts, lightning, and small/moderate hail.

NL: None

Tonight

NS: Chance of thunderstorms continues after midnight across eastern sections and over much of the marine district.

Tomorrow

NB/NS/PEI: An inland risk for single cell convection exists tomorrow across much of the Maritimes.

Labrador: The thunderstorm risk has pushed east near Mary’s Harbour, depicted in grey.

NL: Inland thundershowers are possible near Badger, depicted in grey.

Convective Discussion

A tale of 2 trofs today across the Maritimes. As these features advance from the Eastern Townships of Quebec, the atmosphere will destabilize. A jet at 250 of 112kts also sweeps through western NS late this afternoon, coinciding with the advancing thermal trof. This alignment MAY lead to a cell or two approaching severe limits in the small depicted yellow risk area. Dewpoints this morning hover around 12-15 and should maintain today along the warm frontal feature (sfc). The main hazard this afternoon would be rainfall, but also a brief wind gust to near 90km/h. CAPE is limiting however, and a lot of cloud already around – increasing CIN. MUCAPE values only near 500 today. Decaying storms may brush the HRM area late this evening, but not with any of their severe hazards maintained. CAPE is much higher with Eff shear of 30kts in Labrador. Hence the hail risk and more organized chance of discrete cells forming there. Tomorrows convection is forecast to be single cell and not severe. These will be inland airmass thundershowers, very typical to the region in June.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Tirone.

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

NB: Some isolated thunderstorms are possible over western regions giving brief winds, heavy downpours and small hail.

Labrador: Some isolated thunderstorms are expected for western regions giving brief winds gusts and small hail.

NS/PEI/NL: None

Tonight

None.

Tomorrow

NB/NS/PEI: Risk of thunderstorms across NB in the afternoon into western NS and PEI in the evening giving brief wind gusts and heavy downpours.

Labrador : Scattered thunderstorms across central and southern regions from early afternoon to the evening giving brief wind gusts and small hail.

NL: None

Convective Discussion

As a low pressure system pulls east of Newfoundland this morning, weak ridging build across the eastern Maritimes, Newfoundland and southeastern Labrador today, limiting convection. To the west, a trough of low pressure will slowly advance southeastward from northern Quebec, with another trough of low pressure  across the Great Lakes. Two areas to watch today will be ahead of these two features as they enter western Labrador and western New Brunswick this afternoon. With MLCAPE of 500 J/kg and effective shear of 15-20kt, convection that develops is not expected to be that organized, but could still give be some brief wind gusts and small hail into western Labrador given low freezing levels. For the environment entering western New Brunswick, there is similar CAPE values but a bit more shear of near 35-30kt and precipitable water of near 25 mm, which could lead to some organization across southwestern areas this afternoon. Multicell or possible lines may develop and brief strong wind gusts and small hail are possible, although upper support remains further west today, so are not expected to reach severe limits.

For tomorrow, the ridge holds over Newfoundland, but the two troughs continue further east, with the northern trough over central Labrador and the southern trough across southern Quebec and into northern Maine by the evening. More widespread showers and thundershowers are expected for Labrador with some organization possible into multicell or lines as MLCAPE increased to 1000J/kg and effective shear increasing to near 30 kt. Small hail and strong wind gusts will be the main threats given it will be quite dry in the low levels. For the Maritimes, the trough advances towards Maine with some potential for more organized thunderstorms given increasing shear, but CAPE remains near 500J/kg. There is increasing precipitable water of 35 mm, leading to higher rainfall rates in embedded convection in the evening across southern New Brunswick and western Nova Scotia.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: McArthur

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

NB: Thunderstorms are forecast to develop this afternoon and early evening. Severe storms are possible along and south of Highway 2, with gusty winds and moderate hail. (Depicted in yellow).

PE/NS: Some of these storms may survive across the Strait and Bay entering PEI/NS this evening in their late stages of development. They won’t be building any further at this point. (Depicted in grey)

Cape Breton/Avalon/Burin: Embedded -TS risk near noon and this afternoon along the Atlantic coast and offshore. Heavy rain occurring in areas, but no other hazards forecast.

Tonight

Atlantic: No thunderstorms forecast in the overnight time period.

Tomorrow

Western Labrador: Thunderstorms are forecast to re-develop in the afternoon and evening hours. Some may approach marginal severe limits.

NB: Western and northern areas of the province could see a few lightning strikes as thunderstorms re-develop in the afternoon. Not forecast as severe at this time.

Friday

NS: Western NS and the Annapolis Valley could see organized convection that approaches severe limits. This will be analyzed further in coming shifts.

 

Convective Discussion

There is ample moisture again today across the Maritimes. LL cloud/fog is expected to burn back in NB late this morning, setting the stage. Today, a forcing at the 500mb level is at play. This thermal trof is expected to sweep through NB this afternoon, and brings the chance of all hazards to areas in the province (depicted in yellow). MLCAPE sits near 1800J with Effective shear values 30-40kts. Watches will likely be issued in the area of Woodstock and Fredericton. Dewpoints across NS are also near 15 this AM, but there is a lack of a sfc forcing as the synoptic rain effects most of the central and eastern region at present. If a discrete line of storms is able to form in SW-SE NB, the biggest hazard is the wind threat. Gusts could be over 90km/h in an organized complex – storm motion to the ESE. These cells also may survive across the Northumberland Strait and Bay of Fundy with a strong 700 steering flow late day today. The grey hazard area is extended to reflect this evening risk. It should also be noted that helicity today is non-zero. This, along with low freezing levels, will be monitored closely.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Tirone.

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

NB: Chance of some scattered embedded thundershowers over southern New Brunswick this afternoon and evening with some locally heavy downpours.

Lab: Chance of scattered/frequent thunderstorms through southern Labrador today. These could be marginally severe with gusty winds and heavy downpours (locally).

NS: Scattered embedded thundershowers over most of mainland NS this afternoon and evening. Rain is the biggest hazard.

Tonight

NS: Thunderstorms continue over eastern sections as well as much of the marine district.

Tomorrow

NB: Thunderstorms are forecast to develop late afternoon and early evening. Severe storms are possible along and south of Highway 2, with gusty winds and moderate hail.

 

Convective Discussion

Labrador has lit up quite quickly today with lightning across the southern tier. These storms (spawning from a low centre anchored way back to the west) have a lack of a dominant steering flow and so they could drop quite a bit of rain locally. Elsewhere across the southern Maritimes, an embedded TS risk exists within the broader precip shield that has enveloped the region. Later this afternoon, greater jet support advances east from New England and should create enough lift and charge separation to spark more lightning. Dewpoints remain fairly high near 15 at the noon hour. CAPE is relatively low today given the setup - so severe hazards are not forecast. Tomorrow is a different story across NB. The freezing levels will be much lower creating a possible hail-favoured setup. Additionally, if organized cells do form, they will bring an inherent wind risk. G90 are possible and are depicted by the yellow hazard area. This severe weather risk will be re-analyzed and potentially alerted for on Wednesday.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Tirone.