Day 1 Convective Outlook for Atlantic Canada Valid for June 12th, 2018

Convective Discussion

No convective weather expected across Atlantic Canada today.

Technical Discussion

A low pressure system over western Labrador will track southeastward today. A trailing cold front may give thundershowers this afternoon or evening over regions near and north of the Gaspe Peninsula. CU development is expected over portions of eastern NFLD and LAB today but the airmass is dry so just a few showers will be a result. Synoptic rain and snow is expected over western LAB closer to the low.

Regional impacts

NS/NB/NL/PEI/LAB: Nil.

Andy

Day 1 Convective Outlook for Atlantic Canada Valid for June 11th, 2018

Convective Discussion

No significant weather expected across ATL CAN.

Technical Discussion

Upper level trough remains over the region today with cold, dry air in the low levels. Strong capping associated with an approaching area of high pressure is limiting the cloud development to CU and SC. There is a zero percent chance of TS activity today.

Regional impacts

NS/NB/NL/PEI/LAB: Nil.

Andy

Day 1 Convective Outlook for Atlantic Canada Valid for June 8th, 2018

Convective Discussion

This is a very low probability of non-severe thunderstorms over southern New Brunswick and Western PEI late this afternoon ahead of an approaching cold front. For Eastern PEI and Northern Nova Scotia this risk will continue into this evening. There is a very slight chance of weak embedded thunderstorms with enhanced rainfall amounts possible should they develop.

Technical Discussion

Overall the amount of low level moisture and instability is not favorable for the development of thunderstorms with most unstable CAPE values < 250 J/kg. However with the presence of the approaching cold front stretching from Labrador down into New Brunswick as a trigger and an approaching cold trough aloft there is a slight risk that thunderstorms may develop. This is risk may also be enhanced slightly over areas of higher terrain and max daytime heating later today.

Regional Impacts

New Brunswick: Showers and risk of weaker thunderstorms over southern New Brunswick beginning late this afternoon. No significant impacts expected.

Nova Scotia: There is a slight risk of weak thunderstorms late this afternoon and this evening over parts of northern Nova Scotia. No significant impacts expected.

Prince Edward Island: There is a slight risk of weak thunderstorms late this afternoon and this evening. No significant impacts expected.

Newfoundland and Labrador: There is a slight risk of weak thunderstorms late this afternoon for southern Labrador and this afternoon and  evening for western Newfoundland. No significant impacts expected.

Mel Lemmon

Day 1 Convective Outlook for Atlantic Canada Valid for June 7, 2018

Convective Discussion

 

There is a risk for non-severe thundershowers over northern New Brunswick late this afternoon into the evening and overnight with an approaching low pressure system over central Quebec tracking eastward today. Elsewhere no significant convection is expected with a ridge of high pressure stretching from Labrador to Nova Scotia keeping conditions dry.

 

 

Technical Discussion

 

The warm front in association with the low pressure system over Quebec has pushed north of New Brunswick. The ingredients necessary to initiate and maintain convection this late this afternoon over northern New Brunswick should be present. In the upper levels, there is an approaching  80KT 250mb jet and northern New Brunswick lies in the favourable left exit region. The 500mb level has increasing diffluence, slightly cooling temperatures, as well as increasing 700 and 850mb warming will help to destabilize the air mass. A trough within the warm sector is also expected to push eastward over Northern New Brunswick tonight to kick start the convection.  The biggest inhibitor are the current relatively dry low levels and moist upper levels. Upstream precipital water values are in the range of 15-20mm. There is also widespread cloud cover currently from Quebec into western New Brunswick which may delay convective initiation if convective temperatures are not reached. If they do, only CAPE values maxed near 500 J/kg will be reached. Freezing levels are low so there is the risk of small hail. 

 

Regional Impacts

 

New Brunswick: Showers and risk of thundershowers over northern New Brunswick beginning late this afternoon and may continue into the early overnight hours. Some local heavy downpours, gusts to 50 km/hr, and small hail (<2cm) are possible.

 

Nova Scotia: None

 

Prince Edward Island: None

 

Newfounland and Labrador: None

 

 

Roberta McArthur

 

Day 1 Convective Outlook for Atlantic Canada Valid for June 6, 2018

 

Convective Discussion

 

Nil significant convective weather is expected across Atlantic Canada today. Isolated to scattered shower development is expected over central New Brunswick this afternoon and early this evening. Slight risk of convection this afternoon over southern Nova Scotian waters and late this evening/overnight over southern Newfoundland waters  as a weak low pressure system currently over southwestern Nova Scotian waters will slowly track northeastward throughout the period.

 

Technical Discussion

 

Ridging moving into the region from the northwest, and multiple low pressure systems crossing the southern marine districts of both NS and NL, will generate conditions that are not condusive for the production of severe convection over the provinces today. Capping exists throughout the region and although some dynamic forcings are present, they are not expected to be strong enough to erode the capping inversions. Moisture across the region is also generally low, with the most moisture being confined well south of the Atlantic Provinces and near the Gulf Stream. There is an upper trough that is currently moving through northwestern New Brunswick and is expected to help generate TCU across central and western regions of the province this afternoon. Showers that will develop with the passage of this feature are expected to be generally light with an isolated moderate shower where day time heating and moisture availability is largest.  

 

Regional Impacts

 

Newfoundland and Labrador: Nil sig severe convective weather is expected today.

 

PEI and Nova Scotia: Nil sig severe convective weather is expected today.

 

New Brunswick: Showers associated with the passage of an upper trough are expected to develop this afternoon. No significant convective weather is expected to develop this                afternoon with the passage of the aforementioned feature.

 

Southern Nova Scotia and Southern Newfoudland marine districts: Slight chance of thunderstorms this afternoon associated with the passage of the afforementioned low. Primary regions of potential development are over the southern marine waters with the warmest sea surface temperatures, from Georges Bank to East Scotian Slope. Slight chance of nocturnal thunderstorms associated with the passage of this low over Laurentian fan late this evening and overnight for extreme southern portions of the Southwestern Grand Banks. Should thunderstorms develop, their primary threats would be wind gusts near 35 knots.

 

 

Marshall Hawkins