Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Regional Impacts

 

Southeastern Labrador: Isolated non-severe thundershowers.

Eastern Gulf of St. Lawrence: Gusty winds and possible waterspouts this afternoon into this evening.

Newfoundland: Generally isolated to scattered non-severe thundershowers. For northeastern regions possible wind gusts to 90 km/h and rainfall amounts reaching 25 mm/h locally.

 

Convective Discussion

A trough crossing the Gulf towards Newfoundland, with a cold trough at 700 mb giving some enhanced instability, along with la left exit region currently east of Deer Lake eastwards towards Ganer, will give some strong updrafts. Moisture is modest with PWAT around 20-25 mm, but shear is in the 25-30 kt range. Profiles and the upper air analysis shows fairly dry air from 850 mm and up, combined with the destabilisation associated with the approaching upper cold trough, and should give some healthy downdrafts. Rainfall amounts under individual cells have a slight possibility to reach 25 mm/h with the fairly brisk speed of the individual cells, but some training may boost the amounts to warning levels.

 

The same cold upper trough over waters in the eastern Gulf near or exceeding 20 C, with a unidirectional strong flow up to or exceeding 850 mb, may give waterspouts this afternoon into this evening. For the Newfoundland coast SSTs are slightly cooler, especially north of Corner Brook and Gros Morne, but have more potential offshore for southern Gulf – Port au Port.

 

 

 

 

Thunderstorm Outlook for Day 2

 

A weak east-west trough dropping south over New Brunswick may produce some thundershowers with a possibility for high wind gusts late in the day. For Newfoundland there is a possiblilty for non-severe isolated thundershowers for the middle of the west coast east to the Baie Verte Peninsula.

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Some weak thunderstorms are likely to develop late today over northern New Brunswick. This evening and tonight the risk will spread through the gulf impacting western Newfoundland by the morning..

 

Convective Discussion

 

The atmosphere will continue to destabilize later today and through tonight as a cold upper trough makes its way through the region. Overall the amount of moisture has diminished over the last few days but steepening lase rate should be sufficient to generate stronger updrafts overnight and tomorrow morning for the eastern gulf waters and tomorrow afternoon for parts of Newfoundland.

 

For tomorrow deep shear and CAPE will continue to increase as the upper trough approaches, with ~40 knots of 0-6km shear and ~1000 j/kg. Organised convection is possible with a low probability of supercell formation. Strong wind gusts, 25mm + rain and small hail is possible.

 

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

For New Brunswick… local downpours of 20mm are possible for northwestern areas, however should organized thunderstorms develop possibly more.

 

For Northern Nova Scotia and southern Newfoundland… embedded thundstorms with weaker updrafts possible, some locally heavier rainfall could occur.

 

Convective Discussion

 

Today the vertical velocities should not be overly strong but despite this there is still a decent amount of moisture available with 30 + mm of precipitable water from the Sept-Iles and Caribou soundings. For today some locally heavy downpours and training of thunderstorms is possible and stronger returns are already showing up in Maine this morning. With daytime heating this should intensify further for western areas of New Brunswick into the afternoon.

 

Thunderstorm Outlook for Day 1

 

 

 

For tomorrow falling heights and increasing shear along with lowering freezing levels could lead to a larger hail potential and gusty surface winds.

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

No impacts due to thunderstorms are expected today.

 

Convective Discussion

 

Most of the deep convection today will remain to the west and to the south as an upper thermal ridge will suppress the deeper thunderstorm for the Atlantic Region. Solar insolation will kick in over new Brunswick and TCUs will quickly develop but the storms should not be deep enough to generate thunderstorm activity, although intense showers may be possible. Over the marine area large, heavy rain producing storms can be expected, with respectable deep shear of about 30 knots and CAPE values > 1000 j/kg some organised storms could develop.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Slight risk of a thunderstorm giving brief moderate downpour for Valley and Central NS, PEI, and southern NB.

 

Convective Discussion

Some instability is expected this afternoon but it will manifest itself mostly in the low levels (below 3000m). Precipitable water range from 25-32 mm over southern portions of the Maritimes – hence the possibility of a brief downpour from towering clouds. Some regions have slightly higher dewpoints, and some will experience more surface heating from the sun - this greater instability could lead to the development of isolated thunderstorms.

 

Large high pressure cell over northern Quebec giving stable and dry air mass over Newfoundland and Labrador. Available energy is 0, and the precipitable water is an anemic 9mm at Stephenville.

 

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2