Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Labrador

Today…Risk of a non-severe thunderstorm over southeastern sections during the afternoon, and late in the day in the west

Sunday…Risk of a non-severe thunderstorm over southernmost sections

 

NF

Today…Isolated non-severe thunderstorms over central and northeast sections

Sunday…Risk of a non-severe thunderstorm especially over northeast sections

 

NB

Today…Risk of a non-severe thunderstorm over northern regions, especially the Chaleur region

Sunday…Heavy rain likely from embedded thunderstorms

 

NS and PEI

Today…none

Sunday…Rain with Isolated embedded thunderstorms

 

 

Convective Discussion

The main area of focus this afternoon is over central NF. The convective temperature should be reached fairly early in the period but low level moisture is low and the deep layer shears are too high to produce more widespread / deeper convection. Regardless, conditions will likely produce moderate TCU’s (and even one or two CB’s) with local 5-10 mm and gusts around 50 km/h. For Lab west, there is an approaching surface trough with a large area of cloud is associated with it. Satellite imagery is indicating the presence of embedded convections west of Schefferville (however there is no lightning activity detected). The moisture in the low levels is clearly lacking over YKL-ZUM-YWK but Td’s should increase during the afternoon.. this combined with the long period of early summer surface heating, and the emergence of a low and upper level jet – should provide some support for the development of deeper (moderate) convection ahead of this feature. Having formed in a low moisture environment, rainfall rate potential is 5 mm/h at the most.  

A frontal band over New England will shift north on Sunday and spread rain across the Maritimes. Rainfall rates will be enhanced by embedded thunderstorms, especially over NB

 

 

Thunderstorm Outlook for Today

 

 

Thunderstorm Outlook for Tonight

 

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Isolated non-severe thunderstorms are possible this morning along portions of South Shore NS and offshore across marine areas – slope waters, and Sable Island. Elsewhere across Maritimes the atmosphere is stabilizing.

 

Convective Discussion

Soundings behind the frontal feature are drying out nicely at 700mb as forecast. This is stabilizing the mid levels of the atmosphere with the noticeable change in air mass. No thunderstorms are forecast overnight tonight across the AOR. Pockets of instability are possible in parts of central Newfoundland tomorrow, along parts of the Lab coast, and across extreme northern NB. No dynamics suggest anything near severe limits. Cells will be embedded in shower activity. Sunday late in the day has the potential to be more organized in NB and NS as a frontal feature amps up dew points and lift indices again. This risk will be honed in on in coming shifts, with a particularly watchful eye on shear.

 

Thunderstorm Outlook for TODAY

 

Thunderstorm Outlook for TONIGHT

 

Thunderstorm Outlook for SATURDAY

 

Thunderstorm Outlook for SUNDAY

 

Forecaster: Tirone

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

NS/NB/PEI… Scattered thunderstorms possible across the central Maritimes this afternoon, main risks are heavy downpours, strong wind gusts, and small hail.

NLFD… Isolated thunderstorms possible in central Newfoundland this afternoon, main risks are strong wind gusts and heavy downpours.

 

Convective Discussion…

As very warm temperatures continue across the Maritimes today, a cold front will begin to move south across the region. Surface based CAPE values are forecast to soar upwards of 2000 J/kg in southern New Brunswick and mainland Nova Scotia ahead of the front in addition to decent bulk shear values of 30 to 35 kts. Due to the strength of the ridge south of Nova Scotia, the front is expected to slow down and weaken as it moves across New Brunswick, and stall over southern Nova Scotia tonight. This will cause some issues in the erosion of the thermal ridge, especially over southern Nova Scotia. In addition, the location of the 500 mb jet over central Quebec is not ideal. As such, the main focus for severe thunderstorms will be in southeastern New Brunswick and central Nova Scotia today. PWAT values on the Yarmouth tephigram this morning indicate 45 to 50 mm, which is consistent with what models have been forecasting ahead of the front. With these high PWAT values, heavy downpours of 25 to 50 mm/h are expected to be the main hazard with any thunderstorms that develop, in addition to strong wind gusts of 70 to 90 km/h and small hail up to dime size.

A second round of convection may move through southern Nova Scotia from the west overnight tonight, as a weak shortwave rides the thermal ridge across the region. Heavy downpours may company these storms if they persist over the Gulf of Maine.

In central Newfoundland, similar conditions to central Nova Scotia are expected, however bulk shear values are likely to be slightly lower here (20 to 25 kts), which may prevent more organized thunderstorm activity. Another limiting factor is a layer of warmer air evident in the mid levels persisting over central Newfoundland today. Any thunderstorms that do develop may struggle to get organized, but may produce strong wind gusts of 70 to 90 km/h and heavy downpours up to 25 mm/h, in addition to the small chance of some pea sized hail.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Copp

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

NB

Today…Risk of severe thunderstorms late in the day - heavy rain and strong wind gusts (and some hail)

Thursday… Scattered thunderstorms - heavy rain, strong wind gusts (and some hail)

 

NS

Today…risk of a non-severe thunderstorm late this afternoon

Thursday… Scattered thunderstorms - heavy rain, strong wind gusts (and some hail)

 

PEI

Today…risk of non-severe thunderstorms, except for northern Prince county where strong wind gusts are possible late in the day

Thursday… Scattered thunderstorms - heavy rain, strong wind gusts (and some hail)

 

Labrador

Today…Numerous strong thunderstorms with strong wind gusts, heavy rain (and some hail)

Thursday…Isolated thunderstorms - heavy rain, strong wind gusts

 

NF

Today…isolated non-severe thunderstorms along portions of the west coast

Thursday…Scattered thunderstorms - heavy rain, strong wind gusts (and some hail)

 

Convective Discussion

 

The 500mm heights continue to rise over the region, the highest value reported this morning is Washington and Long Island with 598 dam. The moisture content is also slowly increasing at the surface dewpoint temperatures are ranging from 18 to 24 and derived precipitable water from this morning soundings are ranging from 40 to 50 mm.

Most of the convective action will be occurring over Labrador today and a Watch message has been issued. In terms of forcing the surface cold front extends from Ungava to James bay and is already triggering some thunderstorm activity. This feature will be advancing gradually throughout the day, as the airmass ahead it becomes more unstable with falling 500mb heights. Surface dewpoints of 20 deg., Surface CAPE values between 1000-1500 J/Kg, and deep-layer shears of 40 kt will contribute to the development of hefty thunderstorms capable of producing straight-line 50kt gusts, rain rates of 25-50 mm/h, and to a lesser extent 1-3 cm hail.

Conditions will become more favorable for severe weather over NB-NS-NF on Thursday.

 

 

Thunderstorm Outlook for Today

 

 

Thunderstorm Outlook for Tonight

 

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

NB

Today…slight chance of severe thunderstorms late this afternoon and evening with heavy rain and strong wind gusts

Tomorrow… Occasional thunderstorms bring heavy downpours and some strong winds

 

Labrador

Tomorrow… Thunderstorms wind strong winds and some small to moderate hail, heavy rain possible.

 

Convective Discussion

With the very high moisture making its way over the region and the slowly approaching low pressure system we are in for a multi-day event for convective weather, beginning late today in northwest NB and slowly spreading eastward tomorrow and finally into Thursday. Quebec is expected to see severe thunderstorms today with the edge of the severe thunderstorm risk just coming into NB later today. There is some indication that some thunderstorms could organise into supercell/bow echo cells but with a significant area on convective inhibition around 700 mb it may be a challenge to get thunderstorms going. However the potential for strong surface will be a concern as the day unfolds.

 

Tomorrow things shift a bit becoming more favourable for a multicell situation with the potential for heavy rain, should storms become organised (ie training thunderstorms) some areas of New Brunswick could receive more than the highlighted amounts in the forecast for day 2. For Labrador tomorrow the environment will move to a supercell/bow echo situation so strong wind gust to warning level a certainly possible. Paying close attention to overshooting tops and lightning will be helpful in the absence of radar data.

 

As we move into Thursday the dynamics will become more favourable for severe thunderstorms for the remaining areas of the Atlantic provinces please stay tuned as the situation develops over the next couple of days.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Mel Lemmon