Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Today: isolated thunderstorms over southern marine waters.

Tonight: Isolated thunderstorms possible over western NS and southern NB. Isolated thunderstorms once again for southern marine waters.

Sunday: Isolated thunderstorms for most of NL and some marine waters.

 

Convective Discussion

Some ongoing morning thunderstorms for southern waters today through to Sunday in association with a persistent trough of low pressure. Will likely continue to see the diurnal tendencies for these cells with CTC being favourable (overnight and morning). Some gusty winds are possible especially over the warmer waters.

 

An upper low will approach the MRTMS today bringing some showers, with a risk of a thunderstorm tonight as an area of PVA moves in promoting upper level divergence. The guidance will likely miss this potential in conventional indices. Heavy downpours would be the threat and given the slow movement, localized heavy amounts are also a possibility.

 

The trough that has been south of the region will move northward towards NL on Sunday with the risk for isolated thunderstorms giving heavy downpours.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 1 night

 

Thunderstorm Outlook for Day 2

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

Labrador.. Isolated thunderstorms potentially producing heavy showers with rainfall rates of 10-20 mm/h, gusts to 70 km/h and small hail.

Central New Brunswick.. slight risk of a thunderstorm

 

Convective Discussion

The Upper air analysis this morning shows a 500mb low near Lab City and a 130kt southwesterly jet stretching from New England to SE Lab. Lowest temperatures in the 500mb cold pool range from -18 over Lab west to -20 over Ungava Bay. At the surface a frontal boundary extends from NE NB to Anticosti Island to SE Lab. Light shower activity is detected along the frontal boundary at the current time, but latest Satellite imagery is showing cold cloud tops and some heavier radar echoes over the south side of MT Carleton. There are a couple of moisture plumes over the region, one from NS to SE Lab and another from Laurentian Fan to SE NF. Precipitable water drop quickly below 20 mm west of the upper low. Instability will be prevailing over much of Labrador especially along the Churchill valley and around Lake Melville, a second area of instability is evolving over central NB. Initiation will be favored by surface convergence near the front, but also by the cold pool and the presence of positive vorticity over Labrador. Once again today MLCAPE values of 500-750 J/kg.. shear values of 30-40 kt will prolong the life of individual cells that form over Labrador, and with strong upper dynamics some of these storms could become organized in lines which could possibly be bowing. Also, Predicted DCAPE in excess of 600 J/kg around Lake Melville indicates the possibility of strong gusts. The thunderstorms over NB will be pulse type and are not likely to be significant.

A second frontal feature currently east of Sable Island will advance over Banquereau and Laurentian Fan this afternoon, the plume of moisture will propagate towards SE NF tonight bringing a risk of embedded thunderstorm.  

 

 

Thunderstorm Outlook for tonight

 

 

 

Thunderstorm Outlook for Saturday

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

Western Labrador.. Isolated thunderstorms likely producing heavy showers with rates of 10-15 mm/h

Northwestern NB.. Isolated thunderstorms giving a risk of localised heavy showers with rates of 10-20 mm/h, 1 cm hail, and strong wind gusts.

Convective Discussion

There is an upper level low centered near LG4 with a thermal trough extending southward, ahead of this feature there is thermal ridging along the Labrador coast and NF. At the surface, there is a cold front extending from west of Shefferville to southwestern Quebec. This feature will continue to be the focus for convection this afternoon. A few GLM and CLDN lightning flashes are detected and will become more widespread during the next few hours. The more robust convection will likely occur near the St. Lawrence Valley where low level moisture will combine with better upper dynamics including a 100+kt southwesterly jet and some pos pva advection. Diurnal heating will boost mixed-layer cape values to 500-800 J/kg resulting in strong enough instability to help form CB’s with tops/equilibrium level reaching the tropopause which will lower from 45hft to 35hft as the colder air advances over the region. Deep layer shears of 35 to 45 knots will help to sustain these storms longer and some will likely produce heavy showers/hail/strong wind gusts and could propagate into northern Maine/NB early this evening. Some orographic features could also contribute to the development. For Labrador, while the dynamics may not be as strong, the upper flow is somewhat diffluent and the precipitable water estimates from the morning soundings were around 25-30mm which hints at a treat of heavy showers as reported by YKL earlier.  

 

 

Thunderstorm Outlook for Friday

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Western LAB for today: isolated thunderstorm possible.

 

Western and central LAB/NW NB for day 2: Isolated thunderstorms possible.

 

Southern marine waters today and Thursday: isolated embedded thunderstorms.

 

Convective Discussion

A nearly stationary frontal zone south of Atlantic Canada will give some isolated to scattered thunderstorm for the next couple of days to southern marine waters.

 

A weak short wave trough ahead of the main 500 mb upper trough may come close enough to western LAB this afternoon/evening to give an isolated thunderstorm, but likely to the northwest of Wabush/Lab City.

 

That aforementioned upper trough at 500 mb will be advancing to the east on Thursday which will act as the trigger for some isolated thunderstorms across NW NB as well as western and central LAB. Do not expect any threat of severe weather at this time.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 1 night

 

Thunderstorm Outlook for Day 2

Convective Outlook Valid for Today, and Tomorrow

Thunderstorm Outlook valid for TODAY: Tuesday, Aug 9/2022.

 

Regional Impacts

Very isolated embedded convection is again possible with this slumping frontal feature advancing slowly across the Maritimes today. Pockets of heavy rain (10-15mm/hr) are occurring throughout the Maritimes.

 

Convective Discussion

Significant thunderstorms are not expected to form today (or tomorrow). Pwats are very high (50-60mm) on this morning’s weather balloons, leading to high rainfall rates and a very saturated boundary layer (up to 20,000ft at Yarmouth). 0-6k shear is near 55kts, making any storm structure be very short lived and advected quickly downstream. The grey isolated area has been overdrawn to show where isolated strikes could occur (if any). Tonight, the same lack of dynamics exist over the Avalon.

 

Thunderstorm Outlook for Day 1 - TUESDAY

 

 

Thunderstorm Outlook for Night 1 - TUESDAY OVERNIGHT

 

Embedded thundershower risk shifts slightly east in the overnight hours along frontal wave.

 

Thunderstorm Outlook for Day 2 – WEDNESDAY

 

Weak dynamics for a risk of only isolated TS in extreme western Labrador late in the day (evening) near a developing low centre in northern Quebec (Nunavik) stretching back across the Kivalliq.

 

Forecaster: TIRONE/ASPC