Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today: Scattered embedded thundershower activity within the boundary that’s in the vicinity of the Grand Banks. No severe hazards forecast.

Tonight: No thunderstorms expected.

Tomorrow: No convection forecast. Strong cap.

Convective Discussion

Upper trof is departing Nfld this morning. Convection is possible out ahead of the trof, but would be non-severe and embedded. The risk would only be 5-10mm of rain. Stability increases tonight from a Ridge building in from the west. Building heights are preventing any deep convection on Wednesday. The next trof approaches late in the day on Thursday, and may bring a lightning strike or 2 before midnight over extreme western Lab and NWrn NB.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Thunderstorm Outlook for Thursday

Forecaster: Tirone.

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Today: scattered thunderstorms this afternoon and evening for portions of the MRTMs and southern NL giving gusty winds, small hail and downpours. I do not anticipate severe cells, but rainfall could become a concern in the MRTMs if convection is slow-moving.

Tonight: risk of a thunderstorm for eastern NL giving heavy downpours.

Convective Discussion

Today will feature an incoming sharp upper trough that will swing down across the southern Gulf of St. Lawrence then eventually move east of NL by Tuesday morning. At first glance the trough looks inviting for a good active day but, much like yesterday, there is a lack of instability. There should be some scattered thunderstorms develop but nothing to write home about. As the upper trough continues moving into the region the freezing levels will be dropping so under some of the heavier precipitation bands there could be a fair amount of hail locally…but small in nature (a cm or less in diameter). The shear will be in the 30-40 knot range just ahead of the upper trough, so some strong gusts are possible as well. The PWATs favour the best rainfall potential in eastern NS and southern NL. The risk for thunder will persist tonight for eastern/southeastern NL just ahead of the upper trough.

Things will get quiet for several days after today with nothing expected until later this week.

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Jeremy

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Today: scattered thunderstorms across southern/southwestern NB giving a threat for localized flooding. Further north just some airmass CBs giving brief downpours and possibly small hail. A risk of an afternoon/early evening thunderstorm across the interior of NL.

 

Monday: scattered thunderstorms likely for eastern NB, eastern NS, PEI, and southern areas of NF giving brief downpours, small hail, and gusty winds.

 

Convective Discussion

 

The main area of concern today would be high rainfall rates across southern areas of NB, as PWATs are up around 40 mm (based on the KALB sounding). The instability is on the weak side though, and given the current cloud clover we will need to see formation upstream in ME that could advect into NB this afternoon/evening. Some gusty winds could also accompany the cells as effective shear will be increasing throughout the day. There will likely be some scattered thunderstorms across the northern half of NB this afternoon as an upper trough approaches from QC. Given the increase in shear and lowering of the FZLVLs small hail and gusty winds are possible. Lastly a slight risk of an afternoon/early evening thunderstorm for the interior of NL giving brief downpours and gusty winds.

 

On Monday, the upper trough will be moving through eastern regions of the MRTMs and into southwestern NL, so there should be some scattered thunderstorms associated with it. Small hail looks possible given the lowering of the FZLVLs, but also brief downpours and gusty winds. Like today, the instability looks weak so could be a balance issue with the strong wind shear and updrafts…which would lead to less in the way of activity if the shear is too high.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Jeremy

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today: Slight risk of a thundershower over extreme northern New Brunswick and southwestern Labrador this afternoon.

Tonight: No thunderstorms forecast.

Tomorrow: Risk of scattered thunderstorms across New Brunswick and Nova Scotia tomorrow afternoon. Heavy downpours are the main threat.

Convective Discussion…

A slight risk of thundershowers exists today with a slow moving frontal boundary extending from Labrador into southern Quebec. Most of the convection is likely to occur in Quebec today, though a few thundershowers may poke into extreme northern New Brunswick and southwest Labrador as the trough moves east. The 12Z Caribou sounding this morning indicated some modest instability, however a cap was evident around 500 mb. With some smoke aloft over the area of interest, any storms that initiate are likely to remain sub-severe with the main risk being some locally heavy downpours.

A second trough will intensify as it crosses southern Ontario tonight, and draw in some moisture currently over the eastern United States as it approaches New Brunswick tomorrow. Precipitable water from 12Z soundings over the mid-Atlantic region of the US indicate upwards of 50 mm. Though not as high, PWATs across southwestern New Brunswick are expected to rise into the 30 to 40 mm range by tomorrow afternoon as the trough advects some of this moisture north. Weak lapse rates and moist profiles will likely keep any storms from producing strong winds or hail, so the main risk tomorrow is for some heavy downpours, especially in southwestern New Brunswick. There also exists a slight risk for a few pop-up thundershowers over central Newfoundland and southern Labrador tomorrow afternoon.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Copp

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today: Chance of organized thunderstorms over Cape Breton, Newfoundland and parts of Labrador today. Main hazard is very heavy downpours.

Tonight: Slight risk of an isolated thundershower over eastern Newfoundland.

Tomorrow: Some isolated thunderstorms possible over extreme southwestern Labrador.

Convective Discussion…

A low pressure system with a trailing cold front will be the driver for some organized thunderstorms today across Newfoundland and parts of southeastern Labrador. The cold front prompted severe thunderstorm watches and warnings across eastern Canada and the western Maritimes yesterday, with some organized convection persisting overnight and into this morning. The front will continue to move east today, with a strong stream of moisture being advected in over Newfoundland out ahead of it. The 12Z Stephenville sounding indicates 39 mm of precipitable water and 35 knots of bulk shear, however some warm air evident around 700 mb and weak MUCAPE may inhibit convection from becoming too organized especially given the amount of cloud cover ahead of the cold front. Given adequate clearing though, surface temperatures could rise into the high twenties which could be enough to overcome the warm air aloft and provide just enough energy for some marginally severe storms to develop. Given the high moisture but lack of steep lapse rates, the main threat with any thunderstorms today will be torrential rainfall in the 30 to 50 mm range.

The cold front will quickly move east across Newfoundland this evening, with some isolated thundershowers possible over eastern Newfoundland overnight.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Copp