Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Newfoundland… low chance of thunderstorms overnight and tomorrow.

Labrador... Chance of a thunderstorm, today and tomorrow. Small hail possible.

NS… Some thunderstorms with locally heavy rainfall amounts today. Risk of a thunderstorm tomorrow.

PEI and NB... Scattered thunderstorms with some locally heavy downpours today and tomorrow.

 

Convective Discussion

The higher atmospheric moisture content currently over the Maritimes will shift eastward today, reaching eastern Newfoundland overnight and into tomorrow morning. Across Nova Scotia, precipitable water values exceeding 40 mm, combined with somewhat favourable upper-level dynamics, will support the potential for heavy rainfall. Rainfall rates exceeding 25 mm per hour have already been observed, and there remains the potential for these rates to continue or redevelop over eastern Nova Scotia. With moderate low-level shear and CAPE values of 500–1000 J/kg, some organized convective lines or clusters may develop.

A somewhat drier airmass will move in behind this moisture plume on Friday. As a result, rainfall rates are expected to be lower than those observed today. However, CAPE values are forecast to remain moderate, supporting scattered thunderstorm development. Deep-layer and low-level shear are expected to remain relatively weak, limiting storm organization. Consequently, organized convection is not anticipated.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Mel Lemmon

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NB/PEI/LAB: Scattered thundershowers.

NS/NFLD: None.

 

Tonight

NS/NB/PEI: Chance of thundershowers.

NFLD/LAB: None.

 

Friday

NS/NB/LAB: Scattered thundershowers.

PEI/NFLD: None.

 

Convective Discussion

Scattered thunderstorms are expected across New Brunswick, Prince Edward Island and Labrador today associated with a trough tracking slowly southeastward. CAPE values near 500 J/kg are expected in the Maritimes and 500-1000 J/kg over Labrador. Effective shear near 30 knots is expected over the Maritimes and 20-30 knots over Labrador. These conditions will enable some cells to become organized but should remain below warning criteria. Dry mid-levels will support gusty winds this afternoon. Tonight there is a chance of non-severe embedded thundershowers near and ahead of the trough. On Friday, the trough will track across Nova Scotia. Scattered thundershowers are likely near and in the clearing skies in the wake of the trough. Limited CAPE values near 500 J/kg should contain the thundershower activity to less than severe.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

LAB: Scattered thundershowers.

NS/NB/PEI/NFLD: None.

 

Tonight

LAB: Chance of thundershowers.

NS/NB/PEI/NFLD: None.

 

Thursday

LAB: Scattered thundershowers.

NB: Chance of thundershowers.

NS/PEI/NFLD: None.

 

Convective Discussion

Scattered thunderstorms are expected across Labrador today associated with a trough slowly tracking southeastward. CAPE values near 500 J/kg and effective shear near 30 knots will enable some cells to become organized and approach near warning criteria. Dry mid-levels will support gusty winds this afternoon. On Thursday, the trough will track across southeastern Labrador and into New Brunswick. Scattered thundershowers are once again likely across Labrador ahead of and in the wake of the trough. There is a chance of afternoon thundershowers across southern New Brunswick ahead of the trough.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

NL : Risk of a thunderstorm west of the Avalon Peninsula giving strong winds, small hail and locally heavy downpours. Risk of a thunderstorm over the Northern Peninsula giving strong winds, small hail, and locally heavy downpours.

LAB: Risk of a thunderstorm giving strong winds, small hail, and locally heavy downpours over central and eastern regions.

NS/NS/PEI : NIL

Tonight :

None

Tomorrow :

Lab : Risk of an isolated thundershower over the central regions.

NL/NS/NB/PEI : NIL

Convective Discussion

As a ridge continues to build over the Maritimes, a low-pressure system south of Greenland is allowing several jets to align just off the northern shores. Surface analysis shows these jets stacked on top of each other over the north coast, along with some slight convergence area both at the surface and at 850mb. Additionally, with this storm south of Greenland there is multiple embedded short-waves moving in a Northwest-Southeast direction. These features along with dewpoints forecasted to remain near 12°C with temperatures rising to near 25, there is a risk for some thunderstorms that are capable of producing strong winds, hail up to 2cm. There remains once again some model uncertainty between the RDPS and HRDPS. Upon closer inspection of the 00z Soundings and the 12z Stephenville Soundings, the HRDPS has a much better initialization when compared to the RDPS. This is important to note as there are significant differences in thunderstorm potential between the HRDPS and RDPS for regions near the Avalon (with the RDPS being the lesser of the two). All of this being said, over Labrador, there were some early morning lightning strikes that occurred, but the main struggle for today will be fighting off the smoke in the regions. Looking at the observations from Wabush, there have been consistently reports of smoke, which would act as an inhibitor to convection today.

For tonight, convective activity is not expected to occur. This is primarily due to smoke continuing to move into the region and overnight stability setting in.

Tomorrow, there is a chance of thunderstorms developing. These thunderstorms are likely to be terrain-induced near Happy Valley Goose Bay. There will be continued smoke moving in from Quebec, but models currently show smoke clearing out of this region as a slow-moving system over Hudson Bay progresses eastward.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Lambert/Firth

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

Lab: Risk of a thundershower over western regions this evening giving locally heavy downpours.

NB/NS/PEI/NL : Nil

Tonight

Lab : Slight chance of an isolated thundershower overnight.

NB/NS/PEI/NL : Nil

Tomorrow

NL : Risk of a thunderstorm near the Avalon Peninsula giving strong winds, small hail and heavy downpours. Risk of a thundershower over the Northern Peninsula.

Lab: Risk of a thundershower giving locally heavy downpours over central and eastern regions.

NB/NS/PEI: Nil

Convective Discussion

As a ridge builds through the Maritimes, 850mb and 700mb Jets orientated relatively north-south will aid in the trigger of some thundershowers over Labrador this evening. Generally, for these thunderstorms values of Mixed Layer CAPE (MLCAPE) will be staying close to the 500-700 J/Kg range with Surface Based CAPE (SBCAPE) being slightly higher nearing the 1,000 J/Kg range. Given these CAPE values along with a relatively weak Effective Shear of around 20Kt any convection that does occur will be isolated in nature and is expected to be short-lived. This is also applicable for the overnight hours into tomorrow morning, generally there is a risk for elevated thundershowers over Labrador, though the forcings in the overnight hours will be weaker hence the area outlined does not have any attributes attached to them.

For tomorrow, the ridge moves further southeast and allows for a higher dewpoints and stronger jets to interact with the land-sea boundaries from Trinity Bay and Placentia Bay, which could give rise to more intense thunderstorms in eastern Newfoundland. Currently there is some discrepancy between the Regional and High-Res model guidance for this event. The High-Res currently has higher dewpoints extending further into the atmosphere along with a slight easterly flow, meanwhile the Regional has slightly drier layer with a complete westerly flow throughout the atmosphere column. This discrepancy is enough to not indicate a risk for tornadoes, but is possible with a High-Res solution. With the High-res solution the main region of concern would be from Clarenville to CBS and extending down to Argentia. Meanwhile up in Labrador and the Northern Peninsula, jet streaks still remain the active triggering mechanism though with slightly lower CAPE values the risk for a severe thunderstorm is low.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Lambert/McArthur