Convective Outlook Valid for Today and Tomorrow

Regional Impacts

There is a risk of thundershowers this afternoon and evening across western and central Labrador. These could advect eastward affecting portions of the LAB coast tonight as well. Brief heavy downpours and gusty winds are possible.

There is a slight risk for a severe thunderstorm across the far northwest of NB. The main threat would be torrential rainfall…however strong wind gusts are also a possibility.

Lastly, there is a risk of isolated thundershowers this afternoon across the valley and northern NS. Torrential rainfall is the main threat.

 

Convective Discussion

The main focus today will be to see what forms upstream across southern Quebec and northern Maine. What will be a moot point today is a trigger. The KCAR tephi has ~ 25 knots of shear, PWAT of around 40 and MLCAPE of 1000-1200 j/kg. There is a moist tongue near the surface which would add to the buoyancy as the day progresses. The deep layer trough at 500 mb is further upstream at 12Z, but that should propagate eastward today, resulting in an increase in wind shear across NW NB. If cells do make it to the region, torrential downpours and gusts to 70-80 km/h would be expected. Will have to monitor the upstream development this afternoon and the evolution of movement.

 

For Labrador, where shear is 40-45 knots, and closer to the surface and upper trough, scattered cells are likely. Then only issue would be warm air aloft…however given the dynamics that would be broken fairly easily. Brief heavy downpours and gusty winds are possible with the storms.

 

There is a risk of isolated non-severe thunderstorms across the valley and northern NS this afternoon. There is very little shear (YQI and GYX showing 20 knots), but the PWAT is 40+. CAPE looks to be in the 500-1000 range. Locally torrential downpours will be the threat.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

NB/NS/PEI/Labrador:  No significant impacts expected.

 

Newfoundland: Slight risk of short lived thunderstorms over central and eastern Newfoundland.  Main threat is local heavier showers and gusty winds. 

 

Convective Discussion

 

An area of PVA is currently bringing some showers and thundershowers just southwest of Newfoundland.  This area of PVA along with cooler upper atmosphere temperatures and high insolation will bring some thundershower activity to parts of Newfoundland today.  Wind shear is low so long lived severe thunderstorms is not expected.  Precipitable water is low as well so torrential downpours are not expected.  Still, there is a low potential for short lived severe storms bringing localised heavy rainfall and gusty winds mainly over eastern Newfoundland.  Prog tephis over eastern Newfoundland showing between 500 to 1000 J/kg with low shear and low precipitatble water.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2

 

 

Barrie MacKinnon

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

For Labrador.. Small hail and gusty winds in thunderstorms this afternoon and this evening. Heavy downpours may occur.

 

For New Brunswick.. Isolated thunderstorms possible over norther New Brunswick this afternoon. No Severe Weather expected. Small Hail possible.

 

Convective Discussion

 

Labrador continues to be a main threat area today with an upper trough progressing eastward through northern Quebec. Aloft at 250 there isn’t strong support but the dynamics are somewhat more favourable as you move down through the atmosphere. Good low level shear below 500 mb could favour the development of organised thunderstorms this afternoon, possible affecting western Labrador late this afternoon and early in the evening.

 

Not much is expected southward in New Brunswick with somewhat dry, relatively speaking,  lower levels and upper lapse rate that are not overly conducive to deep convection. However an upper trough may act to destabilize the atmosphere allowing for daytime heating and surface convergence near the northern coastlines to trigger some convection.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

NS/NB/PEI/NFLD/Labrador: None

 

Convective Discussion

 

Lower dew points and a stable airmass has moved into the area. There is a thundershower risk for southern Maritime marine areas today.  On Saturday there is a thundershower risk for NW New Brunswick and parts of Labrador as separate surface troughs move across those regions.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

NS/NB/PEI/NFLD: None

Labrador:  A risk for most regions and a chance of gusty winds and hail southeast.

 

Convective Discussion

 

A low pressure system will track across Labrador today. Ahead of the low, daytime heating will allow temperatures to reach 27 degrees. Modifying the upstream sounding at Sept-Iles yields precipital water of 25- 30 mm, cape of 1000 J/kg and unidirectional shear of 30 kts. Additionally the freezing level is fairly low at 9,000 feet.  An upper level jet will approach this afternoon and southeastern Labrador will be in a favourable area of enhanced lift (left exit). The low freezing levels and decent cape above -10 C will support hail growth. The dry mid levels will support possible wind gusts.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2