Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

Labrador: Isolated thundershowers possible over southwestern Labrador this afternoon with locally heavy downpours.

NS/NB/PEI/NFLD: None.

Tonight

NS/NB/PEI/NFLD/LAB: None

Tomorrow

NS/NB/PEI/NFLD/LAB: None.

 

Convective Discussion…

With a ridge of high pressure over the central Maritimes today, not much is expected in the way of convection. A slight risk area does exist over southwestern Labrador today, where a 500 mb jet exiting the region in conjunction with a weak shortwave may provide enough support for some isolated thundershowers this afternoon given sufficient surface heating. MUCAPE values of 250 to 500 J/kg and effective shear around 15 to 25 kts should be enough to support a few lightning strikes in the area. Although quite a bit of cloud cover is lingering over northern Quebec, some signs of clearing are evident this morning. The only other issue is a lack of low-level moisture over the area which is keeping the risk level low and as such, any storms that do initiate will likely be elevated.

High resolution guidance is hinting at some potential convective activity over the Gaspe Peninsula into northeastern New Brunswick later this afternoon. 12Z soundings in the area indicate a weak thermal trough in the mid to upper levels, however the thermal ridge remains strong and intact at 850 mb. With a lack of upper level support over this region, any storms that do fire would likely be surface-based, but with the capping at 850 surface-based initiation is unlikely. A lack of low-level moisture here in combination with daytime highs near 30 degrees also indicate that storms are unlikely to fire in this region.

Tonight and tomorrow, there is a slight risk of some elevated thundershower activity off the southwest coast of Nova Scotia associated with a weak shortwave, but no impacts are expected over land.

 

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

Labrador: Isolated thundershowers over south-central Labrador this afternoon with some heavy downpours

NS/NB/PEI/NFLD: None.

Tonight

NS/NB/PEI/NFLD/LAB: None.

Tomorrow

Labrador: Isolated thundershowers over western Labrador in the afternoon with some heavy downpours

NS/NB/PEI/NFLD: None.

 

Convective Discussion…

Another quiet day is in store for Atlantic Canada as a ridge of high pressure builds in from the west. A 500 mb jet extends from northern Quebec into southwestern Nova Scotia this morning, however it is not expected to trigger any thunderstorm activity due to the approaching thermal ridge. Surface temperatures are expected to rise near 30 degrees Celsius this afternoon over much of New Brunswick and Nova Scotia, this combined with a lack of low level moisture should also help prevent any convection over the area today.

The main area to watch today will be in south-central Labrador where some isolated thundershowers could develop this afternoon, associated with some weak surface troughing and mid level cooling around the back side of an upper low over the southern Labrador Sea. The risk here however remains fairly low due to a lack of CAPE (less than 200 J/kg of mixed-layer) and fairly weak effective layer shear (10 to 20 kts), though some low level cloud cover this morning hints at just enough low level moisture to fire off a few weak thundershowers later today. The main risk with any thundershowers that do develop here today will be some brief heavy downpours of 5 to 10 mm.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Copp

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Labrador… low risk of thunderstorms over northern areas today, low risk for south-central on Tuesday.

Newfoundland… Slight risk of near shore lightning today

PEI, NB and NS… No impacts from thunderstorms expected.

Convective Discussion

A push of drier air behind a departing trough of low pressure will help settle conditions over the next couple of days. There remains a slight risk that offshore thunderstorms could affect eastern Newfoundland today, but the associated surface low and its weather are expected to move away through the day.

Over Labrador, a weak shortwave may trigger a few isolated thundershowers over higher terrain today. A similar setup could extend slightly farther south tomorrow; however, confidence in this potential remains low.

Looking ahead to the remainder of the week, conditions should remain fairly quiet as a ridge of high pressure builds across the region.

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/NS: scattered risk of an embedded non-severe thundershower across the Maritimes this morning and again this afternoon/evening.

NFLD/LAB: isolated chance of a lightning strike or two later today near the Burin, and also south of Goose Bay along a deformation zone.

 

Tonight

NS/PEI/NFLD: embedded elevated non-severe convection is forecast to pull away to the SE over the marine district tonight. It may graze the Avalon overnight.

NB/LAB: none.

 

Monday

LAB : convection is possible near Nain throughout the day. Forecast to be non-severe in nature.

NB/NS/PEI/NFLD: no thunderstorms forecast. Much of Nfld is receiving synoptic scale rain.

 

Convective Discussion

The dewpoints rose last night as forecast to near 16 across the Maritimes, paving the way for this morning’s first round of early convection. CAPE remains very skinny today, with not much shear involved (in the effective levels). These warm frontal showers are giving bursts of heavy rainfall then subsiding to mist/fog patches. A partial clearing is possible for some areas of central and western Nova Scotia near noon today. Then a slumping cold front will force another round of scattered TS – main hazard again being lightning and heavier pockets of rain. Pwats on morning soundings to the west sit near 35mm. This is under severe alert criteria as long as storms continue moving and don’t sit too long over one location. There is decent flow at 850 and above so storms are expected to progress Ely. The adjacent gulf shores will be gustiest this evening behind the  passage of the front (G70km/h). Nfld will be getting the brunt of the rain from the “now forming” synoptic low tonight and tomorrow. Isolated thundershowers are possible off to its East (depicted in grey area). The Maritimes are stabilizing on Monday and quiet SVR weather wise. Summer heat builds in again this week.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Tirone.

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

 

Today

NB: slight risk of an embedded non-severe thundershower across northern areas of the province near the Que border.

NS/PEI/NFLD/LAB: None.

 

Tonight

NS/NB/PEI: embedded elevated non-severe convection is forecast late overnight tonight across the Maritimes, and into early Sunday morning.

NFLD/LAB: None.

 

Sunday

NB/NS/PEI/NFLD: risk of non-severe embedded thundershower activity continues all day in the broad area of convective showers. There could be a few heavier downpours associated in the Annapolis Valley and Cobequid mountain areas. Late day the shower activity could approach Saint-Pierre and the Burin.

LAB : None.

 

Convective Discussion

The atmosphere will slowly begin to destabilize above 850mb over the next 12-24hrs. A broad area of low pressure is approaching the Maritimes tonight from the Great Lakes region of Ontario. This will bring a change in airmass and bump up dewpoints significantly from 4 to 18. Accordingly, embedded non-severe thundershowers are being forecast and will slowly traverse the Maritimes (and the marine district) this weekend. The greatest impact is repetitive showers, and lightning. Rainfall amounts will be highly variable across regions. There is a low level jet at 850 out of the WSW that strengthens both in the day Sat and again on Sunday. BUT – effective shear remains low at only 10-20kts. 0-3k shear is better at 30-40kts which just confirmed the nature of these cells being mostly elevated. CAPE for the whole column is 400J at best and very skinny.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Tirone.