Convective Outlook Valid for July 9, 2019

Convective Discussion

 

Only one area for potential TSRA is over NL and waters to the NE of the island. Upper level low and some PVA gave some elevated ISOL TSRA to parts of Newfoundland early this morning. Skies are beginning to clear somewhat, which could give way to some ISOL cells this afternoon. Modifying the 12Z tep from YJT could give between 200 and 300 CAPE, but the upper dynamics are weak. There could be slight 500 mb height falls which could lead to some cells. Freezing levels are low, so some small hail is a possibility if they develop. OTWZ nil sig wx for the rest of the region.

 

Regional Impacts

 

Newfoundland: ISOL cells are PSBL this afternoon.

 

Elsewhere: nil.

 

 

Jeremy

Convective Outlook Valid for July 8, 2019

Convective discussion

 

A couple areas show some potential for thundershowers/storms today. The first is a over the Quebec Lower North Shore. A weak trough near the surface could produce some TCU and am ISOL CB that could trickle into portions of the Great Northern Peninsula this afternoon.

 

The better area for possible storms is across SE QC this afternoon. WV imagery shows a good area of PVA east of James Bay that is advecting to the SE. Upper level troughing at 500/250 mb will give some weak divergence. There is also a decent jet at 250 upstream moving south of James Bay, and eventually curving towards the east, putting NRN NB/Gaspe in the left exit region (however the timing appears to be off just a little). Looking at KCAR and YZV, FZLVLs are below 10,000 feet, but PW is low as too the low level moisture. Shear, on the other hand, is pretty good. Expect strong gusty winds and small hail with the stronger storms this afternoon and into this evening. Given the decent dynamics, some cells will propagate over the GLFSTLAWR tonight.

 

Regional impacts

 

Newfoundland and Labrador: Risk for ISOL TSRA advecting from the Lower North Shore into the Northern Peninsula.

 

New Brunswick: SCTD non-severe storms are likely later today and into this evening associated with the PVA and upper level trough. Small hail and gusty winds are quite possible (conditions look ripe for some SVR storms in QC).

 

PEI: PSBL TSRA affecting portions of the island this evening as they move across ERN NB (good upper level forcing).

 

Nova Scotia: nil

 

 

Jeremy

Convective Outlook for Atlantic Canada Valid for July 7th, 2019

Convective Discussion

A quiet day across the Atlantic Region today as the cold front that produced the severe weather yesterday has moved out of the area. There will be some embedded thunderstorms along the cold front over the marine area that is quickly tracking eastward.

 

 

Regional Impacts

Non Expected.

 

 

Convective Outlook Valid for July 6, 2019

Convective Discussion

Non-severe thundershowers possible for much of Atlantic Canada, with possibly near severe impacts for northern and western Labrador this evening, for central New Brunswick for this afternoon possibly into this evening, and for northwestern Newfoundland.

All of this is related to an occluded low south of Ungava Bay, and a frontal system extending southwest from Labrador southwest into Maine. This is giving some dynamic support, mainly for New Brunswick for Today and Labrador for tonight. There’s some convection over Labrador ahead of the occluded low, and some insolation over the west. Dewpoints are a bit on the low side (10-15 C), but PWAT is in the 30 mm range, which isn’t bad. The upper jet approaching has some PVA, and when it sinks southeast there will be some enhanced lift from the Left Exit to the northwest. Shear is on the high side at 50+ kts, which isn’t likely to drop with the approaching jet, and will reduce local rainfall amounts, and may be too high relative to the CAPE to produce supercells.. The basic idea is that convection will persist into tonight.

For New Brunswick. Ingredients are healthy for convection, which may near severe status. Currently there is scattered convection in the clearer air ahead of the front, which may argue for more moderate cells. Moisture is good as the surface with 20C dewpoints, and at 850 mb  near 14C dewpoints. PWAT is near 50 mm. Instability is okay with CAPEs currently near 3-400 J/kg, and possibly a bit higher this afternoon. Later this afternoon CAPEs may near 500-1000 J/kg, which may be enough to near severe. The shear is currently near 30 kts, which is marginal for severe conditions,  but will increase a little this afternoon.

For Newfoundland the approaching front will act a bit like the conditions for New Brunswick, with marginal shear (30-40 kts) , probably lower CAPEs, slightly lower dewponts (near 16 C), and PWAT near 35 mm. Because of the timing and orientation of the trough, things should max out later in the afternoon roughly near the Deer Lake region.

Regional Impacts

Labrador: Non-severe thundershowers for most areas developing this afternoon with high intensity beginning this evening, with stronger cells north of the Labrador Highway and west of the mid Labrador coast. Impacts will be mainly local heavy downpours and some gusty winds. There may also be some hail further north.

Newfoundland: Non-severe thundershowers beginning early in the afternoon. Impacts will be local heavy downpours, followed by gusty winds. The Deer Lake region and points north on the Great Northern Peninsula should have more significant impacts.

Maritimes: Non-severe thundershowers today for New Brunswick and a chance for Prince Edward Island, with the most significant impacts for the southern half of New Brunswick  except for the Fundy Coast. For this evening a risk of thundershowers Nova Scotia. Impacts will be local heavy downpours and gusty winds.

Marine waters: Embedded convection possible for all Maritimes waters today and tonight, with stronger cells over southernmost waters. Also a slight chance near the Labrador Coast, and the Northeast Coast of Newfoundland.

Doug Mercer

Convective Outlook Valid for July 5, 2019

Convective Discussion

Near severe thundershowers  possible for  northern New Brunswick, with non-severe thundershowers possible for much of the Maritimes. Thundershowers possible for western Labrador and the Maritimes.

Maritimes: These will be mostly air mass driven by daytime heating up to the low thirties and dew points near 15-20 C . A deep ridge will move though New Brunswick this afternoon and over eastern Nova Scotia by this evening, having generally sunny conditions. CAPEs near or possibly exceeding  500 J/kg range are reasonable for the Maritimes provinces, with New Brunswick possibly in the 500-1000 J/kg range, and possibly higher central and north. The highest risk are for heavy downpours and high wind gusts. The main factors against these cells developing is a lack of moisture aloft, as well as a lack of upper support. 0-6 km shear is near 30 kts, and will diminish a bit this afternoon. Freezing levels near 13 to 15 thousand feet make significant hail unlikely.

Labrador: For western Labrador  there are two factors that may spawn some weak cells this afternoon, that may become healthier into early this evening. . Near or just east of Churchill falls there is a  north-south trough with some sunny breaks to the west. Farther west there is a weak diffluent upper jet approaching from Quebec.  These, combined with daytime heating may produce some cells with CAPEs up to 500 J/kg, with PWAT near 33 mm, and dew points near 14 C in the west. Wind shear is near 25 kts and will increase from the west into this evening to near 35-40 kts.

Regional Impacts

New Brunswick: : Near severe thundershowers possible this afternoon into this evening with heavy downpours and gusty winds possible.  Highest risk for severe in the north this afternoon.

Nova Scotia: Non-severe thundershowers possible this afternoon into this evening with heavy downpours and gusty winds possible.

Prince Edward Island: Non-severe thundershowers possible this afternoon with gusty winds and occasional heavy downpours.

Labrador: Non-severe thundershowers giving occasional downpours. A slight chance for small hail.

Newfoundland: None

Doug Mercer