ECCC Convective Outlook Valid for Today, and Tomorrow

Thunderstorm Outlook valid for JULY 27^th:

 

Regional Impacts

Isolated non-severe thunderstorms along an advancing frontal feature across the Avalon early today. Additional isolated non-severe thundershowers are possible in the interior of Nfld as air mass modifies slowly.

 

Convective Discussion

The main forcing is the broadly sweeping cold front that continues to trundle eastwards. Directly behind the front remains slightly unstable so in clear skies a pop up shower is possible later this afternoon. Dynamics are not favourable for any significant hazards other than lightning. Across Labrador, there is a strong thermal cap at 700mb and it is quite dry in mi-levels. Low-cloud will also create quite a hindrance. Across the Maritimes, this 700mb cap is even stronger as can be easily deciphered on Caribou and Yarmouth’s soundings this AM. Stable, sunny, relatively dry conditions are the Wednesday forecast here. No TS risk tonight.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Night 1

 

Thunderstorm Outlook valid for JULY 28^th:

 

Northern tier of New Brunswick, largely terrain driven, will de-stabilize slightly adding the risk of late afternoon pop-up showers and thunder. Severe hazard criteria is not expected to be met by these single-cell storms. Skinny CAPE values at best are near 300J/kg, with minimal shear in the background environment.

 

Thunderstorm Outlook for Day 2

 

Forecaster: TIRONE

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

NL: isolated thunderstorms with locally heavy downpours and strong winds

Labrador: isolated to scattered thunderstorms with locally heavy downpours and small hail.

Southern and eastern marine regions: strong winds and heavy downpours

 

Convective Discussion

 

A low pressure system over western Labrador will slowly move eastward today and weaken, while a cold front that moved off of Nova Scotia this morning will continue eastward across the marine slope waters and north across Newfoundland today. This front is currently being maintained  over the slope waters by favourable upper dynamics the assist of a strong 250 mb jet axis over Nova Scotia and strong bulk shear of 45KT. The upper levels beyond 500 mb are warm based on the Stephenville sounding but that should degrade some with a cold trough this afternoon depending on breaks in cloud cover to increase surface based heating to further destabilize the air mass. Thunderstorms currently over southern portions of Newfoundland could continue or reignite this afternoon.

 

Some convection is expected for southern Labrador south along a elongated trough axis where the thickness ridge will move to the northeast. Some clearing this morning will also help to increase instability in the area where CAPE values are indicating near 1000J/kg. Storm are expected to be non-severe multi-cell type but with little bulk shear, there is the possibility of heavy downpours and small hail given lowering freezing levels.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 1 Night

 

Thunderstorm Outlook for Day 2

 

Weak short wave trough moves into Newfoundland. Any surface based heating over inland areas could trigger some non-severe convection that will move to the northeast during the day. Although precipitable water will be lower than today, with values still near 30 mm and CAPE values near 500 J/kg, there could be some local heavy downpours and brief wind gusts.

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

NB: scattered strong to severe storms capable of producing strong winds, hail, heavy downpours and a possible funnel cloud or tornado

PEI: isolated to scattered strong storms capable of producing strong winds, hail and heavy downpours

NS: isolated thunderstorms giving heavy downpours

NL: isolated non-severe thunderstorms over western regions

LAB: isolated non-severe thunderstorms over southwestern regions

 

Convective Discussion

 

Active weather is expected for most of the Maritimes today and tonight. An upper low pressure system over central Quebec slowly pushes eastward today while a trailing cold front pushes from southern Quebec into New England. The front then moves into New Brunswick this afternoon and into Prince Edward Island and Nova Scotia in the overnight period.

 

Most of New Brunswick remains in cloud this morning with some showers moving through this morning but some breaks in the clouds are now occurring over eastern regions. Temperatures in central to southern New Brunswick are expected to be in the low 30s and dewpoints near 20C. A cyclonic 250mb jet will track slowly southeast into New Brunswick with a strong southwesterly jet of 35KT at 850 mb. With MUCAPE values around 2000 J/kg and strong southwesterly 0-6km shear of 40KT combined with low level shear (SRH around 100) and upper divergence, storms that develop will be able to be maintained this afternoon and possibly continue into the evening as elevated convection over PEI and Nova Scotia. The main storm motion will initially be supercells with a mean motion of storm to the northeast at 35KT A possible tornado cannot be ruled out, mainly over central to eastern New Brunswick given similar dynamics to yesterday which saw some splitting supercells over northwestern New Brunswick with generally an eastward motion. Supercell composities for this afternoon are indicating values of 2 to 3 with significant tornado parameters of 1 to 2. Towards the late afternoon, squall or bowlines with strong wind gusts will likely be the main storm threat as storms begin to lose energy but elevated convection may continue into the overnight period with heavy rainfall.  

 

Over Newfoundland, a warm frontal features continues to track northward and convection that occurred early this morning will weaken. Isolated convection this afternoon from the trough over central Quebec will move into southwestern Labrador this afternoon and weaken by this evening.

 

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 1 Night

 

Thunderstorm Outlook for Day 2

 

Upper low moves into Labrador for Tuesday where area of southern Labrador will see scattered showers and thundershowers. The cold front over the Maritime waters will continue to weaken but there could be some isolated thundershowers remaining through the Slope waters, Grand Banks and eastern Newfoundland. A warm cap at 700 mb may inhibit surfaced based convection.

 

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

SE Labrador/NE Newfoundland: Scattered strong to severe thunderstorms expected this afternoon and evening for central and eastern Newfoundland, and southeastern Labrador. Main hazards will be lightning, gusty winds, hail and locally heavy downpours.

 

New Brunswick: Scattered strong to severe thunderstorms possible late this afternoon and evening for Northwestern New Brunswick. Main hazards will be lightning, gusty winds, hail and locally heavy downpours.

 

 

Convective Discussion

 

Several areas of concern for this afternoon/evening for the Atlantic region with particular focus for eastern Newfoundland, Labrador and northwestern New Brunswick where a very hot and humid air mass resides over the region.

 

For Newfoundland and Labrador, a strong short wave tracking into eastern Labrador extending into Newfoundland will help enhance convection today. Interior parts of central to eastern Newfoundland will see high temperatures near 30C and dewpoints between 17-19C. MUCAPE values near 2000 J/kg, 0-6k shear at 35kts and precipitable water above 30 mm combined with increasingly favourable upper dynamics will help maintain strong storms that develop. Strong multicell type storms are most likely but there could be the risk of supercells.  A funnel cloud or short lived tornado cannot be completely ruled out, however the probability of that remains very low at this time. Storms will weaken in the evening as they head out over much cooler ocean waters and become de-coupled from the surface. There is a bit of a low-level capping inversion to break based on the 12Z Goose Bay sounding, limiting surface based convection over southeastern Labrador, however, a 500mb cold trough over the southeastern regions could kick off some elevated convection this afternoon. Dynamics are a bit weaker but heavy rain is possible.

 

For New Brunswick, an approaching trough currently over SW Ontario will move eastward into southern Quebec today and to the Maine/New Brunswick border this evening/overnight. 12Z KCAR sounding suggest ample energy given temperatures near 30C and high dewpoints near 19C, MUCAPE values reaching 2000 J/kg and strong 0-6km shear near 40KT. There is also the enhancement of being in the left exit region of a 100KT 250mb jet. This will promote severe limits on convection especially over Maine this afternoon which will move northeastward into parts of western New Brunswick later this afternoon into this evening. With a dryer 500-700mb, strong winds associated with organized multicell or bowlines will be the biggest threat.  

 

Thunderstorm Outlook for Today (Sunday July 24^th)

 

Thunderstorm Outlook for Day 1 night (Monday July 25^th)

 

 

For Monday, isolated thunderstorms are expected for western Labrador, parts of Newfoundland and possible storm to severe storms for New Brunswick/Prince Edward Island. A cold front will move through New Brunswick in the afternoon. With ample energy still in place over much of the region, the risk of severe thunderstorms continues further into New Brunswick then into Nova Scotia in the evening/overnight.

 

Thunderstorm Outlook for Day 2 (Monday July 25^th)

ECCC Convective Outlook Valid for Today, and Tomorrow

Thunderstorm Outlook for SATURDAY:

 

Regional Impacts

Isolated non-severe thunderstorms possible this afternoon in many different areas of the Atlantic provinces, due to various weak forcing features. An approaching trof in northern Quebec may produce a marginally severe thunderstorm this afternoon in extreme western Labrador – greatest hazards being heavy rain and lightning.

 

Convective Discussion

Various features will create weak and short-lived thunderstorms today. A decaying trof over northern Nfld, a weakening low centre with associated occluded fronts near James Bay, and a weak sea breeze convergence zone over interior NS are the easiest to pick out from this morning’s air mass analysis. The ongoing heat wave across the Maritimes is keeping mid levels quite dry. Surface dew points are over 19 already, bringing Humidex values near 40 in Cape Breton this morning. Across NS/NB/PEI the expected weak thermal trof-ing at 850 to 500 is also occurring. Hence a shower that struggles to build will do just that, struggle.

 

Thunderstorm Outlook for Day 1 - JULY 23, 2022

 

Thunderstorm Outlook for SUNDAY:

 

Regional Impacts

Scattered non-severe thunderstorms possible tomorrow afternoon in parts of New Brunswick and Labrador. Isolated severe thunderstorms are possible in central Newfoundland including Gander and vicinity. Main hazards will be gusty winds, small hail, and frequent lightning. Rainfall rates could exceed 30mm/h in local pockets of heaviest downpours.

 

Convective Discussion

The focus of this discussion will be central Newfoundland. A strong short wave setup will destabilize a very hot and humid air mass currently established over the interior mid-day Sunday. As such, MU CAPE values are very high at over 2000J/kg, and ML CAPE is near 1300. ML CAPE is the most important here as we need the dew points to remain over 16 to have heights climb to severe levels. 0-6k shear is at 40kts. Storm type will be Supercell in this environment, and storm motion will be Bunkers RM. This has the potential to become a complex weather situation if the ingredients all line up at the right time of day. A funnel cloud or short lived tornado cannot be completely ruled out, however the probability of that remains very low at this time. Hail and strong winds have been included on the Day2 graphic in Area B to express the severe weather risk to the public. This weather threat may be upgraded to HIGH in future forecast issues. Storms will weaken in the evening as they head out over much cooler ocean waters and become de-coupled from the surface. Elevated lightning (from 700mb and above) could continue along the coast late into the evening.

 

Thunderstorm Outlook for Day 2 - JULY 24, 2022

 

Forecaster: TIRONE.