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.

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Today

Southern LAB/western NL: scattered elevated thunderstorms possible.

NS: slight risk of an isolated thunderstorm for eastern mainland.

 

Tonight

Southeastern LAB/NL: isolated thunderstorms possible

 

Saturday

Western LAB/northern NB/northeastern NL: isolated thunderstorms possible.

 

Convective Discussion

A much quieter day compared to the severe weather in NW NB yesterday. Some ongoing elevated thunderstorms associated with the upper trough moving over the GLFSTLAWR will likely be on and off this afternoon and into tonight as it slopwly progresses eastward over southern LAB and NL. Only some locally heavy downpours are expected but could be some gusty winds as well in some of the stronger cells. That same trough will likely give some isolated stuff overnight and into Saturday morning for parts of Newfoundland. And a slight risk of a thunderstorm this afternoon for eastern mainland NS close to that 500mb trough.

 

On Saturday a new 500 mb trough/short wave will approach from Quebec increasing the chance for thunderstorms across western LAB and far northwestern NB. Also a slight chance for an isolated cell for northeastern NL close to that first departing trough.

 

Thunderstorm Outlook for Day 1 afternoon/evening

 

Thunderstorm Outlook for Day 1 night/Day 2 morning

 

Thunderstorm Outlook for Day 2 afternoon/evening

 

Jeremy

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Today

NB: scattered strong to severe thunderstorms expected this afternoon and into the evening across NW portions of the province.

 

Tonight/Friday morning

NB/Western NS/PEI: isolated thunderstorms possible.

Central LAB: isolated thundershowers possible.

 

Friday afternoon/evening

MRTMS/central LAB/western NL: isolated to scattered thunderstorms possible. Some of the cells could be strong.

 

Convective Discussion

It appears prime for possible strong to severe thunderstorms across northwestern NB this afternoon and evening. From top down: an approaching 250 jet maxima (right quadrant) and associated divergence by mid to late afternoon approaching northern ME and NW NB; an approaching 500mb trough currently over QC and a strong 50-50 knot jet just ahead of it; good dry air in the mid levels as is currently evident in conventional SAT PIX; Very moist air from 850mb to the surface and a strong LLJ of around 30 knots (~925mb) which was seen upstream in the 12Z Albany sounding. The really interesting area that would have been nice to have a sample from was missed, but adjusting the Grey and Albany soundings produces 1000-2000 j/kg SBCAPE, with 0-6 km effective westerly shear up around 50 knots and decent 0-3 km srh helicty of just shy of 200. That area will be advecting northeastward coinciding with the approaching trough (both at the surface and 500 mb), which in most circumstances spells trouble. Given the observed data and higher resolution model support we expect winds to be the main issue, however owning to the strong updrafts in the deeper cells hail is also a potential. PWAT is around 40, but storms should be moving fast enough to not produce a significant amount of rain (unless there is slight back-building or training of storms). In line with the Storm Prediction Center there is also a slight risk of seeing a tornadic supercell.

 

In summary: Strong to severe storms producing wind gusts of 60-100 km/h and hail up to 2 cm for northwestern counties in NB possible this afternoon and evening.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for tonight and Friday morning

 

Thunderstorm Outlook for Day 2 afternoon and evening

 

Jeremy