Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NB: isolated thunderstorms this afternoon/early evening giving some gusty winds, heavy downpours, and possibly small hail. Do not expect any cells to become severe.

NS and southeastern NL: risk of an elevated thunderstorm today and into this evening giving locally heavy downpours.

 

Tonight

Southeastern NL: continuing with the risk of an elevated thunderstorm through the overnight and into Saturday morning giving locally heavy downpours.

 

Saturday

Lab: slight risk of an afternoon thunderstorm.

 

Convective Discussion

 

A couple features of interest today: one is a frontal trough passing south of NS and the other a 500 mb trough entering NB. There has been some history of activity with both features, more notably the upper trough. The instability doesn’t appear as deep as it was yesterday when the trough was upstream in Quebec, and the feature itself is showing some signs of weakening. There should be some isolated storms in Maine that will drift across inro western NB through the afternoon giving some gusty winds, locally heavy downpours and small hail. The 12Z tephi out of caribou has pretty weak shear but the FZLVL is just above 10,000 ft so the chance for small hail seems legit.

 

The trough currently passing south of NS and approaching southeastern NF will produce some isolated thunderstorms offshore with a slight chance it could touch the Burin and southern Avalon tonight and into Saturday morning. The instability is pretty good but quite high so we shall see if anything does materialize. Locally heavy downpours would be the only threat.

 

Lastly a weak surface trough could be enough to trigger an isolated thunderstorm or 2 across parts of the Big Land on Saturday.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Jeremy

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

NB: Risk of thundershowers with heavy downpours and strong wind gusts.

NS/southwestern marine waters: Risk of embedded thundershowers.

Tonight:

NB: Risk of thundershowers with heavy downpours.

NS/southern marine waters: Risk of embedded thundershowers.

Tomorrow:

NB: Risk of thundershowers with heavy downpours, small hail and strong wind gusts.

NS/PEI/southern marine waters: Risk of embedded thundershowers.

Convective Discussion

A slow moving trough over southern Quebec along with daytime heating and increasing shear will aid in the development of thunderstorms for southern Quebec and Maine this afternoon and this area will slowly move into northwestern New Brunswick tonight and tomorrow. Ahead of the trough, daytime heating will aid in destabilization with mainly non-severe pop-up thundershowers in north central New Brunswick and southwestern Labrador this afternoon. The main threat this evening and overnight will be heavy downpours if cells redevelops over one area with moderate precipitable water with this air mass. Meanwhile, embedded thundershowers are possible along a boundary off New England that will move into the southern Maritime marine waters and across southwestern Nova Scotia this evening and overnight into tomorrow. With precipitable water increasing over southwestern Nova Scotia into the 40s overnight and early tomorrow morning, there is a risk of heavy downpours.

For Friday, the trough will lie over New Brunswick and there is a possibility of moderate rain, small hail and strong wind gusts and the upper levels cool and freezing levels lower. With CAPE values above 500 J/kg and increasing shear towards 35 kts into the afternoon, some storms could form into lines or possible supercells.  A low pressure system that develops south of Nova Scotia will aid in thundershower development across central and eastern Nova Scotia and eastern Prince Edward Island towards southern Newfoundland by the evening.

Thunderstorm Outlook for TODAY

Thunderstorm Outlook for TONIGHT

Thunderstorm Outlook for TOMORROW

 

Roberta McArthur

 

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today: Organized convection is occurring this morning offshore of Baccaro Pt, NS. Frequent lightning and heavy rainfall are the associated hazards. Pop-up shower risk in extreme western Labrador and northern NB - a few of these could be TCUs tall enough to create a few lightning flashes. No sig rainfall expected here.

Tonight: No thunderstorms forecast under stable conditions.

Thursday: Approaching trof brings risk of discrete cell thunderstorms in NB late day, and embedded thunderstorms across SW NS late day. These storms are not expected to be severe at this time.

Convective Discussion

Morning sounding at YQI remains very saturated at all levels, much like yesterday. But today’s limiting factor is a trigger. There isn’t really a strong forcing to create anything organized other than the shortwave offshore that is causing ongoing convection. TCUs in NB will remain unorganized and not overly tall, if they even develop. Similar setup in Labrador of weak dynamics. Tomorrow brings an approaching trof interaction late day that cools the column aloft after maximum daytime heating and will destabilize the column over the western Maritimes. However, it is fairly skinny cape for the time of year.

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: Embedded convection with the influential coastal troughing across NS – specifically the South Shore. Only hazards forecast are potentially high rainfall rates and lightning.

Tonight: Offshore deep convection continues, but slowly pulling away.

Wednesday: Pop-up shower risk in extreme western Labrador and northern NB. A few of these could be TCUs tall enough to create a few lightning flashes.

Convective Discussion

Pwats remain high this morning and early this afternoon across parts of NS, particularly the SW. Organized convection could bring locally very heavy rainfall. YQI sounding this AM is basically wet adiabatic from 900mb to the stratosphere. Caribou is much drier above 600mb as it is out of the tropical airmass. The depth of moisture is being closely monitored today and alerts will be issued if a storm back-builds or stalls over a particular region. The special weather statement continues to highlight the potential. The tropical dynamics pull off land this evening, but remain over the marine district tonight. Tomorrow is much quieter with minimal cape to work with, and a return to seasonal temperatures and humidity.

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: Isolated severe supercell structure is possible along colliding boundaries across western NB this afternoon. There is an elevated risk of rotation within these cells. Damaging winds, heavy rain, and hail are also NB hazards today. Across NS, storms are also likely to fire along “the spin” of eastern mainland. These cells are capable of producing moderate rainfall.

Tonight: With a tropical push of moisture and enhanced lift, scattered-numerous strong thunderstorms are forecast across mainland NS during the overnight hours. These storms bring a significant rainfall risk. A special weather statement has been issued to provide the public with advance notice of this event.

Tuesday: As the forcing pulls away over the marine district, embedded thunderstorms are still possible midday. The hazards are diminishing at this time.

Convective Discussion

--Potentially Impactful Next 24hrs--  There are 2 events that are shaping up to affect the Maritimes district. (Nfld and Labrador are quiet for this forecast period.)

1. Supercell development is possible in western NB this afternoon driven by high moisture and high shear. Pwats support deep convection, and there is a 65kt Jet supporting the activity. Effective shear is over 55kts at max daytime heating today. Sig tor and EHI flag tornadic potential, similar to yesterday but with stronger signals. This poses a wind risk, hail risk, and heavy rain risk. The yellow area on today’s outlook conveys this message. Alerts may be required. The dynamics upstream in Maine are being closely monitored at the typing of this report. Organized storms are also possible across inland NS – but these storms don’t have the same enhanced shear dynamics to work with. Mositure across NS is impressive this morning, dewpoints over 20, with fog patches.

2. Tonight brings even more moisture into the equation, from the remnants of what was once Tropical Storm Chantal interacting with a longwave nearly-stationary trof. This stream of juicy air is entering our AOR this evening. As such, Pwats soar over 65 in places, and columns are fully saturated by midnight. The main hazard tonight is heavy rainfall. The yellow area on tonight’s graphic depicts this risk area. KF Rainrate products are depicting hourly rainfall rates of 60 mm/hr. This seems potentially too high. But it cannot be fully ruled out. The system has tropical influence and a history of producing locally very heavy downpours. If storms are training or slow moving, then higher precip amounts are possible. Forecasters will be paying close attention to this tonight.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: Tirone.