Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

None

 

Convective Discussion

Cold low over Ungava Bay with a shortwave trough extending southwestward to James Bay. 500mb temperatures fall to -15 to -20 range in the cold pool. Several lightning flashes were detected earlier along the trough. 500mb Heights and Temperature will fall and a secondary cold low will emerge over Labrador tonight, and then over NF Tuesday into Wednesday bringing a slight risk of a thunderstorm.

 

 

 

Thunderstorm Outlook for Tonight

 

 

 

Thunderstorm Outlook for Tuesday

 

 

 

 

 

 

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

None.

 

Convective Discussion

No thunderstorms expected today and Monday.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2

 

Jeremy

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Western LAB: isolated thunderstorms possible this afternoon.

 

Convective Discussion

A vigorous upper trough of low pressure will move into western Labrador this afternoon giving the risk of a thunderstorm. A stationary frontal trough over the southern Grand Banks will continue to give isolated thunderstorms today and Sunday. OTWX nil sig wx expected.

 

Thunderstorm Outlook for Day 1 day

 

Thunderstorm Outlook for Day 1 night

 

Thunderstorm Outlook for Day 2

 

Jeremy

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

NB/NS/PEI/Labrador: None

NL: Isolated/embedded lightning east

 

Tonight

NS/NB/PEI/NL/Labrador: None

 

Saturday

NB/NS/PEI/NL/Labrador: None

 

Convective Discussion:

 

A slow moving trough of low pressure over the Avalon Peninsula will continue eastward today and will lie east of Newfoundland tonight. Some embedded/elevated lightning and downpours are occurring along and ahead of the trough. The trough will only affect offshore waters tonight and Saturday.

 

Thunderstorm outlook for today:

 

Thunderstorm outlook for tonight:

 

Thunderstorm outlook for Saturday:

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

NB/NS/PEI: None

NL/Labrador: Isolated lightning and locally heavy downpours

 

Tonight

NS/NB/PEI/Labrador: None

NL: Isolated lightning and locally heavy downpours

 

Thursday

NB/NS/PEI/Labrador: None

NB/NS/PEI: Isolated lightning

 

Convective Discussion:

 

A slow moving trough of low pressure extending from a low over northern Quebec will advance eastward across Newfoundland and Labrador today and tonight. Ahead of the trough embedded lightning and downpours are occurring. Precipitable water values are in the mid 40s and rainfall warnings are in effect for the southern Newfoundland coast. Over western Labrador there is a risk of surface based lightning in the wake of the trough this afternoon. The CAPE and shear values are quite low so only small hail or wind gusts are likely there.

 

As the trough continues eastward on Friday there is a risk of thundershowers for eastern Newfoundland and associated waters.

 

Thunderstorm outlook for today:

 

 

Thunderstorm outlook for tonight:

 

Thunderstorm outlook for Friday:

 

 

 

 

 

 

 

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

NB/NS/PEI: isolated lightning and locally heavy downpours

NL/Labrador: None

 

Tonight

Labrador/PEI/NS: isolated lightning and locally heavy downpours

NB/NL: None

 

Thursday

Labrador/NL: isolated lightning and locally heavy downpours

NB/NS/PEI: None

 

Convective Discussion:

 

A slow moving trough of low pressure extending from a low over central Quebec will advance eastward across the Atlantic region today into Thursday. This trough is pulling in a lot of moisture from the Gulf Stream, reaching far into northern Labrador with precipitable water values in the mid 40s. Convection is expected to remain isolated in nature as the air mass is quite warm at 500 mb over the Maritimes today and reaching further north and east towards Labrador and Newfoundland overnight and into Thursday, enhancing rainfall amounts. The western Maritime waters lie along the right entrance of a 120KT 250mb jet so the convection may remain mostly over the marine waters but an isolated strike cannot be ruled out further north.

 

As the trough continues eastward on Thursday, another short wave trough will move through western and central Labrador. CAPE values near 700 J/kg and some cooling aloft will prompt some convection in the afternoon. Effective shear will be too high (near 60Kt) to maintain any organized convection but anything that does develop could have some small hail.

 

Thunderstorm outlook for today:

 

Thunderstorm outlook for tonight:

 

Thunderstorm outlook for Thursday:

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

Northwestern NB: isolated lightning, locally heavy downpours and gusty winds

PEI/NS/NL/Labrador: None

 

Tonight

Western NB/NS: Isolated lighting and locally heavy downpours

 

Tuesday

NB/NS: isolated lightning and locally heavy downpours

PEI/NL/Labrador: None

 

Convective Discussion:

 

A low pressure system will advance northeastward over Hudson Bay with a trough extending southward into New England today. There is a risk for convection over northwestern New Brunswick ahead of the trough and will continue eastward into the evening. The limiting factor is a warm nose at 850 mb and 500 mb as seen on the 12Z KCAR sounding. However, should daytime surface temperatures reach 30 degrees, along with the thermal trough at 500 mb pushing eastward, it should be enough to initiate convection over central Maine this afternoon. With increasing 0-6km shear and precipitable water above 40 mm, more organized lines that develop could maintain into New Brunswick into the evening.

 

An isolated TCU is possible over northeastern New Brunswick as well but there may be too much warming aloft to initiate any CBs.

 

As the trough continues to approach overnight and into Wednesday, convection will be more elevated and isolated in nature. A short wave will develop south of Long Island this evening and get wrapped into the main trough as it tracks through the Maritimes. This moisture will get drawn northeastward towards western Nova Scotia early Wednesday morning and continue through the Maritimes and towards southern Labrador by Thursday morning. The main threat will be locally heavy downpours with precipitable water values near 50 mm along the Atlantic coast of Nova Scotia.

 

Thunderstorm outlook for today:

 

Thunderstorm outlook for tonight:

 

Thunderstorm outlook for Wednesday:

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

Labrador: Isolated lightning and locally heavy downpours

NB/PEI/NS/NL: None

 

Tonight

None

 

Tuesday

NB: Isolated lightning and locally heavy downpours over northern sections

PEI/NS/NL/Labrador: None

 

Convective Discussion:

 

An elongated quasi-stationary front rides from Hudson Bay across central/northern Quebec and across central Labrador. Convection will be isolated and embedded in nature along this feature as the atmospheric profiles are moist adiabatic, but with some slight cooling at 700 mb and lower level jets at 850 mb and 700 mb to help provide lift over the higher terrain. With CAPE values of 200-300 J/kg, weak to moderate effective shear and precipitable water in the 30 to 40 mm range, locally heavy downpours will be the biggest impact.

 

A low pressure system will advance northeastward over Hudson Bay with a trough extending southward into New England on Tuesday. There is a risk for convection over northwestern New Brunswick for tomorrow ahead of the trough. A sea-breeze set up combined with surface-based heating over the Acadian Peninsula may also provide enough lift to push past a warm nose between 700 and 500 mb in order to produce isolated convection in the afternoon.

 

Thunderstorm outlook for today:

 

Thunderstorm outlook for tonight:

 

Thunderstorm outlook for Tuesday:

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

NS: isolated lightning

NB: none

PEI: none

Labrador: none

NL: isolated lightning

 

Tonight

None

 

Sunday:

NS: none.

NB: none.

PEI: none.

Labrador: isolated lightning

NL: none.

 

Convective Discussion:

A decaying cold front could act as a trigger for a few isolated CBs later today, especially where surface convergence will be enhanced by S-SW flow off the Atlantic. Instability appears sufficient with MLCAPEs ranging from 300-500 J/kg, however skinny CAPE profiles and dry entrainment above 650 mb could act to limit updraft strengths in the IC growth zone for sufficient charge separation. A similar scenario appears likely in eastern NL however it appears dry air entrainment does not appear to be as much of a limiting factor, despite skinny CAPE profiles. Effective shears of 20-30 kts in NL appear more reasonable given the instability as opposed to NS where shear might be too strong for the available instability (effective shears of 30-40 kts).

 

Tomorrow appears rather quiet, western Labrador may see some elevated convection with as a shortwave from northern MB moves eastward along a zonal Baroclinic zone.

 

Thunderstorm outlook for today:

 

 

Thunderstorm outlook for Sunday:

 

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook valid for TODAY – FRIDAY, Aug 26^th:

 

Regional Impacts

Scattered thunderstorms are expected to enter into NB this afternoon along an approaching frontal feature. Moderate rain is expected, and wind gusts near 80km/h are possible. Pockets of stronger severe weather are possible IF the dynamics align favourably with storm motion and the overhead jet support. A squall line/bow echo signature cannot be completely ruled out with this feature. If ingredients build, a watch will be used to achieve lead time for residents of NB.

 

Convective Discussion

The aforementioned frontal feature is digging quite deep as it comes through upstate NY, New Hampshire and Vermont at this hour. This is the main forcing of the day for NB. With surface moisture pooling ahead of the front (Pwats over 30mm), and 0-6k shear values near 35kTs, thunderstorms are forecast to develop this afternoon and evening. Morning soundings across the Maritimes show quite a dry level above 700mb, but this will saturate as the day progresses. A challenge does remain with the existing junky cloud, but clearing is expected to occur at the prime time for peak insolation. The HRRR solution remains as an outlier, bringing a very strong bow echo signature through Maine and all the way to Bathurst this evening. The probability of this particular scenario remains low at this time, but forecasters are closely monitoring upstream data to alert to a strong signature should it develop. In this case, the yellow hazard area for wind may be underdone for max gusts. (A stationary boundary is also offshore still producing ongoing lightning and shower activity on the southern Grand Banks of the marine district.)

 

TODAY

 

Thunderstorm Outlook valid for TOMORROW – SATURDAY, Aug 27^th:

 

Thundershowers are expected to continue through the overnight hours and affect areas in Nova Scotia early Saturday morning. These partially elevated storms will likely bring bouts of showery weather and lightning. Mainland NS will clear out by noon at the latest. Late day weekend events do not need to be rescheduled due to svr weather. Nfld can expect the same thundershowers and dynamics in the afternoon, near Gander. Lightning will be the main hazard with any cell that does develop.

 

TOMORROW

 

Forecaster: TIRONE/ASPC

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

NS: isolated lightning

NB: none

PEI: isolated lightning

Labrador: isolated lightning

NL: none

 

Tonight

None

 

Friday:

NS: none.

NB: moderate-high rainfall rates, gusty winds, small hail and lightning.

PEI: moderate rainfall rates, and lightning.

Labrador: isolated lightning

NL: none

 

Convective Discussion:

A weakening cold front moving through the southern Maritimes may trigger a few thunderstorms this afternoon in eastern NS and PEI. Instability will be limited by dry air intrusion, with profiles quite dry above 720mb. Dynamics look less impressive than yesterday with shear near 20 kts at most. Regardless with a convective temperature of 26, MLCAPE near 700 J/kg may be realized. Further north in southern Labrador elevated convection associated with a vigorous upper trough may continue to produce some isolated lightning. Cloud cover looks too extensive to allow surface based convection.

 

Tomorrow an upper trough from northern Ontario is expected to move through southwestern new England during peak insolation bringing a risk for severe storms there. In New Brunswick the situation becomes a little tricky as moisture advection ahead of the trough will begin to destabilize southwestern sections of the province in the afternoon; increasing the risk for higher rainfall rates in any storms that do develop. However it appears the best Dynamics, and lift associated with the upper trough itself will remain to the southwest over Maine during peak insolation. It is possible that early evening storms remain surfaced based upon crossing the boarder, which would bring a wind and hail hazard to go with the higher rainfall rates. Storm motion will initially be 20 to 30 kts out of the SW, but increase as dynamics improve later in the day (perhaps as high as 40 kts by 0z Saturday). Later in the evening it is expected storms will maintain a moderate rainfall hazard as they become elevated and move into eastern sections of NB and westernmost PEI.  

 

Thunderstorm outlook for today:

 

Thunderstorm outlook for tonight:

 

Thunderstorm outlook for Friday:

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

NS: high rainfall rates, gusty winds, lightning and small hail.

NB: isolated lightning

PEI: none

Labrador: isolated lightning

NL: high rainfall rates and lightning.

 

Tonight

None

 

Tuesday:

NS: moderate rainfall rates, gusty winds and lightning.

NB: moderate rainfall rates, gusty winds and lightning.

PEI: moderate rainfall rates, gusty winds and lightning.

Labrador: isolated lightning

NL: none

 

Convective Discussion:

 

A slow moving cold front along the eastern periphery of a longwave trough in Quebec will act to trigger a few isolated thunderstorms in south-central Labrador beginning early this afternoon. Instability is modest, with MLCAPEs of 400-600 J/kg and respective effective shears of 20 – 25 knots. This same feature may clip northwestern NB latter this evening and provide the odd storm as insolation diminishes with the diurnal cycle.

 

A trough currently over the eastern Gulf of St. Lawrence  should act to trigger isolated storms over much of central NL later this afternoon. The environment from a dynamics standpoint is good, with ascent aided by the left exit of an upper jet more or less vertically aligned with mid tropospheric southwesterly flow of ~40 kt. Instability represented by MLCAPEs of ~500-700 J/kg in combination of close to 30 kts of effective shear could yield a multicellular environment. Given an abundance of moisture represented by PWATS near 40 mm, rainfall looks to be the primary hazard today. Nevertheless storm motion should be rather quick given a mean wind of 25 kts out of the SW which should act to limit this hazard somewhat. Wind and hail are not expected to be an issue given relatively skinny CAPE shape, marginal mid level lapse rates and the lack of a strong low level jet.

 

An upper trough over New England will slowly move eastward this afternoon should focus convection develop mainly across the western mainland of NS late this afternoon through the early evening hours. The risk diminishes further east as it appears this triggering feature will be moving through well after peak daytime insolation. Here like NL PWATs are expected to be near 40 mm, which help to pose a rainfall hazard. However unlike NL instability and effective shears appear more robust, with MLCAPEs near 1000 J/Kg and effective shears of 30 to 40 kts. Generally speaking there should be multicells, but it is possible the odd storm could take on a few super cellular characteristics, especially if low level shear is enhanced by a local sea breeze.  Therefore a secondary, less certain hazard of gusty winds and small hail also exists. Storm motion should generally follow the mean wind out of the SW at 25-30kts, with any deviant motions causing storms to move more to the west at 30 kts early this evening.

 

Tomorrow the same cold front responsible for convection in southern Labrador will be moving through the southern Maritimes and eastern Labrador, triggering some thunderstorms. Uncertainty remains with regard to the level of instability that will be available for this feature, but the environment does appear to be drier than today making a rainfall hazard less likely.  

 

Thunderstorm outlook for today:

 

Thunderstorm outlook for tonight:

 

Thunderstorm outlook for tomorrow:

Convective Outlook Valid for Today, and Tomorrow

Thunderstorm Forecast for TUESDAY:

 

Regional Impacts

Isolated non-severe embedded thunderstorms with 1010mb low tracking through Maritimes today. Synoptic rain and fog is the main story, but a few lightning strikes are possible ahead of the fronts.

 

Convective Discussion

There is a lot of speed shear aloft, but not much to work with in the low levels. There is, however, a plethora of low-level moisture to work with. This in turn, means Pwats of 30-40mm on the AM soundings. Skinny MLCAPE of 500-700J/kg can only produce a strike or two. Any heavy pockets of rain could be handled with a SWS or a short fused 1-hr Rainfall warning. Watches from the ASPC will not be required today.

 

Thunderstorm outlook for Today:

 

 

Thunderstorm Forecast for WEDNESDAY:

 

Thunderstorms approaching severe criteria limits of 25mm/hr rainfall rates could occur in central Nfld. Labrador and the northern tier of NB will also see some slight terrain-induced instability. NS is quite conditional on sea-breezes and a Tc of 24C in clearing. NS cells will remain down the spine of the province, and will also be good rain-makers. Data will be re-assessed on tomorrow’s 12z soundings.

 

Thunderstorm outlook for Tomorrow:

 

Forecaster: TIRONE

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

Labrador: Isolated to scattered thunderstorms giving lightning, locally heavy downpours and gusty winds

Northwestern NB: Isolated thunderstorms

NS/PEI/NL: None

 

Tonight

NS/NB: Elevated/embedded thunderstorms

NL/PEI/Labrador: None

 

Tuesday

NS/PEI/NB: Elevated/embedded thunderstorms

NL/Labrador: None

 

Convective Discussion:

 

A trough over eastern Quebec/southern Labrador will drift southward while weakening. Ahead of the trough over southern Labrador scattered thunderstorms will develop this afternoon. Precipitable water near 25 mm and CAPE values 500-1000 J/kg are expected. Strong shear of 30-40 kts and dry mid-levels may support squall lines. Over northwestern NB, a weak shear environment and marginal cape may support pulse type storms with locally heavy downpours and brief wind gusts possible later this afternoon. Tonight and Tuesday a risk of elevated thunderstorms exists as a weak low pressure approaches.

 

 

Thunderstorm outlook for today:

 

Thunderstorm outlook for tonight:

 

Thunderstorm outlook for Tuesday:

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

Labrador: Isolated to scattered thunderstorms giving lightning, locally heavy downpours and gusty winds

Northwestern NB: Isolated thunderstorms

 

Tonight

Labrador: Isolated thunderstorms

Northwestern NB: Isolated thunderstorms

 

Monday

Labrador: Isolated to scattered thunderstorms giving lightning, locally heavy downpours and gusty winds

Northwest NB: Isolated thunderstorms giving local heavy downpours

 

Convective Discussion:

 

An upper trough of low pressure is slowly track eastward from Hudson Bay toward central Quebec today while a ridge of high pressure stalls over southeastern Newfoundland into Monday. Ahead of the trough, an increasingly unstable air mass will aid in the formation of scattered showers and thunderstorms over western and central Labrador and into northwestern New Brunswick. Precipitable water is increasing to near 30 mm and CAPE values around 500 J/kg, however, shear will remain weak with little upper dynamics. This environment may sustain some pulse type storms with locally heavy downpours and brief strong wind gusts possible. Some TCUs in brief showers are expected along the eastern coast of New Brunswick and northern Nova Scotia today.

 

On Monday, the upper trough will track through eastern Newfoundland. With increasing vorticity, moisture and shear of 30KT, there is the possibility for more organized convection into squall lines but there will be some warming at 500 mb which may inhibit convection.

Convection Is expected along a near stationary boundary extending from southern Quebec into northwestern New Brunswick and the Gaspe Peninsula. Lighting, locally heavy rain and strong gusty winds are the main risks.

 

 

Thunderstorm outlook for today:

 

Thunderstorm outlook for tonight:

 

Thunderstorm outlook for Monday:

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

Central-western Labrador: Isolated thundershowers

 

Tonight

None

 

Saturday

Labrador/NB: Isolated to scattered thunderstorms

 

Convective Discussion:

 

A ridge of high pressure moves through the region today while the tail end of a trough of low pressure moves southeastward over Newfoundland today. Isolated showers with the slight risk of a thunderstorm is expected over central Labrador this afternoon. Convective temperatures near 25C are expected to be reached. With CAPE values of 500 J/kg but little moisture in the low levels and weak effective shear, the main threat would be some gusty winds. Some robust TCUs are expected over central to southeastern Newfoundland this afternoon but will be fighting a thermal ridge between 700 and 500 mb. Some locally heavy downpours are possible.

 

For Sunday, a trough of low pressure will slowly track eastward over Hudson Bay toward central Quebec. Ahead of the trough, an increasingly unstable air mass will aid in the formation of scattered showers and thunderstorms over western and central Labrador and into northern and western New Brunswick. Although there is an increase in precipitable water and CAPE, shear will remain weak so pulse type storms with locally heavy downpours and strong wind gusts are possible.

 

Thunderstorm outlook for today:

 

Thunderstorm outlook for tonight:

 

 

Thunderstorm outlook for Sunday:

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

NB/NL: Isolated thunderstorms.

NS/PEI/Labrador: None

 

Tonight

None

 

Saturday

None

 

Convective Discussion:

 

An upper low pressure system is slowly tracking northeastward over the northern Gulf of St. Lawrence and northern Newfoundland by Saturday morning. Scattered TCUs and isolated CBs were present along the frontal axis extending from the Great northern Peninsula and south over the Grand Banks earlier this morning. Some convection is possible along the northern Newfoundland coasts this afternoon if a cap at 850 mb can be broken. With precipitable water values of 30 to 40 mm, weak to moderate unidirectional wind shear, locally heavy downpours and strong wind gusts are possible. Isolated convection is also possible along the cold front which is tracking through the Grand Banks.

 

There is the possibility of isolated thunderstorms over New Brunswick today, however a capping inversion at 700mb with be the main inhibitor along with current cloud cover. KCARs 12Z sounding indicates that the RDPS is slightly overdoing this cap and with sufficient surface based heating, this cap may be able to break by this afternoon. Any showers that do develop will be slow to move given little upper flow around the upper low and with precipitable water near 30 mm, some locally heavy downpours are possible. Given more dry air in the mid level, some strong wind gusts are also possible.

 

For Saturday, a ridge of high pressure moves into the region, keeping most areas hot and dry. Some isolated TCUs are likely for Newfoundland as they remain under the influence of a trough and western Labrador as a low pressure system approaches central Quebec.

 

Thunderstorm outlook for today:

 

Thunderstorm outlook for tonight:

 

Thunderstorm outlook for Friday:

Convective Outlook Valid for Today and Tomorrow

Regional Impacts:

 

Today

NL: Isolated/embedded thunderstorms.

NB: Chance of afternoon thunderstorms.

PEI/NS/Labrador: None

 

Tonight

NL: Isolated/embedded thunderstorms.

NS/NB/PEI/Labrador: None

 

Thursday:

NB/NL: Isolated thunderstorms.

NS/PEI/Labrador: None

 

Convective Discussion:

Isolated/embedded thunderstorms are possible over Newfoundland this afternoon. Over northern New Brunswick, surface based convection may develop this afternoon and Friday afternoon. It is also possible for Newfoundland Friday afternoon. MLCAPE near 500 J/Kg is anticipated. For both days there is a cap near 700 mb so it may inhibit initiation. Not much of a trigger other than diurnal heating and a supportive upper low. The shear is very low so if thunderstorms do develop they will be pulse type and very slow moving. Pwat values near 30 mm exist so good downpours are likely with this slow moving system. Small hail and gusty winds are also possible.

 

Thunderstorm outlook for today:

 

Thunderstorm outlook for tonight:

 

 

Thunderstorm outlook for Friday: