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: