RE: Convective Outlook Valid for Today , Tonight and Tomorrow

*** Updated Thunderstorm Outlook for Tuesday. See image below ***

 

Regional Impacts

NB NS PEI: none.

NF: Scattered thunderstorms, possibly strong later this afternoon, localized downpours of 15 mm, small hail, and gusty winds near thunderstorms.

 

Convective Discussion…

The plume of tropical moisture has now moved east of NF. At 500mb, a trough extends from the James Bay region to the Gulf of St. Lawrence, leaving NF in a fairly unstable airmass. Precip. Water calculated from the area soundings are ranging from 30 to 50 mm, except for AYT (55 mm) which has some residual tropical moisture. VIL of the day guidance is showing values of 35-50 kg/m^2 - fairly strong updrafts and large CAPE values are in store in today’s environment which may lead to some small hail.  

A 90kt southwesterly upper jet extending from NS to the Avalon will add some dynamic for some stronger surface-based convection over the region. Moderate unidirectional deep layer sheers will also provide an opportunity for some clusters of thunderstorms to semi-organize.  

Tomorrow, the environment found over QC/NE US will advance over NB and Lab.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

NB NS PEI: none.

NF: Scattered thunderstorms, possibly strong later this afternoon, localized downpours of 15 mm, small hail, and gusty winds near thunderstorms.

 

Convective Discussion…

The plume of tropical moisture has now moved east of NF. At 500mb, a trough extends from the James Bay region to the Gulf of St. Lawrence, leaving NF in a fairly unstable airmass. Precip. Water calculated from the area soundings are ranging from 30 to 50 mm, except for AYT (55 mm) which has some residual tropical moisture. VIL of the day guidance is showing values of 35-50 kg/m^2 - fairly strong updrafts and large CAPE values are in store in today’s environment which may lead to some small hail.  

A 90kt southwesterly upper jet extending from NS to the Avalon will add some dynamic for some stronger surface-based convection over the region. Moderate unidirectional deep layer sheers will also provide an opportunity for some clusters of thunderstorms to semi-organize.  

Tomorrow, the environment found over QC/NE US will advance over NB and Lab.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

NB NS PEI: Isolated thunderstorms, giving localized downpours.

NF: Scattered embedded thunderstorms over western sections, torrential rain with 30-60 mm with the highest amounts in the southwest.

Lab: Scattered thunderstorms, possibly strong later this afternoon, localized downpours of up to 20 mm, small hail, and gusty winds near thunderstorms.

 

Convective Discussion…

Satellite imagery shows the tropical moisture feed over western Newfoundland. Precip. Water calculated from the area sounding are ranging from 40 to 45 mm, VIL of the day guidance is showing values of 40-60 kg/m^2.  While convective inhibition is still fairly high over eastern parts of NF, in the west where the 500mb thermal through lies, embedded convection will continue to support moderate to heavy rain. A slightly cyclonic southwesterly 90kt upper jet will add some dynamic support for some stronger surface-based convection over Labrador. Moderate to strong deep layer sheers will also provide an opportunity for some clusters of thunderstorms to semi-organize.  

A 500mb through extends from Hudson’s Bay to the Gulf of Maine. This feature along with the upper jet and some limited insolation may provide enough energy/support for the development of isolated CB’s in the still very moist environment found over the Maritimes. Convective temperature is running around 28 for most of the areas – for areas with less cloud cover CAPE values will be approaching or even surpass 500J/kg at the peak of insulation later this afternoon. Tomorrow, the stronger convective activity will shift over eastern portions of the island of NF.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today, Tonight, and Tomorrow

Regional Impacts

NS: Embedded thunderstorms today, torrential downpours of 30-50 mm in convection.

NB: Isolated thundershowers possible this afternoon, locally heavy downpours of 10-15 mm.

PEI: Embedded thundershowers possible this afternoon, locally heavy downpours of 10-15 mm.

NL: Isolated thundershowers possible over extreme northern Labrador, locally heavy downpours.

 

Convective Discussion…

A stream of tropical moisture has made its way into southwestern NS this morning. Embedded convection is expected to continue along this stream as it slowly moves northeast over the next few days, bringing torrential rain across much of the Atlantic coast. The 12Z UA sounding from Yarmouth indicated PWAT values of 42 mm, with this forecast to increase to near 50 mm by this afternoon between Yarmouth and Halifax. Rainfall warnings have been issued along the Atlantic coast of NS for total rainfall amounts of 40 to 70 mm, with possibly higher amounts in areas of more intense convection by tomorrow night.

 

Tomorrow, an additional area of interest exists in NW NB, associated with a low pressure system that brought widespread severe weather to southern Ontario yesterday. This low is forecast to slowly track northeast along the St. Lawrence river tomorrow. Significant cooling aloft and ample moisture in NB will allow for SBCAPE values to build to 2000 J/kg tomorrow afternoon, with convective temperatures around 23 degrees, making this a suitable environment for severe weather. Bulk shear values of 30-40 kts will allow for some sustained updrafts, with the potential for 1 to 2 cm hail with these storms. Strong wind gusts to 70 km/h and locally heavy downpours of 20-40 mm are also possible.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

Copp

Convective Outlook Valid for Today, Tonight, and Tomorrow

Regional Impacts

NS: Pop-up thundershowers possible in central NS this afternoon. Locally heavy downpours of 10-15 mm.

NB: Pop-up thundershowers possible in SE NB this afternoon. Locally heavy downpours of 10-15 mm.

PEI: None.

NL: Embedded thundershowers possible for south-central NFLD. Heavy downpours of 20-40 mm.

 

Convective Discussion…

The main threat for severe weather today exists with an embedded low currently moving into Banquereau waters towards NFLD. Strong upper dynamics and mid level instability will support convection as this low approaches NFLD this afternoon. No lightning has been detected, however the feature remains highly convective with rainfall rates over 25 mm/hour possible. This feature is forecast to quickly weaken once it reaches the southern coast of NFLD later today.

 

A few pop-up thundershowers are also possible in central NS and SE NB this afternoon. Warm, moist air will bring SBCAPE values near 1500 J/kg which will aid in the development of convection this afternoon, a lack of upper level support however, should hinder the life span of any storm that initiates. Locally heavy downpours of 10-15 mm will be the main threat with these cells.

 

On Friday, another stream of moisture from the tropics will move into southwestern NS. Embedded convection within this moisture stream will lead to locally heavy downpours. PWAT values are forecast to build to 40-50 mm by the afternoon, so rainfall rates upwards of 25mm/hr are not out of the question.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Copp