Convective Outlook Valid for Today , Tonight and Tomorrow

Correction for a typo…

 

Regional Impacts

Today…

NS, PEI and NB… Thunderstorms giving locally 25mm today. Gusts to 70 km/hr.

Southwest NS… Possibly heavy downpours this afternoon in thunderstorms, 25 to 50mm.

 

Convective Discussion

 

There are two main areas of convection today, the first area of thunderstorms is the embedded convective activity with the front that is already over eastern NS. The intensity of the convection has diminished from the overnight period where heavy rain impacted western and central areas and is not expected to re-intensify today. It is however still possible to get some heavier embedded showers and gusts in thunderstorms to 70 km/hr or slightly higher.

 

A second weak trough currently tracking towards the western NS will be the potential trigger for afternoon thunderstorms. High precipitable water and most unstable CAPE values over 1000 J/kg could bring some potential for heavy downpours. The wind shear will not be significant in terms of prolonged severe thunderstorms but could be sufficient to allow the initiation of back building thunderstorms. Watches are not likely to be required but may be sent out if the potential for heavy rainfall develops.

 

 

Thunderstorm Outlook for Today

 

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

 

Mel Lemmon

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Today…

NS, PEI and NB… Thunderstorms giving locally 25mm today. Gusts to

Southwest NS… Possibly heavy downpours this afternoon in thunderstorms, 25 to 50mm.

 

Convective Discussion

 

There are two main areas of convection today, the first area of thunderstorms is the embedded convective activity with the front that is already over eastern NS. The intensity of the convection has diminished from the overnight period where heavy rain impacted western and central areas and is not expected to re-intensify today. It is however still possible to get some heavier embedded showers and gusts in thunderstorms to 70 km/hr or slightly higher.

 

A second weak trough currently tracking towards the western NS will be the potential trigger for afternoon thunderstorms. High precipitable water and most unstable CAPE values over 1000 J/kg could bring some potential for heavy downpours. The wind shear will not be significant in terms of prolonged severe thunderstorms but could be sufficient to allow the initiation of back building thunderstorms. Watches are not likely to be required but may be sent out if the potential for heavy rainfall develops.

 

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

 

Mel Lemmon

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts:

 

Today

NB/NS/PEI/NL/Labrador: None

 

Tonight

NS/NB: Thundershowers giving local downpours.

PEI/NL/Labrador: None.

 

Wednesday

NS/NB/PEI/NL: Thundershowers giving local downpours.

Labrador: None

 

Convective Discussion:

A low approaching from the Great Lakes area will track across the region on Wednesday. There are already rainfall warnings in effect for areas of New Brunswick and they will be expanded to the southwest and issued for areas of central and western Nova Scotia. No surface based convection is expected however the mid level instability ahead of the low is quite significant and is represented in very low Showalter indices.  Gusty winds up to 60 km/h are possible. PWAT values of 40-50 mm enhance the downpour threat and that is evident in observations currently coming out of areas of New England where 25 mm/hr or higher have been reported.

 

Thunderstorm outlook for today:

 

Thunderstorm Outlook for Tonight:

 

Thunderstorm Outlook for Tomorrow:

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NB/PEI/Les Iles/NS: none

NL&LAB: showers exiting the province

 

Tuesday

NB/NS: A few embedded thunderstorms late in the day in warm air advection over western regions.

PEI/Les Iles: none

NL&LAB: Risk of a thunderstorm over northern and central portions of Labrador

 

Convective Discussion

The upper low has moved east of NF this morning, and the associated residual shower activity will taper off during the day. An upper ridge is building over the Maritimes, however as the diurnal instability increases cumulus field will develop across the region. Cloud top between 2-4 km with maximum of 5 km can be expected.

On Tuesday, bands of thunderstorms from New England/Gulf of Maine will be advancing in the warm advection over the Maritimes late in the day. To a lesser extent warm air advection will also promote some thunderstorm activity over northern Que, possibly reaching Labrador. Instability will not be the greatest but this moisture-rich airmass will bring surface dewpoints to 18-20, and at the end of the day, a swath of moisture with precip water of 40-50 mm will extend from Browns bank/Lurcher to the St. Lawrence valley. The main forecast models show a surface low moving across eastern Ont/southern Que Tuesday, and then over NB and Gulf of St. Lawrence Wednesday. At this time, an average of the precipitation guidance would suggest totals of 50-80 mm with the maximum amounts over the lower St. Lawrence/Gaspé/northern NB. These numbers are preliminary for the large scale and could be augmented if smaller embedded/elevated convective features become more predominant.

 

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NB/PEI/Les Iles: Isolated thunderstorms giving heavy downpours and gusts near 50 km/h

NS: Scattered thunderstorms over eastern half of the province giving localised heavy downpours, small hail and wind gusts near 70 km/h.

NL&LAB: None

 

Convective Discussion

An upper low high pressure near the Gaspe peninsula will slowly advance eastward today and tonight, at the surface there are two areas of rain associated with a couple of low pressure systems, one near Anticosti island and a second one south of the Burin peninsula. NF radar estimates for the past 12 hours suggest rainfall amounts of 20 to 40 mm with the highest amounts just off the west coast and south of the burin, however observations from autostations suggests amounts of 10 mm. There will likely be another 10-20 mm to come until tomorrow.

The focus for surface-based convection this afternoon will be over the NErn half of NB, PE, and especially Ern NS. Under a cold pool (-16) associated with the upper low, the cumulus field is already starting to grow and diurnal instability will be on the increase during the afternoon. Surface temperature of 24 or 25 will likely be plenty to bump MLCAPE values to nearly 500 J/kg / LI of -2. There are some interesting upper dynamics combining with these conditions, including 500 mb positive vorticity advection and a slightly cyclonic 80 knots upper jet branch south of NS, placing CB and Cabot strait near a right exit. The Shearwater Hodograph shows about 30 knots of effective deep layer shear. Eastern-most areas of NS mainland and Srn CB could get stronger thunderstorms that could evolve into longer-lasting linear features and produce downpours/small hail/high winds.

A high pressure system will build in from the west tonight and Monday.

 

 

Thunderstorm Outlook for Today

 

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Monday