Convective Outlook Valid for Today and Tomorrow

Thunderstorm outlook for Day 1.

 

Convective Discussion

A slight chance of embedded convection today and tonight as a low currently south of Nova Scotia tracks towards NFLD tonight.  If any convection does get initiated, it would have to go through a significant warm nose before reaching a level of positive buoyancy at which 200 to 300 J/Kg is possible which is not significant.  However, a few cells passed over Sable island early this morning bringing near 60 mm over the island in a span of 3 hours (34 mm was reported in 1 hour).  There was no lightning detected on these cells but due to the amount of rainfall over a short period of time, this does indicate that there could be some convective activity.  This area of convection is expected to reach eastern Newfoundland later today so if the cells maintain their strength, it could result in some significant rainfall over a small period of time for parts of eastern NFLD.

 

Regional Impacts

Maritimes…

A slight chance of embedded convection over eastern NS.  No impacts expected.

 

Newfoundland…

A chance of embedded convection this afternoon and tonight over NFLD. Locally heavy downpours possible.

 

 

Thunderstorm outlook for Day 2.

 

 

Convective Discussion

Some instability expected over southeastern NB Monday afternoon but a capping inversion at around 11,000 ft could limit the vertical extent and thus hamper convective activity.  If this capping inversion is less significant than currently expected then non-severe thunderstorms are possible.

 

Regional Impacts

Maritimes…

None at this time.

 

Newfoundland…

None.

 

Barrie MacKinnon

Program Supervisor – Operations Support

Atlantic Storm Prediction Centre

Meteorological Service of Canada

45 Alderney Drive, Dartmouth

Nova Scotia, B2Y 2N6

Weather - Environment Canada

(902) 497-9317

 

Surveillant de Programme - Soutien aux Opérations

Centre de prévision des intempéries de la région de l'atlantique

Service météorologique du Canada

45 promenade Alderney, Dartmouth

Nouvelle-Écosse, B2Y 2N6

(902) 497-9317

 

Convective Outlook Valid for Today and Tomorrow

Convective Discussion

Generally a chance of embedded/elevated thundershower activity today. A low pressure system with lots of cloud and rain will move across the region today and Sunday. Rain training is possible today as lines of convectively enhanced rain move across localities. Over southwestern NB, brief clearing skies are possible. If this in turn causes temperatures to rise much higher than currently forecast then surface based convection could occur. 40 kts of linear shear and Cape values of 500+ J/kg would result, giving the potential for gusty winds, downpours and small hail. On Sunday the low will give a chance of thundershower activity for eastern regions.

 

Regional Impacts

Maritimes…

A chance of thundershower activity today and Sunday. A slight chance of severe weather for SW NB today.

 

Newfoundland…

Nil.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Day 2

 

Convective Outlook Valid for Today and Tomorrow

Convective Discussion

Just a chance of thundershower activity today. Cape values are quite low while shear values are quite high.  Some embedded/elevated thundershowers are possible across the Maritimes on Saturday as a low pressure system moves across the region.

 

Regional Impacts

Maritimes…

A chance of thundershower activity today and Saturday .

 

Newfoundland…

A chance of thundershowers late this evening and overnight.

 

Thunderstorm Outlook for Day 1

 

 

Thunderstorm Outlook for Day 2

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

Regional Impacts

 

For Eastern Newfoundland…

No significant impacts are expected do to thunderstorm activity today, some locally heavier embedded showers in thunderstorms and occasional lightning might affect the forecast.

 

Convective Discussion

 

For today there will be sufficient moisture and instability east of the most of the public areas to generate occasional embedded thunderstorms just ahead of the 250 jet that is slowly swinging northeastward today.

 

The dynamics are coming together for tomorrow with the upper level jet becoming a supporting factor for the development of Thunderstorms. Central Newfoundland is currently the most likely area to be impacted with a low potential for severe storms. Low level moisture could be the limiting factor but areas of enhance low level convergence could see some thunderstorms develop.

 

Thunderstorm Outlook for Day 2

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

 

 

Regional Impacts

Widespread rain across NS, rain also across Labrador mixing with some snow in the west. Scattered shower activity across the rest of the Atlantic provinces.

 

Convective Discussion

Vertically stacked low near Anticosti Island at 12z with an east-west orientated frontal wave over Labrador. Cold front has moved past Newfoundland with pressure rises of about 4mb in behind between 9-12z over eastern portions of the island. The airmass has dried out significantly behind the frontal feature but it remains fairly unstable as indicated by the YJT sounding. In this unstable environment, bands of TCU with tops to 15,000ft or more will develop giving scattered showers. Note that surface based CAPE values of more than 250 J/kg are attained simply by warming the surface to 16C, so in this context the development of a small CB with tops over 22,000ft is not out of the question over west-central and northern Newfoundland this afternoon. The latest satellite imagery is showing more and more breaks in the cloud which could be the key to the last point.

Further away from the low, and around the cold pool aloft we find a couple of troughs, one over the Saint. Lawrence Valley and another one over NS where overcast stratiform conditions with widespread rain will prevail, the Shearwater sounding shows some instability between 5,000 to 10,000ft which will result in localised heavier rain with these embedded TCU’s.

Over NB, The airmass is quite dry but small warming of the surface will produce bands of TCU’s with tops between 12,000 to 14, 000ft and spotty showers.    

 

 

Thunderstorm Outlook for Day 2