Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts…

 

Today

NB: Scattered thunderstorms developing, some becoming strong with potential for damaging wind gusts and 1-2 cm hail. Severe weather watch for western portions of the province for the afternoon into the evening.

NS/PEI: risk of non-severe thunderstorms

NF: A slight chance of thunderstorms south coast

Labrador: None

 

Tonight

NS and NF: A chance of embedded thunderstorms

NB/PEI/Labrador: None

 

Monday

NS and NF: A chance of embedded thunderstorms

NB/PEI/Labrador: None

 

Convective Discussion…

Low pressure near Sept-Iles with an attached frontal wave system is slowly moving eastward. In the warm sector, a 50-60kt SWly low-level-jet has been pushing very moist air northward and a large area of area of moderate-heavy rain has spread across NS earlier this morning which resulted in amounts of 10-30mm. This activity will advancing towards NF during the day.

 

To the west, an upper  trough over western Quebec will be advancing towards the Maritimes today and will be the focus severe weather (the main threat is the potential for damaging wind gusts WINDEX gusts estimates 50kt). There is not much convective inhibition ahead of this feature, and towering clouds are already noticeable north and south of the St. Lawrence valley. The main forcing will be a sharp area of convergence at the surface, emerging 30kt Wly low-level-jet, right entrance of a slightly cyclonic upper level jet, and 500mb PVA. Temperature and Dewpoint combination of 23,18 are sufficient to produce surface-based CAPE values of 1,000 J/Kg (MU 1,500) with Lifted index of -3 to -5, and deep-layer shear of 40-60kt. Under this very strong flow, hodograph is indicating straight/linear winds with storm motion of 260/35kt. Some of the storms could be long-lived especially over central Maine later this afternoon. This could produce bowing lines which could advance east of the international border.  

 

 

Thunderstorm Outlook for Today

 

 

Thunderstorm Outlook for Tonight

 

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts…

 

Today

Labrador: A chance of thunderstorms north coast.

NB/NS/PEI/NL: None.

 

Tonight

NB/NS: A chance of embedded thunderstorms.

PEI/NL/Labrador: None.

 

Sunday

NB/NS/PEI/NL: A chance of embedded thunderstorms. Over New Brunswick, surface based storms will likely give severe weather in the afternoon.

Labrador: None.

 

Convective Discussion…

A low pressure system tracking across northern Labrador may give a few elevated thundershowers to that area this afternoon.  Tonight an approaching low pressure system will give rain across the Maritimes starting overnight. On Sunday, embedded/elevated thundershowers are expected across the region. Sunday afternoon with some clearing ahead of the low’s associated cold front, surface based thundershowers are expected over portions of New Brunswick and they will likely become severe. CAPE values of 500-1000 J/kg, shear of 40-50 knots and strong low level winds below 6000 feet will likely produce multicell and bow echo elements.  Wind is the main threat (possible 90 km/h +) but 2 cm hail and torrential downpours (PWAT values 30-40 mm) are also likely. Because of some uncertainty with clearing in the afternoon and daytime high temperatures, the Sunday (day 2) chart below is likely a bit on the conservative side but will be updated again Sunday morning.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts…

 

Today

NB: A chance of thunderstorms east.

NS/PEI/NL/Labrador: None.

 

Tonight

NB/NS/PEI/NL/Labrador: None.

 

Saturday

NB/NS/PEI/NL/Labrador: None.

 

Convective Discussion…

A low pressure system will track northeastward across Newfoundland today. Unstable air in the wake of the low will give a chance of non-severe (CAPE values of 200 J/kg or less) thundershowers over eastern New Brunswick this afternoon.  There is a slight chance of thundershowers in areas of prolonged sunshine (if there are any) in central Newfoundland this afternoon.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts…

 

Today

NB/NS/PEI/NL: Scattered thunderstorms giving possible giving rainfall rates of 10 to 20 mm/h.

Labrador: None.

 

Tonight

NL: Scattered thunderstorms giving possible giving rainfall rates of 10 to 20 mm/h.

NS/NB/PEI/Labrador: None.

 

Friday

NB/NL: Scattered thunderstorms giving possible giving rainfall rates of 10 to 20 mm/h.

NS/PEI/Labrador: None.

 

Convective Discussion…

A trough of low pressure stretching from New Brunswick to Newfoundland will slowly track eastward today and Friday.  Embedded thunderstorms are occurring near and ahead of the trough and are giving downpours of 10-20 mm/hr. Some pop-up thundershowers are possible this afternoon over New Brunswick. Cape values are 200-300 J/kg with shear of 40-60 kts. The shear will be too much to assist with the thunderstorm development so these should remain non-severe.  More pop-up thundershowers are possible Friday afternoon over New Brunswick but again the Cape values are quite low.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts…

NB… Scattered thunderstorms possible over northwestern New Brunswick early this afternoon. Rainfall rates of 10 to 20 mm/h and wind gusts up to 70 km/h.

NL… Isolated thunderstorms possible over southwest Labrador this afternoon. Rainfall rates of 10 to 20 mm/h and wind gusts up to 70 km/h.

NS/PEI… Embedded thundershowers possible tomorrow morning and afternoon. Rainfall rates of 10 to 20 mm/h.

 

Convective Discussion…

A trough entering New Brunswick today brings the risk for some scattered thunderstorms early this afternoon. The biggest threat for severe weather exists in northern New Brunswick, where better thermodynamics and forcing are present. However, dense cloud cover northern New Brunswick is preventing CAPE values from rising too much, though some brief clearing behind this is expected. The risk remains low due to this, in addition to a stalling thermal trough this afternoon. The thermal ridge sitting over southern New Brunswick should remain intact and inhibit much thunderstorm activity here today, as the frontal boundary slows down and stalls over northern New Brunswick later this afternoon. Bulk shear values of 40 to 50 kts are present (though quite linear), as well as PWAT values in the range of 30 to 35 mm. As such, the main threats with any storms today will be strong wind gusts up to 70 km/h and heavy downpours of 10 to 20 mm/h.

A second system, that is expected to bring severe weather to parts of the northeast US today, will approach the Maritimes over the Gulf of Maine tonight, reaching southwest Nova Scotia early tomorrow morning. Strong dynamics and adequate instability in the mid-levels will aid in sustaining convection overnight and into tomorrow morning as the trough passes over the Gulf of Maine. With PWAT values expected around 40 to 50 mm, heavy downpours up to 20 mm/h are possible tomorrow morning across southern Nova Scotia and potentially into the Bay of Fundy.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Copp