Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

 

NB: Chance for an isolated thundershower.

 

LAB: Slight chance for an isolated thundershower.

 

NS/PEI/NB/NFLD: Nil.

 

Tonight

 

NB: Chance for isolated thundershowers.

 

NS/PEI/NFLD/LAB: Nil.

 

Tomorrow

 

NB: Likely chance for severe thunderstorms. Most significant hazards: a possible tornado; 1-2 cm hail.

 

NS/PEI/LAB: Likely chance for isolated thundershowers.

 

NFLD: Nil.

 

Convective Discussion

 

After an active upper trough moved through Atlantic Canada, today is expected to be relatively quiet as a ridging is in place over most of the Atlantic provinces. There is however a progressing frontal system moving through Quebec which is giving some short waves passing through Labrador today with enough jet support to have Effective shear values nearing 25KT which could support some isolated thunderstorms is they form. For New Brunswick, there is the chance that prefrontal thundershowers form over the extreme Northwestern sections of the province. But they are currently not expected to become severe.

 

Overnight with the approaching frontal system from Quebec there is the chance of isolated thundershowers off the southern Coast of New Brunswick and Nova Scotia which could drift inland over New Brunswick.

 

Tomorrow, the frontal wave is sweeping through the Maritimes giving a collection of ingredients for severe thunderstorms to have a chance at forming. As the cold front progresses through the Maritimes, effective shear values are expecting to be near 40KT along with having a classically curved hodograph and ample low-level helicity it is possible that a tornado or two could form tomorrow. Additionally, looking at soundings the risk for hail is likely to be near 1-2cm. It is worth noting that some sounding analogues do indicate over 2cm of hail, so it is something to keep in mind for tomorrow, but it does appear unlikely to have hail this significant.

 

Thunderstorm Outlook for Today

 

 

Thunderstorm Outlook for Tonight

 

 

Thunderstorm Outlook for Tomorrow

 

 

Forecaster: Lambert

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

 

NS/PEI/NB: Likely for scattered thunderstorms. Hazards: 50-70 km/h wind gusts; 0-1 cm hail; 20-40 mm rainfall.

 

NFLD: Chance for isolated thundershower(s). Hazards: 15-25 km/h wind gusts.

 

LAB: Slight chance for isolated thundershower(s).

 

Tonight

 

NB/NS/PEI/NL/LAB: No thunderstorm risk expected.

 

Tomorrow

 

NB: Chance for isolated thunderstorm(s) over Northwestern NB.

 

NS/PEI/NFLD/LAB: Nil.

 

Convective Discussion

 

Today's surface analysis shows that there is predominantly an upper trough over the Maritimes which will act as a trigger for convection today. The most significant hazard is expected to be rainfall rates approaching 40mm/hr. This is largely due to the high PWAT's near 35mm still in play over most of the Atlantic Provinces. For Newfoundland and Labrador, there remains the same synoptic setup however there is expected to be a degradation in both trough strength and PWAT's over the island of Newfoundland. Over the Maritimes, specifically in the regions under the “B” location can see CAPE values nearing 1200 J/Kg meanwhile in Newfoundland, specifically in the southwest can also see CAPE values nearing 1000 J/Kg. Within this trough on the Eastern side of the trough there is jet support at the 500mb level nearing 40Kt and at the 250mb there is a stronger jet nearing 100Kt. On the western side of the trough there is a similar jet support at the 500mb level though at the 250mb level the jet drops down to a modest 60Kt.

 

As the trough passes through tonight, slight ridging is expected to build in, this combined with a fast approaching nighttime there is no convection anticipated over the Atlantic provinces.

 

An approaching cold front that is currently over Lake Superior, is expected to start impacting Northwest New Brunswick late in the day on Thursday. There is some uncertainty with the timing currently, but previous outlooks have indicated that there is a potential for strong winds and hail with this front. The area in Grey is given this as the timing uncertainty would cause a large variance in what is and is not possible during the designated timeframes.

 

Thunderstorm Outlook for Today

 

 

Thunderstorm Outlook for Tonight

 

 

Thunderstorm Outlook for Tomorrow

 

 

Forecaster: Lambert

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NS/NB/PEI/LAB: Scattered thunderstorms.

NFLD: A chance of embedded thundershowers.

 

Tonight

NFLD: A chance of embedded thundershowers.

NS/NB/PEI/LAB: None.

 

Wednesday

NS/PEI: Scattered thundershowers.

NFLD/LAB: A chance of thundershowers.

NB: None.

 

Convective Discussion

The tropical moisture feed ahead of a broad upper low approaching New Brunswick will continue over most of Atlantic Canada today. Over Newfoundland there is a chance of embedded convection and synoptic warnings and statements are already in effect there. Clearing skies elsewhere will allow surface based convection. The area of most concern today is over portions of Nova Scotia, New Brunswick and PEI where CAPE values of 1000-1500 J/kg and effective shear near 30 knots are expected. An upper level jet may also contribute with the development but that is east of the main area of concern. While wind gusts and hail are possible, once again it will be training thunderstorms giving copious amounts of rain that is the main concern. On Wednesday, the upper low and afternoon destabilization will move over the eastern Maritimes and into southwestern Newfoundland. Conditions similar to today are expected but the shear will be a bit less so more muted impacts are likely.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

 Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NS/NB/PEI/NFLD/LAB: A chance of thundershowers.

 

Tonight

NS/NFLD: A chance of thundershowers.

NB/PEI/LAB: None.

 

Tuesday

NS/NB/PEI/NFLD/LAB: A chance of thundershowers .

 

Convective Discussion

The tropical moisture feed ahead of a broad upper low over southern Quebec will continue over portions of eastern Nova Scotia, Prince Edward Island and Newfoundland today. Precipitation amounts are highly variable but anywhere within that area could receive significant amounts as rainfall rates approach 25 mm/hr at times or higher. Over northern New Brunswick clearing has occurred and surface based convection is possible this afternoon. MLCAPE values are expected to be 500-750 J/kg and the effective shear will be near 30 knots. Do to the limited CAPE, severe thundershowers are not expected however gusty winds, small hail and downpours are still possible.  On Tuesday, the tropical moisture feed and embedded thundershowers will persist over eastern Cape Breton and Newfoundland. Skies will be clearing elsewhere in the Maritimes as the upper low tracks across New Brunswick. MLCAPE values of 500-750 J/kg and effective shear near 30 knots are expected once again so a repeat again of the conditions forecast for northern New Brunswick today.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

Maritimes: Embedded thunderstorms within the greater rainfall area bringing enhanced rainfall rates and totals. The main hazard is very heavy downpours, and potentially training storms.

 

Tonight/Tmrw Morning

Ongoing moderate to heavy rain shower activity with embedded thundershowers advances across the Gulf of St. Lawrence and to the southern part of Nfld.

 

Monday

Atlantic Canada: Widespread risk of thundershowers in the large scale synoptic flow. Local torrential downpours remain the main concern, enhanced further by any repetitive thunderstorms. Clearing begins from west to east into Tuesday.

 

Convective Discussion

Rain is the name of the game today. A strong moisture feed has developed into the Maritimes stemming all the way from Florida. This is very evident on water vapour imagery this morning. This morning’s soundings also show a completely saturated column. Pwats are near 60, and observed dew points of 20. Synoptic rainfall warnings and special weather statements are already in effect. If embedded thunderstorms train over one specific area, or rates exceed 25 mm/h, thunderstorm warnings will also be used for the local area to describe the hazard/risk further. This weather event is forecast to continue into Monday for the Maritimes, and begin affecting Nfld in the next 18 to 24hrs. Conditions are forecast to improve on Tuesday in Nova Scotia.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 Forecaster: Tirone.