Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Today

NB/PEI: Slight chance for isolated thunderstorm(s). Hazards: 70 km/h wind gusts; 0-1 cm hail; 15-25 mm rainfall.

LAB: Slight chance for isolated thundershower(s).

NS/NFLD: Nil.

Tonight

PEI/NS/NFLD: Chance for isolated thundershower(s). Hazards: 70 km/h wind gusts; 15-25 mm rainfall.

NB/LAB: Nil.

Tomorrow

NFLD: Slight chance for isolated thundershower(s).

NS/PEI/NB/LAB: Nil.

Convective Discussion

Looking at today's surface analysis, there is a low off the coast of Labrador along with a cold upper low over Northern Quebec into Labrador. Additionally with this setup we have two significantly strong curved jets, a 55KT jet at 500mb and a 95KT jet over northern New Brunswick. As the cold upper low progresses to the south with these jets, we can expect to see some isolated thunderstorms in New Brunswick, western PEI, and Southeastern Labrador. Looking at Surface based CAPE, we are seeing CAPE values remain mainly around 700 J/Kg with some isolated areas over NB and PEI reaching 1,000 J/Kg, over these areas we do have Effective Shear reaching 30 to 35Kt over most of NB and PEI.

With the progression of this system sweeping through the Maritimes and Newfoundland there is guidance to suggest that overnight thundershowers are possible over eastern PEI, Nova Scotia, and Eastern Newfoundland. It is worth noting that in this outlook we have a region "B" this is to denote the possibility of waterspouts. As the system moves over Nova Scotia, guidance is suggesting that it could develop into a squall line which if that occurs there is a possibility that waterspouts could develop. Overnight Most Unstable CAPE (MUCAPE) values are expected to stay within the range of 500 J/Kg, except over warm waters where they could approach the 1,000 J/Kg mark. Additionally shear values are still expected to remain near 30Kt over warm waters but reduce down to 20Kt over land.

Tomorrow will begin a relatively quiet period as this system should depart eastern Newfoundland early into the valid period of the outlook. Once this system had departed a ridge is expected to develop over most of Atlantic Canada.

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

LAB: Scattered thunderstorms.

NS/NFLD: A chance of thundershowers.

NB/PEI: None.

 

Tonight

NS/NB/PEI/NFLD/LAB: None.

 

Sunday

NB/LAB: A chance of thundershowers.

NS/PEI/NFLD: None.

 

Convective Discussion

Over eastern Labrador today, a tropical moisture feed is expected ahead of a broad upper low and surface trough. This same system gave copious amounts of rain and gusty winds to parts of New Brunswick and Prince Edward Island yesterday. CAPE values near 1000 J/kg and effective shear of 30 to 40 knots are expected. While wind gusts and hail are possible, it will be training thunderstorms giving copious amounts of rain that is the main concern. Due to much lower CAPE values, the trough will give just a chance of thundershowers for parts of Newfoundland and eastern Nova Scotia. On Sunday an approaching trough will give a chance of thundershowers for northern New Brunswick and southeastern Labrador.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today

 

NB: Potential for severe thunderstorms giving strong wind gusts, small hail, locally heavy rainfall and slight risk of a tornado.

 

NS/PEI/LAB: Chance of isolated thundershowers giving local heavy rainfall.

 

NL: None.

Tonight

NB/PEI/NS/LAB: Isolated thunderstorms giving locally heavy rainfall.

NL: None

Tomorrow

NL/LAB: Scattered thunderstorms giving brief strong wind gusts, small hail and locally heavy downpours.

NS/PEI : Isolated thundershowers.

NB: None

Convective Discussion

A stationary upper low sits over Hudson Bay, with a cold front that will progress eastward today across Maine and into New Brunswick by late this afternoon. Ahead of the front this morning, showers and embedded isolated thundershowers have persisted across northeastern New Brunswick, with some clearing expected early this afternoon prior to the cold front. This should allow for enough daytime heating for MLCAPE values to reach of exceed 1250 J/kg across central and western New Brunswick. With stronger southwesterly winds increasing with the approaching front, effective shear may reach 40 kt, with some indications of moderate low-level shear and storm relative helicity, storms that develop may either organize into lines or possible supercells with the risk of a tornado ahead or along the front. There is also an increasing 250mb jet moving into the Maritimes, and in an ideal left exit region, allowing for divergence aloft and the maintenance of storms. The main hazards will be strong wind gusts of 90 km/h, hail of 1-2cm and heavy downpours with rainfall rates of 30-40 mm/h possible.  The front extends also into southwestern and southcentral Labrador with possible isolated embedded thunderstorms.

A short-wave trough is also moving across the southern Maritimes marine district and some interaction with this system, possible clearing skies in the western Nova Scotia and the cold front may help with potential storm development also along the Bay of Fundy extending northeastward into Prince Edward Island late this afternoon and evening. Heavy downpours are the likely main threat with these given the orientation of storm development and possible training storms.

With an increasing 250mb jet spreading into the Maritimes tonight, storms may persist overnight across southeastern New Brunswick, Prince Edward Island and central Labrador giving heavy downpours.

For tomorrow, the cold front continues into eastern Labrador and Newfoundland while the shortwave moves across the eastern Maritimes marine waters and across southeastern Newfoundland with convection. There will be the risk of brief strong wind gusts, small hail and locally heavy downpours.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Forecaster: McArthur

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