Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Today

NB: Scattered strong to severe thunderstorms.

Labrador: isolated to scattered thundershowers in the west.

NS/PEI/NL: isolated thundershowers.

 

Tonight

MRTMS: None.

Labrador: isolated thundershowers.

 

Sunday

NB/NS/PEI/Labrador: isolated thundershowers

NL: None.

 

Convective Discussion

An approaching cold front will track across New Brunswick later today and Nova Scotia on Sunday. There is a fair amount of shear (30 to 40 knots and linear) and the cape is 500-1000 J/kg. Additionally, areas of western NB and southern Labrador are in the favourable left exit region of an upper level jet. PWAT values of 25-35 mm will give downpours. Guidance is suggesting hail of 1-2 cm. Dry mid levels support the model guidance of wind gusts to 50 kts.

 

Garden variety pop-up thundershowers are possible on Sunday. Cape values due not look very high but shear is high and my be too strong to maintain cells.

 

 

Thunderstorm Outlook for today

 

 

Thunderstorm Outlook for tonight

 

 

Thunderstorm Outlook for Sunday

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

 

Today

NB: isolated thunderstorms in the northwest.

Labrador: isolated thundershowers in the west.

NL: isolated embedded thundershowers over the Grand Banks.

 

Tonight

MRTMS: isolated thundershowers.

Labrador: isolated thundershowers.

 

Saturday

NS/PEI: scattered thundershowers

NB/Labrador: scattered strong (nearing severe) thunderstorms.

 

Convective Discussion

An approaching trough of low pressure  which was analyzed near the St. Lawrence river valley will likely trigger some isolated thunderstorms in northern ME this afternoon that will advect into NW NB as the day progresses. There is a fair amount of shear (close to 40 knots and linear) so could be some gusts to 70 km/h in some of the heavier cells (assuming they develop). But don’t really expect severe storms today as the more favourable dynamics remain further upstream for now. There is some lightning in QB that may make it to the Wabush/Lab City area this afternoon but that looks pretty marginal at best. Weakening upper level low could still give some isolated CBs to the Grand Banks today.

 

That same trough feature could give an isolated thundershower tonight across the MRTMS as cloud top cooling could help things a little. But certainly nothing to write home about.

 

The more favourable dynamics appear to be in store for Saturday based on latest computer models. I will not delve into details since that notion can change. Right now strong winds, small hail and heavy downpours are possible in some areas in the stronger cells. PWATs could be very high across parts of the MRTMS so high rainfall amounts in a short period of time may occur even outside the moderate (yellow) risk areas.

 

Thunderstorm Outlook for Day 1

 

Thunderstorm Outlook for Friday night/Saturday morning

 

Thunderstorm Outlook for Saturday afternoon

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

NB: downpours and scattered lightning

NS: downpours and scattered lightning most of mainland

PEI: Isolated lightning western half

NF: None

Labrador: Isolated lightning Eagle River region

Marine waters: Scattered lightning eastern marine district into southwestern Grand Banks. Isolated lightning near Anticosti. Isolated lightning western Northumberland strait.

 

 

Convective Discussion:  Generally unstable with an upper trough over the Maritimes providing steep mid tropospheric lapse rates. Shear will be minimal today with slow storm motion initially easterly at 5-10 kts becoming southeasterly later in the afternoon into the early evening. Given slow storm motion and PWATs into the upper 20mm, the primarily hazard today will be downpours over the Maritimes. In eastern Labrador over meager instabilities of ~300 J/kg aided by a deformation zone on the western periphery of the upper trough may allow for the odd strike, however bulk shears in excess of 40 kts may prove to be too much to allow for convection to reach heights sufficient to generate lightning. Differential heating near the deformation zone may also allow for the odd strike near Anticosti island. Much of the southern/eastern Marine district remains in a moist unstable environment, with PVA from the upper trough continuing to trigger scattered thunderstorms. This region of instability is expected to slowly advect east with the upper trough, giving continued scattered convection over the next 36 hours.

 

On Canada day (tomorrow), little thunderstorm activity is expect. However storms may move into northwestern NB from eastern Quebec in the early evening hours as a cold front moves towards Atlantic Canada.

 

Thunderstorm outlook for today:

 

 

Thunderstorm outlook for tonight:

 

 

Thunderstorm outlook for Friday (Canada Day):

 

 

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

Labrador: Scattered thundershowers for western and northern regions.

NB: Isolated thundershowers in the northwest.

NL/NS/PEI: None.

Slope waters: Isolated thundershowers.

 

Convective Discussion

Today: The only area with marginal excitement for a forecaster is western Labrador where there is an approaching deep layer trough from the surface to 500 mb, wind shear in the 40-50 knot range and modest instability. The only caveat would be solar insolation which will be somewhat difficult given the current cloud cover. The Maniwaki TEP profile from 12 UTC is decent for thunderstorms but realistically is too far upstream to give a good indication for western Labrador. Expect some scattered cells embedded along the frontal feature as it approaches this afternoon but non-severe in nature. Some isolated thundershowers are possible in NW NB later today as that aforementioned front approaches the St. Lawrence valley. Lastly high PWATs, Tds and a weak surface trough will give some isolated cells mainly south of the slope waters…some may trickle into the southern marine district later on.

 

Tonight: Some instability is indicated on guidance in conjunction with a surface trough and falling 500 mb heights in western NB, which may give some isolated thundershowers through the overnight and into Thursday morning. That trough south of the marine district will begin to push northward bringing some scattered thunderstorms tonight and Thursday morning.

 

Thursday afternoon: Scattered thunderstorms are likely for most of NB and convergence areas across the usual areas in NS as an upper trough of low pressure crosses the MRTMS. Cells will be very slow moving so locally heavy rainfall is possible. Scattered thunderstorms associated with the surface trough for waters south of NS and NL.

 

Thunderstorm Outlook for Today

 

Thunderstorm outlook for tonight

 

Thunderstorm outlook for Thursday

Convective Outlook Valid for Today and Tomorrow

Regional Impacts

NB: Isolated thundershowers for southern regions

NS: None

PEI: Isolated thundershowers for western regions

NF: None

Labrador: Isolated thundershowers over southeastern regions

Marine waters: Isolated thundershowers for Laurentian Fan.

 

 

Convective Discussion:  Clearing behind an upper trough will allow for modest instability to develop this afternoon (MLCAPES ~350 J/kg), causing  isolated convection initiation over areas of enhanced differential heating. A secondary area for potential CBs also exists over southern NB into western PEI later this afternoon into the evening. Here SBCAPES of ~400 J/kg should develop with clearing early occurring early this afternoon, convection looks to be triggered by an upper trough moving eastward from Vermont, aided by a right entrance region of a 130 kt upper jet, and surface convergence that was already evident on the 12z analysis from ~CYFC to Kent County. Primary hazards would be isolated lightning, downpours should be limited by rather low PWATs ~ 20mm.

 

Tomorrow another cold front is expected to move through north-central Quebec into western Labrador triggering CBs with modest CAPES on the order of 400 J/Kg. High LCLs on the order of 1.5-2 km, unstable PBL lapse rates will present an additional hazard for some strong wind gusts outside of lightning and some small hail,  given the position of the HGZ and shear character. CBs associated with this feature further south may also move into NW most NB late tomorrow evening, but felt the risk was low enough to leave it out of the day 2 outlook at this time. Another marginal area left off the outlook tomorrow is immediately inland along the northern coast of NL, where an upper trough, coastal convergence and modest instability of 200-300 J/Kg may allow for the odd strike before a 700 mb thermal ridge moves in bringing capping issues. Again felt probability was a little too low to be included in the day 2 outlook at this time.

 

The slope waters present reasonable instability at T/td’s of 22/20, with isolated lightning becoming scattered by Wednesday evening, with a persistent LLJ.   

 

Thunderstorm outlook for today

 

Thunderstorm outlook for tonight

 

 

Thunderstorm outlook for Wednesday