Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts…

 

Today

Labrador:  Scattered thunderstorms gusts 50-70 km/h and brief heavy showers 15mm/h.

NB/NS/PEI/NL:  None.

 

Tonight

Labrador:  A chance of thunderstorms.

NB/NS/PEI/NL:  None.

 

Tuesday

NB/Labrador:  Widespread thunderstorms with some of them becoming strong, rainfall rates 15-25 mm/h, hail possible, and gusts 50-80 km/h.

NS/PEI/NL: None.

 

Convective Discussion…

 

The airmass between James Bay and Labrador has become very unstable this morning ahead of an approaching upper level disturbance. At this point, the instability is triggered by 500 dam heights fall amplified by straight sunshine. In terms of dynamic support, A cyclonic jet over the Quebec far north is slowly descending, while a 40kt SWly low-level-jet is pumping moisture and energy into the mix. Surface CAPE values in excess of 1000 J/kg, LI of -4 and (increasing) 0-6 km shears of 25-35kt, will help support long-lived clusters.  

 

Fair weather cumulus along with warm and humid conditions are expected over the rest of the region.

 

For Tuesday, precipitable water will be on the increase and the upper disturbance and weak cold front will approach from Quebec/Lab and set the stage for the next round of thunderstorms. Current forecast guidance is suggesting the possibility of strong convective features but confidence is only starting to increase. This activity will likely occur during the peak daytime heating period of the day.

 

 

Thunderstorm Outlook for Today

 

 

Thunderstorm Outlook for Tonight

 

 

Thunderstorm Outlook for Tomorrow

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts…

 

Today

NB/Labrador:  Scattered afternoon thunderstorms. A chance of becoming severe over NB.

NS/PEI/NL:  None.

 

Tonight

Labrador:  A chance of thunderstorms late Monday morning.

NB/NS/PEI/NL:  None.

 

Monday

NB/Labrador:  A chance of afternoon thunderstorms.

NS/PEI/NL: None.

 

Convective Discussion…

A trough of low pressure tracking across Labrador will give scattered afternoon thundershowers over portions of Labrador. Cape values are near 500 J/kg so any cells that form are no likely to be severe. Over New Brunswick, surface based thundershowers that could become severe are possible this afternoon. There are no real surface forcing mechanisms but Cape values are 500-1000 J/kg and shear is linear at 40 knots.  There is the potential for heavy rain at times as PWAT values are near 30 mm. There is also a supportive right entrance to an upper level jet to give support.

 

 

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:  A chance of thunderstorms.

Labrador:  None.

 

Tonight

NB/NS/PEI/NL:  A chance of thunderstorms.

Labrador:  None.

 

Sunday

NB/PEI/Labrador: A chance of thunderstorms. Over New Brunswick, surface based storms will may give severe weather in the afternoon.

NS/NL: None.

 

Convective Discussion…

A trough of low pressure tracking across the Maritimes will give a chance of embedded thundershowers for those areas today. There is the potential for heavy rain at times as PWAT values are 30-50 mm. Surface based thundershowers are possible this afternoon over portions of Newfoundland but the CAPE values are less than 500 J/kg so they should stay non-severe. On Sunday, surface based thundershowers are expected over most of New Brunswick and portions of Labrador. Over Labrador the CAPE values are expected to be less than 500 J/kg so non-severe cells are expected. Over New Brunswick, CAPE values near 1000 J/kg and shear of 30-40 knots will help support possible severe thunderstorms.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Scattered to widespread thundershowers are expected across NB later today and overnight tonight across Fundy shores. Some storms near Grand Falls and the Trans-Canada Highway over western NB could reach severe limits due to hail and heavy rain (and wind gusts). Severe storms are expected to be quite isolated. The general thundershowers will extend across the Northumberland and Gulf marine regions.

 

Convective Discussion

The frontal analysis today is complex. A trailing cold front across eastern Labrador may spawn a few lightning strikes today. Another cold front currently located over the St. Lawrence river approaching the Gaspe peninsula will act as a trigger this afternoon for storms in NB and western PEI. Storms near the American border will have decent jet support, and 0-6k shear over 35kts. Moderate hail is possible *IF* a discrete cell can form in a clearing of the prevailing cloudy skies. Overnight, this trough-ing will force embedded thunderstorm development along Fundy shores and western NS. On Saturday, this instability becomes quite widespread across Atlantic Canada with rain being the main hazard. Sunday brings in stabilizing conditions throughout the day.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Thunderstorm Outlook for Sunday

 

Forecaster: Tirone.

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Scattered thunderstorms this afternoon and evening across western and possibly northern LAB. Gusty winds, small hail and brief downpours are likely.

 

Isolated thunderstorms possible for central NB Friday afternoon.

 

Convective Discussion

Warm frontal trough crossing LAB today will be followed by an approaching cold which will likely give scattered thunderstorms across the west, and possibly the north coast later in the day. The LA Grande TEP has about 30-35 knots of shear, and also a fairly decent LLJ so some cells could get close to being severe. But the instability is not that great, and CAPE is nothing to write home about (in the vicinity of 500 J/KG – based on lifting from a surface temperature of 22 or so).  Lastly there are not too many breaks in the SC deck upstream so unless things break open soon it might be difficult getting deeper cells. For now, a compromise of gusts to 70 km/h or so and small hail seems to be legit.

 

On Friday a weak surface boundary and short wave trough could give some isolated afternoon storms for a portion of central NB. Locally heavy downpours seems to be the main threat.

 

A side note: there is some indication of isolated convection tonight and early Friday morning for parts of the island portion of NL associated with a weak short wave, but confidence is pretty low on that scenario.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Jeremy