Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Maritimes: Risk of embedded TS with rainfall rates of 10 to 15 mm/h this afternoon and overnight.

Labrador: Slight risk of a thundershowers for western areas tomorrow.

Convective Discussion

A trough associated with a low pressure system over James Bay will bring a broad destabilization with cooling aloft throughout the day but MUCAPE remains minimal with at most 250 J/kg and may not break through the warmer air still remaining from 700 to 500 mb. There will be some lift near 850 mb from a 35 KT LLJ and weak effective shear to help generate a few embedded thundershowers across western New Brunswick this afternoon ahead of the main trough still over Quebec. Storm motion should keep overall precipitation lower and the system moves across the Maritimes tonight, but with precipitable water of 30 to 40 mm moving through with this system, there may still be periods of moderate to heavy rainfall.

The trough moves into Newfoundland on Wednesday with moderate rainfall possible while behind and south of the low as if tracks over northern Quebec will enable weak pop-up convection over western and central Labrador.

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Roberta McArthur

 

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today:

Labrador: Non-severe risk of a thundershower in south-central Labrador.

Maritimes and Newfoundland: Nil

Tuesday and Tuesday night:

Maritimes: Risk of embedded TS with rainfall of 10 to 20 mm.

 

Convective Discussion

Slight risk of a thundershower today along a trough extending from central Quebec southeastward across Labrador that will move southeast and weaken by tonight. Goose Bay sounding shows a cap between 700 and 500 mb that is not likely to be breached, so mainly expecting on TCUs but the cap may be broken south of the public regions. Upper smoke from fires over central and western Canada continues to linger across Atlantic Canada, also adding to the unlikelihood of exceeding the necessary surface heating.

Tomorrow, a trough associated with a low pressure system over James Bay will bring a broad destabilization with cooling aloft throughout the day. There will likely be enough lift near 850 mb from a 35 KT LLJ to generate embedded thunderstorms across western New Brunswick and Nova Scotia by early evening and into the overnight. Moderate to heavy rain in possible across the Maritimes as higher precipitable water of 30 to 40 mm comes in from the Gulf Stream.

The trough moves into Newfoundland on Wednesday and behind and south of the low as if tracks over northern Quebec will enable pop-up convection over western Labrador.

 

Thunderstorm Outlook for TODAY

 

Thunderstorm Outlook for TONIGHT

 

Thunderstorm Outlook for TOMORROW

 

 

Roberta McArthur

 

 

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today: Offshore embedded TS risk this morning continues with frontal departure from last nights L pressure system. No other convection forecast with invading smoke from the north, and building ridge.

Tonight, into Monday morning: Ridge over Maritimes. Nil sig weather. Frost risk under clear skies.

Monday afternoon: Maritimes are capped and stable. Non-severe thundershowers are possible in western and central Labrador along a W-E translating trof line.

Tuesday: Ridge erodes late in the day with an advancing disturbance/cooling column aloft and causing a risk of -TS. Details will be better forecast in next 24hrs.

 

Convective Discussion

Nil sig convective weather across Nfld/Maritimes Day1, Night1, Day 2. Thundershowers expected to pop up along a ridge-riding trof line across Labrador on Monday. Hazards would simply be moderate rainfall as forward progression of trigger is slow. Tuesday brings a broad destabilization with cooling aloft throughout the day – leading to skinny Cape again and moderate shear. Single cell storms are forecast for western NB/mainland NS by evening.

 

Thunderstorm Outlook for TODAY

 

Thunderstorm Outlook for TONIGHT

 

Thunderstorm Outlook for MONDAY 

 

Thunderstorm Outlook for TUESDAY

 

Forecaster: Tirone.

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today: Non-severe convective showers and thunderstorms ongoing late this morning will continue this afternoon across central and northern mainland Nova Scotia. Only hazard foreseen is possible moderate rainfall. In New Brunswick, thunderstorms are entering the northwest from northern Maine and are expected to bring gusty winds and moderate rainfall. The is also a slight risk of convection in SE Labrador, if can overcome the smoke cap and dry air intrusion.

Tonight, into Sunday morning: In the warm sector of and approaching low, embedded thundershowers are possible along Nova Scotia’s slope waters and Atlantic coast.

Sunday afternoon: Clearing trend – no thunderstorms expected.

Monday: Building ridge – no thunderstorms forecast.

 

Convective Discussion

Smoke is continuing to mix into boundary layer from the northeast sfc flow, but the flow aloft has veered across the Maritimes to Westerly. A low is churning near the Avalon this morning with a trof hanging back over the Gulf waters. Another stronger trof is hanging back over the St Lawrence river valley, and the next Low with associated fronts is cutting thru New England. As such, the forcings amount to the grey risk areas depicted today and tonight. Tonight’s weather will not be discrete cells like yesterday in NS, or the day before in NB. But rather, embedded TS in a broader synoptic rain field. The triple point is expected to pass very close to Halifax. 0-6k shear off this morning’s soundings is near 32kts, but ML CAPE is low and skinny again. This allows most hazards to easily be ruled out. G70 and rainfall max 30mm in slowest moving storms is the “storm of the day” solution. Ridge builds on backside of low mid-day Sunday. Monday is stable and dry in a weak N flow. Nil sig weather expected to start the work-week.

 

Thunderstorm Outlook for TODAY

 

Thunderstorm Outlook for TONIGHT

 

Thunderstorm Outlook for SUNDAY 

 

Thunderstorm Outlook for MONDAY

Forecaster: Tirone.

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Today: There is an ongoing risk of thunderstorms across southwestern areas of Nova Scotia this morning. Storms are expected to re-develop across southern NB and NS this afternoon along a 2^nd frontal boundary. Main hazards being repetitive rain and small hail.

Tonight, into Saturday morning: A risk of thunderstorms, likely embedded, continues across much of the same areas of the Maritimes.

Saturday afternoon: Some minor convection possible across extreme northwestern tier of NB and to the southeast of Goose Bay. (highly dependent on smoke in mid levels and aloft). Synoptic rain and strong gusty winds are forecast for much of the southern/central Maritimes Saturday night.

Sunday: No Thunderstorms expected with synoptic low pulling away.

 

Convective Discussion

A complex weather set up synoptically with many factors at play. First off: the smoke. A smoky cap should remain in place across central and northern NB today, preventing sufficient lift. Secondly, a low churning south of NS over the marine district is firing storms this morning with enhanced lift both off the associated inverted trof and the terrain of inland NS. The 3^rd feature will be later today that will bring another round of TS activity – the broader trof cutting thru New England at this time. With dew points near 16 and climbing, there is ample moisture and moisture advection. This leads to the hazard forecast being rain, and rounds of rain. Pwats range 20-40mm today and tonight. This corresponds to a Grey hazard area, but if a storm doesn’t move much or keeps re-developing over 1 area, it could amount to a warning level of rainfall locally. A watch will be carefully considered early this afternoon for southwestern NS. Small hail is also possible in the most organized cells. Skinny Cape, and a small warm nose this morning was easily overcome by the synoptic forcings at play. Sunday (Day3) is progged to be quiet at this time on the stable backside of a departing Low.

 

Thunderstorm Outlook for TODAY

 

Thunderstorm Outlook for TONIGHT

 

Thunderstorm Outlook for SATURDAY 

 

Thunderstorm Outlook for SUNDAY

 

Forecaster: Tirone.