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.

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Today: there is a risk of severe thunderstorms this afternoon across the northern half of NB today giving strong winds, small hail and torrential downpours. There is slight risk of thundershowers this evening over the north LAB coast near the Nain area.

 

Tonight, into Friday morning: a risk of thundershowers across southern NB, PEI and NS.

 

Friday afternoon: isolated afternoon thunderstorms possible for western mainland NS, west of Halifax.

 

Convective Discussion

We have the ingredients for a potentially active afternoon across a good chunk of NB as a cold frontal trough slowly approaches from the west. Tds are now on the rise, and so too is the PWATs, which will get into the low 40’s by mid to late afternoon. As mentioned yesterday the instability is nothing to write home about but sufficient to aid in the development of strong cells. The shear does seem a little weaker on model guidance compared to 00z and 12Z yesterday, but still maxes out to about 40 knots as the day progresses. And of course, our trigger is the frontal trough. The Albany 12Z sounding might be the best to use to sample the upstream airmass, and it looks quite prime for a convective day. There is a strong inversion though at about 750 mb that will have to be broken but given the large area of cloud-free skies with little in the way of smoke aloft that should be breached as we reach the convective temperature of about 30 degrees. Lapse rates are not great so I don’t expect large hail as CAPE, overall, will be skinny. It should be noted the new criteria for significant hail is 2.5 cm (which is quarter-sized). Strong wind gusts of 90-100 km/h and intense rainfall rates over a short period of time are the main concerns in the stronger cells.

 

A severe thunderstorm watch will most likely be issued for the northern half of New Brunswick sometime over the lunch hour.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow  

 

Jeremy

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today and tonight: no sig weather in the region.

 

Thursday: the potential for strong to possibly severe thunderstorms across central and northern NB. Main threat will be strong wind gusts, but brief torrential rain and small hail are also possible.

 

Convective Discussion

Quite today across the region under the influence of a strong ridge of high pressure. Upstream, a frontal trough currently in the vicinity of the Great Lakes, will eventually make its way into NB on D2. We will see what kind of activity this produces today across portions of ON and QB to get a feel for what kind of day may be in store in our neck of the woods on Thursday. Based on model guidance alone, there is a chance for strong to severe thunderstorms for the northern half of NB in the afternoon and evening, with strong wind gusts being the primary threat at this time. Cells should be moving fast enough with little back-building so that locally heavy rainfall amounts won’t be too concerning. Mixed layer CAPE is expected to be around 1000 J/Kg (give or take a little), so some stronger updrafts could produce small hail. Low level moisture should be present during the afternoon, as well as 0-6 km shear increasing during the day to about 40 knots. The instability is nothing to write home about, but enough to support storms. For now, there will be a yellow threat zone on D2 – but based solely on model guidance! The only caveat at play is the smoke aloft. It can sometimes hinder the development of storms, and other times is not a factor.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Jeremy

Convective Outlook Valid for Today

Regional Impacts

NB.. A few isolated showers this afternoon will bring a very slight risk  of thunderstorms with a few lightning strikes.

NS..A non zero chance of a thunderstorm, with a slight chance of a shower, no impacts.

Elsewhere.. No thunderstorms expected.

Convective Discussion.. Today marks the first day of the summer severe weather desk at the ASPC and it seems we will be off to a slow start. As is often the case this time of the year low moisture in boundary layer will be a limiting factor with surface Dewpoint Temperatures remaining in the single digits through the day. However there will be some instability as an upper trough tracks across New Brunswick with most unstable CAPE values likely below 250 J/kg. The upper trough will move through rather quickly so the potential will be short lived as we settle into calm weather for the next couple of days. No significant hazards are expected today but a few lightning strikes are possible with the showers as they move through the Maritimes.

Thunderstorm Outlook for Today..