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..

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Isolated thundershowers over a portion of the southern GB today.

 

Tonight and Tuesday offers the potential for waterspouts for a good portion of the Gulf of St. Lawrence and into southern Gulf-Port au Port.

 

Convective Discussion

A weak frontal wave will give isolated thunderstorms today over a portion of the southern Grand Banks today. A fairly cold upper trough will be moving down from Quebec and Labrador tonight and Tuesday that will create favourable conditions for non-tornadic waterspouts for a good chunk of the GLFSTLAWR and into the Port au Port Peninsula area.

 

OTWZ nil sig wx xpctd.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Jeremy

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Risk of a thunderstorm in western LAB, NW NB and SW NS later today.

 

Risk of thundershowers tonight along most of the ATL coast of NS.

 

Risk of thundershowers later today and tonight over the SRN GB.

 

Convective Discussion

3 separate features evident in SAT imagery: one being a weak surface low southeast of MRTM waters that will move up and over the southern GB later today and tonight giving the risk of thundershowers. The second feature will be an approaching cold frontal trough that is currently in Quebec. This will likely produce isolated thunderstorms upstream today, with the chance that one or 2 cells survive and make it to far western LAB and NW NB. Gusty winds and brief downpours are possible. The 3^rd feature will be a surface trough that is currently sliding towards NS. There is a chance of some late day and overnight thundershowers associated with it near Atlantic coastal NS. However there is no history with this so confidence on that happening is on the low side. Locally heavy downpours would be the only concern.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Jeremy