Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NB: Scattered thunderstorms developing this afternoon and evening, risk of severe thunderstorms in organized bands/features in the NW. Rainfall rates in excess of 25mm/h, gusts to 80km/h, and hail diameter near 2cm.

NF&LAB: Isolated non-severe thunderstorms in western Labrador, also south coast of the Island.

 

Tonight

NB: Isolated thunderstorms possible  giving mainly heavy downpours.

 

Saturday

NB: Isolated thunderstorms likely for a good portion of NB giving possible some hail, strong wind gusts and heavy downpours.

LAB: A slight risk of a thundershower over southern portions giving locally heavy downpours.

 

Convective Discussion

At 12z a surface low was located east of James Bay with a warm front extending eastward to Lake Melville, and a decaying cold front southward to New England. A couple of cold trough are rotating around a 500mb low located over Hudson’s Bay, one of which is linked to the surface frontal boundary. A 85kt cyclonic upper jet stretches from Long island-central Maine-Lower Quebec North Shore. Convection from yesterday has vanished for the most part, some lingering cells are detected north of the St. Lawrence. The cold front will enter the region later in the day and will be the focus for surface-based instability. Convective temperature in the upper 20’s should be reached fairly easily and robust dynamics should lead to some organized convection over northern Maine around the middle of the afternoon. The steering flow will promote propagation of the activity into Madawaska-Victoria and potentially into Carleton county. Surface-based CAPE of 1000-1500 J/kg and deep layer shear values of nearly 50kt indicates a potential for supercell development.

 

 

Thunderstorm Outlook for Today

 

 

Thunderstorm Outlook for Tonight

 

 

Thunderstorm Outlook for Tomorrow

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Today

NS: There is a risk of a severe thunderstorm this afternoon and evening for a portion of the Valley, with torrential rainfall in the order of 25-50 mm/h the main threat. Elsewhere for NB and most of the rest of mainland NS, some isolated non-severe thunderstorms are possible.

 

Tonight

NW NB: Some isolated thunderstorms possible  giving mainly heavy downpours.

SW NL: A slight risk of an embedded thundershower giving locally heavy downpours.

 

Friday

NB: Isolated thunderstorms likely for a good portion of NB giving possible small hail, strong winds and heavy downpours.

SW NL/WRN LAB: A slight risk of a thundershower giving locally heavy downpours.

 

Convective Discussion

 

The main area of threat today will be the Valley of NS, with a lesser threat for areas of NB and most of the rest of the mainland of NS. The 12Z tep out of YQI looks decent for possible torrential rainfall and small hail. Adjusting for a surface temperature of 31 gives over 1000 j/kg of MUCAPE, with fairly fat CAPE below 500 mb owing to some decent updrafts. Tds are in the lower 20’s, so surface moisture if plentiful…as well at 850 mb. The instability is modest with LI’s of around -4 or so. The concern will be for training convection and hence locally very high rainfall rates in a relatively short period of time. The shear is very weak so wind gusts won’t be a big deal. Will have to see how things unfold this afternoon.

 

Some isolated thunderstorms are possible later tonight across NW NB as some development in ME might drift across the border. Also a slight risk of an elevated, embedded thundershower for SW NL associated with a very slow moving trough of low pressure.

 

More thunderstorms are likely for a good portion of NB and western LAB Friday afternoon and evening. Dynamically speaking, tomorrow is a better day for convection as the large scale trough to the west makes its way into our region. That aforementioned trough over NL will continue to give a slight risk of an embedded thundershower as well across SRN NL.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Friday

 

Jeremy

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Today

NB…thunderstorms likely late this afternoon, beginning over northwestern areas. Small to moderate hails, gusty winds and torrential rain possible.

NS PEI and Labrador…low probability of thunderstorms, likely non severe. Rainfall less than 25mm.

Elsewhere…embedded thundershowers possible.

 

Tonight

Slight chance of lingering thunderstorms, no significant weather expected.

 

Tomorrow

NS, NB and PEI… Isolated thunderstorms, some locally heavy downpours possible greater than 25mm.

 

Convective Discussion

 

Thunderstorm development with moderately favourable dynamics and instability will come together this afternoon over New Brunswick. Upper dynamics are not overly good with only a very weak upper level jet moving over southern Quebec later today. However significant low level moisture, likely underdone by the models, will aid in the development of thunderstorms this afternoon. Mid level shear is moderate with about 30 knots in the 0-6 km layer. Mixed layer Cape will also be upwards of 1000 J/kg, what is less clear is if mid-level air will dry out this afternoon leading to an increased potential for downdrafts. There is however a strong possibility for torrential downpours and moderate hail with the thunderstorms. This will be a closely monitored situation and Severe Thunderstorm Watches are likely to be issued later today.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

 

Mel Lemmon

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Today

NB…Heavy Rain with thunderstorms, low probability of severe thunderstorms.  

Elsewhere…Embedded thunderstorms with trough of low pressure, heavy downpours possible.

 

Tonight

Embedded thunderstorms with trough of low pressure, some lightning.

 

Tomorrow

NB… Thunderstorms with heavy Rain and strong wind gusts possible.

NS… Isolated thunderstorms with some moderate rain.

 

Convective Discussion

Most of the Atlantic provinces will remain on the upward side of an slow moving trough of low pressure. Some embedded thunderstorms can be expected with some heavier downpours possible for the eastern half of Nova Scotia this evening. The 500 hPa through will make its way towards northern NB this evening with some upper level cooling and solar insolation expected.  This will likely lead to some potential for surface based thunderstorms with mixed layer Capes between 500 and 1000 J/kg. Upper level where is expected to diminish somewhat in the vicinity of the upper trough, somewhat limiting the potential for severe thunderstorms, however torrential rain is still a threat. Severe thunderstorm watches are a possibility, but will largely depend on weather or not there is sufficient solar heating to boost up the surface based Capes.

 

Tomorrow the thermodynamics are slightly more significant with the probability of severe thunderstorms being slightly higher for New Brunswick.

 

Thunderstorm Outlook for Today

 

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Mel Lemmon

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

 

Today

Southern New Brunswick and western Nova Scotia: Embedded thundershowers are possible this evening continuing until midnight, with the hazard being moderate rain.

Labrador: over western portions non-severe thunderstorms are possible this afternoon and evening.

 

Tonight

Elevated convection is forecast for most areas in the Maritimes overnight tonight, continuing into the morning hours of Tuesday.

 

Tuesday

Maritimes: Thunderstorms are forecast for many areas, with the hazard being heavy rain.

 

Wednesday

Energetics and dynamics are the most favourable in New Brunswick for organized storm development. Some cells could produce heavy rain and moderate sized hail.

Nova Scotia: Surface convergence is expected to aid in development of storms on the spine in western NS near Kejimkujik NP to the community of New Ross.

Newfoundland and Labrador: Embedded thundershower risk continues under same forcing progressing east slowly.

 

 

Convective Discussion

 

An approaching long wave trough will track eastward today with instability increasing over the AOR today. Thundershowers are in the forecast this evening and tonight into Tuesday morning in the maritime region. The biggest threat with any cells that develop is lightning, and moderate rain. Tomorrow, more widespread synoptic rain is forecast over parts of the Maritimes. VILs are over 60 in model guidance (70+ offshore). This tropical air mass with very high dew points will certainly be a rain producer in pockets. The shear environment today is complex. Low level flow is straight out of the SE. Aloft, we are W-ly. This gives a 0-6k shear of 20-25kts. CAPE today is only 200-300 J per kg in central NB in clearing. This gives an LI of only -1, so no severe hail is expected. Pwats are near 35 in most prog soundings in the RDPS. Most of this moisture can be realized so no correction factor needs to be applied (RH greater than 90 this week).

 

Thunderstorm Outlook for TODAY

 

Thunderstorm Outlook for TONIGHT

 

Thunderstorm Outlook for TUESDAY

 

Thunderstorm Outlook for WEDNESDAY

 

Forecaster: Tirone