Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

Slight risk of a thundershower this afternoon over southeastern Labrador.

Risk of a thunderstorm for NW New Brunswick Tuesday late afternoon and evening.

 

Convective Discussion

As an upper trough moves into western Labrador this afternoon, daytime heating (inland temperatures into the mid 20s) and convergence ahead of the trough could help trigger an isolated CB over southeastern Labrador this afternoon. Some strong convective gusts are possible, however, increasing shear above 50kt may shear off any developing TCUs. Moisture is also only low to moderate with precipitable water less than 20 mm.  

 

A ridge of high pressure dominates south of the Maritimes today while an upper warm front weakens as it tracks into the southwestern Maritimes this afternoon and tonight.

 

A trough approaches New Brunswick tomorrow and there is a risk of a thunderstorm reaching northwestern areas by the late afternoon or early evening. Although there is good thermodynamic potential with daytime highs reaching 30C, there is increasing warmth in the lower to mid layers may cap convection.

 

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

 

Roberta McArthur

 

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Slight risk of a thunderstorm this afternoon across central NL.

Slight risk of a afternoon thunderstorm for SE LAB Monday afternoon.

 

Convective Discussion

An upper trough will cross NL today giving the chance for an isolated thunderstorm. The 12Z tephi out of YJT has a pretty good warm nose at 700 mb, but steep lapse rates below that layer so, if there is ample surface heating, the cap could be breached and an isolated CB could develop this afternoon. There is a fairly strong jet of 30-35 knots in the lower levels so gusty surface winds are possible (even in areas of TCU). PWATs are low so rainfall is not a concern.

 

There will be a slight chance of an afternoon thunderstorm in SE LAB on Monday in association with a short wave trough.

 

OTWZ nil sig wx is xpctd.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Jeremy

 

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts:

 

Today

NB/NS/PEI/NL/Labrador: None.

 

Tonight

NS/NB/PEI/NL/Labrador: None.

 

Tuesday

NB/NS/PEI/NL/Labrador: None.

 

Convective Discussion:

A trough moving across the region will usher in a cooler and drier airmass today. No thundershowers are expected today or tomorrow over land although according to the ECMWF, there is a very slight risk over interior Newfoundland on Sunday.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

NB … Strong thunderstorms possible this afternoon and into this evening with 70 to 90 km/h wind gusts, rainfall rates of 20 to 40 mm/h, and pea sized hail.

NL … Risk of some scattered thunderstorms this afternoon in western Labrador with rainfall rates of 20 to 30 mm/h and wind gusts of 60 to 80 km/h.

NS/PEI … Risk of an isolated thundershower later this evening with rainfall rates of up to 15 mm/h.

 

Convective Discussion …

An upper trough moving into the Maritimes brings the threat for strong thunderstorms across New Brunswick this afternoon. Good moisture advection at the surface will increase dewpoints to near 20 degrees in western New Brunswick, as such MUCAPE values are expected to climb to 1000 to 1500 J/kg this afternoon in this region. Remnant cloud from yesterdays convection over Ontario and Quebec moving through New Brunswick this morning will keep surface temperatures in the low to mid twenties, nonetheless an approaching cold front should provide ample surface lift to break any capping inversion that remains this afternoon. High shear values upwards of 50 knots will allow these storms to remain fairly organized throughout their lifespan, with a few supercells even possible. The main hazards with these storms will be strong wind gusts of up to 90 km/h, and heavy downpours of 20 to 40 mm/h. There is also a chance for some pea sized hail in some of the stronger cells. These storms are expected to die off as they approach the cooler waters of the Bay of Fundy and the Gulf of St. Lawrence later this evening, though a few lightning strikes are possible over southern Nova Scotia overnight.

In Labrador, some scattered thunderstorms are possible from Labrador City to Churchill Falls as the aforementioned upper trough approaches from the west. Thunderstorms may become organized this afternoon, as bulk shear values of 40 to 50 knots move through the region. Cape values are expected to reach 1000 J/kg this afternoon, however cloudy skies this morning may inhibit CAPE from getting this high. Thus the threat for any strong thunderstorms remains low. Any storms that do become organized may bring locally heavy rainfall of 20 to 30 mm/h and strong wind gusts of 60 to 80 km/h.

 

Thunderstorm Outlook for Today

Thunderstorm Outlook for Tonight

Thunderstorm Outlook for Tomorrow

Copp

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

NS/NB … Disorganized thundershowers possible along enhanced terrain this afternoon, rainfall rates of 10 to 15 mm/h are possible.

NL … A few thunderstorms are possible in western and central Labrador this afternoon along a cold front, rainfall rates of 15 to 20 mm/h are possible.

PEI … None

 

Convective Discussion …

A few pop up thundershowers are possible over portions of Nova Scotia, New Brunswick, and central Newfoundland this afternoon. Any cells that develop today will likely be restricted to areas of enhanced topographic forcing, as limited triggers are available across the region. Weak wind shear (15 to 25 kts) in addition to warm air advection in the mid and upper levels increasing throughout the day should inhibit any organized thunderstorm activity. Some more organized thunderstorm activity is expected in central Labrador this afternoon and into this evening with an incoming cold front over northern Quebec.

 

Tomorrow looks to be more interesting in terms of severe weather. The remnants of a trough that brought tornadoes to southern Manitoba on Wednesday, and has prompted tornado watches in central Ontario and southern Quebec today, moves into the region. Models have been struggling to get a handle on this system once it crosses the St. Lawrence River tonight. Model runs have also consistently been backing off on CAPE values tomorrow afternoon across New Brunswick, with current guidance indicating 1000 J/kg in western New Brunswick tomorrow afternoon, down from over 1500 J/kg in previous runs. Much of this model inconsistency seems to be due to the slowing down of the trough as it approaches New Brunswick tonight. Timing of the thermal trough moving in tomorrow afternoon will also be crucial for organized thunderstorms to develop, thus the highest risk for severe weather is likely to be restricted to western New Brunswick where the thermal trough will erode the capping inversion. Any strong cells that do develop, are likely to produce strong wind gusts up to 90 km/h, hail of 1 to 2 cm, and rainfall rates of 25 to 40 mm/h.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Copp