Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1

A frontal trough with an associated vort max from WV near Yarmouth maintained a line of thunderstorms this morning, with pcpn amounts up to 30 mm observed. This feature will continue into the afternoon for Nova Scotia with gradual weakening. There may be some thundershowers later this afternoon in northwestern New Brunswick. Nothing significant is expected for Labrador nor Newfoundland.

 

Regional Impacts

Maritimes: Local heavy showers ending later today for Nova Scotia and possibly for northwestern New Brunswick, who might also see some gusty winds.

Newfoundland and Labrador: nothing significant. A strike ot two south of forecasts areas are possible.

 

Convective Discussion:

For Newfoundland and Labrador there are significant inversions, preventing any significant convection in their forecast areas.

 

There is currently a deep ridge over eastern Newfoundland and a deep low slanting down from 250 mb over Hudson Bay to near Ungava Bay at the surface.  There is also a trough over the Gulf with a couple of vort maxes, with the one near Yarmouth this morning giving some extra support for convection. Things should weaken a bit this afternoon along the trough. For New Brunswick there’s some moisture and low stratus trapped under an inversion that should erode with daytime heating this afternoon, especially in the northwest, where the shear should reach or exceed 30 kts. PWATs are healthy and around 30 mm. Impacts there are local heavy downpours and gusty winds.

 

 

 

Thunderstorm Outlook for Day 2

On Friday a deep trough extending southwest to the Great Lakes will move into our region with a healthy jet and a fair amount of moisture. Unadjusted ML CAPEs are near 500 J/kg, and with some extra heating things could get interesting.

 

 

Convective Outlook Valid for Today and Tomorrow

 

Thunderstorm Outlook for Today

 

Regional Impacts

Slight risk of a thunderstorm over southwestern NB late in the day, and later in the evening in the northwest. Main threat is heavy downpours

from storms that would advance over NB from Maine and the St. Lawrence valley.

Convective Discussion

The Upper ridge has continued to build over eastern Atlantic Canada in the past day or so. A moderate southwesterly flow in behind is advecting

warmer temperatures and higher humidity values across southern Ontario/Quebec/Maine. The environment will remain stable over NB, however

over western Maine the airmass will likely destabilize during the afternoon. Using a combination of Maniwaki and Albany for this morning's sounding -

MCAPE values of 600-1100 J/kg will likely produce deep convection to the west, which will result in scattered thunderstorms capable of producing

very heavy downpours in this moist environment. All sounding in the area of interest are showing precipitable water of 40+mm, with a maximum

of 44 for Maniwaki. Early this evening, some of the storms will try to enter the stable environment over western NB.

 

 

Thunderstorm Outlook for Thursday

 Warm and humid airmass, slight risk of thunderstorms over parts of the region.

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

No thundertorms expected

 

Convective Discussion

Upper and surface ridge dominating over Atlantic Canada.

 

 

Thunderstorm Outlook for Wednesday

 

Warm front approaching from the Great Lakes, warm and humid airmass may destabilize late in the day. Isolated

thunderstorms are possible with fairly high precipitable water values.

 

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Today

 

Regional Impacts

Isolated thunderstorms over central and southeastern NF, brief heavier showers and gusty winds to 75 km/h. Some of these

Storms could advance in the Northern Avalon.

 

Convective Discussion

Trough moving across eastern part of NF today while an Upper low remains anchored off Labrador with a cold pool aloft.

There is enough energy (300-500 J/Kg) to push CB tops up to 6-7km. Westerly deep layer shear is quite strong so vertical

Development is limited. The main threat will be gusty winds in the outflow ahead of the storms.

 

 

 

Thunderstorm Outlook for Day 2

Convective Outlook Valid for Today and Tomorrow

Thunderstorm Outlook for Day 1 – July 11th

 

Regional Impacts

Isolated thunderstorms across New Brunswick expected late this afternoon or early evening with the possibility of a severe thunderstorm over northernmost NB.  Local heavy downpour and strong gusts are the main threats.

Convective Discussion

Thunderstorm development later this afternoon or early evening over New Brunswick is possible.  Current conditions are not favourable for tstorm development as a capping inversion generally around the 700mb level will inhibit any convective activity.  However, this cap may begin to erode later in the day as cooling in the mid levels will help destabilize the column.  An upper level jet also begins to descend from the north which could help enhance vertical lift.  If the capping inversion does erode, 500 – 750 J/kg of CAPE may be realized and wind shear around 35 kts will help to tilt the updraft and may help realize longer lived cells.  A trough moving in later today will help kick off any convective activity.  Low level moisture is not impressive as Td’s sit around the 15C mark so this could inhibit stronger cells.  Overall, it’s a marginal situation for severe tstorm development with the uncertainty of the capping inversion and dry lower levels so I will not be issuing watches and will see how things develop this afternoon.

 

 

Thunderstorm Outlook for Day 2 – July 12^th