Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

NS… Scattered thundershowers possible today with heavy downpours of 20 to 30 mm/h.

NB… Isolated thunderstorms possible this afternoon with heavy downpours of 15 to 25 mm/h.

PEI/NL… None

 

Convective Discussion

Today, an upper low sits stalled over the central Maritimes with two thunderstorm risk areas existing today with this feature; the first located over Nova Scotia, and the second over northwestern New Brunswick. MLCAPE values of 1000 J/kg are similar over both areas of interest, however better dynamics (35 to 40 kts of bulk shear) can be found over northwestern New Brunswick, so a few discrete thunderstorms are possible here this afternoon. These storms will have the potential to produce locally heavy downpours of 15 to 25 mm/h. In Nova Scotia, similar to yesterday, storms are expected to be more stationary leading to an increased risk of higher rainfall accumulations over localized areas today. Some of these storm may have the potential to produce rainfall rates of 20 to 30 mm/h, with higher accumulations possible under stationary cells.

 

Thunderstorm Outlook for Today

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Copp

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

NB… Isolated thunderstorms giving some heavy downpours, mainly for western areas.

PEI… Isolated thunderstorms giving some heavy downpours, a chance of a funnel cloud east or potentially a waterspout over eastern marine areas.

NS.. Some thunderstorms, some potential for locally amounts over 25mm. A chance of a funnel or possible waterspout west of Cape Breton.

 

Convective Discussion

Yesterday back building thunderstorms tended to produce more local rain than expected, while not as likely there is still a chance that we may have more of these weak, slow moving, storms that seem to reform over areas of convergence/terrain and linger longer than would normally be expected with these types of thunderstorms. For the most part the airmass is fairly similar to yesterday with CAPE values ~ 1000 J/kg and surface Td’s in the mid teens. Rainfall rates could once again exceed 30mm/hr, if storms end up back building once again local amounts could be more than that rate. No doubt the slow moving upper trough over the gulf will aid in the instability through the day as storms are expected to slow intensify. A lack of solar insolation may slow things down somewhat when compared to yesterday but some areas will no doubt clear up a bit during the day.

 

There is a slight chance that a funnel cloud or possibly a water spout could form in the vicinity of the upper low over eastern gulf waters today and possibly into tomorrow. These should pose little risk to non marine areas but it is possible that they could impact some coastline if they occur. Marine waterspout watches have already been issued, and the funnel cloud sign on the outlook is for that possibility.

 

Thunderstorm Outlook for Today

 

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Mel Lemmon

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Maritimes… Scattered showers and thunderstorms developing early, local 20mm rain, small hail and some wind gusts.

NFLD.. Isolated thunderstorms possible southwestern parts of the island.

 

 

Convective Discussion

 

Like yesterday, thunderstorms have broken out early under the upper trough. Convective temperatures are likely around 23 C although with terrain and local convergence in a few areas thunderstorms may break out earlier in some areas. Cape values are near 1000 J/kg but with low shear organised storms are not expected. However given the low freezing levels around 9000 ft and some downdraft potential small hail, with some wind gusts can be expected. Things should settle down tonight as the upper trough pulls away, however tomorrow a second upper trough will move in and stall over the area for a period. Conditions for tomorrow will not likely be quite as unstable however there is still a risk of thunderstorms for some western areas.

 

Thunderstorm Outlook for Today

 

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Mel Lemmon

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

 

Labrador.. Slight chance of isolated thunderstorms.

NFLD.. Slight risk of thunderstorms for central regions.

NS.. Chance of heavy downpours in thunderstorms over central region, local 15 - 25mm or more possible.

PEI.. Chance of isolated thunderstorms.

NB.. Scattered thunderstorms over northern areas, local 20 mm possibly more in clustered thunderstorms. Isolated Thunderstorms south.

 

Convective Discussion

 

An upper trough moving across the region will generate thunderstorms throughout the day across northern NB, and possibly later this afternoon for NS, PEI and NFLD. Dynamics further south, over NS and southern NB are more favourable for severe storms than over northern NB were thunderstorms have already begun, but the updraft strength is likely to be much lower. However, the warm cap aloft will break down as the upper tough approaches and some intense storms are possible, the most likely area begin over central NS, central NFLD has a slightly lower risk of organised convection. Although severe thunderstorms are not expected for NB, we will be monitoring closely for backing building thunderstorms and alerts may be required should the set up happen. Some thunderstorms can be expected to persist overnight and begin fairly early again tomorrow.

 

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Mel Lemmon

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Risk of a thunderstorm today across southern LAB.

 

Scattered thunderstorms likely across NB and a portion of Labrador on Monday. Slight risk of a thunderstorm for a portion of NS and PEI.

 

Convective Discussion

Not much on the go today aside from a weak upper trough that might give a thunderstorm or 2 across southernmost Labrador. An upper trough will advance from the Great Lakes region on Monday giving more support for scattered thunderstorms across NB and portions of Labrador. Some small hail, gusty winds and torrential downpours possible in the deeper cells. OTWZ nothing else to talk about.

 

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Jeremy