Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Interior Newfoundland and Northern New Brunswick.. Low probability of isolated showers or thunderstorms giving 10-15mm.

Southern NS.. 25-25mm possible in embedded thunderstorms.

 

Convective Discussion

Overall instability is somewhat diminished from yesterday which doesn’t bode well for thunderstorm potential, however many areas likely received 10-15 mm yesterday which is similar to todays potential for some showers. No severe thunderstorms are expected in the general airmass thunderstorms and the main focus of interest is with the broader synoptic area to the southwest of NS. Most of the potential for high rainfall should pass just south of NS but rainfall rates of 25-35mm could just clip southwest parts of the province tonight. However this system seems to have less potential for heavy downpours when compared to some of the recent systems which tended to have significant convection and thunderstorm activity, most of that type of weather will remain further to the south. This system does have high precipitable water values approaching 50mm but the instability is not expected to be significant, these weaker updrafts are less likely to realize the full potential rainfall rates, nevertheless some uncertainty remains and this system could track slightly further north than expected.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

Maritimes.. Isolated thunderstorms giving 20mm rain with small hail and gusts to 50 to 70 km/hr possible.

NF.. Embedded thunderstorms with amounts 20-40 mm.

 

Convective Discussion

There are two main areas of concern once again, that associated with the low, and the unstable airmass behind that system. The system will likely impact some areas of Newfoundland with amounts in the 20 to 40mm in the heaviest areas of rain. This system is likely to be slightly weaker than is was as it passed over Nova Scotia which saw some amounts over 50mm. Over the Maritimes there are a couple factors coming together that could make this a possibly impactful day. Overall CAPE values are moderate with mixed layer values near 1000 J/kg, and sfc dew points approaching 20C. PW values are somewhat less than they have been but still sufficient for thunderstorms producing moderately heavy rainfall. In addition the dynamics are somewhat favourable with mid level wind shear values above 30 knots and some low level helicity in the vicinity of the surface trough. Later this afternoon the upper level jet could also aid in the development of severe storms over eastern NB.

 

It should be noted that although updraft are weak, there is some potential for severe weather to occur and it is unlikely albeit not impossible that waterspout or land spout tornado could occur along some coastal waters including the Northumberland Straight and Cape Breton shores.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for Tomorrow

 

Mel Lemmon

Convective Outlook Valid for Today , Tonight and Tomorrow

Regional Impacts

NB and PEI.. Showers and thunderstorms possibly giving 25mm, small hail.

NS.. Showers and thunderstorms, possibly intensifying tonight, 15- 25mm today. Possibly exceeding 25 mm tonight.

NL.. Possible isolated thunderstorm over southwest Labrador.

 

Convective Discussion

A low pressure system will slowly make its way across the Maritimes today, passing over southern Newfoundland tonight. Instability aloft will trigger deeper convection across mainland NS today and overnight. This system is expected to move with enough speed that a prolonged period of heavy downpours are not expected, however shorter lived periods of heavier rain perhaps lasting over an hour could bring upwards of 25mm, with rainfall rates of up to 40mm per hour possible.

Over NB most of the potential for intense thunderstorms will be associated with thunderstorms that will initiate over Maine and Southern Quebec today.  Surface CAPE values over 1500 J/kg are expected across Maine and some intense storms could move over western NB later in the day. Dynamics are somewhat favourable for organised convection with approximately 35 knots of deep shear. The outlook maybe slightly conservative with the risk, however watches could be issued if organised thunderstorms form in Maine, with the expectation that some stronger cells could track over NB.

 

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

Nfld: Scattered strong thunderstorms with high mid-level moisture leading to pockets of heavy rain. Hazards – heavy rain. This weather is expected on the heels of this morning’s initial round of precipitation.

Labrador: Isolated chance of a lightning strike or 2 along deformation zone.

 

TOMORROW

NB+NS+PEI: Thunderstorms approaching severe limits are expected late in the day and into the overnight hours. Hazards – gusty winds, heavy rain, small hail.

 

 

Convective Discussion

Strong thunderstorms continued as forecast in the overnight hours for Gulf waters, the Magdalen Islands, and Nfld. This initial wave of weather has passed to lie offshore of Nfld. Convection is expected to spark up again in partial clearing across interior areas along a jet streak that has a history of producing tops to 19,000ft and heavy rain. Pwats remain near 40mm on this AMs soundings. The max vil of the day in the RDPS is 45. Decent agreement there. Storms will be fast moving, with moderately high shear, so precip amounts should not exceed this maximum in any one location. DAY 2 is a bit more complex as favourable dynamics approach the Maritimes from the west. Sunday will start out very calm, but by late evening, severe weather is possible. Storms will mainly be rain makers, but small hail and gusty winds are also possible. Details will be added to tomorrow’s progs on the exact hazards and locations expected.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for SUNDAY (noon-midnight)

 

Forecaster: TIRONE

Convective Outlook Valid for Today, Tonight and Tomorrow

Regional Impacts

TODAY

NS+NB+PEI: Widespread thunderstorms and synoptic rain is advancing from west to east early in the day as forecast. Hazards – lightning, and heavy rain has been observed. A local rainfall warning and SWS remain in effect at this time.

Annapolis Valley of NS: Repeated rounds of convection continuing this afternoon. Hazards – torrential rain possible. Watches may be required if atmosphere destabilizes further.

 

TOMORROW

Gulf waters and Nfld: Thunderstorms with high mid-level moisture leading to persistent heavy rain. Hazards – heavy rain.

 

 

Convective Discussion

Ongoing convective rain is spreading across the Maritimes as the trof moves east. The jet axis placement is a very important feature today. Heaviest rain is falling just north of it. And a second round of convection is forecast to develop south of it. This axis at 10am lies across the Bay of Fundy. Rain in NB will end from west to east this afternoon. Rain in PEI will continue for much of today. Northern and central NB will see convection bubble up again under a partial clearing this afternoon. LL helicity in the Keji area of NS will play into the strength of possible squall line this afternoon that the HRRR depicts, if it can hold together. LL moisture is ambient, and mid-level moisture is also over 40. These dynamics drift over Gulf of St Lawrence waters tonight and into Nfld tomorrow morning. Heavy rain is the expected hazard on day 2. Isolated waterspout formation across eastern maritime marine areas is also likely this evening and tonight. A watch may be issued this afternoon for marine interests.

 

Thunderstorm Outlook for Today

 

Thunderstorm Outlook for Tonight

 

Thunderstorm Outlook for SATURDAY

 

Forecaster: TIRONE