The conversation associated with winter storms is frequently associated with snowfalls. While the storm on Sunday will certainly be accompanied by heavy snow, the combination with other severe weather elements will result in substantial impacts.
Snowfalls: The expected track of the storm along the Atlantic coast of Nova Scotia typically results in the heaviest snowfalls inland Nova Scotia, Southern New Brunswick and Prince Edward Island. This far in advance, it’s useful to look at likelihoods of high amounts. An ensemble of international computer models generated by our colleagues in the US National Weather Service suggests there is a good chance most areas will receive 15cm or more, with very high probability of more than 30 cm in southern New Brunswick and western Prince Edward island. In Nova Scotia, the best chance for 30cm is in the Valley and Cumberland-Colchester.
Along the Atlantic coast and over Eastern Nova Scotia, the shift in winds to the southeast coming off of the ocean waters (which are above zero) will warm the lower part of the atmosphere, making a changeover to rain most likely there. At this point, there is no indication of warm air aloft of the storm, so freezing rain and ice pellets are a lower risk.
Very strong winds will accompany the storm, especially the Northeast winds in the same region of heaviest snow. This would result in widespread blizzard conditions (near zero visibility). These winds might create a Storm Surge. The combination of very strong onshore winds combined with low pressure and high tide may be most pronounced along the Northumberland Strait. Since the Strait is ice covered, this storm does provide the risk of ice pile-up along the Northumberland coastline on Sunday.
Timing: The snow will start before dawn in Halifax and southwestern Nova Scotia and southern New Brunswick, making its way elsewhere through the morning hours and into Cape Breton by lunchtime. The changeover to rain may take place around lunchtime in Halifax… visibilities and winds will improve in Halifax in the afternoon and early evening before strong north winds and some more snow returns overnight.
All indications that this is a very potent storm. Venturing out on the highways during blizzard conditions is extremely risky. Air and ferry travel will also be impacted. Extended power outages in winter require additional considerations for the potential loss of a heat source.
The additional snow (and rain in parts of Nova Scotia) will add to the existing weight of the snowpack, putting a strain on structures like roofs and decks.