Two beautiful March days followed by icy mix of weather in Maritimes

CTV meteorologist Kalin Mitchell is tracking a system that will change the Maritimes from mild March temperatures over to a snowy, icy mix of weather.

A fair weather start to the second week of March in the Maritimes will give way to a snowy, icy mix of weather for parts of the region Wednesday into Thursday.

Partly cloudy conditions along with areas of fog and drizzle can be expected in the Maritimes Monday night and Tuesday morning.

The most widespread and thickest fog will develop on the Bay of Fundy coastline of New Brunswick and the Atlantic coastline of Nova Scotia Monday night into Tuesday morning. For those areas, the fog may be accompanied by some patchy drizzle.

On Tuesday, the fog should retreat to or slightly offshore of the coastline by the afternoon. The fog would then start moving back Tuesday evening.

Aside from the fog action for coastal areas, the rest of the Maritimes can expect a mix of sun and cloud. High temperatures for coastal areas and northern New Brunswick will reach 7-to-11 C. High temperatures for the rest of the Maritimes reaching the low-to-mid teens.

Midweek snow

A slow-moving low-pressure system moving from southern Ontario into the St. Lawrence River Valley will then bring a change in weather to the Maritimes Wednesday and Thursday.

Colder air arrives in a northeast wind late Tuesday night. That will have the effect of bringing some surface temperatures back to freezing for most of the Maritimes by Wednesday morning. The precipitation from the low develops through the day Wednesday.

With colder air in place, northern New Brunswick can expect an accumulating mix of snow and ice pellets with some freezing rain mixed in. That part of New Brunswick is under a Special Weather Statement advising that the potential snowfall could by 15-to-25 cm.

While there is unlikely to be as much snow and ice pellet accumulation, the remainder of New Brunswick and parts of Prince Edward Island are at risk of a period of freezing rain that could extend several hours.

A lower risk of freezing rain extending into northern and eastern areas of Nova Scotia including Cape Breton. There is a risk of freezing rain there Wednesday evening through Thursday morning. At this time, much of the rest of Nova Scotia is likely to have temperatures warm enough that rain can be expected.

Impacts of freezing rain

Often, it’s not how much freezing rain comes down but how much collects in the form of ice on surfaces that determines the impacts. That collection of ice is known as ice accretion.

Ice accretion of up to five mm typically results in a glaze that can make for slippery surfaces. Ice accretion of five-to-10 mm is more problematic as it can start to weight down branches, bowing or snapping them. Those branches can then contact power lines contributing to outages.

Ice accretion of 10 or more millimetres is even more serious. That amount can cause entire trees to bow, damaging them. It can also be enough weight on the electrical infrastructure itself to contribute to outages. The amount of ice making for very hazardous travel conditions.

Current indications are for much of New Brunswick along with western Prince Edward Island to be at risk of five-to-10 mm of ice accretion. As above, the impacts would include a slippery glaze and a risk of scattered power outages. Pockets of higher ice accretion in central and western areas of New Brunswick can’t be ruled out.