As temperatures turn mild today and Friday, wintry precipitation will not be in most people’s minds.  However, Friday night, as rain spreads southwards across the Maritimes. a cold ridge of high pressure over Quebec will spread cold air over parts of the Maritimes.

Although it is Thursday, there is still big differences in the possible outcomes for Friday night and Saturday.

Snow: Heavy snow over the St. Lawrence Valley may affect only parts of Northern New Brunswick, or a great deal of that region (see pic).  This snow, while likely impacting Montreal, is still uncertain for Toronto (which would impact air travel that goes through Toronto).

Further south, Freezing Rain is likely… but again the models are still not consistent in the forecast… since only a degree one way of the other… or a slight wind shift, will make the difference between rain, freezing rain, snow or ice pellets.

Over the southern Maritimes, some areas may get very heavy rain (50-100mm?).  Even this forecast is uncertain.

So the best advice is to prepare for potentially heavy precipitation Friday night and Saturday.  Heavy rain over the south will make driving tough and could lead to local flooding.  Freezing rain is a hazard to air and road travel, as well as power outages.  Heavy snow and ice pellets also impacts road and air travel.

Environment Canada has had Special Weather Statements… which express the uncertainty.  As

A very intense storm passed across the Maritimes Thursday night 04-05 January 2018.  There was significant media attention associated with this storm, given it’s impact with snow, wind and storm surge along the eastern seaboard of the USA.  While the reference to the storm as a “weather bomb” might have been seen as media hype, the term is actually a meteorological term to designate an explosively intensifying storm.  John Gyakum and Fred Sanders coined the expression during some research at MIT in 1980 to describe storms whose central atmospheric pressures lower by 24mb in 24hr.

The storm originated off the coast of Florida as a 1011mb low on Tuesday morning 03 January.  The combination of warm tropical air over the storm and the frigid air moving off the east coast allowed the storm to rapidly intensify to a 958mb storm off the coast of the Carolinas 24 hours later.  That’s a 53mb difference in central pressure in 24 hours, more than double the criteria established by Sanders and Gyakum.

As the storm continues into Canadian waters, it was accompanied by hurricane force gusts.  Enormous waves of over five stories in height were measured by a couple of weather buoys.

Over the Maritimes, the storm brought some hurricane force gusts from the east ahead of the storm then from the south or southwest behind the storm.  Saint John recorded its lowest atmospheric pressure on record as the low passed through the Bay of Fundy.

The strongest winds were along the Atlantic coast of Nova Scotia and in Les Suetes winds in western Cape Breton.

While there were hundreds of thousands of individual power outages, many were restored quite quickly.  I attribute this to the fact that the ground was very frozen after more than a week of frigid temperatures.  The frozen ground helped keep large trees from uprooting.  Nevertheless, the winds were responsible for extensive damage to some structures.

Along the coast, high waves and a storm surge resulted in significant damage to some coastal infrastructure.  In parts of Nova Scotia, the high tide arrived when the winds were not at their highest.  Nevertheless, the surge measured about 0.8m in Halifax, with the water level reaching 2.73m, just 18cm below the record 2.9m set by Juan in 2003.  Peak waves, as measured by the buoy in Herring Cove, exceeded 7m.  This combination caused some impressive damage.

Herring Cove Smart Buoy

While the wind and rain were impacting Nova Scotia, parts of Central and Northern New Brunswick were undergoing blizzard conditions.

CoCoRaHS volunteer observations

Behind the storm, frigid air returned, causing snow squalls to form and high wind chills in gusty northwest winds.  Warnings and watches have been issued for the squalls in parts of southwest Nova Scotia across the Valley into the Minas shore where visibilities drop to near zero in spots.  Extreme cold warnings and special statements also in place.

The good news, as is often the case, the atmospheric patter is changing as a result of the storm.  A more normal pattern will return… in fact above normal mild temperatures setting in later this week.

Take care of yourself this weekend… and for those who need a warm up… it’s on its way.

Jim

The strength of the storm forecast to develop over the ocean to our southwest on Thursday is powerful enough to justify more details.  Although a winter storm, the size and strength of this storm in some ways has more energy than some hurricanes.   Therefore, some of the wind and storm surge threats are significant and hazardous.

Snow will spread across the Maritimes Thursday morning.  The snow will become mixed or chance to ice pellets and rain quite quickly over southwestern parts of the Atlantic and Fundy coasts, then later in the afternoon and evening in other parts of the southern Maritimes.  The rain will chancge back to snow early Friday morning then to flurries later in the morning.

This makes snowfall forecasts quite tricky for Saint John and Halifax, where the downtown areas may get much less snow and much more rain than inland.  The highest snowfalls can be expected in New Brunswick with up to 40cm likely.  Elsewhere amounts will be variable… with 15 to 25 cm likely in Prince Edward Island and possible in inland areas of Nova Scotia.  Up to 50mm of rainfall may occur over southwestern parts of Atlantic coastal Nova Scotia and 40mm along parts of the Fundy coast in New Brunswick.

While folks normally worry about the snowfall amounts with winter storms, this storm may be remembered for it’s strong winds.  There is the threat of very strom easterly winds ahead of the storm then equally if not stronger southwest winds in the wake of the system.  The threat is widespread for winds gusting well over 100km/h, especially over exposed coastal communities.  These winds will be dangerous and cause extensive power outages that may last for a number of days in some communities.   Everyone should have in their mind what is needed if power is out for several days: cash, gas, food, water etc.

The low pressure and strong winds will result in higher than normal water levels due to storm surges with high waves.  Coastal flooding is therefore a threat, especially over southwestern Atlantic coast of Nova Scotia and the PEI & New Brunswick coasts of the Gulf of St. Lawrence.  Check your tide tables to check if high tide lines up with the strongest winds.

Environment Canada has issued Winter Storm Warnings for much of New Brunswick and for PEI for the combination of all the threats discussed.  Wind and Storm surge warnings are in place where there will be less snow in southwest Nova Scotia.

Stay safe and prepare

Jim

The December statistics overall were not too remarkable.  Rainfalls was above normal, especially in Nova Scotia, and snowfall was below normal.  Temperatures overall were near or slightly below normal in Nova Scotia, about one degree below normal in Prince Edward Island, and two-three degrees below normal in New Brunswick.  However, the most remarkable weather was the winter storm on Christmas Day and the extensive frigid temperatures that followed and persisted through the holidays into the start of 2018.

In spite of the early arrival of what has become known as the “Polar Vortex”, 2017 was generally a warmer than normal year in much of Canada.  Certainly the late summer and Fall was amazing.

As we move into 2018, models are suggesting that this colder than normal pattern will persist over much of eastern North America.  This persistent cold pattern (“Polar Vortex”) that has been appearing over the last number of winters, is being attributed to the dramatic reduction in sea ice in the Arctic.  As we start 2018, there is about one million square km less ice cover than normal.  Further background.

It appears likely we will be facing another major storm for the first week of 2018.  The weather models have been consistent of developing a powerful and fast moving storm that will cross the Maritimes on Thursday-Friday with very strong winds and heavy precipitation.

It is too early to forecast the details… I have shared two model forecasts for snowfall that suggest the potential for very heavy snowfalls away from the Atlantic Coast.

Perhaps more disturbing is the potential for damaging winds that may result in extensive power outages and coastal storm surges.  A sample model output shows the potential strength of this storm, with the threat of wind gusts in excess of 100km/h (purple colours).

Environment Canada has already issued a Special Weather Statement to advise the public on the threat associated with this storm.  Keep yourself updated on the forecasts and warnings… and I’ll be tweeting daily with updates on this storm.

Happy New Year and stay safe.

Jim

There are a fair number of folks that ask me for a travel outlook.  Decided there may be some value in sharing a post on that topic.

This is a busy time of year; travellers should try and be patient… flights are sometimes delayed, and roads can be slippery.  This post is intended to give you an idea where and when some issues might develop, to assist in your planning.

There is a chilly west wind today.  Winds off the Bay of Fundy are generating some snow over southwest NS across parts of the valley into central Nova Scotia (see radar pic).  There are also some flurries in Inverness county and plenty of snow from the strong winds in western Newfoundland.

Tonight and early on Saturday a system is passing south of Nova Scotia and Newfoundland.  Only a few cm of snow for Nova Scotia with this system, however, a snowstorm is likely on the Avalon Peninsula in Newfoundland.

On Saturday night, the winds will shift to brisk out of the northwest generating onshore flurries in parts of eastern NS, PEI, Cape Breton, and western Newfoundland.  There may some blowing snow and snow covered roads in these areas that will persist into Sunday.

On Monday conditions will be fine over much of Atlantic Canada there will be light snow over the Ottawa-Montreal area as well as parts of northern New England.  This light snow will move into the Maritimes Monday night and persist as showers or flurries Tuesday.

Another system will move from the St.Lawrence valley into northern New Brunswick later Tuesday.  Some of the northern parts of New Brunswick, and perhaps PEI and Cape Breton may have accumulating snow later Tuesday.  Behind this system, Wednesday and Thursday will be back to a cold northwest flow with onshore snow squalls returning.

It looks like a major storm will pass north of the Maritimes Friday or Saturday… snow changing to rain?  The rain may ruin the chances of a White Christmas over the southern Maritimes. Back to a cold westerly flow on Christmas behind this system.

This is just an outlook…. the weather will change and stay updated to Environment Canada’s forecasts and warnings (and my tweets

Stay safe

Jim

#weather