Northern America is facing a disruptive winter/ice storm with more than half of the US preparing for impactful cold. Extreme cold is surging through the interior of Canada, over the Maritimes, down through the north-central of the US into the southern Plains and Midwest. This is potentially historic as “dangerously cold Arctic air spills out over the Great Plains and eastern US through the weekend.” NWS
The National Weather Service (NWS) in the USA states that this will be a “Significant Winter Storm” which will bring heavy snow and ice. There will be dangerous cold weather as this long-duration winter storm is set to bring widespread heavy snow, sleet, and freezing rain from the Southern Rockies to New England through into the start of next week. Southern Canada also has orange and yellow cold weather warnings and lake-effect snow is expected downwind of the Great Lakes on Friday.
People are being told to finish their preparations as “widespread travel disruption, prolonged power outages, and vast tree damage is likely.” It is not only the deep cold but there will be “dangerous wind chills”. The tree damage is the risk of so-called “exploding trees” as the sudden extreme cold arrives and causes tree sap to freeze and expand. The tree bark can then crack or split apart in the drastic temperature change. This can produce a loud sound, almost like a whip or a gunshot but there is no actual explosion of wood. What can be dangerous in these conditions is the build-up of heavy snow on upper branches, which then snap and fall.
Snow squalls are a danger to traffic as conditions can suddenly deteriorate and people are being warned not to suddenly brake if visibility plummets in the swirling snow as this can then lead to mass pile-ups on the highways. The sheer depth of the snow and drifting conditions will make routes impassable
The wind chills pose a life-threatening risk of hypothermia and frostbite to any exposed skin and power outages seem likely in the heavy snow and strong winds. Freezing rain and ice accretion also add to this risk. Authorities are reminding people to ensure that their pets and animals have protection from the extreme cold too.
This plunge of very cold air will eventually come up against the warmer waters of the Atlantic and the deep temperature contrast will invigorate the jetstream. This could then develop low pressures heading towards the UK and Europe next week. So it's not that we will get the American snow, but it could result in stormy weather heading our way.
UK
Here in the UK, snow is expected over the Scottish mountains as the ongoing rain event continues for central and eastern areas. There was heavy and persistent rain for many parts of northern Britain and Northern Ireland on Thursday with some Scottish rivers bursting their banks.
“Flooding from rivers and surface water is likely in Tayside, Angus and Aberdeenshire on Friday, Saturday and Sunday due to further periods of persistent rain along with continued high river levels from rainfall during previous days.” Scottish Flood Forecast.
There is also a Wind & Rain warning over SW Britain linked to a slow-moving low pressure (Ingrid), which will stick around into the weekend. This is helping to steer the onshore SE flow for NE Britain but is also bringing very unsettled and windy weather for SW England today with more showers on Saturday before it heads to Northern Ireland on Sunday. This will throw a band of rain and wet hill snow over the Pennines and Southern Uplands later this weekend
Colder air from Scandinavia will reach over NE Scotland with any precipitation over Shetland likely to fall as snow, even through next week. The Scottish ski resorts in the Grampian will be pleased with the snowfall and lighter winds this weekend, but there has been wet weather and a heightened avalanche risk this week.
What about the cold weather in the east and the risk of snow as Altantic weather fronts reach over the UK? You can see that the GFS is keen to bring the deep cold from Russia across to southern Scandinavia by next weekend, closer to us but the ECM is less keen on the mass movement but does extend some cold across the North Sea to Scotland.
Still uncertainty about the end of January, but there will be colder air from the northeast for the UK next week and there are signs that a low from the southwest could bring frontal rain northwards over the UK and it might turn to snow (for a time) on Tuesday. The ECM snow charts do focus on the high ground of Britain.
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