The past week has been astonishingly mild in Stornoway: The average daily high has been +11.8C, with a daily low of +7.1C; these values are more akin with early-to-mid October than December!
However, major changes are afoot in Northern Hemispheric atmosphere over the next few days. In stark contrast with the winter so far, a dome of extremely cold air (with a 1000-500hPa thickness of less than 480dam) will collapse over eastern Canada, surging out over Labrador and Newfoundland during mid-week. This will create an intense thermal (baroclinic) gradient, likely leading to super-powerful storms in the western North Atlantic (933hPa is forecast near Newfy on Thurs). It's not certain yet whether such energy will transfer east to Scotland - but it's worth keeping on eye on my blog and Twitter in the coming days just in case (NAVGEM met model T+84 and T+126 charts below).
@eddy_weather, Stornoway, 11 Dec 2016