The biting polar winds could see temperatures plunge as low as -8C, with up to five centimetres of snow expected to settle in some areas.
Today will be a great deal milder than tomorrow, with highest temperatures of 8 to 12 degrees.
The Met Office is warning that frequent heavy hail and snow are to be expected throughout Sunday which will lead to snow accumulating on many surfaces. However, persistent or heavy rain will spread from the west through the late afternoon and evening.
As if we hadn't had enough snow and ice, now there's wind and rain on the way..
Two other yellow alerts warn of strong winds as strong as 110km/h and heavy rainfall across the country.
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Daytime temperatures only 1 to 4 degrees with a wind chill effect from a gusty west to northwest wind.
"Elsewhere a frost, but, sunny skies, and already we will start to see further wintery showers pushing into the west".
But the says conditions are set to improve across the nation as rain and cold moves eastward off the coast, allowing for highs of 7C in London, 4C in the north of England and 3C in Scotland later tonight.
The longer-term forecast is for it to be cold, with ongoing wintry showers. Wind will be a feature later in the day. Download it today and continue to enjoy STV News wherever you are.
He added: "On Sunday we're back into a westerly air flow, which normally wouldn't be particularly cold, but as the air is originating from the very cold Arctic Canada region the air will be cold enough to bring snow to sea level". Highest temperatures will range from 9°C to 12°C.