It's been a long time in coming, but there's been a remarkably consistent signal in the last couple of days that later on Saturday into Saturday night a large part of the UK will be affected by the first widespread fall of snow so far this winter.

It's a classic meteorological battle between cold Continental air from the east, and milder Atlantic air from the west.

The dry, cold air which has its origins in Siberia, has led to numerous deaths, particularly across Eastern Europe.

Thankfully the UK is on the periphery of this cold.

The milder air from the Atlantic will try and force its way across the country through the weekend, and where the two meet, widespread snow is expected.

Around 5-10cms is expected - with Central and Eastern England most at risk, for a change.

For our region current timings bring the snow into Pennine areas early Saturday afternoon, reaching the coast late afternoon and into the evening.

As it clears on Saturday night the snow will to turn to rain or drizzle leading to widespread ice on Sunday morning.

The areas affected are covered by a Met Office amber alert, shown below.

In these areas temperatures will remain well below average, under the continued influence of a large area of high pressure across Central and Northern parts of Europe, with an on-going wintry theme.

Getting the forecast details correct next week will be a real challenge.

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For the first time this winter, after a relentless spell of westerly winds, many areas are expected to see a general change to colder conditions as we head through the weekend and into next week.

As the colder air becomes established it will be competing with milder air from the Atlantic. Where the two meet, snow is likely, with western areas most at risk.

Here in Yorkshire there is a risk of some patchy snow later in the weekend and into monday mainly in western areas - although it is unlikely to be heavy. At the same time wintry showers may affect coastal areas.

But the exact location of this battle between cold air from the east and milder air from the west is still a source of uncertainty, and getting the detail right will cause problems.

Much of the country will then have a period of quiet, settled & cold weather as we head through next week, with sharp overnight frosts developing.

After that, the outlook remains a major headache for forecasters, as it has for some time. In fact I can't remember the last time there has been so much disagreement between the major forecasting models.

As I've explained before, each computer model runs many times, and each time the initial starting conditions of the atmosphere are changed by a very small amount, in order to see what happens.

An example of this can be seen below, from the American GFS model, from midnight.

It clearly shows that after a few days, when all the model runs are in broad agreement, each separate run of the model thereafter yields different results - with some solutions showing a 15 Celsius difference in temperature at 5000ft.

The latest information gathered so far today shows a shift away from the milder south-westerly scenario described above - but such run to run changes have been common this week and until there's more consistency it's impossible with any degree of confidence to determine which scenario will ultimately win.

That said, a cold early February is the more likely scenario.

Finally, since my blog has featured articles in the past about the merits of different private forecasting companies before, and how some newspapers often use their long range forecasts for front page headlines, I thought you might be interested in this article about Positive Weather Solutions which appeared in the Guardian yesterday.

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The Northern Lights, or Aurora Borealis, featured prominently across the skies of Northern Britain last night. The fabulous photograph below, taken at the Tan Hill Inn in North Yorkshire, is courtesy of North news and pictures.

These atoms, having absorbed the energy from the collision, become excited; they then emit this energy which is seen by us as different coloured lights.

It's exactly the same process when a neon light glows when charged with electricity.

A pale green is the most common Northern Light, caused by the charged particles colliding with oxygen atoms.

Normally, most charged particles are directed no further south than 20 degrees from the North (or South) Pole, but during high solar activity, or a 'solar storm', auroras can be seen much further south.

It's not the first time we've seen Northern Lights recently, and it's all part and parcel of the general increase in solar activity in the last few months. This follows a prolonged period of very low solar activity in the last few years.

Experts believe there is a chance to see the Northern Lights again tonight by looking towards the northern horizon. Skies will be clear for much of the night, too.