ROANOKE, Va. – The first half of January has been warm for the most part, especially this past weekend. Looking ahead to Martin Luther King weekend, however, things are going to change big time.

That starts Saturday, when a wintry mix develops in parts of the area. We’ll start with the shortened version, and then dive into things a little more.

What we know

• We know that wintry weather is possible this Saturday, given the setup of moisture overrunning colder air.

• We also know that this likely won’t be an all snow kind of ordeal.

• Lastly, we know that this is a Saturday-only event.

What we will learn

As this system comes on land in the western U.S. and time passes by, weather balloons will survey it and forecast data will become more reliable. It’s because of that we expect to be able to nail down the exact type of precipitation, timing, totals and impacts in the coming days.

Analyzing the pattern

Let’s start with a broad view.

This shows high pressure to our north. Clockwise wind around high pressure brings colder air into the region, wedging it up against the Appalachian Mountains through Saturday.

At the same time, an area of low pressure will develop to the west. Counter-clockwise wind around low pressure allows moisture to overrun the cold air, which sets us up with the potential for a wintry mix Saturday.

Because we don’t have true Arctic air in place at all levels of the atmosphere, it’s likely that we see more of a mixed bag of precipitation rather than just all snow. How cold we’ll be at the surface and at a few thousand feet above us will determine whether you see rain, freezing rain, sleet or snow.

This temperature profile is something that can be more carefully analyzed 1-3 days prior to a storm.

Where do we stand?

At the moment, the most likely spot to see a wintry mix is near and north of 460. This is typically where the colder air stays bottled up longer. This would include Roanoke, Blacksburg, Giles, Craig, Botetourt, Lexington, and the Highlands.

It’s possible still that you see a wintry mix in places like Lynchburg, Bedford, Rocky Mount, Floyd and Pulaski. Chances go down, however the farther south and east you go.

Low pressure being west, rather than due south, may delay the arrival of precipitation and also may help usher in above-freezing air for areas in the white (see map above).

It’s premature to talk totals, as things can still change depending on the a) amount of cold air and b) arrival time of precipitation.

What we can tell you is that this doesn’t appear to be a crushing blow for us (since low pressure is more west than due south). This again looks like one of those systems that could be inconvenient and make travel difficult at times before things change over to rain.

Beyond the weekend

This system is the beginning of a shift in the overall weather pattern. In fact, the second half of January is going to look and feel a lot different than the first half. Highs Martin Luther King Day will be in the 30s for most of the area with lows at night in the upper teens and lower 20s.

It’s likely that we stay cold through the end of January. Drier weather prevails for a few days after Martin Luther King Day. We’ll let you know if any systems develop after that, as they could potentially turn wintry too.