Y’all Ready For Another One?

No sooner are we rid of our first winter storm of the season that we have to sound the alert for another one that looks to be on the way for later this week.

First, though, there is a lingering concern from Sunday’s storm that needs to be addressed. It’s a cold day and the snow cover over the Upstate is melting slowly. Tonight is going to be very cold across the state with teens and low 20s over areas which still have snow and ice on the ground.

Visible satellite picture from around 1:30 p.m. showing thick clouds over Georgia,
patchy clouds over much of SC, more widespread clouds over NC,
and snow and ice cover over the Upstate.















Forecast lows for Tuesday morning from the National Weather Service


So, lingering snow and ice on roads in the Upstate will freeze solid again tonight and lead to icy areas tomorrow morning. This is primarily going to be a concern for the back roads. Thanks to the hard work of SCDOT, county and municipal road crews, and this afternoon’s sunshine, primary routes will largely be clear tomorrow morning (though caution will be necessary). Roads which have not seen a plow or salt truck, though, will be very icy.

It will get below freezing again Tuesday night and Wednesday morning, so any lingering snow and ice on the roads will freeze up again. Most roads should be generally clear by tomorrow evening, though. Just be careful again Wednesday morning.

Now, to deal with the next storm risk for later this week. This story begins with our next cold front, which will arrive in South Carolina later Wednesday night or early Thursday.

The weather map for 7:00 a.m. Thursday morning according
to forecasters


















This will bring some rain to South Carolina on Thursday, starting before daybreak in the Upstate. The front will make steady progress across the state Thursday but then stall over or just off our coastal areas Thursday night.

The front will usher in some very cold air. Notice on the weather map above that the center of the high pressure area over South Dakota is forecast to have a barometric pressure of 1044 millibars. That’s 30.83 inches of mercury, a very high pressure. This is indicative of a very cold air mass because very cold air has a higher density and, in turn, higher pressure. So, usually, a very cold air mass will have a very high barometric pressure.

By Friday, a storm in the Gulf of Mexico will be forming and it will track northeastward along the front through Florida and off the Carolina coast over the following 24-48 hours.

The weather map for 7:00 a.m. Friday according
to forecasters

If you’ve been around South Carolina for many years, or even spent part of that time in a surrounding state, you have seen the weather throw this pitch at you before. This track is ideal for this part of the country to see a snowstorm, particularly when fresh arctic cold air has just arrived.

The metaphorical pitch that’s being thrown, however, is a metaphorical slider wicked enough to stun any metaphorical major league slugger. I mentioned that arctic air is very dense, compared to the air mass that it will be displacing. That means that as the fresh cold air comes in, it will be sliding in underneath the not-as-cold air which will be in place. Aloft, temperatures will remain above freezing over a large part of the state as the next storm system coming from the Gulf of Mexico arrives. This results in a setup for much of the state to see an ice storm.

This is where we run into uncertainty. While there is general agreement among our computer model guidance that another winter storm is on the way, they differ on storm track, temperatures aloft, and timing of the event right now. So, it is too early to exactly pin down where the worst of the sleet and freezing rain will occur, and where it will turn out to be cold enough aloft that we see a snowstorm instead. Exactly when this will occur is in question as well.

However, forecasters have enough confidence to make a few general statements right now:

Very cold air will arrive in South Carolina on Thursday and Thursday night, which sets the stage for a winter storm when the next storm system moves in.

It’s likely that more of the state will be affected by the storm compared to Sunday’s storm since the surface air in place for this next storm will be below freezing over a wider area.

It will be cold enough aloft for a snowstorm on the northwestern part of the storm’s precipitation area, and it is probable that this area is over the Upstate. There is a good chance for a substantial, plowable, accumulation. However, a farther north storm track is possible, which would result in some mixing with sleet or freezing rain. Also, a farther south storm track could lead to only a small amount of snowfall. The storm’s character is not certain yet, but those in this area can begin planning for a significant winter storm causing hazardous travel.

The Midlands, Central Savannah River Area and inland Pee Dee region has the potential to see a mix of snow, ice and rain. The proportions of each precipitation type is in question. There is potential for a major winter storm in these areas, with impacts such as very hazardous travel along with tree and power line damage, but this is not guaranteed yet. A farther north storm track would result in a freezing rain and rain mix in these areas, while a farther south storm track can result in a big snowstorm. Early preparations would be wise at this point for those in this area.

The Lowcountry region and coastal Pee Dee likely sees a mix of rain and freezing rain, but it is too early to say how much ice might accumulate. Substantial impacts in terms of icy roads as well as tree and power line damage are possible, though. If the storm tracks farther north, this area ends up with all rain, but a farther south storm track would mean a wintry mix for this area that includes snow. It would be wise to make sure that your disaster kits are properly stocked.

The storm will begin at some point Friday and end at some point on Saturday, lasting about 24 hours, but the storm could start as early as predawn Friday or as late as Friday night.

This is a wide range of possibilities, but this is the best which can be done at this point given the large amount of differences between all of our computer models with both potential storm track and timing. The range of possibilities will narrow over the next couple of days and we should have a good idea of how this storm will behave by Wednesday.