Winter Storm Risk This Weekend

A strong storm system is expected to arrive from the west over the weekend, according to forecasters. Accumulations of snow, up to two inches in some parts, as well as sleet, and freezing rain will be possible late Saturday through Sunday.

Meteorologists with the National Weather Service said that the winter weather impacts could be substantial, but remain highly uncertain at present.

We will continue to closely monitor this system with the 24/7 Weather Team.

Here is what forecasters with the South Carolina State Climate Office, a division of the State’s DNR, are thinking right now, about the potential for a winter storm this weekend…

The tables have turned after weeks of warmth to start our winter period (December to February from a meteorologist’s perspective). We have concerns about a potential winter storm this weekend. Where is this coming from? Well, the storm headed our way for this weekend is still over the North Pacific right now.

Visible satellite picture of the northeastern Pacific and U. S. West Coast

Being over the Pacific puts it in an area where we don’t have the best weather observations. We still have weather satellite data, ship reports, and airplane reports, but it’s far less than we would have with the storm over land. This means that our computer model guidance for the storm isn’t as reliable as it will be once we get this storm over North America; lower quality data going into the models means that the forecast quality coming out of them may be worse. So, until then, all forecasts for this storm have to be taken with a large grain of salt. We will be more confident in our computer models after the storm reaches North America on Thursday afternoon.

That being said, our weather pattern is favorable for a winter storm to occur in South Carolina. Upper-level ridges (northward buckling of the main jet stream aloft) are in place over the Atlantic and along the West Coast, while an upper trough (a southward dip in the main jet stream aloft) is forming and getting stronger over eastern North America. Having those features in place gives us a chance for a winter storm, so having computer models showing one potentially coming our way is no surprise.

Short term (Tuesday evening) upper air (500 mb) forecast heights and wind speed with important features highlighted

So, our storm, now out over the Pacific, has to track northeastward over the West Coast ridge before diving southward toward us, following the flow around the developing upper trough over the eastern two-thirds of North America. This somewhat winding path will take some time to travel, so we won’t see the storm get underway until Saturday night at the earliest.

The big question is the track, and there is a range of possibilities with this. But, in the last day or so, our computer models have generally agreed on the storm following a path favorable for South Carolina to see ice and snow. You know, the “low coming out of the Gulf of Mexico” or “it’s coming at us from Atlanta” sort of track.

One model’s (the highly-regarded ECMWF) forecast for the storm track through the Southeast this weekend

So, it’s starting to look as though we’ll have to deal with a winter storm over at least a part of South Carolina beginning Saturday night or early Sunday. However, there is still a lot of devil in the details for the reasons I outlined above. Much can go wrong with the forecast at this point. It’s pointless to say that there could be a foot of snow in parts of the Upstate right now or that parts of the Midlands could see over a half-inch of ice accretion, even though some recent computer model runs have shown this. Confidence is much too low. The storm track could be farther south or north, bringing the worst of it to different areas, perhaps not even in South Carolina.

We can say right now that the best chance for a significant winter storm is in the Upstate. While we can’t say how much snow and ice will fall, this is currently the area of greatest concern. It also appears that there’s a good chance for impactful snow and ice over the northern Midlands and Central Savannah River Area, looking like more ice than snow in this area for now. Travel disruptions on Sunday are likely in these areas. Other areas may see some ice and snow at the start or end of the storm, but it will mostly be rain. The rain might be heavy, not necessarily a bad thing since it was so dry in November and December, but perhaps enough for localized flash flooding. It also looks cold for a while behind the storm, so where snow and ice do fall, it will melt slowly and may keep the roads slick in some areas for a couple of days. The forecast for your neighborhood will change, perhaps flip-flopping back and forth once or twice as the computer models may struggle a bit with the weather pattern.

With all this uncertainty and potential confusion in this forecast right now, what should you do about it? The most important thing is to stay tuned to your favorite reliable weather source because there is a very real risk for a winter storm this weekend, perhaps even a big one for parts of the state. You can make sure that you have all the supplies you need in your disaster preparedness kit, such as some non-perishable food, batteries and refilled critical prescriptions. The South Carolina Emergency Management Division has a winter weather preparedness guide which you can follow to make sure you’re ready.