Key Points:
- A Winter Storm Watch is now in effect for much of northern South Carolina, including the Upstate, Catawba Region, the northern Midlands and northern Pee Dee.
- Confidence continues to increase that at least a part of South Carolina will be affected by a major, long-duration winter storm this weekend.
- Computer models have come into better agreement about the storm, but some uncertainties remain, and at least minor changes to the forecast remain likely.
Most likely scenario:
- The Upstate will see precipitation begin late Saturday, likely as sleet. Any snow that falls would be for less than an hour at the onset. Sleet is likely to accumulate an inch or two along and north of I-85 before a change to freezing rain, while areas southeast of I-85 see less sleet with an earlier transition to freezing rain. A damaging ice buildup is likely across the region, especially west of I-26 and southeast of I-85 further east. Tree and power line damage could be widespread, and travel will become difficult to dangerous Saturday night through at least Monday morning, likely through Tuesday morning.
- Across the Central Savannah River Area, the Midlands, and northern Pee Dee, freezing rain may dominate north of I-20, with a damaging ice accumulation and slippery travel Saturday night into Sunday night. Areas along and south of I-20 see freezing rain for a time, then rain as temperatures warm above freezing on Sunday. Those areas may still see enough ice accretion for spotty tree and power line damage.
- The Lowcountry and Grand Strand primarily see rain Saturday night through Sunday, though a period of freezing rain is possible over the inland Lowcountry and the Grand Strand Saturday night. Elevated road surfaces can become slippery for a time, but the potential for tree and power line damage is low. Some models show it warming up enough on Sunday for thunderstorms in this area, especially in the Lowcountry.
- Extreme cold early next week behind the storm will lead to slow melting, especially in areas where a substantial sleet accumulation occurs. Burst pipes and water mains will be a concern, and those with no power and no backup heating source will experience severe hardship.
Worst-case scenarios include:
- A severe ice storm with over 0.50" ice buildup (possibly up to 1.00") with widespread tree and power line damage is an increasing concern for areas where freezing rain is dominant and long-lasting; the best chance appears to be in the Upstate, the Catawba Region, the northern CSRA, and the northern Midlands.
- A northward trend in the forecast track or a trend toward a warmer storm would shift the potential for significant sleet accumulations out of South Carolina. However, a damaging ice storm would still occur in the Upstate. Less of the state would be at risk for a damaging ice buildup.
- A more southerly track of the storm or a trend toward a colder storm would bring heavy snow and sleet back into South Carolina, with the potential for a damaging ice storm shifting or expanding further south.
- Should the sleet accumulation in the Upstate be greater than what's forecast, the extreme cold Monday night into Tuesday morning will also be more severe.
We're finally seeing better agreement among the computer models, so we're gaining confidence in the forecast for this weekend's winter storm.
The forecast for now through Friday night is only slightly changed:
- A cold front slowly crosses South Carolina through Friday, bringing light rain to much of the state; temperatures remain mild across the Coastal Plain on Friday, while the Upstate turns cooler.
- A second cold front arrives Friday evening, leading arctic air into South Carolina.
Our next storm, now affecting Southern California, will reach us on Saturday afternoon or evening, and travel conditions will go downhill, with roads becoming slick as grease and much of the state seeing a damaging ice storm. We've reached the point that I can throw some numbers at you. First, here's a potential 𝚜̶𝚗̶𝚘̶𝚠̶ sleet accumulation map from the National Weather Service (NWS):
It's a 'snow' forecast because sleet counts as snow when it comes to weather records. The one concern we have is that there's a chance for the sleet to last much longer than forecast along and north of I-85 from Greenville east to the border of the vinegar sauce zone. (Though that part features a vinegar-tomato hybrid ... I'm a fan ... there's good 'cue to be had in Shelby.) There's a realistic chance for 2-3 inches of sleet in that area. That would be nice because it holds down the potential ice buildup, but in exchange, the area would have longer lasting travel issues due to slow melting of the glacier of ice that the storm would leave from freezing rain on top of thick sleet.
Now, for the NWS's ice buildup forecast:
I have highlighted an area on that map where there is a chance the ice buildup could exceed a half-inch. A half-inch of ice accretion is the threshold for where you start to see widespread tree and power line damage. My gut feeling is that some areas will see that much ice; the uncertainty is where exactly it will occur, which will depend on the storm track and other factors. I excluded a part of the Upstate because I think there's a good chance that longer-lasting sleet limits the ice buildup somewhat, at the expense of longer-lasting travel problems.
As mentioned above, it looks really cold early next week. I mean, "Pennsylvania called, they want their weather back," kind of cold. Here's the current NWS forecast lows for Monday night / Tuesday morning:
Zoinks, Scooby Doo!!! That would be the coldest the I-85 Corridor has seen in a long, long time, since early January 7, 2014, in fact (when it got down to 5° at GSP Airport). It'll be bitter over the rest of the state, too! You'll want to take steps to ensure your home and car are ready for the cold. Wrap your home's pipes, if necessary, and check your car's antifreeze if it's more than a few years old.
The extreme cold will slow the melting of the potential glacier cover early next week. Slippery travel will probably linger into Tuesday morning and may even hold on into Wednesday if enough sleet falls in the Upstate.
It would be best to start your preparations soon if you're in an area that still may be hit by a damaging ice storm and slippery travel. How do you deal with it? SCEMD's SC Winter Weather Guide is a good starting point, and you can get more tips on winter storm preparedness at ready.gov. Pay close attention to the generator safety (I tested mine last night) and kerosene and propane heater safety tips; carbon monoxide is quite the villain.
See y'all again Friday, when we should be able to bring the picture of our upcoming winter storm into even better focus.