Winter Storm Risk Continues For Sunday

Not a lot has changed since yesterday. We’re still on for a potential winter storm for Saturday night and Sunday, but details remain sketchy. Our storm is still centered over the Pacific Ocean west of Washington and Oregon.

Oconee County Director of Emergency Services Scott Krein has more…

The storm will push ashore over the next 24 hours and this will allow us to start getting better observations of the storm, which, in turn, will give us better forecasts for how it will affect South Carolina.

For now, we still expect that this storm will bring a variety of impacts to the state, and each region of the state will be affected differently. We expect that the Upstate will see a winter storm, with some snow and ice. This area has the potential to see the most snow, but how much will depend on whether or not it warms above freezing at some point aloft over region and how long it stays above freezing. This ‘warm nose’, we meteorologists call it, melts snowflakes, but this area will likely see subfreezing air firmly wedged in at the surface through the entire storm. When the melted snowflakes fall into this subfreezing air, they either freeze once landing on something, or, if the near-surface cold air layer is thick enough, refreeze into sleet before reaching the ground.

So, when all is said and done Sunday evening, the Upstate could end up with a big snowstorm, a big ice storm, or concrete-like coating of mixed precipitation. Either way, the Upstate has the best chance for seeing a major winter storm and if that’s where you live, you should be playing very close attention to the forecast and getting ready for the storm.

This is not to say that the rest of the state will escape potentially serious impacts. The Midlands, Central Savannah River Area and Pee Dee appear less likely to see a lot snow (though there can be a little) from Sunday’s storm. The potential is there for sleet and freezing rain, potentially a lot of it, because the warm layer aloft will likely be thick over those areas. Today’s computer model guidance is showing the potential for a serious, crippling ice storm for the northern Midlands, northern CSRA and northern Pee Dee region. How serious it actually will get in the end will depend on how long temperatures hold below freezing while rain is falling, which is the uncertain part of the forecast right now. This is because the models, none of which we have high confidence in for reasons already mentioned, are not in good agreement about how much freezing rain will fall. Some show very little but most show a lot.

Over the rest of the state, it looks as though temperatures spend less time below freezing and, for most of the Lowcountry, no time at all below freezing. So, the effects in these areas will be less. Nonetheless, there is the potential for some ice buildup on trees and power lines, at least for a time, along with slick elevated road surfaces. Another concern is that most models are showing the storm center tracking right across the Coastal Plain. This might lead to a low-end severe thunderstorm and tornado risk for immediate coastal areas. We’ll be watching for this carefully as we get closer to the event. Another potential problem for coastal areas is that onshore winds will get strong Sunday and may coincide with a high tide cycle, leading to coastal flooding.

There still remains a silver lining to this cloud, which is that the drought-stricken eastern part of the state will get another soaking rain from this storm. The rain might even be heavy enough for localized minor flooding in this area.

We’re still four days away from the storm, so the forecast can change, either for the better or worse, due to the lower confidence in our models, but we should have the general idea right at this point. Prepare accordingly; if nothing else, at least have your disaster readiness kit fully stocked. A good starting point for winter storm preparations is SCEMD’s Severe Winter Weather Page.