We're still on track to see a stormy period across the Palmetto State this afternoon and evening. The culprit is a storm currently centered near St. Louis. It's pulling a warm front northward into the state with rain and embedded thunderstorms. A cold front will move through this evening with another round of thunderstorms.
This radar composite view from midday today shows a band of rain and thunderstorms along a warm front moving into South Carolina from Georgia and another band of thunderstorms over Mississippi and Alabama associated with a cold front moving toward the Palmetto State
Source: University of Wisconsin
The Storm Prediction Center (SPC) maintains a level 2 of 5 severe storm risk over most of South Carolina. There is a level 1 risk over a small part of the Upstate, which will mostly remain protected from severe storms by a near-surface layer of cool and stable air.
SPC's Severe Weather Outlook graphic for today and tonight with South Carolina highlighted.
The primary concern for today's storms will be locally damaging wind because fast-moving air will be found at relatively low levels (increasing to around 50 mph at only 1,500-2,000 feet and around 70 mph at only 3,000-4,000 feet later today). Thunderstorm downdrafts will pull some of that momentum down to the surface. We also have ample quantities of the storm ingredient that leads to tornadoes, which is wind shear.
However, the tornado risk is in question because of limited instability. The Coastal Plain will see the most substantial intrusion of warm and humid air between the warm front and cold front. That area will have the highest instability and highest tornado risk through this evening. A few spots could see damaging hail, but this is a low-end risk.
We still expect to see gusty winds even outside of thunderstorms once the warm front moves through. There will also be a gusty west wind behind the cold front tonight. For most areas, peak wind gusts will be 35-45 mph. In this case, the Midlands, Central Savannah River area, and upper Pee Dee appear to have the highest non-thunderstorm wind risk.
The Upstate will get a soaking rain this afternoon and tonight; for most places, rainfall will be a half-inch to an inch. There can be locally higher amounts in northern parts of Oconee, Pickens, Greenville, and Spartanburg Counties. The flash flooding risk in the Upstate area is low but not zero. The rest of the state will see mostly a quarter-inch to a half-inch, which isn't enough to cause flash flooding. Many of our rivers are at minor or moderate flood stage right now; the rain won't send them any higher, but river stages will be slower to fall in the coming days.
The risk for coastal flooding has passed, though we saw minor flooding along most of our coast this morning.
There are no changes from Thursday to the weekend forecast. Saturday looks brisk and chilly despite sunshine, then Sunday looks tranquil with a decent afternoon thanks to near-average temperatures.
A lot of people have Monday off for the King Holiday as well, and it's likely to be dry but with increasing clouds ahead of our next storm. Look for another round of rain Monday night and Tuesday as it moves through. Amounts are in question, but a light-to-moderate rain looks most likely. As discussed Thursday, some rather cold air arrives as this storm departs, but likely too late for any snow or ice in South Carolina. Only the Upstate, primarily our small mountainous area, has even a slight chance for a few flakes or a bit of freezing rain during the event. If you plan to travel into western North Carolina on Tuesday, the potential for slick roads is much higher there and for points farther north and west. You'll hear from me on Monday if the winter weather potential for any part of South Carolina looks noteworthy.
The rest of next week looks cold. Wednesday morning starts with temperatures in the teens in the Upstate and 20s elsewhere, even at the coast, then highs will only be in the 30s and low 40s. Thursday looks less harsh, with highs in the 40s to low 50s.
Another storm could be coming our way at the end of next week. However, models are all over the place with storm track, timing, and the amount of moisture it will have available. Furthermore, they differ on how much cold air will be available, with some hinting at some snow and ice potential for the Upstate.
The cold weather pattern likely continues until around the 25th, so we'll have to be on the lookout for winter weather events until we enter a period of milder temperatures at the end of the month.
This plot of the GFS output from the 1200 UTC Friday run shows an example of a model calling for rain and even winter precipitation over parts of South Carolina next Friday. Don't panic yet (or get excited if you like to see snow and ice) because a lot can change over the next week.
Source: WeatherBELL