textproduct: Charleston

WHAT HAS CHANGED

A Freeze Warning has been issued for parts of the area for Tuesday morning. The Aviation section has been updated for the 06z TAF issuance.

KEY MESSAGES

- 1) An isolated severe thunderstorm or two will be possible across southeast Georgia and southeast South Carolina through daybreak.

- 2) A powerful cold front will sweep through southeast Georgia and southeast South Carolina today, bringing an increased risk of severe thunderstorms, very gusty winds outside of storms, and brief bursts of moderate to heavy rainfall. The entire area is highlighted in an Enhanced Risk (level 3/5) for severe weather with the SPC Day 1 Severe Weather Outlook.

- 3) Frost/freeze is possible tonight through Wednesday night.

DISCUSSION

KEY MESSAGE 1: An isolated severe thunderstorm or two will be possible across southeast Georgia and southeast South Carolina through daybreak.

The forecast area will sit within the warm and moist south to southwesterly flow ahead of strong cold front to the west. Hi- res model guidance suggests we will see periodic clusters of thunderstorms develop and pass through, as there is a corridor of 500-1,000 J/kg of MLCAPE. Effective bulk shear is currently in the 25-35 knot range, but should continue to strengthen overnight as increasing low and mid-level flow spreads in. In fact, the KCLX VWP suggests there is already 35-40 kt of flow in the 2-4 kft layer. We've already seen some excitement as a strong thunderstorm developed across western Charleston County and produced a 50 kt gust at KCHS and golf ball sized hail in Goose Creek around 11-11:30 pm. All of this to say that there will be an isolated severe threat through sunrise with any clusters of showers and storms that develop and move through the area. Perhaps the threat is highest along the coast, but it could occur anywhere.

KEY MESSAGE 2: A powerful cold front will sweep through southeast Georgia and southeast South Carolina today, bringing an increased risk of severe thunderstorms, very gusty winds outside of storms, and brief bursts of moderate to heavy rainfall. The entire area is highlighted in an Enhanced Risk (level 3/5) for severe weather with the SPC Day 1 Severe Weather Outlook.

As we have discussed for several days now, a strong cold front will sweep across southeast GA/SC and bring several hazards to the area.

Severe Thunderstorms: The primary hazard associated with this cold front will be the potential for significant severe weather. Overall, the near storm environment appears to be on track consistent with what we have seen for a number of forecast cycles. A very strong wind field will overspread the area, resulting in impressive ambient shear. Guidance suggests 0-6km shear on the order of 50-60 kts, 0-3 km shear on the order of 40-50 kt, as well as pockets of SRH values up around 200 m2/s2. Model soundings continue to mostly show nearly unidirectional shear so it makes sense that the SRH values aren't particularly high. The biggest change noted this morning is the much earlier arrival time in the suite of hi-res models. This earlier arrival time will have notable impacts on the overall severe threat, mainly in the form of lower instability values. Model soundings now suggest MLCAPE in the 500-1,000 J/kg range, with a few pockets of values in excess of 1,000 possible. This lower instability will lessen the potential of discrete cell development ahead of the line and will favor more linear bands. Soundings also show considerable mid-level dry air, yielding DCAPE values into the 700-900 J/kg range. So, the primary threat remain damaging wind gusts (with potential for 75+ mph gusts), an isolated line-embedded QLCS tornado or two, and a much lower hail threat compared to previous forecasts. Another thing to keep an eye on is the fact that near-surface winds are expected to be from 210 degrees which means that at some point up the coast, trajectories will start to be sourced from the nearby cooler shelf waters. This marine influence will likely begin around and north of the Savannah River entrance, potentially altering and lower the severe weather threat for the immediate SC coast from around Hilton Head, to Beaufort, Edisto, Charleston, and McClellanville.

The earlier arrival time of the convective line will lead to some notable adjustments for the timing of the severe threat. The line should be knocking on the door of Jenkins, Candler, and Tattnall counties ~9-10am, the Savannah area around 11am-noon, and the Charleston area around 1-2pm. This would put the main convective line offshore by around 2-3pm, which would be the end of the severe threat.

Gusty winds: The strong wind field across the area will produce gusty winds outside of thunderstorms. Strong momentum and the onset of mixing should produce an environment suitable to increasing gusts beginning around sunrise and continuing until the front moves offshore. Gusts into the 30-35 mph range should be relatively common just about everywhere, with the best gust potential into portions of the Charleston area region. Gusts in excess of 40 mph will be possible, and a Wind Advisory remains in effect for the Charleston metro area. Also, a Lake Wind Advisory is in effect for Lake Moultrie.

Rainfall: The convective line will certainly be capable of producing short-lived bursts of moderate to heavy rainfall. However, the line will be moving fast enough to prevent too much residence time and will therefore reduce the heavy rainfall threat. Rainfall amounts should mostly end up the 0.25-0.50" range with some locally higher amounts possible. Therefore, the risk for intense rainfall producing flooding remains rather low.

KEY MESSAGE 3: Frost/freeze is possible tonight through Wednesday night.

Cold high pressure will spread over the area behind the cold front tonight. Temps will quickly drop this evening. A brief advection freeze is expected Tuesday morning, mainly across far interior GA/SC where temps could dip to 30-32F. We felt confident enough that we upgraded the Freeze Watch to a Warning, and also added Inland Colleton County.

Tuesday night the high will be centered close to the area, allowing surface winds to decouple in the evening. Skies should be clearing out during the evening, so good radiational cooling will occur overnight. Temps are expected to dip into the upper 20s far inland with lower to middle 30s elsewhere. Even where temps don't hit freezing, frost formation seems pretty likely. We will likely need another round of Frost/Freeze headlines for Tuesday night.

Wednesday night could also feature some frost issues across the inland half of the area where temps dip to the low/mid 30s and skies remain mostly clear.

AVIATION /06Z MONDAY THROUGH FRIDAY/

The 06z TAF period begins with VFR conditions at KCHS, KJZI, and KSAV. The first issue is that there could be a short window of LLWS before winds increase. It should be short-lived as the low-level wind field is increasing and will become breezy even before sunrise. Thereafter, the main forecast concern is for the arrival of a line of thunderstorms later today. Based on expected faster timing we have moved the TSRA TEMPO groups earlier. For KSAV, the line is expected to move through during the 15-17z time period and for KCHS and KJZI it is expected to be 17-19z. A period of very heavy rain with IFR visibilities will be possible as well as very strong winds. We have introduced gusts up to 40 kt with the thunderstorms and there is potential for even higher. Once the line moves through there will be a period of showers behind it before precip comes to a complete end this evening. Winds will ramp up quickly after sunrise and will be gusty in advance of the thunderstorm line. Winds will remain gusty while turning westerly this evening.

Extended Aviation Outlook: VFR conditions are expected to prevail.

MARINE

Strong low-level wind fields will result in gusty winds over the waters today as a strong cold front approaches. 35 kt gusts are likely over the SC nearshore waters and Charleston Harbor where we maintained a Gale Warning. Small Craft Advisories exist elsewhere.

Winds will abruptly shift to WNW by early this evening after the cold front sweeps through. The gusty winds and elevated seas will subside by Tuesday morning.

EQUIPMENT

The KCLX radar is scheduled for radome panel replacement March 17-20, 2026. The radar will be down during this time. Users are encouraged to use data from the following nearby radar sites during the maintenance outage:

KCAE - Columbia, SC KLTX - Wilmington, NC KJAX - Jacksonville, FL KVAX - Moody AFB, GA KJGX - Robbins AFB, GA

CHS WATCHES/WARNINGS/ADVISORIES

GA...Freeze Warning from 4 AM to 10 AM EDT Tuesday for GAZ087-088- 099-100-114-115. SC...Freeze Warning from 4 AM to 10 AM EDT Tuesday for SCZ040-042- 043. Lake Wind Advisory until 2 AM EDT Tuesday for SCZ045. Wind Advisory from 8 AM this morning to 8 PM EDT this evening for SCZ050-052. MARINE...Gale Warning until 8 PM EDT this evening for AMZ330-350-352. Small Craft Advisory until noon EDT Tuesday for AMZ354-374.