textproduct: Charleston

WHAT HAS CHANGED

Overall, no significant changes to the Key Messages. The Aviation section has been updated for the 06z TAF issuance.

KEY MESSAGES

- 1) Scattered thunderstorms expected today with an isolated severe threat possible.

- 2) A strong cold front will pass through southeast GA and southeast SC on Monday bringing the potential for severe thunderstorms, very gusty winds outside of storms, and brief periods of moderate to heavy rainfall.

- 3) Frost/freeze is possible Monday night and Tuesday night.

DISCUSSION

KEY MESSAGE 1: Scattered thunderstorms expected today with an isolated severe threat possible.

Surface analysis shows high pressure centered across New England extending down the Eastern Seaboard and into GA and the Carolinas while a coastal trough sharpens just off the coast. This trough is expected to lift northward through sunrise across the coastal waters, and then push further northward and inland through the early afternoon clearing the forecast area. The suite of hi-res models seem to be telling a similar story. The best coverage of showers and thunderstorms seems to align well along and just behind the leading edge of the boundary. This belt of low-level lift will gradually track inland through midday and leave the forecast area solidly within the warm sector for the afternoon with likely what will be isolated thunderstorm coverage at best due to the lack of any real initiation feature. So there is a bit of a disconnect between the best forcing (morning), and the best ambient severe environment (afternoon). During the afternoon, model soundings suggest MLCAPE values on the order of 1,000-1,500 J/kg, ~30 kt of 0-6 km shear, and some decent veering in the low-levels. However, by the afternoon, the airmass becomes a bit homogeneous there isn't much for the convection to develop on. So, the area remains in a Marginal Risk (level 1/5) in the Day 1 SPC Severe Weather Outlook. This makes sense covering what appears to be a conditional threat.

KEY MESSAGE 2: A strong cold front will pass through southeast GA and southeast SC on Monday bringing the potential for severe thunderstorms, very gusty winds outside of storms, and brief periods of moderate to heavy rainfall.

A strong cold front is expected to move through southeast GA and southeast SC beginning late Monday morning and shifting off the coast by mid afternoon Monday. The front will bring a multitude of hazards to the region. Overall, not much change to these threats from the past few forecast cycles.

Severe Thunderstorms: A strong cold front is expected to begin entering the western portion of the forecast area by mid to late morning Monday and then quickly push to the east, exiting the coast by the mid afternoon hours. The first severe concern will come with more discreet convection that could develop ahead of the cold front and the main line Monday morning. Then the primary severe threat will be associated with the linear convection forced by the front that will track eastward into the afternoon. The forecast area will be situated within the warm sector ahead of the front with temperatures warming into the mid to upper 70s and dewpoints rising into the mid to upper 60s. There is solid support for MLCAPE values rising into the 1,000-1,500 J/kg range coincident with a rather impressive wind field. Guidance suggests 0-6km wind shear on the order of 50 knots, 0-3km wind shear 40-50 knots. Model sounding suggest wind profiles are pretty unidirectional, though there could be some low-level backing of the flow yielding some higher SRH values. As such, damaging wind gusts are the primary threat, followed by an isolated tornado threat, and hail being a distant third. Setting the goal posts wide, the timing of the severe threat probably begins around 9-10 am and ends by around 4-5 pm. The SPC Day 2 Severe Weather Outlook now includes the entire forecast area in an Enhanced Risk (level 3/5).

Gusty Winds: As stated above with the severe threat, the wind field will be pretty impressive and with temperatures warming into the mid to upper 70s, there will be sufficient momentum to mix down some strong wind gusts from the morning and through the afternoon ahead of the front. There remains potential for gusts in excess of 35 mph outside of any thunderstorms with gusts of 25-30 mph being more common. We will almost certainly need a Lake Wind Advisory for Lake Moultrie and there is still the possibility of needing a Wind Advisory for portions of the area.

Rainfall: The environment will be quite moist ahead of the front and guidance suggest a ribbon of precipitable water values approaching 1.50 inches (above the 90th percentile according to SPC's sounding climatology). However, the line of convection is expected to be very fast moving which will limit the significant rainfall potential. Most likely rainfall amounts are in the 0.25-0.75, with potential for a few isolated amounts approaching an inch depending on how convection evolves. Therefore, the risk for intense rainfall producing flooding appears rather low.

KEY MESSAGE 3: Frost/freeze is possible Monday night and Tuesday night.

Cold high pressure will build into the area behind the cold front late Monday afternoon through Monday night. An advection freeze is increasingly likely late Monday night over interior portions of southeast SC/GA. We felt confident enough to hoist a Freeze Watch for Bulloch, Candler, Evans, Jenkins, Screven, Tattnall, Allendale and Hampton Counties. Elsewhere, low temps are expected to dip into the mid 30s, but frost formation doesn't seem likely due to fairly strong winds continuing overnight.

Tuesday night may be slightly cooler due to radiational cooling as the surface high settles over the area and winds diminish late in the evening. We'll likely need another Freeze Watch for most non-coastal zones, and a Frost Advisory is possible for the remainder of the area.

AVIATION /06Z SUNDAY THROUGH THURSDAY/

The 06z TAF period begins with VFR conditions at KCHS, KJZI, and KSAV. The main forecast concern is for a period of showers, and possibly a thunderstorm, to move through the terminals this morning as a warm front lifts northward and inland. The general time period of concern begins around 12z and continues through about 16z. These showers could bring periods of light to moderate rain with MVFR conditions. Once this activity lifts to the north by midday or the early afternoon, the chance of showers and storms is lower in the afternoon. Winds will remain east until the boundary passes, then becoming southerly and a little breezy for the afternoon.

Extended Aviation Outlook: Periods of flight restrictions are possible with showers and thunderstorms Sunday night and then especially on Monday as a strong cold front moves through. Very gusty winds are expected outside of any shower and thunderstorm activity at all terminals Monday.

MARINE

Gusty southerly winds will develop late tonight and continue into Monday ahead of a strong cold front. An abrupt wind shift will occur early Monday evening as the front sweeps through. Solid Small Craft Advisory conditions expected for all waters late tonight through Tuesday morning. We cannot completely rule out a period of Gale force gusts in the Charleston County nearshore waters Monday afternoon immediately ahead of the cold front, but confidence was too low to issue a Gale Watch.

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 Watch from late Monday night through Tuesday morning for GAZ087-088-099-100-114-115. SC...Freeze Watch from late Monday night through Tuesday morning for SCZ040-042. MARINE...Small Craft Advisory from 8 AM Monday to midnight EDT Monday night for AMZ330. Small Craft Advisory from midnight tonight to noon EDT Tuesday for AMZ350-352-354-374.