textproduct: Charleston

WHAT HAS CHANGED

Key Messages 1 and 2 have been updated to reflect severe weather potential and cold weather early next week. The Aviation Section has been updated to reflect the 0Z TAF issuance. The Marine Section has been updated to reflect latest trends for Small Craft Advisories this afternoon and the potential for additional marine hazards next week.

KEY MESSAGES

- 1) A strong cold front will bring rain, gusty winds, and the possibility of severe thunderstorms on Monday.

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

DISCUSSION

KEY MESSAGE 1: A strong cold front will bring rain, gusty winds, and the possibility of severe thunderstorms on Monday.

Just east of the Rockies a deep upper level trough will develop and push eastward Sunday into Monday, ejecting off the East Coast Wednesday. At the surface a strong low pressure system will develop associated with the upper level trough and impact the region Sunday into Monday. Sunday evening a warm front will lift north through the region, yielding very mild overnight temperatures in the low to mid 60s. Additionally the warm front could bring some showers and possibly thunderstorms to the region Sunday afternoon. On Monday a cold front will push through the region, accompanied by a line of showers and thunderstorms. Models are fairly consistent in the timing of the line, generally in the afternoon. With the region positioned in the warm sector dew points are forecast to reach into the mid to upper 60s. Instability looks to be the limiting factor in the severe potential, with around 700-1000 J/kg forecast across the region. Shear looks impressive with 30-45 knots in the GFS/ECMWF for Monday. Strong to severe thunderstorms are possible, highlighted in the 15-30% severe weather outlook from the Storm Prediction Center. Given the favorable shear values and low level helicity values around 100 m2/s2 the main hazards will be damaging wind gusts and tornadoes.

Moisture will not be an issue for rainfall on Monday, with PWAT values forecast to push upwards of 1.4", which would be above the 90% value according to SPC climatology. Generally around 0.5-1" is expected across the region between Sunday and Monday's precipitation. The NBM shows ~35% probability of exceeding 1" generally across the SC Lowcountry.

In addition to the rainfall and the severe threat, breezy conditions are expected across the region outside of any showers/thunderstorms. The NBM shows probabilities of 30 mph wind gusts upwards of 60 to 70% across the SC Lowcountry and southeastern GA on Monday. A Lake Wind Advisory may be required for Lake Moultrie and a Wind Advisory cannot be ruled out for portions of the forecast area.

KEY MESSAGE 2: Frost/freeze is possible Monday night and Tuesday night.

In the wake of the cold front mentioned in Key Message 1, drastically cooler temperatures will be advected into the region. Monday night and Tuesday night could see freezing temperatures, generally west of I-95. Winds will remain elevated Monday night, negating the threat of frost formation. However, with calm and clear conditions Tuesday night could yield frost formation across the coastal counties, where temperatures will dip into the mid to upper 30s. A Freeze Warning/Frost Advisory may be required for portions, if not all, of the local forecast area.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

0z TAFs: Winds should decrease to light and variable by 1Z across the terminals. As temperatures cool in the low 50s late tonight, ground fog or patchy fog is possible. Based on recent runs of the HRRR, sfc condensation pressure deficits will remain the lowest across KSAV. The KSAV TAF will feature a TEMPO from 9-12Z for MVFR fog. Any fog should dissipate during the first hour or two of daylight Saturday morning.

Extended Aviation Outlook: Brief flight restrictions are possible at in showers and thunderstorms Sunday through Monday evening at CHS/JZI/SAV terminals. Gusty winds are also expected on Monday at all terminals.

MARINE

This Afternoon and Tonight: High pressure will prevail across local waters under a zonal flow aloft, resulting in winds/seas that steadily improve throughout the day and overnight. In general, east- northeast winds will range between 10-15 kt this afternoon, then decrease to 5-10 kt or less late afternoon and tonight as a weak pressure gradient is placed directly across the region. Seas will should range between 3-4 ft across waters this afternoon, then continue to subside to 2-3 ft overnight. The exception is across outer Georgia waters, where seas briefly remain in the 4-6 ft range into mid-late afternoon, before subsiding to 4-5 ft late day into tonight. A Small Craft Advisory remains in place until 5 PM across outer Georgia waters due to lingering 6 ft seas.

Saturday through Wednesday: High pressure will prevail across local waters with a weak pressure gradient in place through Saturday, keeping wind/seas below Small Craft Advisory levels across local waters. A warm front should lift north across the area Sunday, setting up strong southerly winds across local waters Sunday night into Monday ahead of a cold front arriving Monday afternoon. Although a warm flow across cooler waters would suggest some limitation to low-lvl mixing, 1000mb geostrophic wind fields approaching 40-45 kt suggest a solid Small Craft Advisory level setup across all local waters for a bulk of the day Monday, along with the potential for gale force wind gusts across nearshore SC waters (including the CHS Harbor where low-lvl mixing could be enhanced due to land influences) and outer Georgia waters.

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...None. SC...None. MARINE...None.