textproduct: Charleston

WHAT HAS CHANGED

All sections updated.

KEY MESSAGES

- 1) Isolated severe thunderstorms possible this afternoon.

- 2) Unsettled weather returns Friday night and lingers through early next week.

DISCUSSION

KEY MESSAGE 1: Isolated severe thunderstorms possible this afternoon.

A deep trough aloft over the eastern CONUS will slowly shift eastward through the remainder of today and by tomorrow morning will be pushing off the Eastern Seaboard. At the surface, a cold front will approach the local forecast area from the northwest this afternoon, pushing through the region this evening/early tonight. While the threat for severe thunderstorms is not completely gone, the threat is much lower than forecast earlier. Due to widespread thick cloud cover over the region, few areas have been able to see sunshine. Without the sunshine conditions will likely remain too stable for severe thunderstorms to develop. There are a few locations in southeast Georgia (south of I-16) which have a low end risk to see severe weather, with an isolated damaging wind gust the main threat. SPC Mesoanalysis shows that the region currently has <500 J/kg of surface based CAPE.

KCLX radar shows a line of showers and thunderstorms located along Jenkins/Screven/Allendale Counties. CAMs this morning are in decent agreement that this line will dissipate as it approaches I- 95, likely only being isolated showers by the time it arrives at the coastline. However, a strong to possibly severe gust will be possible across SE GA, especially in areas that have seen some sunshine today.

Later this evening/early tonight a thin line of showers is possible as the actual front pushes through the region.

KEY MESSAGE 2: Unsettled weather returns Friday night and lingers through early next week.

Dry high pressure will briefly rebuild on Friday, then the front will lift back north and stall south of the area Friday night into Saturday morning. In addition, a series of upper level shortwaves will ripple through the Southeast during this period and continue into Sunday. PWATs approaching 1.75-2.0" are expected to advect into the area Saturday through Sunday, providing ample moisture for shower development. Pockets of surface-based instability will support isolated thunderstorms, particularly during the afternoon hours across coastal Southeast GA. Total precipitation Friday night through Sunday expected to range from 0.75"-1.5", though a few locations could see amounts in excess of 1.5" if a strong shower or thunderstorms rolls through. Given the prolonged event to reach those rainfall totals, rainfall rates are not currently expected to result in a significant flooding threat.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

A cold front is approaching the local area this afternoon, expected to push through this evening. Ahead of the front a line of showers and thunderstorms is approaching Jenkins/Screven/Allendale Counties this afternoon as of 2 PM. This line is expected to weaken as it progresses eastward, however some impacts may still occur at KCHS/KJZI/KSAV. Have included a TEMPO group at all 3 TAF sites, with SHRA at KCHS/KJZI and TSRA at KSAV. Another line of weak showers is possible later this evening associated with the actual front, however impacts are expected to be minimal so no direct mention of additional precip has been included in the 18Z TAF. Some MVFR cigs are possible this afternoon at KCHS/KJZI behind the initial line of showers. Otherwise, prevailing VFR from this evening through the remainder of the 18Z TAF period. ions are then expected by late evening and are likely to persist through 12Z Friday.

Extended Aviation Outlook: Occasional flight restrictions Saturday through Monday as a stalled front brings showers and thunderstorms.

MARINE

Rest of Today and Tonight: A cold front will push through the region this evening, with winds this afternoon out of the southwest shifting to the northeast by daybreak. Gusts this afternoon within the Charleston Harbor will be up to 25 knots and a short duration Small Craft Advisory is in effect through 6 PM. Elsewhere, gusts will likely top out around 20 knots. Conditions will improve through the overnight period as high pressure builds into the region behind the departing cold front.

Friday - Monday: Surface high pressure builds across the southeast region bringing a round of breezy northeasterly winds, though they are expected to remain below Small Craft Advisory criteria. Winds will decrease in the afternoon bringing the brief return of weaker winds and calm seas through the weekend. As the surface high slides off into the Atlantic Monday into Tuesday, expect winds to swing around to become out of the south-southeast. Ahead of an approaching cold front, the pressure gradient along the coast does get pinched a bit on Monday and Tuesday, leading to some marginally breezy south- southeasterly winds. As the cold front continues to approach, Small Craft Advisories may be needed as wind speeds increase. NBM currently has 50-70% chances for reaching 25 knot gusts across the coastal and offshore South Carolina waters and offshore Georgia waters, dropping to below 40% across coastal Georgia waters.

Rip Currents: Enhanced winds along the lower South Carolina coast coupled with building 2-4 ft swell supports a Moderate Risk for rip currents along the Charleston County beaches for today.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for AMZ340.