textproduct: Charleston

WHAT HAS CHANGED

All Key Messages and sections were updated.

KEY MESSAGES

- 1) There is a risk or showers and thunderstorms today with sea fog possible along parts of the Charleston County coast this morning. Above normal temperatures persist.

- 2) Unseasonably warm temperatures continue through Wednesday.

- 3) Showers and thunderstorms likely Thursday as a cold front moves through.

DISCUSSION

KEY MESSAGE 1: There is a risk or showers and thunderstorms today with sea fog along parts of the Charleston County coast this morning. Above normal temperatures persist.

A large bank of sea fog off the Charleston County coast will buffet the barrier islands and immediate coastal areas through daybreak. The fog may meander into the upper parts of Charleston County over the next few hours, but widespread dense fog is not expected at this time. This can likely be handled with a Special Weather Statement given the expected limited impacted area, but trends will be monitored in case a Dense Fog Advisory is needed. The fog may expand southwest to off the Colleton and Beaufort County coasts with time.

Warm and moist conditions remain in place today with the region located along the western flanks of subtropical high pressure. Regional radar composites show a decaying mesoscale convective system (MCS) moving through western/central Georgia early this morning. This complex will continue to move east while gradually weakening as it approaches the local area. Some degree of measurable rainfall could make into parts of the Lowcountry and far interior Southeast Georgia prior to daybreak and slight chance to chance pops are being highlighted to reflect this possibility. In addition to some light rain a few rumbles of thunder could occur. A moist southerly flow will keep a risk for isolated to perhaps scattered showers/tstms going through the rest of the day. The best chances look to remain centered north of I-16 and especially from Colleton-Beaufort Counties north where guidance places the axis of highest 850 hPa theat-e values later this morning into the afternoon. Pops 20-30% were highlighted along with a continued mention of tstms. The risk for showers/tstms will quickly end this evening with the loss of insolation and the onset of boundary layer stabilization, particularly in the wake of the inland moving resultant sea breeze circulation.

The trend of well above normal temperatures continues. High today are poised to reach into the mid-upper 80s away from the coast. The record highs at both KCHS and KSAV look safe. A well-defined resultant sea breeze circulation will begin to develop along the beaches by early afternoon and translate inland as the mid- late afternoon progresses. This will keep beach locations quite a bit cooler with highs only expected to top out in the upper 60s/lower 70s. Typical for late winter, there will be very tight thermal gradient within ~5 miles of the coast. Warm conditions will persist overnight with lows only dropping into the lower 60s and the record high minimums could be challenged for KCHS, KCXM and KSAV.

KEY MESSAGE 2: Unseasonably warm temperatures continue through Wednesday.

Upper level ridging holds tight across the region Wednesday, resulting in yet another day of above normal temperatures. Currently have highs in the mid to upper 80s, with a few areas across interior Georgia taking a shot at 90 degrees, which could put a few records in jeopardy (more on this in the Climate section below). Similar to Tuesday, also have those along the coast staying in the upper 70s. Otherwise, look for lows to remain mild, as temperatures only fall into the lower 60s.

KEY MESSAGE 3: Showers and thunderstorms likely Thursday as a cold front moves through.

Upper level flow will shift on Thursday as a trough and surface cold front move east from the Tennessee River Valley toward the Atlantic. South to southwest flow ahead of the front will support increasing moisture across the region. Combined with unseasonably warm temperatures, this should provide enough instability for numerous showers and thunderstorms to develop ahead of the advancing front. Models show a line/broken line of convection pushing across the area in the late morning/afternoon period. The current time of FROPA (progged for Thursday evening) should keep instability somewhat limited, with SBCAPE values likely remaining below 1000 J/kg. Nonetheless, with decent shear in place (60-70 kt), can't rule out seeing a few isolated strong thunderstorms. Alternatively, if the front slows and delays rainfall into the evening hours, slightly greater instability could develop, increasing the potential for strong to marginally severe storms. Certainly something to keep an eye on in the coming days. Rainfall amounts of around one-half to one inch are expected. Flooding is not anticipated, especially as rainfall will be moving through relatively quick, though minor drainage issues could occur in urban or low-lying areas.

Otherwise, look for temperatures to drop noticeably in the wake of FROPA Thursday afternoon as CAA surges across the region, though the most significant cooling looks to occur Thursday night. Lows will fall into the upper 30s across interior southeast South Carolina and into the 40s elsewhere away from the beaches. A much cooler day is then expected Friday, with highs in the upper 60s to lower 70s. Temperatures then rebound into the 70s and 80s over the weekend.

AVIATION /06Z TUESDAY THROUGH SATURDAY/

10/06z TAF Discussion: KCHS/KSAV: VFR should prevail for both KCHS and KSAV for much of the 06z TAF period. Low stratus/sea fog from off the Atlantic may approach KCHS over the next few hours, but most should remain east of the terminal. Isolated showers/tstms could impact KCHS just about any time through the afternoon. Confidence in a particular temporal window or direct impacts is too low to justify any mention of showers/tstms at this time.

KJZI: Satellite shows an area of low stratus and possible sea fog lurking near the terminal early this morning. Expect IFR conditions to expand into the terminal soon, but there is a possibility the sea fog/stratus will remain just east of the terminal. Opted for TEMPO IFR conditions below alternate minimums 09-12z for now, but amendments will most certainly be needed as trends become more apparent. VFR should return by 14z and persist for the remainder of the 06z TAF period. Isolated showers/tstms could impact the terminal just about any time through the afternoon. Confidence in a particular temporal window or direct impacts is too low to justify any mention of showers/tstms at this time.

Extended Aviation Outlook: Flight restrictions due to low stratus/fog remain possible through mid-week. Otherwise, look for a cold front to bring additional flight restrictions and breezy winds on Thursday.

MARINE

Through Tonight: There remains a risk for sea fog this morning, particularly over the South Carolina nearshore waters. Satellite shows a large area of dense sea fog and/or stratus just off the Charleston County coast. The fog looks pretty thick based on webcams at Folly Beach, so a Marine Dense Fog Advisory has been posted until 9 AM for the South Santee-Edisto Beach nearshore leg. Otherwise, southwest winds will back to the south this afternoon with the formation of the resultant sea breeze circulation. Speeds should generally remain less than 10 kt, but may be closer to 10-15 kt in the Charleston Harbor and along the land-sea interface within the circulation itself. Winds will veer to the southwest overnight with speeds 10-15 kt. Looks like winds will be too strong for sea fog formation. Seas will average 2-2 ft nearshore waters and 3-4 ft over the Georgia offshore waters today and tonight.

Wednesday through Sunday: High pressure will be the dominant weather feature across the local waters through the middle of this week. This will result in S/SW winds 5 to 10 kt and seas 2 to 4 ft. A cold front will approach from the west late Wednesday, causing winds and seas to increase. At the least, Small Craft Advisories will be likely for most marine zones where we anticipate gusts to reach 25- 30 kt and seas 4-7 ft as early as Wednesday night. The cold front should cross through our waters Thursday, causing winds to veer out of the northeast in its wake. Gusts to gale force are possible across portions of our waters Thursday night and a brief Gale Watch/Warning could be needed. High pressure building into the region will lead to improving conditions into the weekend.

CLIMATE

Record High Temperatures:

March 11: KCHS: 85/2015 KSAV: 87/2015

Record High Minimum Temperatures:

March 10: KSAV: 63/1909

March 11: KCHS: 63/2015 KCXM: 64/2016 KSAV: 64/1974

EQUIPMENT

The KCLX radar is scheduled for radome panel replacement March 14-16, 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...Dense Fog Advisory until 9 AM EDT this morning for AMZ350.