AFD_CHS

FXUS62 KCHS 251025 AFDCHS

Area Forecast Discussion National Weather Service Charleston SC 525 AM EST Tue Nov 25 2025

.SYNOPSIS...

High pressure will prevail through today, then a strong cold front will sweep through late Wednesday. High pressure will usher in colder weather Thursday through the weekend.

.NEAR TERM /THROUGH TONIGHT/...

High pressure centered offshore of the Mid-Atlantic coast will shift farther east into the Atlantic today as dampening shortwave energy ejects out of the Mid-Mississppi Valley and across the Ohio Valley. This shortwave will help drive a cold front east which is on target to propagate across the Deep South tonight, staying west of the local area. This will keep the entire area in the warm sector through daybreak Wednesday.

Marine surface observations suggest a weak coastal trough is beginning to sharpen offshore of the beaches. This feature will meander closer to the beaches this morning before washing out later in the day within the increasing southerly flow along the backside of the high to the north and the approaching cold front from the west. Guidance is similar in showing a region of enhanced isentropic ascent rooted along the 295-305K surfaces brushing the lower South Carolina beaches later this morning before exiting to the north and northeast by early afternoon. Isolated showers have already noted at times off the coast in the vicinity of the coastal trough, but will likely increase in coverage after daybreak as the corridor stronger isentropic forcing pushes through. Some of this activity will likely brush parts of the Charleston Tri-County, so mentionable pops of 20-30% consistent with the 25/01z NBM were highlighted roughly along/east of an Edisto Beach-North Charleston-Moncks Corner line (highest along the upper Charleston County coast) to account for this. These pops may end up being underdone with a number of high-resolution data sets and 25/00z HREF probabilities supporting pops closer to 40-50%; however, due to national policy constraints, no adjustments to reflect higher pops were made since no local decision support (DSS) services are being supported currently. The risk for measurable rainfall should end quickly by early afternoon as isentropic downglide spreads in from the south and southwest. Highs this afternoon will warm into the mid-upper 70s across the South Carolina Lowcountry, the upper 70s/lower 80s across Southeast Georgia with the upper 60s/lower 70s at the beaches.

A warm, southerly flow will persist into tonight as a cold front approaches from the west and a pronounced pre-frontal low-level jet intensifies across the Southeast States. This will keep the boundary layer fairly well mixed with lows only expected to drop into the 58-62 range inland with lower 60s at the beaches.

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...

Longwave troughing will dominate aloft as it shifts into the central and then eastern CONUS through the period. At the surface, a strong cold front will sweep through the local forecast area Wednesday night. The band of showers along and ahead of the front is expected to be in a weakening state as it pushes through the region. Therefore, rainfall totals will be meager, with most areas seeing little if any measurable rainfall. Far interior southeastern GA could see a few hundredths of rainfall. Temperatures on Wednesday will once again reach above November normals, topping out in the mid to upper 70s. The cold front will then usher in a cooler airmass, with overnight lows on Wednesday dipping into the upper 30s inland with 40s elsewhere.

High pressure will build into the region at the surface Thursday into Friday, while the longwave troughing aloft shifts to zonal flow. Quiet conditions are expected and a rainfree forecast has been maintained for both days. Temperatures will be noticeably cooler, with highs in the 60s Thursday and the 50s on Friday. Overnight lows will dip into the 30s across most locations Thursday night, with freezing temperatures likely across the far interior. However, the local frost/freeze program ended earlier this month with the widespread freeze, so no Freeze headlines will be issued.

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...

Zonal flow will dominate aloft through the weekend and into early next week, with high pressure prevailing at the surface. This pattern will yield a cool and dry forecast, with no rain chances and below normal temperatures forecast.

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...

25/12z TAF Discussion: KCHS/KJZI/KSAV: VFR through 26/12z. A cluster of showers could pass near KJZI by mid-morning and exiting to the north by early afternoon. Most of this activity should remain over the Atlantic, but could be close enough to pass through the 5-10 NM vicinity ring of the terminal. VCSH was highlighted 15-19z to account for this. Winds aloft will increase overnight as a pre- frontal low- level jet intensifies across the region. The situation looks too marginal for a mention of low-level wind shear (LLWS), but it could get close. The need for LLWS will be reevaluated with later TAF cycles.

Extended Aviation Outlook: Prevailing VFR.

.MARINE...

Through Tonight: Influences from a subtle coastal trough just offshore will wane later this morning as the increasingly southerly flow head of an approaching cold front washes the feature out. East to northeast winds will therefore veer to the south and southeast through the day with speeds less than 15 kt and seas 1-3 ft. Southerly winds will increase overnight in response to increasing low-level jetting ahead of the front. Speeds could reach as high as 15 kt across the nearshore waters and 15-20 kt over the Georgia offshore waters. Seas will average 2-3 ft nearshore and 3-4 ft offshore.

Wednesday through Friday: A cold front is forecast to push through the region Wednesday night. SW winds on Wednesday will surge to 15 to 20 knots with some gusts to 25 knots possible ahead of the approaching front. Post-FROPA will see shift to the NE as high pressure builds into the region, with winds around 15 knots with gusts to 20 knots. Small Craft Advisories may eventually be needed for portions of the marine waters. Seas are forecast to average 2 to 3 ft with some 4 ft seas in the 20 to 60 nm offshore GA waters.

.CHS WATCHES/WARNINGS/ADVISORIES...

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