FXUS62 KCHS 230623 AFDCHS
Area Forecast Discussion National Weather Service Charleston SC 123 AM EST Fri Jan 23 2026
.WHAT HAS CHANGED...
The aviation section has been updated for the 06Z Friday TAF issuance. Key message 1 includes timing and minor changes in regards to freezing rain potential inland. Key message 2 includes increased potential for colder wind chill temperatures Tuesday night into Wednesday morning.
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.KEY MESSAGES...
- 1) Widespread precipitation is expected Saturday through
Sunday night, with freezing rain possible Saturday night across inland portions of the SC Lowcountry.
- 2) Very cold temperatures will occur early next week, with
lows in the upper teens to lower 20s away from the coastline.
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.DISCUSSION...
KEY MESSAGE 1: Widespread precipitation is expected Saturday through Sunday night, with freezing rain possible Saturday night across inland portions of the SC Lowcountry.
A closed upper low off the SW California coast this morning will move east toward southern TX through Saturday night while a northern stream shortwave drops into the Upper Midwest. An unseasonably strong Arctic airmass will overspread the eastern half of the CONUS through Saturday. The interaction between the cold airmass and the strong upper level dynamics is expected to produce a large-scale winter storm over parts of the country.
As the Arctic high shifts east toward New England on Saturday, it will ooze down the lee side of the Appalachians, creating a typical cold air damming regime. The cold air wedge will become further entrenched Saturday night over inland portions of the Carolinas as a surface low develops off the SC coast. Furthermore, extensive light to moderate precipitation falling into the boundary layer will reduce temperatures due to evaporational cooling. The big question mark is if and/or where temperatures are able to drop to or below freezing. Guidance has been surprisingly consistent over the last 48 hours that the most likely area for this to occur would be along and north of a line from Millen, GA to Allendale-Walterboro-Summerville-Moncks Corner, SC. Mid-Saturday evening through daybreak Sunday stands the greatest chance of sub-freezing temperatures in these areas. Model soundings continue to show a very strong warm nose centered around 900 mb, with the sub-freezing temperatures only occurring in a shallow surface layer. This is a solidly freezing rain pattern since any snow or sleet would easily melt when passing through the robust warm layer aloft.
Fortunately, the quantitative precipitation forecast (QPF) Saturday evening is quite low, and we're forecasting less than a tenth of an inch of ice accumulation in the inland SC areas. It's worth noting that small errors in the temperature forecast or QPF could have a significant impact on location and impact of any freezing rain.
On Sunday, a pattern shift is expected, though the timing of that shift is somewhat uncertain. A secondary surface low associated with the southern stream shortwave (formerly the upper low off the CA coast) will move across the northern Gulf and then up the spine of the Appalachians late Sunday. A warm front will lift north through the area at some point on Sunday. Our northwest tier will probably remain cold-sectored most of the day, while southeast GA sees temperatures rise into the upper 60s to lower 70s. Another point of uncertainty is how quickly our far inland SC areas rise above freezing Sunday morning. It's not out of the question that temps could remain at or slightly below freezing through much of the morning, in which case another 0.05" of ice accumulation could occur. At the moment we are showing temps just above freezing by 9am Sunday.
A strong cold front will approach Sunday evening, by which point all areas should be in the warm sector. A fairly robust band of precipitation will accompany the front, with areal average QPF around 0.5". There could be enough elevated instability to support isolated thunderstorms Sunday evening. Colder air will filter in behind the front, but the precip should be off the coast by daybreak Monday and thermal profiles only support rain.
KEY MESSAGE 2: Very cold temperatures will occur early next week, with lows in the upper teens to lower 20s away from the coastline.
Strong high pressure building in wake of a departing cold front will usher arctic air into the region Monday night into Tuesday morning, which should then linger into early Wednesday prior to the airmass modifying/warming under a more zonal flow type pattern well in advance of another front approaching during the later half of the week. As a result, low temps are forecast to dip into the teens west of I-95 and across much of the Francis Marion Forest while low to mid 20s are anticipated along the coast Tuesday morning. These temps in combination with a north/northeast wind generally in the 5-10 mph range should result in widespread wind chill values in the mid-upper teens. A Cold Weather Advisory should eventually be needed for the entire area across Southeast South Carolina and Southeast Georgia.
Latest guidance has trended slightly cooler heading into early Wednesday, sufficiently to produce another round of cold sfc temps with light westerly winds supportive of wind chill values dipping into the upper teens/lower 20s, lowest inland from coastal counties. A Cold Weather Advisory could eventually be needed for areas inland Tuesday night into early Wednesday.
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.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
VFR conditions will prevail at CHS/JZI/SAV terminals through 06Z Friday.
Extended Aviation Forecast: Periods of MVFR and/or IFR conditions are likely at all terminals this weekend as a storm system impacts the area. There is a low-end threat for freezing rain late Saturday night into Sunday, mainly at the CHS terminal, but trends suggest this activity to stay inland. VFR conditions should prevail at all terminals once a cold front shifts offshore early Monday.
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.MARINE...
Today and Tonight: Weak high pressure will prevail for much of the day, favoring marine conditions well below Small Craft Advisory level thresholds. A cold front is then expected to shift across the local area starting early tonight, with cold air advection and a strengthening pressure gradient supportive of deteriorating marine conditions across all waters. Small Craft Advisories will follow the trend, starting across northern South Carolina at midnight tonight, then remaining coastal waters late night (except in the Charleston Harbor).
Friday night through Tuesday: A strong cold front will move across the waters Friday night and bring a period of hazardous marine conditions. Northeast winds will begin to surge Friday night and continue through Saturday. Sustained winds are forecast to increase into the 20-25 kt range with frequent gusts into the 25-30 kt range. There also remains a window of time later in the day on Saturday when gale force gusts could occur, primarily in the Charleston County waters. Winds will likely then diminish Saturday night into Sunday as an area of low pressure moves away from the region. However, conditions are expected to ramp back up Sunday night through Monday as the main cold front passes through from the west with gusts up to 30 knots occurring again into Monday night. Conditions should then improve Tuesday as high pressure returns and the gradient relaxes.
Saturday through Wednesday: Strong cold air advection and an enhanced pressure gradient across local waters continues to support deteriorating conditions across all local waters Saturday as low pressure attempts to develop/strengthen near a cold front offshore while some element of wedging attempts to spread across the region to the north/northwest. Guidance continues to indicate solid Small Craft Advisory conditions across all nearshore and outer waters Saturday and Sunday with a potential of low-end gale force gusts across northern South Carolina waters Saturday afternoon and night. Small Craft Advisories should eventually be needed at some point for the Charleston Harbor as well Saturday/Saturday night. Northeast winds gusting up to 25-30 kt appear common across most waters while seas build upwards to 7-10 ft (largest away from the coast). High seas should linger across most waters into Monday, while another burst of cold air advection takes place near/post cold fropa. Small Craft Advisories will remain in place for most if not all coastal waters into Monday night as a result, with again another low-end chance for gale force wind gusts to occur across outer Georgia waters and northern South Carolina waters during the peak of the event.
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.EQUIPMENT...
The KCLX radar will remain out of service until at least Saturday. Critical parts are on order. Users should use adjacent WSR-88D sites, including KCAE, KLTX, KJAX, KVAX and KJGX.
The Beaufort/Green Pond NOAA Weather Radio transmitter (WXJ-23) is operating at low power with diminished service. Repairs are scheduled to be made today to restore full service.
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.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None. SC...None. MARINE...Small Craft Advisory from midnight tonight to 10 AM EST
Tuesday for AMZ350. Small Craft Advisory from 3 AM Saturday to 10 AM EST Tuesday for AMZ352-354. Small Craft Advisory from 3 AM Saturday to 1 PM EST Tuesday for AMZ374.
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DPB/JRL