FXUS62 KCHS 221738 AFDCHS
Area Forecast Discussion National Weather Service Charleston SC 1238 PM EST Thu Jan 22 2026
.WHAT HAS CHANGED...
The aviation section has been updated for the 18z TAF issuance.
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.KEY MESSAGES...
- 1) Widespread precipitation is expected this weekend,
bringing the potential for a winter weather event across portions of the region.
- 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 this weekend, bringing the potential for a winter weather event across portions of the region.
As this Baja low swiftly exits and moves across the southern half of the CONUS, a northern stream shortwave will dive into the Mid-west on Saturday ushering cold, arctic air along with it. At the surface, a remarkable high pressure will wedge itself across the region Sat. into Sat. night creating a strong cold- air damming (CAD) event to set-up. There has been a decent shift in the forecast over the last 36 hours as the track of the aforementioned low has shifted a tad to the north. Taking a look at the 22.00Z WPC Cluster Analysis (e.g., 50% of the GEFS contained in Cluster 1), it appears ensemble guidance has now become less dispersive over the last 36 hours. This reveals that this recent northerly, warm trend seems legitimate. Also, the aircraft recon data that was implemented in the 22.00Z data has certainly helped increase confidence in this forecast. This recent trend can be commended to the swift ejection of the Baja low as this the pattern downstream and allow for an impressive warm-air advection to push across the Southeast. The 22.12Z GFS still stays a bit to the south, however this seems to be the outlier out of all the models.
It's important to note that there is some concern that the models could be under-playing the CAD, and this is something that we will need to pay close attention to over the next couple days as colder temps. could result in higher chance of freezing rain over portions of the area. It's valuable to take a look at the NAM 22.12Z regarding this concern over the weekend, as this is a good example of model favoring a strong CAD set-up, and has temps. holding onto the mid 20s to low 30s on Sunday morning. However, a large portion of the guidance shows a much weaker CAD set-up and effectively puts the region in a warm- sector on Sunday, therefore we've been sticking with the weaker CAD solution for the moment.
Recent model soundings continue to indicate a prominent warm nose aloft this weekend, therefore the largest threat with this system remains to be freezing rain. In regards to timing, the period of greatest concern remains to be Sat. evening into Sun. morning, with the highest probabilities of accumulating ice along and west of a line from Moncks Corner to Walterboro to Hampton and Millen. Latest NBM probabilities indicate a 20-40% of freezing rain >0.01", with a near zero percent chance for >0.25". Elsewhere, probabilities of freezing remain to extremely low, and impacts remain negligible at this time. To match up with this thinking, the probabilistic Winter Storm Severity Index (WSSI-P) shows a 5-10% chance across the northern tier counties for this weekend.
A rather impressive temp. gradient is apparent on Sunday with mid 60s to low 70s across southeast GA and upper 50s to low 60s across southeast SC. Hence, it's not out of the question to see a couple thunderstorms develop in the afternoon/evening on Sunday. Nevertheless, precipitation should come to an end on Sunday night into early Monday as the cold front passes through the region. It's important to note that there might be an overlap with precip. and colder temps. on Sunday, resulting in some lingering p-type concerns into the evening.
There is still some uncertainty with this system and it's important to remember to exercise caution here as the forecast can change, and will likely change over the next couple days.
KEY MESSAGE 2: Very cold temperatures will occur early next week, with lows in the upper teens to lower 20s away from the coastline.
As a strong arctic high pressure ushers cold, dry air into the region on Monday night, low temp. are forecast to drop 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 Monday night/Tuesday morning. There conditions combined with a light north- northeasterly wind could result in widespread wind chills in the mid to upper teens. Therefore, a Cold Weather Advisory appears likely as probability for temps. < 20 range from 50-75%.
Forecast has is a bit warmer on Tuesday night/Wednesday morning as temps range in the low to mid 20s across the interior counties with low 30s along the coastline. Thus, confidence with needing a Cold Weather Advisory seem less likely for this time period with probabilities for temps. < 20 range from 20-40%.
It's important to note that model confidence continues to be fairly high as the IQR shows a 2 to 3 degree spread for lows Tuesday and Wednesday morning. However, in regard to the system this weekend, it's possible the cold air could stick around into mid-week and yield colder temperatures.
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.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
VFR conditions are expected to prevail at KCHS, KJZI, and KSAV through 18z Friday.
Extended Aviation Forecast: MVFR or IFR conditions will be possible at all terminals this weekend as a storm system impacts the area. The threat for freezing/frozen precipitation continues to diminish and should remain north of the KCHS and KJZI terminals.
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.MARINE...
Tonight through Friday: Quiet conditions are expected to prevail across the local waters through Friday. Winds will turn more northeasterly with time and increase to around 10 kt or up to 10-15 kt by late Friday. Seas should average 2-4 feet through the period.
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.
In summary, Small Craft Advisories have been initiated for all waters for both winds and seas starting around or just after midnight Saturday and continuing into Tuesday morning. A Small Craft Advisory could eventually be needed for Charleston Harbor as well. There remains a low chance that a Gale Watch could be needed for the Charleston County waters on Saturday.
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.EQUIPMENT...
The Beaufort/Green Pond NOAA Weather Radio transmitter (WXJ-23) is operating at low power with diminished service. Repairs are scheduled to be made Friday to restore full service.
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.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None. SC...None. MARINE...Small Craft Advisory from midnight Friday night 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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BSH/Dennis