AFD_CHS

FXUS62 KCHS 301843 AFDCHS

Area Forecast Discussion National Weather Service Charleston SC 143 PM EST Fri Jan 30 2026

.WHAT HAS CHANGED...

A Winter Storm Warning has been issued for all of the SC Lowcountry, in Georgia, Effingham, Bulloch, Candler, Jenkins, and Screven Counties from 7 AM Saturday to 1 PM Sunday. Winter Weather Advisory for areas along and south of Interstate 16 across southeast Georgia from noon Saturday to 7 AM Sunday. Extreme Cold Watch has been upgraded to a Warning from Saturday night/Sunday morning. Lake Wind Advisory from 7 PM Saturday to 9 AM Sunday.

.KEY MESSAGES...

- 1) A significant winter storm is expected to bring moderate to

heavy impacts across portions of the South Carolina Lowcountry and southeast Georgia Saturday morning into Sunday morning. Snow is forecast to be the primary precipitation type.

- 2) Extremely cold temperatures are expected across our entire

area this weekend into early next week. Historically cold wind chills are expected Saturday night into Sunday morning and an Extreme Cold Warning has been issued for the entire area.

.DISCUSSION...

KEY MESSAGE 1: A significant winter storm is expected to bring moderate to heavy impacts across portions of the South Carolina Lowcountry and southeast Georgia Saturday morning into Sunday morning. Snow is forecast to be the primary precipitation type.

A deepening and postively-tilted H5 trough will dig south across the Mid-West to the Southern Appalachians tonight. At the sfc, a broad area of low pressure will track across GA/FL this evening, with deepening low pressure over the Gulf Stream off the GA and Carolina coast tonight. Guidance indicates a notable trough will remain on the west side of the low, generally over GA south of a sfc ridge. NAM12 indicates that areas of 925-700mb frontogenesis developing over Charleston and Berkeley Counties by daybreak Saturday, then expanding across the interior counties through mid-day Saturday. Forecast soundings Saturday morning indicate a subtle warm nose at 975 mb, Bourgouin technique indicates that the warm/cold nose strength may yield freezing rain across the inland counties Saturday morning. It appears more likely with shallow moisture in place, likely with little to no ice nuclei present. The forecast will indicate some freezing rain or drizzle inland Saturday morning. Ice accumulations of trace to 0.05 inches will be indicated in the storm total ice across northern portions of Berkeley and Dorchester Counties.

By Saturday afternoon, the warm nose will cool below freezing and moisture will deepen into the dendritic growth temperatures. Deep forcing is expected to ramp up sharply Saturday afternoon into the overnight hours. GFS1deg H5 Q-vector convergence to over a 100 units, with the core of the 520DM tracking directly over the region Saturday evening. The combination of the passage of deep synoptic scale forcing and PW in excess of 0.7 inches will yield a developing area of snow across the forecast area. As the coastal low tracks to the northeast, CAA will increase across the SC Lowcountry and SE GA, resulting in temperatures to become steady or gradually cool from mid-morning through the afternoon. As conditions cool in the 20s during the afternoon, snow ratios will increase to at least 12:1 across the inland counties. As temperatures plummet into the low 20s in the evening, snow ratios should range around 20:1 and will remain through the rest of Saturday night. The high snow ratio with rather light QPF, generally 0.1 per 6 hrs, warning level snowfall is likely north of I-16. Snowfall rates are forecast to peak Saturday evening as the greatest forcing, moisture, and higher snow ratios overlap across the region. Snowfall should decrease from west to east around daybreak Sunday morning, as the center of the closed low swings over the Atlantic. It is interesting to note that the dry snow with gusts around 30 mph may lead to some drifting of blowing snow along the coast, possibly reducing visibilities at times.

A Winter Storm Warning has been issued for all of the SC Lowcountry, in Georgia, Effingham, Bulloch, Candler, Jenkins, and Screven Counties from 7 AM Saturday to 1 PM Sunday. Snowfall totals within the warning should range between 2 to 4 inches, with 3 to 5 inches across the CHS Tri-county. Areas to the south, generally south of I- 16, snowfall may range around one inch. This area will be highlighted with a Winter Weather Advisory from noon Saturday to 7 AM Sunday. This winter storm should make travel dangerous, if not impossible on bridges and overpasses, within the warned area.

Given full sun and above freezing temperatures on Sunday and Monday, some melting of the snow pack should occur. However, cold temperatures Sunday night and Monday night should refreeze melt water on untreated surfaces, creating black ice.

KEY MESSAGE 2: Extremely cold temperatures are expected across our entire area this weekend into early next week. Historically cold wind chills are expected Saturday night into Sunday morning and an Extreme Cold Warning has been issued for the entire area.

An impressive upper-lvl trough will amplify along the Eastern Seaboard as a coastal low develops offshore of the Carolina coastline. This will push a strong polar airmass across the region on Saturday and expect temps. to steadily decline through Sunday morning. Temperatures over the weekend are forecast to be well below normal and the ESAT NAEFS highlights this well with a standard deviation of -6.8 for minimum temperatures on Sunday morning. It's also fairly high model confidence as IQR shows a 1 to 2 degree spread for minimum temperature values Saturday night into Monday morning.

Expect high temperatures on Saturday to range in the mid to upper 30s in the morning, and then slowly drop through the afternoon and the overnight. Mixed the NBM/NBM25 into the overnight temperatures as the NBM appeared to be struggling to realize the strength of the polar air funneling into the region. Also, northwesterly winds will become quite blustery in the afternoon as the coastal low strengthens offshore and a Lake Wind Advisory has been issued for Lake Moultrie for 7PM Saturday through 9AM Sunday. This conditions combined with the polar air ushering into the region will yield temperatures in the upper-teens to low 20s with wind chill values in the single digits Saturday night into Sunday morning. Even taking a look at the 850mb temps. overnight, they dip below 0C across the entire region. Therefore, an Extreme Cold Warning has been issued for entire region from 7PM Saturday until 12PM Sunday. It'll slowly warm back up on Sunday morning as skies clear out and sunshine adds some warmth back to the surface. This will also help melt some of the snowfall on Sunday before temperatures drop down into the upper- teens and low 20s again overnight. 30.13Z NBM indicates a 60-80% chance of temperatures dropping below 20 degrees on Sunday night into Monday morning and therefore a Cold Weather Advisory might be warranted for this time period.

Luckily, temperatures should start to warm back up to near normal on Tuesday through the end of the week, and any remaining snowfall should melt.

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...

VFR conditions will prevail through the 18Z TAF period.

Extended Aviation Outlook: The probability of widespread flight restrictions will increase for Saturday and Saturday night as an area of low pressure develops off the coast. There is also increasing potential for snow and gusty winds at the terminals.

.MARINE...

Through tonight: Relatively quiet conditions through the evening across the local waters with northeasterly winds at 5 to 10 kt and seas ranging from 1 to 2 ft. After midnight, expect a coastal low to develop offshore ahead of a strong upper-lvl trough and conditions to rapidly deteriorate overnight.

Saturday through Tuesday: Hazardous marine conditions persist through the weekend as the coastal low strengthens and the strong upper-lvl trough shifts into the region. Expect northwesterly winds from 15 to 20 kt with gusts up to 25 kt on Saturday morning, increasing to 25 to 35 kt with gusts up to 40 kt out of the west- northwest by Saturday evening. Therefore, a Gale Warning has been issued for all the marine zones (including the Charleston Harbor) for Saturday afternoon into Sunday. Small Craft Advisories might be needed after the Gale Warning ends for portions of the marine zones. Also, an impressive northeasterly swell surges into the local waters Saturday evening with seas increasing to 4 to 7 ft in the nearshore waters and 8 to 10 ft in the outer Georgia waters overnight through Sunday afternoon. Thereafter, expect the swell to taper back as the coastal low shifts northeastward across the Atlantic waters. Marine conditions will improve slowly overnight on Sunday through Monday.

.CLIMATE...

Record Low Temperatures:

January 31: KCHS: 15/1966 KCXM: 19/1966 KSAV: 16/1966

February 1: KCHS: 21/1977 KCXM: 23/1900 KSAV: 23/1977

February 2: KCHS: 19/1980 KCXM: 17/1917 KSAV: 18/1917

Record Low Maximum Temperatures:

January 31: KCHS: 36/1948 KCXM: 34/1936 KSAV: 37/1909

February 1: KCHS: 38/1980 KCXM: 36/1900 KSAV: 38/1900

February 2: KCHS: 38/1980 KCXM: 38/1898 KSAV: 38/1951

Record Snowfall:

January 31: KCHS: 0.6/1977 KSAV: 1.3/1977

February 1: KCHS: no record established KSAV: no record established

.EQUIPMENT...

The KCLX radar remains out of service. We hope to have the radar restored by Saturday. Users should use adjacent WSR-88D sites, including KCAE, KLTX, KJAX, KVAX and KJGX.

.CHS WATCHES/WARNINGS/ADVISORIES...

GA...Winter Storm Warning from 7 AM Saturday to 1 PM EST Sunday for

GAZ087-088-099>101. Extreme Cold Warning from 7 PM Saturday to noon EST Sunday for GAZ087-088-099>101-114>119-137>141. Winter Weather Advisory from noon Saturday to 7 AM EST Sunday for GAZ114>119-137>141.

SC...Winter Storm Warning from 7 AM Saturday to 1 PM EST Sunday for

SCZ040-042>045-047>052. Extreme Cold Warning from 7 PM Saturday to noon EST Sunday for SCZ040-042>045-047>052. Lake Wind Advisory from 7 PM Saturday to 9 AM EST Sunday for SCZ045.

MARINE...Small Craft Advisory from 1 PM to 7 PM EST Saturday for AMZ330.

Gale Warning from 7 PM Saturday to 9 AM EST Sunday for AMZ330. Gale Warning from 1 PM Saturday to 1 PM EST Sunday for AMZ350- 352-354-374.

Dennis/NED