AFD_CHS

FXUS62 KCHS 010121 AFDCHS

Area Forecast Discussion National Weather Service Charleston SC 821 PM EST Sat Jan 31 2026

.WHAT HAS CHANGED...

The aviation section was updated for the 00Z TAFs. Updated ongoing trends for key message 1. No changes to current winter, cold, and wind headlines.

.KEY MESSAGES...

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

major impacts across portions of the South Carolina Lowcountry and Southeast Georgia through Sunday morning. Winter Storm Warnings and Winter Weather Advisories are in effect.

- 2) Extremely cold temperatures are expected this weekend into

early next week. Historically cold wind chills are expected tonight into Sunday morning, thus, an Extreme Cold Warning remains valid for our entire area.

.DISCUSSION...

KEY MESSAGE 1: A significant winter storm is expected to bring moderate to major impacts across portions of the South Carolina Lowcountry and Southeast Georgia through Sunday morning. Winter Storm Warnings and Winter Weather Advisories are in effect.

Recent satellite water vapor products indicated a deep closed low over the Southeast, helping produce light to moderate snow locally along the southwestern edge of low pressure departing to the northeast across the Mid-Atlantic. Thermal profiles continue to display temps well below freezing with some moisture in the dendritic growth zone, favoring bands of moderate snowfall as currently depicted on radar imagery across southern portions of Southeast South Carolina, but the latest 00Z CHS sounding does depict drying in the low-lvls, which coincides to lighter snowfall amounts across the Tri-County Area early this evening.

As temperatures plummet into the low 20s in the evening, snow ratios should range around 20:1 and will remain through the rest of tonight. Snowfall rates should be highest through evening hours as the greatest forcing, moisture, and higher snow ratios overlap parts of the region. Guidance has indicated that the CHS Tri-County Area remains under the deformation zone through much of tonight. As a result, snowfall total amounts remain unchanged for the time being, but radar trends are suggesting amounts may need to be adjusted 1-2 inches lower across the Tri- County Area if additional snow banding does not develop just upstream of the area prior to midnight.

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 between 30 to 35 mph may lead to some drifting of blowing snow along the coast, possibly reducing visibilities at times. A Winter Storm Warning will remain in effect for all of the SC Lowcountry, in Georgia, Effingham, Bulloch, Candler, Jenkins, and Screven Counties until 1 PM Sunday. The area generally south of I-16 will remain under a Winter Weather Advisory until 7 AM Sunday. This winter storm should make travel dangerous, if not impossible on bridges and overpasses, within the warned area.

Given sunny conditions 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.

Lake Moultrie: Winds on Lake Moultrie will increase this evening. Speeds will reach 20-25 kt with gusts as high as 30-35 kt. Waves will peak 2-3 ft with local sets in excess of 4 ft. Lake Moultrie is a fresh water lake. As winds become gusty and sub- freezing temperatures (30 deg or lower) settle in, the risk for freezing spray will increase over the open lake waters and along the downwind side of the lakeshore, including Pinopolis and Short Stay. This could result in a glaze of ice on trees, piers and other structures, in addition to the expected snow.

KEY MESSAGE 2: Extremely cold temperatures are expected this weekend into early next week. Historically cold wind chills are expected tonight into Sunday morning, thus, an Extreme Cold Warning remains valid for our entire area.

Through Sunday: Bitterly cold air settles across the region tonight as breezy northwesterly winds persist into Sunday. Temperatures haven't deviated much from the last issuance, with lows ranging from the teens inland to around 20 degrees along the beaches. With a fresh snowpack in place, expect wind chill values to plummet into the lower single digits by Sunday morning, which is an extremely rare occurrence for areas this far south. Thus, an Extreme Cold Warning remains valid for our entire area. If you can't limit time outdoors, be sure to bundle up, and remember, if you're cold, your pets are too. Have a plan to keep them warm and dry.

Highs Sunday will be heavily influenced by a lingering snow pack, especially across the Charleston Tri-County. Highs will only peak in the lower-mid 30s in the Charleston Tri-County to the lower 40s near the Altamaha River. Despite full sun, some areas in the deepest snow pack may not get above freezing. Some further downward adjustments in the highs may be needed pending the final area/depth of the snow pack.

Sunday Night through Tuesday: Upper level troughing over the eastern CONUS gradually shifts offshore Monday into Tuesday, keeping us situated in the northwest flow aloft. So, similar to Saturday night, the combination of northwesterly winds, a fresh snowpack, and clear skies will result in overnight lows in the teens for much of the region. Areas along/near the coast will be a touch warmer though, with temperatures in the lower 20s. Fortunately, winds will be on the lighter side, which should limit wind chills from dipping into the single digits. Thus, a Cold Weather Advisory will likely be needed in the coming shifts.

Monday, there should be a noticeable spread in high temperatures, mostly due to a remaining snowpack over our SC counties. They'll range from around 40 degrees near the Santee River, to around 50 degrees near the Altamaha River. Monday night, very light southwest winds are expected. Skies will start out clear in the evening, but clouds will gradually increase from south to north overnight. This may limit some of the radiational cooling. Lows should range from the lower 20s inland to near freezing at/near the beaches. Since winds will be very light, it doesn't appear wind chills will drop to 20 degrees or lower, so we likely won't need any additional Cold Weather Advisories. Tuesday, temperatures moderate further with highs ranging from near 50 degrees near the Santee River to the lower 60s near the Altamaha River.

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...

00Z TAFs: Light to moderate snow will continue to impact CHS/JZI/SAV terminals this evening, producing periods of MVFR conditions during the next several hours. TEMPO vsbys in the 1/2 to 1 SM range are also possible between 00Z-02Z. Gusty north/northwest winds are expected at all terminals tonight and through morning hours Sunday (up to 20-25 kt), but cig/vsby conditions should improve late night as snow departs the area, eventually resulting in prevailing VFR conditions at all terminals by around daybreak Sunday. VFR conditions will then prevail for the remainder of the TAF period through 00Z Monday.

Extended Aviation Outlook: Extended Aviation Forecast: A cold front may bring flight restrictions Wednesday, mainly due to rain showers.

.MARINE...

Through Sunday: Gale force winds will be possible across all our waters into Sunday morning. While a Gale Warning is currently in effect for all zones, do want to note that storm-force winds may develop across the Georgia offshore waters and the outer portions of the South Santee-Edisto Beach nearshore leg. Thus, will continue to monitor trends to determine if an upgrade to Storm Warning is needed.

Sunday Night through Wednesday: Surface high pressure builds across the lower Mississippi Valley Sunday night, then shifts eastward - passing over Florida on Tuesday before drifting offshore Tuesday night into Wednesday. A cold front will then approach from the west in its wake. In terms of headlines, any remaining zones (most likely the outer GA waters) should come to an end by Monday evening. Conditions then look to remain below SCA levels through Wednesday, before seas and winds gradually deteriorate Wednesday evening.

.CLIMATE...

Record Low Temperatures:

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:

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 is operational, but could go down at any time. Additional repairs are needed.

.CHS WATCHES/WARNINGS/ADVISORIES...

GA...Winter Storm Warning until 1 PM EST Sunday for GAZ087-088-

099>101. Extreme Cold Warning until 1 PM EST Sunday for GAZ087-088- 099>101-114>119-137>141. Winter Weather Advisory until 7 AM EST Sunday for GAZ114>119- 137>141.

SC...Winter Storm Warning until 1 PM EST Sunday for SCZ040-042>045-

047>052. Extreme Cold Warning until 1 PM EST Sunday for SCZ040-042>045- 047>052. Lake Wind Advisory until 10 AM EST Sunday for SCZ045.

MARINE...Gale Warning until 7 AM EST Sunday for AMZ330.

Gale Warning until 10 AM EST Sunday for AMZ350-352-354. Gale Warning until 1 PM EST Sunday for AMZ374.

DPB/NED/ST