FXUS62 KCHS 181310 AFDCHS
Area Forecast Discussion National Weather Service Charleston SC 810 AM EST Sun Jan 18 2026
.WHAT HAS CHANGED...
An update has been issued to better reflect short term trends. KCLX CC products show precip is poised to change over to either a rain/snow mix or all snow across far interior areas. The change over line is approaching Tattnall-Jenkins Counties, at least aloft. Small Craft Advisory has also been extended into the South Carlina nearshore waters.
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.KEY MESSAGES...
- 1) Risk for a rain/snow mix with minor accumulations possible
across far inland areas late morning into early afternoon as a coastal low develops over the Atlantic.
- 2) Cold temperatures in the low to mid 20s (upper 20s to
lower 30s along the coast) possible Monday, Tuesday, and Wednesday morning.
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.DISCUSSION...
KEY MESSAGE 1: Risk for a rain/snow mix with minor accumulations possible across far inland areas late morning into early afternoon as a coastal low develops over the Atlantic.
A high-amplitude trough is expected to pivot across the East CONUS today, forcing a strong cold front offshore early this morning, which then becomes a focal point of cyclogenesis off the Southeast and Mid-Atlantic Coast during the day. Strong mid-upper lvl forcing associated with h5 vort energy and favorable divergence in the right- rear quadrant of an h25 jet streak along with ample low-mid lvl moisture advecting across the local area within a southwest flow will set the stage for precipitation across the region this morning into early afternoon, before activity departs offshore as dry high pressure builds across the region from the west. The main issue continues to focus on the possibility of a rain-snow mix across the far interior as strong cold air advection commences post fropa and moisture lingers, with freezing temperatures off the surface becoming somewhat favorable for snow during a few hour period late morning into early afternoon.
The main question continues to focus on the low-lvl thermal profile and ability to maintain snow prior to reaching the sfc and accumulation once setting on warmer grounds. Latest model soundings indicate near sfc temps remaining above the freezing mark under widespread clouds through the entire event, even across far inland areas where snowfall accumulation is possible. Some guidance has come in a bit warmer in regards to the sounding profile off the sfc initially, suggesting a delay to a rain-snow mix and therefore a shorter window of snowfall accumulation mid-late morning into early afternoon prior to moisture becoming quickly removed to the east and offshore. Profiles continue to suggest it will take ample moisture in the dendritic growth zone for the snow to accumulate across far inland zones well west of the I-95 corridor, mainly along a stretch from Allendale County, SC to Tattnall County, GA, but given the shorter window for accumulation and warmer grounds likely melting a good portion of any snow reaching the sfc, a dusting to perhaps as much as 1/2 inch snowfall is possible across the noted area by early afternoon. An all rain event is favored for all areas along and east of the I-95 corridor.
Winter weather impacts from this system remain on the low side as most snowfall accumulation is likely confined to grassy areas and other elevated surfaces such as roof tops. Isolated slick spots could occur on bridges and overpasses, but significant travel impacts are not expected at this time given temperatures will largely remain above freezing.
KEY MESSAGE 2: Cold temperatures in the low to mid 20s (upper 20s to lower 30s along the coast) possible Monday, Tuesday, and Wednesday morning.
CAA begins to infiltrate the region Sunday night in the wake of a departing sfc low and shortwave aloft, resulting in notably cooler temperatures to start the week. Currently have morning lows in the mid 20s inland to low 30s along the coast. While westerly winds look to remain relatively light during the early morning hours, think clear skies and efficient radiational cooling could result in wind chills dropping into the upper teens to lower 20s. In terms of probabilities, latest ensemble guidance suggest around a 30-40% chance of seeing wind chills less than 20 degF (Cold Weather Advisory levels) in areas west of I-95. Given that these probabilities continue to waiver, have opted to forgo any headlines for the time being, allowing the coming shifts to monitor trends and refine values as needed.
Expect similar conditions to prevail Tuesday and Wednesday morning in the wake of a strong cold front and budding sfc high pressure. Again, with winds remaining relatively weak, expect dropping winds chills to mainly be a factor of efficient radiational cooling. Ensemble guidance continues to only suggest around a 20-40% chance of reaching Cold Weather Advisory levels, keeping overall confidence rather low. Nonetheless, whether we hit headline criteria or not, still want to encourage folks to take necessary precautions for these cold temperatures. This can include dressing in warm layers, limiting time outside, and insulating/exposing pipes to heated air.
Otherwise, expect afternoon highs to remain seasonally cool, as temperatures only rise into the upper 40s to 50s.
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.AVIATION /13Z SUNDAY THROUGH THURSDAY/...
TEMPO MVFR conditions are possible in 12-14Z Sunday timeframe at CHS/JZI and 12-13Z Sunday timeframe at SAV. IFR conditions then prevail at all terminals, starting around 13Z Sunday at SAV and around 14Z Sunday at CHS/JZI, likely persisting until 20-21Z Sunday afternoon. Gusty northwest winds up to 15-20 kt should help improve conditions to MVFR at all terminals for a few hours late afternoon. Drier air then enters with high pressure building from the west, leading to VFR conditions returning at all terminals around 00Z Monday. VFR conditions then persist through 12Z Monday.
Extended Aviation Forecast: Any flight restrictions look to end Sunday afternoon, allowing VFR conditions to return for the remainder of the extended forecast.
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.MARINE...
Per recent buoy and short term model trends, the Small Craft Advisory has been extended into the South Carolina nearshore waters.
Today and Tonight: Strong cold air advection associated with high pressure building across the region in wake of a front departing well offshore will favor gusty northwest winds upwards to 25-30 kt and seas as large as 3-6 ft across Georgia waters today into the evening. Small Craft Advisories remain in effect across Georgia waters as a result, but conditions will begin to improve late day as the pressure gradient weakens with high pressure continuing to build across the region. As a result, the Small Craft Advisory across nearshore waters likely ends mid-late afternoon today, followed by outer Georgia waters shortly after midnight tonight.
Monday Onward: High pressure gradually builds across our area heading into the new week, keeping conditions quiet across our waters. Northwesterly winds may become a tad breezy on Tuesday though, with gusts up to 20 kts possible through the afternoon. Otherwise, expect wave heights to trend upwards on Wednesday as swells move in from the Atlantic.
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.CLIMATE...
Snowfall Records for January 18: KCHS: 0.4/1977 KSAV: 1.0/1893
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.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None. SC...None. MARINE...Small Craft Advisory until 8 PM EST this evening for AMZ350-
352-354. Small Craft Advisory until 1 AM EST Monday for AMZ374.
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