FXUS62 KCHS 291835 AFDCHS
Area Forecast Discussion National Weather Service Charleston SC 135 PM EST Mon Dec 29 2025
.SYNOPSIS...
A strong cold front will push away from the region this evening. High pressure will then prevail for the remainder of the week. Another cold front could affect the area this weekend.
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.NEAR TERM /THROUGH TONIGHT/...
A fine line of showers associated with the cold front will push east across the adjacent Atlantic waters this afternoon. Strong CAA should result in temperatures to gradually cool through the rest of this afternoon. In fact, temperatures may cool from mid-day highs by 5 to 8 degrees by 4 PM.
Gusty west-northwest winds should continue across the forecast area this evening (see Lake Wind section below). NAM12 indicates that H85 temperatures will cool from 10C at 21Z along a line from KSAV to KCHS to between 4-5C by 12Z Tuesday. Using a blend of guidance, low temperatures are forecast to range from the upper 20s inland to the low to mid 30s along the coast. The cold temperatures combined with steady NW winds around 10 mph will create chilly wind chills during the pre-dawn hours Tuesday morning. Min wind chills may reach 20 degrees briefly across portions of inland GA around daybreak, with values in the mid to upper 20s elsewhere. Given the brief period and spotty locations of wind chills around 20 degrees, no Cold Weather Advisory will be issued with this package.
Lake Winds: The marine-layer will quickly mix out after FROPA with soundings showing thermal profiles becoming increasing favorable for vigorous mixing with the onset of post-frontal CAA. Expect winds to reach 15-20 kt with gusts to 25 kt by mid-late afternoon then peaking 20-25 kt with gusts to 30 kt this evening as CAA maxes out. Winds will then quickly diminish after midnight as CAA begins to wane. A Lake Wind Advisory is in effect from 3 PM until 1 AM. Waves will build 2-3 ft with the highest winds and strongest wave action occurring over the central and southeast portions of the lake.
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.SHORT TERM /TUESDAY THROUGH THURSDAY/...
Quiet and notably cooler temperatures return Tuesday in the wake of FROPA, as CAA limits highs to the upper 40s to lower 50s. With the aid of clear skies and efficient radiational cooling, will see most locations inland drop into the mid to upper 20s Tuesday night, with areas along the coast hovering near freezing. As noted in the previous discussion, winds look to remain fairly light during this time, which should negate the need for any cold weather headlines.
Northwesterly flow, albeit weak, will persist on Wednesday. This coupled with ample sunshine should allow highs to moderate back into the mid 50s. Warming trend continues into Thursday as a weak front shifts winds a bit more westerly. Thus, look for highs in the upper 50s to lower 60s to become common.
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.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Should see largely dry conditions prevail Friday ahead of an advancing cold front. Rain chances then gradually return heading into Saturday as the aforementioned front encroaches upon the region. While a bit of model variability still exist concerning timing, most guidance generally agrees that Saturday morning and afternoon will be the best time frame for seeing showers. In terms of QPF, the GEFS ensemble only showcases a 25-45% chance of seeing accumulations greater than or equal to 0.25 in. Whereas the ENS/GEPS ensemble both suggest around a 50-75% chance. All guidance then shows a less than 45% chance of seeing greater than or equal to 0.50 inch. So, all this to say - will likely only see a few tenths of rain with system, which should keep any flooding concerns low. Outside of a few lingering showers along the coast Sunday morning, expect dry conditions to return to the region.
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.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Prior to the 18Z TAFs, a fine line of showers was located generally over the I-95 corridor, moving east around 25 kts. This band should bring a round of showers to the terminals around the onset of the 18Z TAFs. Until the passage of the showers, terminals should experience MVFR ceilings and gusty SW winds. In the wake of the line of showers and cold front, conditions should improve to VFR with gusty west-southwest winds. Gusty conditions will likely remain through this evening with strong H85 CAA. The rest of the TAF period should feature steady northwest winds and VFR.
Extended Aviation Outlook: VFR.
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.MARINE...
Tonight, the combination of a steep pressure gradient and CAA will support gusty conditions across all marine zones through late tonight. Wind gusts are forecast to peak between 25-30 kts, with some higher gusts possible with the pre-frontal showers. Seas are forecast to peak between 4 to 8 ft around midnight, then gradually subside. Small Craft Advisories will remain in effect until 1 AM, then will gradually taper down through Tuesday.
Blow Out Tides: Strong offshore winds could result in tides dropping to -0.6 to -0.8 ft MLLW at Fort Pulaski and Charleston Harbor at low tide this evening. Levels should remain above critical low water thresholds of -1.5 ft MLLW in the Charleston Harbor and -2.0 ft MLLW at Fort Pulaski. Mariners should still exercise caution as some structures that are typically underwater could become exposed and pose a risk to navigation.
Tuesday through Friday: Conditions continue to improve throughout the day as northwesterly winds weaken and seas calm, allowing for the small craft advisories to expire. Winds remain out of the northwest overnight and throughout most of Wednesday as surface high pressure builds across the southeast. Winds pickup overnight into Thursday as a front moves towards and then through the area, bringing the waters from Savannah to Altamaha Sound 20-60nm out to Small Craft Criteria as winds gusts near 25 knots for a few hours Thursday morning. Westerly winds remain gusty throughout the day, weakening overnight into Friday.
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.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None. SC...Lake Wind Advisory until 1 AM EST Tuesday for SCZ045. MARINE...Small Craft Advisory until 1 AM EST Tuesday for AMZ330.
Small Craft Advisory until 5 AM EST Tuesday for AMZ350-352-354. Small Craft Advisory until 1 PM EST Tuesday for AMZ374.
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NEAR TERM...NED SHORT TERM...SST LONG TERM...SST AVIATION...NED/SST MARINE...NED/SST