FXUS62 KCHS 021120 AFDCHS
Area Forecast Discussion National Weather Service Charleston SC 620 AM EST Mon Mar 2 2026
.WHAT HAS CHANGED...
The Dense Fog Advisory along the GA coastal counties and the adjacent nearshore waters has been canceled as observations indicate that fog is very patchy. The Aviation Section was updated for the 12Z TAF issuance.
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.KEY MESSAGES...
- 1) A Cold Air Damming regime will set up over the SC
Lowcountry and Southeastern GA today, leading to a low confidence high temperature forecast today.
- 2) Unseasonably warm temperatures are expected this week with
increasing rain chances late week into the weekend.
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.DISCUSSION...
KEY MESSAGE 1: A Cold Air Damming regime will set up over the SC Lowcountry and Southeastern GA today, leading to a low confidence high temperature forecast today.
This morning a dry cold front is forecast to push through the region. Behind the cold front high pressure will build into the region from the northeast. The high pressure will be centered over the Mid- Atlantic, building into the southeastern states along the eastern side of the Appalachian Mountains. Guidance tends to not handle CAD events well, typically eroding the wedge too early. High temperatures today are a blend of the NBM and the NAM. While the temperature forecast today remains a low confidence forecast, there will likely be a tight gradient of temperatures across the region. Areas in the northeastern portion of the forecast area (Berkeley Co and northern Charleston Co) could struggle to reach 60, while along the Altamaha River in GA temperatures could reach into the mid 70s.
KEY MESSAGE 2: Unseasonably warm temperatures are expected this week with increasing rain chances late week into the weekend.
On Tuesday, the wedge of high pressure/CAD setup will gradually erode and shift offshore as a 586 dm ridge builds over the Florida Peninsula. This will establish a deep-layered high pressure pattern centered offshore around midweek, persisting through the weekend. The pattern will promote a drastic warming trend and unseasonably warm conditions. Despite a small spread in maximum temperature guidance, confidence remains high that, aside from Tuesday, highs each day will reach the upper 70s to lower and middle 80s away from the cooler coastline, around 10 degrees above early March normals. Overnight lows will also trend milder, gradually rising into the upper 50s to lower 60s. There is potential for overnight temperatures to approach within a couple of degrees of record high minimum values this weekend. See the Climate section below.
Additionally, moisture will increase late week as ensemble guidance indicates precipitable water values rising to around 1.1 to 1.2 inches, near the 85th percentile for early March. While large scale forcing appears weak, the presence of deeper moisture and modest instability should support isolated to scattered showers from late week into the weekend, primarily during the afternoon and evening hours. Thunder chances remain low, though an isolated storm cannot be ruled out. Flooding risk appears minimal at this time, with probabilities of more than a quarter inch of rainfall in any 24-hour period through Saturday night generally at or below 20% per NBM.
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.AVIATION /12Z MONDAY THROUGH FRIDAY/...
A backdoor cold front will push southward through the forecast area this morning with high pressure building in behind it. Low cigs are being observed on the backside of the front and are expected to impact KCHS/KJZI by mid morning, with IFR cigs likely and LIFR cigs possible. Cigs at KSAV will most likely be MVFR to IFR. Restrictive cigs will linger into the afternoon when all terminals are forecast to go VFR. Another round of fog/low cigs is expected tonight, however given timing and intensity uncertainty the 12Z TAFs only feature MVFR cigs.
Extended Aviation Outlook: Restrictive ceilings are possible overnight into the early morning hours each night through late week due to low stratus/fog.
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.MARINE...
A backdoor cold front is progged to push through the region mid-morning and will end the threat for sea fog as winds out of the NE increase as high pressure builds in behind the front. Small Craft Advisories are in effect for all waters outside of the Charleston Harbor for wind gusts of 25 knots.
Surface flow will shift out of the east by midweek then out of the southeast by late week on the backside of high pressure, with speeds and seas staying well below Small Craft Advisory levels. We will need to monitor the potential for sea fog given the warm, moist air that is expected to move over the cooler shelf waters.
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.CLIMATE...
Record High Minimum Temperatures:
March 7: KCHS: 63/1992
March 8: KCHS: 63/2022 KSAV: 65/1880
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.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None. SC...None. MARINE...Small Craft Advisory until 7 AM EST Tuesday for AMZ350.
Small Craft Advisory until 1 AM EST Tuesday for AMZ352. Small Craft Advisory from 10 AM this morning to 7 PM EST this evening for AMZ354. Small Craft Advisory from 10 AM this morning to 7 AM EST Tuesday for AMZ374.
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BRS/CPM