952 FXUS62 KCHS 252117 AFDCHSArea Forecast Discussion National Weather Service Charleston SC 517 PM EDT Thu Sep 25 2025
.SYNOPSIS... A weak front will approach the region late this week, likely stalling just offshore through the weekend. Tropical low pressure could approach the Southeast U.S. early next week.
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.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... A mid-level trough stretching from the Great Lakes region into the Lower Plains this evening will shift east, becoming located over the Northeast U.S. and stretching south into the Lower MS Valley. At the surface, a cold front will approach from the west. This setup will yield southwest flow, ushering moisture into our area. PWATs could hit 2" late tonight, which is above normal. The CAMs and the deterministic models have isolated to maybe scattered showers across our far inland counties this evening, with showers spreading eastwards and towards the coast overnight. Though, the coverage should decrease overnight, becoming more isolated. Either way, significant rainfall is not expected. It will be another mild night with lows only dipping into the low 70s for most of our area.
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.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... Sfc cold front edges closer to the region Friday, bringing with it increased chances showers and storms. That being said, should see largely dry conditions prevail throughout the morning hours, as highs warm into the mid to upper 80s.
While the overall severe threat is expected to remain low, want to point out the heavy rainfall could still become an issue as PWATs near 2 inches. As noted in the previous discussion, WPC`s latest Day 2 outlook has maintained a Marginal Risk (Level 1 of 4) of excessive rainfall for our entire area, with a Day 3 Marginal Outlook mainly highlighted across northern Berkeley County. Though some lulls in precipitation may occur overnight, expect showers and storms to continue through Saturday evening as the front stalls along the coast. In regard to accumulations, have totals ranging from 0.5 inch to 1.5 inch along and west of I-95 - with those near the Charleston Metro ranging between 0.25 inch to 0.75 inch. However, could easily see higher totals occur (localized pockets of 2 to 4 inches) if training storms develop and/or storm motion is slower than anticipated.
Otherwise, expect much of the same for Sunday in terms of showers and storms given the close proximity of the cold front and synoptic- scale lift in the vicinity, though uncertainty grows given 94L and TS Humberto in the western Atlantic.
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.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... The forecast becomes exponentially uncertain into early next week as a complicated set up begins to take shape over the southeastern CONUS and adjacent western Atlantic waters. What we do know is that TS Humberto has formed, and is expected to track west-northwest over the coming days, becoming a major hurricane by early next week. We don`t however, have great certainty on how 94L will evolve or interact with TS Humberto. NHC`s latest forecast now includes a 80% chance of formation over the next 48 hours, and a 90% chance of formation over the next 7 days. Thus, think there is enough agreement in place to suggest that at a minimum, 94L will evolve into a TS. Nonetheless, having two systems so close to one another complicates matters even more, especially concerning the overall track. While more observations (Hurricane Hunters and additional UA soundings at WFOs) are currently being ingested into model data, still want to point out that we will likely not have a clear picture of what is to come at least for another day or so. In the meantime, we encourage folks to continue monitoring the forecast for the latest updates. Given that we are still a few days out from any impacts, also want to encourage folks to review their evacuation plans and emergency kits.
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.AVIATION /20Z THURSDAY THROUGH TUESDAY/... 26/00z TAF Discussion: KCHS/KJZI/KSAV: VFR this evening. Later tonight, the forecast becomes a bit uncertain as a number of guidance members suggest quite a bit of stratus with some fog could approach the terminals behind a band of weakening convection. It is unclear how widespread these conditions will become given the number of possible solutions noted in the data. The higher impact chances are at KSAV where a TEMPO for MVFR cigs were introduced 09-13z. For now, VFR were maintained at KCHS and KJZI. As for shower/tstm chances, isolated to scattered showers could approach the two Charleston terminals around daybreak, where VCSH was denoted. For KSAV, a few should could approach around midnight. The risk for showers/tstms looks to peak during the afternoon Friday, mainly at KSAV where VCTS was depicted from 19z on. Risk looks too low at KCHS and KJZI for a mention with this forecast cycle.
Extended Aviation Outlook: Brief flight restrictions are possible Friday and Saturday afternoons with showers/tstorms. Otherwise, prevailing VFR.
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.MARINE... Through Tonight: A cold front will approach from the west, especially late. This will cause S winds 10-15 kt this evening to back to the SW overnight, then easing a few kt towards daybreak Friday. Seas are expected to average 2-3 ft this evening, building to 3-4 ft overnight.
Friday through Monday: Marine conditions into the weekend will remain rather tranquil as high pressure dominates over the marine waters. A weak front will push into the marine waters Saturday and linger in the vicinity through the weekend and into early next week. Through Sunday conditions are expected to remain below Small Craft Advisory criteria, with winds generally 10 to 15 knots and seas 2 to 3 ft. The forecast becomes significantly more uncertain late this weekend and into early next week due to potential impacts from either 94L or TS Humberto.
Rip Currents: The Moderate Risk of rip currents will remain at all of our beaches through this evening.
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.CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None.
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NWS CHS Office Area Forecast Discussion