000 FXUS62 KCHS 161940 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 340 PM EDT Sat Oct 16 2021 .SYNOPSIS... A cold front will push offshore this evening. High pressure will prevail across the region most of next week, followed by a cold front toward the end of next week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... This evening and tonight: The polar cold front is poised to move off the coast early this evening, and will be followed by a modified cP (Continental Polar air mass) that arrives tonight. Given a deep westerly flow in advance of the front and only limited instability and CAPE, plus the higher Theta-E air and deep moisture convergence to pull offshore, we are not looking at anything more than isolated to perhaps scattered showers. Given warm temps aloft and limited thermodynamics and kinematics, plus a zero chance per the HREF, we have again opted to not mention t-storms in the forecast. The rain chance will end completely over land by around 8 pm with the passage of the front. Strong high pressure centered in Texas will build into the area through the night, bringing with it our first truly autumnal air mass of the season. Comparing the low level thickness forecast at 12Z Sunday with those thicknesses from upstream at 12Z Saturday, this will yield min temps some 30-40F colder than it was for max temps on Saturday. Lake Winds: Deep mixing will exist across Lake Moultrie, with winds within that layer extending to 3-4K ft as high as 30 kt. Combine that with geostrophic winds at 1000 mb at similar strength and steady isallobaric pressure climbs, conditions will easily reach Lake Wind Advisory criteria. Winds over the open lake waters will be as great as 20 kt with gusts to 25-30 kt, while waves will average 1-2 ft, but up to 3 ft along parts of the south and southeast side of the lake. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/... Cool and dry high pressure will settle over the area Sunday and persist through Tuesday. Highs Sunday and Monday will be in the lower 70s while Tuesday highs will be in the mid/upper 70s. Lows will dip into the mid 40s inland with lower 50s near the coast. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... Temperatures will slowly moderate through the period with highs reaching the lower 80s by late in the week. A cold front will pass through on Friday, potentially spurring isolated showers. A slight cool down is possible late next weekend as Canadian high pressure rebuilds. && .AVIATION /20Z SATURDAY THROUGH THURSDAY/... VFR will prevail. Isolated -SHRA will occur in advance of a cold front that moves off the coast early this evening. But even if one should move through a terminal, no impacts will occur. SW and W winds will be a little gusty in advance of the cold front, and remain somewhat elevated tonight as they veer around to the NW and N. Some gusts will return again Sunday morning. Extended Aviation Outlook: VFR will prevail. && .MARINE... This evening and tonight: Mariners should be prepared for an abrupt change in conditions as a polar cold front pushes through this evening. Hazardous conditions will occur over all waters late this evening and overnight as winds surge in response to modest post-frontal cold air advecting over the warm Atlantic waters. There is deep mixing of 30-35 kt geostrophic winds at 1000 mb, which will allow for solid Small Craft Advisory over the entire marine area. Winds will veer around from the SW prior to dark to the W and NW early on tonight, before shifting to the N by around 11 pm. Speeds will peak as strong as 20-25 kt with gusts of 30 kt to occur. Seas will be held somewhat in check by the offshore trajectories, but still enough to build to 3-5 feet within 20 nm and up to 5 or 6 ft further out. Even in Charleston Harbor the waves will reach up to 2 ft, with some 3 footers to occur at times. While we can't rule out a few t-storms, the risk looks too low to include in the forecast. Gusty north winds will continue into Sunday morning, though conditions will rapidly improve as the surface high moves overhead and the gradient relaxes. The Small Craft Advisory for the nearshore waters and Charleston Harbor will drop off at 15Z Sunday while the SCA for offshore GA waters continues through the afternoon due to lingering 6 ft seas. For the remainder of the week, high pressure will prevail with tranquil marine conditions. && .CLIMATE... Record High Temperatures for October 16: KCHS: 90/2018 KSAV: 91/2018 KCXM: 88/2018 && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...Lake Wind Advisory from 8 PM this evening to 8 AM EDT Sunday for SCZ045. MARINE...Small Craft Advisory from 8 PM this evening to 11 AM EDT Sunday for AMZ330-350-352-354. Small Craft Advisory from 8 PM this evening to 5 PM EDT Sunday for AMZ374. && $$ NEAR TERM... SHORT TERM...JRL LONG TERM...JRL AVIATION...JRL MARINE...JRL CLIMATE...