473 FXUS62 KCHS 230845 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 345 AM EST Mon Nov 23 2020 .SYNOPSIS... A cold front will move away today, followed by high pressure through Wednesday. Another cold front will stall over the area Thursday. Low pressure will move through Sunday and Monday. && .NEAR TERM /THROUGH TONIGHT/... Early this morning: The next cold front has not yet arrived, but will pass through by around 7 or 8 am as it heads to the east and southeast. In advance of the front we are experiencing a huge area of stratus and dense fog, that will continue to build eastward within a highly favorable environment where condensation pressure deficits are down near or at zero millibars. As a result we have issued a Dense Fog Advisory through 7 AM for the entirety of the region. Once the front passes through there will be a small increase in winds from the west and northwest, along with a little drier air. Because of this we have opted to end the advisory at a time earlier than what is more of the climatological favored mid to late morning time frame. For today: Once the cold front gets offshore this morning, it is followed by strong high pressure and a rapid drying out of the atmosphere. Skies will become sunny as winds veer around to the north by afternoon, with average speeds around 10 or 15 mph with some higher gusts. We undercut the low level thickness forecast a tad for max temps given the fog and stratus, as they cut down on a couple of hours of insolation. This means that max temps for the afternoon will reach 70-75F, making it about the 18th or 19th day this month above the normal daytime high. Tonight: High pressure will dominate as it continues to build into the area from the Great Lakes and Ohio Valley. Under clear skies and winds going light or calm quickly in the evening away from the coast, good radiational cooling will commence. Lows will range from the upper 30s northwest tier to as high as the upper 40s to around 50F near the immediate coast, in downtown Charleston and near Lake Moultrie. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... Cool, dry high pressure will prevail on Tuesday. Highs will be in the lower 60s north to upper 60s south. Warm air and moisture advection will develop Tuesday night as the surface high shifts offshore, resulting in a southeast flow. By Wednesday afternoon, dewpoints will rise into the lower 60s near the coast. However, the area will remain under the influence of a broad upper ridge during this time so no precipitation is expected. High temperatures will be considerably warmer than Tuesday with readings well into the 70s. A series of shortwaves will move through Wednesday night and Thursday while a weak cold front approaches from the west. Although the overall forcing will be weak, modest moisture return ahead of the front should support isolated to scattered showers Wednesday night and Thursday. Models are showing some weak instability on Thursday, potentially enough to support isolated thunderstorms as well. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... Dry weather is anticipated Thursday night through Saturday morning. Then a front will stall over the area Saturday afternoon through Sunday, followed by a strong cold frontal passage on Monday. Fairly good rain chances expected Sunday into Monday. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... The primary forecast challenge will concern the low ceilings and fog early this morning. A cold front will approach from the west, expected to sweep across KCHS and KSAV between 12-13Z. Widespread stratus and an expanding area of fog will occur in advance of the cold front, with flight restrictions through around 13-1330Z. We are currently showing conditions down near airfield mins at KSAV, with at least conditions down into the IFR range at KCHS. In the wake of the front, conditions will become clear with steady north winds. Extended Aviation Outlook: Intermittent MVFR ceilings possible late Tuesday night. Brief flight restrictions possible Thursday as a cold front moves through, accompanied by scattered showers. && .MARINE... Today: Due to widespread fog and stratus that is expanding east this morning, we have raised a Dense Fog Advisory through 9 AM for the waters about 10 to 15 nm out from Edisto Beach south to the Altamaha River entrance. The fog will also impact Charleston Harbor and the Charleston County Atlantic waters out about 10 nm. But since winds will be increasing behind a cold front and the fog hasn't yet reached those bodies of water as of this Area Forecast Discussion issuance, we instead have mention of patchy dense fog. We continue to monitor for potentially expanding the Dense Fog Advisory to cover Charleston Harbor and the nearby Atlantic waters. The other concern for today will be the increase in winds as continental high pressure builds in behind the cold dont, leading to winds clocking around to the N as high as 15 or 20 kt. Frequent gusts of 25 knots along with 6 foot seas will impact the Georgia waters beyond 20 nm off the coast, so it is there hat we have raised a Small Craft Advisory. Tonight: Strengthening high pressure will continue to advance into the local waters, leading to a tighter gradient, good mixing and steady isallobaric pressure rises. Due to these conditions we anticipate reaching advisory thresholds on the Charleston County waters out 20 nm, and also for the outermost Georgia waters beyond 20 nm off the coast. The other waters certainly could need a Small Craft Advisory at a later time. But for the moment it appears o be too marginal to hoist the advisory flags. Relatively quiet marine weather expected Tuesday through Saturday as the flow becomes southerly midweek and the overall gradient remains weak. Decent NE flow and 6 ft seas expected to linger into Tuesday evening over the offshore GA waters where a Small Craft Advisory is in effect. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Dense Fog Advisory until 7 AM EST this morning for GAZ087-088- 099>101-114>119-137>141. SC...Dense Fog Advisory until 7 AM EST this morning for SCZ040- 042>045-047>052. MARINE...Dense Fog Advisory until 9 AM EST this morning for AMZ352-354. Small Craft Advisory from 7 PM this evening to 7 AM EST Tuesday for AMZ350. Small Craft Advisory from 7 AM this morning to 4 AM EST Wednesday for AMZ374. && $$ NEAR TERM... SHORT TERM...JRL LONG TERM...JRL AVIATION... MARINE...