702 FXUS62 KCHS 141315 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 915 AM EDT Sat May 14 2022 .SYNOPSIS... A weak cold front will push offshore Monday night. High pressure will build into the region through the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... This is a quick update to expire the Dense Fog Advisory. A more complete update will follow a bit later this morning. Today: The synoptic pattern will begin to transition back to a more summer type configuration today as the pesky upper low that has been meandering near the region over the past several days begins to open up and subtropical ridging offshore starts to nudge in from the east. At the surface, Atlantic high pressure centered well offshore will begin to extend west into the area. Any lingering low clouds and fog remaining after daybreak will quickly mix out and be replaced with a cumulus field through the day. A modest sea breeze circulation will begin to take shape along the beaches by early afternoon which will move slowly inland. Although instability will not be over impressive, enhanced low-level convergence in the vicinity of the sea breeze could spark off a few showers/tstms. HREF 3-hr measurable rainfall probabilities are generally in the single digits, but some of the more reliable CAMs are supportive of isolated convection. Slight chance pops were maintained near the sea breeze this afternoon with dry conditions elsewhere. Highs will range from the lower-mid 80s inland to the mid 70s at the beaches. Tonight: The sea breeze will quickly breakdown after sunset with isolated convection likely dissipating before then. Dry conditions will prevail overnight. Another round of fog and stratus will likely develop again early Sunday as low-level moisture pools within a decoupled boundary layer. Guidance is mixed on exactly how widespread the fog/stratus will become, likely because of issues trying to resolve the shallow nature of the fog. A mention of patchy fog was maintained for now to bridge any potential increases in coverage with later forecast cycles. Lows will range from the lower 60s inland to around 70 at the beaches. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... A weakening upper trough situated over the Southeastern U.S. will lift north Sunday into Monday, pushing a relatively dry cold front offshore before stalling in the Atlantic. A Bermuda High looks to dominate the surface pattern with no discernible systems over the region. A "summertime" diurnal pattern with afternoon/evening showers and thunderstorms are expected Sunday along an inland advancing sea breeze. Chance pops are in place mainly over inland locations where isolated to scattered, pulse-like thunderstorms due to weak steering are possible. On Monday, strengthening southwesterly synoptic flow ahead of the front will largely pin the resultant sea breeze along the coast. Guidance depicts a nearly rain-free Monday afternoon as model soundings show slightly less low and mid-level moisture than previous days. However as the front approaches from the northwest late afternoon, showers across the SC Midlands will gradually taper off as they cross the western fringes of the forecast area as upper forcing diminishes. Thus low-end slight chance pops are mentioned in Monday's forecast for the extreme interior counties. Models remains quite mixed Tuesday with the GFS solution showing some convection developing mainly along the coast due to hints of llvl convergence. However due to the absence of deep moisture and deep forcing, the forecast highlights unmentionable pops for now. This could very well change in future forecasts. Temperatures through the short-term will increase with highs in the mid/upper 80s Sunday, and upper 80s/low 90s Monday and Tuesday. Lows will range in the mid 60s inland to the upper 60s closer to the coast, and low 70s along the beaches. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... Quasi-zonal, weak flow aloft will keep rain chances low through the week with the next chances for any decent rainfall not expected until the following weekend. Temperatures look to creep above normal through the period, with the warmest of days to occur near the end of next week. Increasing humidity should also lead to heat indices reaching well into the mid 90s to possibly the upper 90s inland. && .AVIATION /13Z SATURDAY THROUGH WEDNESDAY/... KCHS/KJZI: Widespread dense fog is in place at both terminals. The fog is quite shallow based on vertical visual observations, so expect conditions to improve rather rapidly once the sun comes up. The 12z TAF will be initialized based on last minute observations and trends before being transmitted, but expect VFR to return by 13z, if not sooner. Isolated showers/tstms could develop near the terminal this afternoon with the sea breeze, but probabilities are too low to include a mention at this time. Another round of fog/stratus will possible again tonight, but best chances remain west of the terminals. KSAV: Any lingering fog/stratus should be gone by the 12z TAF issuance, so VFR will prevail. Isolated showers/tstms could develop near the terminal this afternoon with the sea breeze, but probabilities are too low to include a mention at this time. Another round of fog/stratus will possible again tonight, but best chances remain west of the terminals. Extended Aviation Outlook: Flight restrictions possible due to low clouds and/or fog early Sunday. Otherwise, VFR conditions are expected to prevail. && .MARINE... The Marine Dense Fog Advisory has expired for Charleston Harbor. Previous discussion... Through Tonight: Light winds this morning will become south to southeast this afternoon as Atlantic high pressure tries to build in from the east and a modest sea breeze circulation develops. Winds will largely remain 10 kt or less with seas building to 2-3 ft nearshore waters and 3-4 ft over the Georgia offshore waters. Southerly winds will continue into tonight with speeds less than 10 kt. Seas will remain in the 2-4 ft range. Sunday through Thursday: Weak low pressure and/or troughing will linger before a cold front pushes into the local waters late Monday night. Southerly winds less than 15 knots look to persist through the period, with an otherwise brief period from Monday evening into Tuesday morning where southwest winds increase to 15 kt with gusts around 20 kt. However, conditions should remain below Small Craft Advisory thresholds. Seas will average 2 to 4 feet through the period. Rip Currents: Current wave model data and observed swells this morning at the various buoys show swell periods should only average around 8 seconds in the surf zone today. Local rip current calculations support a high-end low risk today which matches the latest rip current MOS guidance for Isle of Palms, Folly Beach, Kiawah, Hilton Head and Tybee Island. A moderate risk for rip currents is in place for all beaches Sunday, due to onshore flow and long-period swells. An enhanced risk could continue into early next week, mainly due to astronomical effects and southeast swells. && .TIDES/COASTAL FLOODING... Tide levels in Charleston Harbor are currently progged to peak around 6.9 ft MLLW with high tide this morning. This is slightly below minor flood thresholds. Even at this level, some very minor flooding will still occur in a few spots in Downtown Charleston, mainly adjacent to Gadsden Creek along the west side of the peninsula. This includes Hagood Avenue and Fishburne Street. Additional minor to perhaps moderate coastal flooding will be possible during the late evening high tides through at least the middle of next week as astronomical influences peak. Although, less favorable southerly winds should help to mitigate the effects of coastal flooding to an extent. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM... LONG TERM... AVIATION... MARINE... TIDES/COASTAL FLOODING...