938 FXUS62 KCHS 131126 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 726 AM EDT Sun Jun 13 2021 .SYNOPSIS... An area of low pressure will develop just off the South Carolina coast today and will depart to the northeast tonight. A cold front could approach the region by the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... As of 720 AM: The forecast appears on track. PoPs will be increased across Charleston County and the adjacent waters this morning. Hourly temperatures will be updated to align with latest observations. As of 530 AM: KCLX detected several clusters of showers across the region with a well defined cyclonic circulation centered around 30NM off the Charleston County coast. Near term guidance indicates that the coastal low will continue to deepen this morning, then tracking to the ENE this afternoon. As the low organizes, spokes of showers will pass from north to south over the CWA early this morning. In addition, latest SPC mesoanalysis indicates that the non-supercell tornado parameter values over the nearshore waters were greater that 5 units this morning. Given the shower activity and the environment around the sfc low we have issued a statement for waterspouts this morning, see Marine section. Later this afternoon, the axis of the mid-level trough will remain over the region. At the sfc, weak high pressure is forecast to ridge south across the Carolinas and SE GA as the sfc low departs. LLVL moisture convergence increase along the coast during the mid to late afternoon, likely associated with a pinned sea breeze. This feature should provide a focus for showers and thunderstorms. These storms are expected to be slow moving, producing localized areas of heavy rainfall. High temperatures are forecast to range from the low 80s across the SC Lowcountry to the upper 80s across SE GA. This evening, convection should gradually dissipate, remaining over the waters well into the overnight hours. Low temperatures are expected to favor values around 70 degrees. && .SHORT TERM /MONDAY THROUGH WEDNESDAY/... Monday: A mid-level trough will shift farther offshore during the day as surface low pressure lingers in the vicinity. Heights should begin a slow rise throughout the day and the 00Z model runs are showing a slight drying trend as subsidence moves into the region. In regards to showers, the best coverage will be in far SE GA where PWATs will linger around 2.0 inches. Although, with the formation of the sea breeze/boundaries, showers/thunderstorms will be possible across the entire area but will be limited. Highs will be in the mid 80s to mid 90s with low 80s just along the coast. Lows will be in the 70s. Tuesday and Wednesday: A cold front is expected to approach the region on Tuesday, before moving offshore, possibly Wednesday. Although, there are some model differences with the timing and placement of the cold front. For Tuesday, lingering moisture from deep troughing will remain across the area, which should enhance showers/thunderstorms, mainly in the afternoon/evening. Then on Wednesday, there are some hints of much drier air moving into the region as ridging becomes the dominate mid-level feature. POPs are limited to slight chance. Similarly, could see thunderstorms with decent instability in place. High temps will be in the upper 80s to mid 90s inland with mid 80s just along the coast on Tuesday. Then, a few degrees cooler on Wednesday. Lows on Tuesday will be in the mid 60s to mid 70s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... By late week, high pressure and subsidence are expected to prevail across the region. While there could still be showers/thunderstorms along any boundaries and/or sea breeze that forms, have limited POPs to isolated to scattered. Then, over the weekend, shortwave energy will increase and could see increased showers/thunderstorm activity ahead of another cold front. High temperatures will be in the mid 80s to low 90s inland with low 80s just along the coast. Lows will be in the mid 60s to mid 70s overnight Wed/Thurs, then low to upper 70s Fri/Sat nights. && .AVIATION /11Z SUNDAY THROUGH THURSDAY/... A sfc low will develop off the SC coast this morning as high pressure continues to ridge over the Coastal Plain of SC and GA. Deep moisture and weak forcing should preserve of LIFR to VLIFR ceilings across the terminals early this morning, lifting to MVFR by 16Z. A band of showers and thunderstorms is forecast to develop right along the coast this afternoon. The TAFs will feature a TEMPO at KSAV between 20-24Z for TSRA, with VCSH at KCHS and KJZI by 18Z. By this evening, VFR conditions are forecast across the terminals as the coastal low departs to the NE. Extended Aviation Outlook: Flight restrictions will be possible during showers/thunderstorms each afternoon. Otherwise, no concerns. && .MARINE... An area of low pressure will gradually deepen off the South Carolina coast early this morning. Rounds of showers and isolated thunderstorms will develop in the vicinity of the low pressure this morning. The environment across the nearshore waters of South Carolina and Georgia could support the formation of waterspouts, especially with showers and thunderstorms. Otherwise, winds are forecast to remain from the NE at 10-15 kts today, decreasing to around 5 kts tonight. Seas should range between 2-3 ft. Monday through Friday: A southerly flow will prevail across the waters. Ahead of an approaching cold front mid-week, the pressure gradient will tighten. Winds could approach gusts of 25 knots with seas approaching 6 feet. Small Craft Advisories could be needed Tuesday/Wednesday. Thereafter, no other marine concerns. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...NED SHORT TERM...RAD LONG TERM...RAD AVIATION...NED/RAD MARINE...NED/RAD