870 FXUS62 KCHS 112206 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 606 PM EDT Sat Aug 11 2018 .SYNOPSIS... Low pressure will persist near the region through the weekend. A weak front could drift into the area during the middle of next week. High pressure will then prevail during the second half of the week before weak low pressure returns next weekend. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Isolated to scattered convection remains anchored in the higher theta airmass in the wake of the sea breeze early this evening. Sea breeze convergence remains fairly weak with SMC values averaging only 20-30 g/kg/12hr. This pattern will change little over the next few hours. Farther to the west, a line of convection moving across central Georgia is steadily weakening with time as it encounters a slightly less favorable thermodynamic environment that is in place across interior Southeast Georgia. Some remnants of this activity could breach the far interior Georgia zones around sunset, but should not amount to too much. Pops have been lowered by 10-20% for most areas with the early evening update. The risk for severe weather remains quite limited as weak convergence will curtail the formation of robust updrafts. Isolated to perhaps low end scattered convection could redevelop after midnight as H8-H7 shortwave energy draw closer and interacts with higher moisture/coastal convergence in the wake of the sea breeze. Maintained lowish pops through the overnight period at the coast. Lows from the lower-mid 70s inland to the upper 70s at the beaches look on track. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/... Sunday: Aloft we find a closed low spiraling near Lake Erie and over Ohio, with its associated deep cyclonic flow to extend across the local area. At the surface, a stationary front will remain just off to the W-NW of the CWA, with a trough just out ahead of the front, located over or near the forecast district. While there will be some showers/t-storms mainly across the Charleston tri-county and coastal Colleton and maybe Beaufort County to start the day in the region of the best convergence, most areas will remain capped through early afternoon. Given that much of the flow throughout the troposphere is from the SW, this maintains a moisture-laden air mass featuring PWat around 1.75 to 2.00 inches. MUCAPE is as great as 1500-2500 J/kg and with the resultant sea breeze, the nearby trough and the usual meso- scale boundaries that form, we have chance to high end chance PoP in the afternoon. Coverage looks to be highest inland from US-17 to as far inland as near US-301. The overall severe weather threat is low given unimpressive thermodynamics and poor lapse rates. But with DCAPE as much as near 1000 J/kg, there could be one or two storms that produce strong or severe wind gusts. If convection from upstream is able to move in late, the severe coverage would be greater further inland. H8 temps are near 18-19C, a little above normal for mid-August, and this will support max temps in the lower 90s inland from the coast. Sunday night: Lingering convection will generally fade during the mid evening hours, before the coverage of convection ramps up over the coastal areas, especially South Carolina during the overnight period due to increasing moisture convergence. PoP is capped at slight chance/chance, highest over the Charleston tri-county closer to daybreak. Areas of stratus and patchy fog could form in a few far inland locations if skies clear out enough. Lows will average in the lower and middle 70s most communities. Monday and Tuesday: The cut off low eventually transitions into more of a closed low as it moves into the NE part of the nation Tuesday, while its associated mid and upper trough persist across the entire eastern third to quarter of the country. Meanwhile at the surface, there is still a nearby stationary front and trough, with the axis of the Bermuda High aligned across Florida. Monday looks to be a little more active regarding convection than Tuesday, with some support from the RRQ of the upper jet and its resulting divergence and the tail of a weak short wave moving through the South Carolina upstate and North Carolina. MUCAPE is around 1500-2500 J/kg both days, but the elevated moisture on Monday is less so on Tuesday as a deeper W-NW flow develops due to the parent low associated with the front to pull off the Delmarva and mid-Atlantic. We're carrying 40-50% poP Monday, mainly to "blend" better with our neighbors, thane mostly 30% Tuesday. There could be some multicell clusters that form Monday due to the support aloft, with damaging winds and heavy rainfall the main hazards. Any severe threat Tuesday is low due to more pulse- type activity. Temps both days will peak in the lower 90S inland from the coast. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... Drier conditions are anticipated mid week as high pressure builds over the region Wednesday/Thursday while sfc low pressure is less pronounced inland. Other than a few afternoon showers/thunderstorms, the pattern should support slightly warmer conditions with high temps peaking in the low-mid 90s. Higher precip chances could return next weekend as the sfc trough becomes more pronounced inland while a front shifts toward the Mid-Atlantic states. && .AVIATION /22Z SATURDAY THROUGH THURSDAY/... VFR. Extended Aviation Outlook: Brief flight restrictions are possible at KCHS Sunday and Monday morning, and at both KCHS and KSAV each afternoon and evening due to SHRA/TSRA through Thursday. Otherwise VFR will prevail. && .MARINE... Tonight: Broad low pressure will remain across the east coast through tonight. Winds across the marine zones should continue from the southwest between 10-15 kts with seas 1-2 ft. Sunday through Thursday: The sub-tropical ridge will remain positioned to the SE through the period, with occasionally strengthening of the gradient to occur with slightly lower pressure inland. There is the typical fluctuations in winds to the SSW with the sea breeze each afternoon and evening, then around to the WSW with the "cooling" land each night. On average winds will be no greater than around 15 kt (except occasional stronger gusts in Charleston Harbor during the day), and since there remains the lack of swell energy, seas won't be any more than 2-4 ft. The coverage of showers and t-storms will be highest each post-midnight period into the mid or late morning hours, although some organized convection with damaging winds could occur late Monday and early Monday night. && .TIDES/COASTAL FLOODING... Tides are expected to peak 7.0-7.2 ft MLLW in Charleston Harbor and 8.9-9.1 ft MLLW at Fort Pulaski. A Coastal Flood Advisory remains in effect for most of the South Carolina coastal zones until 10 PM. Trends are being monitored along the Georgia coast and it is possible the advisory may need to be expanded. Elevated high tide levels will continue into early next week due to lingering astronomical influences and occasional onshore winds. The evening high tides are the most problematic and could result in coastal flooding. As a result, additional Coastal Flood Advisories are possible. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...Coastal Flood Advisory until 10 PM EDT this evening for SCZ048>050. MARINE...None. && $$