590 FXUS62 KCHS 100531 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 131 AM EDT Wed Oct 10 2018 .SYNOPSIS... Hurricane Michael will move north across the Gulf of Mexico before making landfall along the Florida Panhandle Wednesday. Michael will then weaken to a tropical storm as it moves northeast across Georgia and South Carolina Wednesday night into Thursday. Cooler high pressure will then build in through early next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Strong low level moisture transport and deep moisture convergence has plenty of PWat to tap into, with values approaching 200% of normal for this time of year. With weak mid level differential vorticity advection and subtle upper divergence, and a nearby inverted trough hugging the coast, we will continue to experience scattered to numerous showers through the night, with even widespread coverage at times across parts of South Carolina. While there will be pockets of heavy rains, this will be more the exception rather than the rule overnight, with the bulk of the rain more moderate in intensity. There still hasn't been any indications of t-storms with poor lapse rates and minimal instability. Thus for the most part there doesn't look to be any risk of t-storms over land. We remain on track for possible record high minimums at all 3 Climate sites. && .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/... On Wednesday the main feature will be the weak inverted trough off to the northeast of Hurricane Michael. The center of this trough will be along the SC/GA coastline at daybreak Wednesday, then move north-northeast through early afternoon. We expect numerous heavy showers with isolated tstms across the area during the morning with the greatest coverage and intensity over southern SC closer to the trough. Unseasonably high PWATs in excess of 2.1" will support torrential rainfall at times. During the afternoon the best convergence associated with the trough are is forecast to move north of the area though we then expect some outer rain bands from Michael to start rotating through the area. A bit of a lull is possible Wednesday evening, then the rain shield associated with Michael is expected to move into interior southeast GA with some outer bands farther to the north and east. The brunt of the torrential rainfall associated with Michael's circulation will move through on Thursday with the greatest effects over our inland zones. Latest storm total QPF shows 2-4 inches across coastal sections and 3-5" inland. The strongest winds will begin in southeast GA late Wed night and affect most of southern SC during the day Thursday. An enhanced tornado threat appears likely from Wednesday afternoon through at least Thursday morning based on model progs for low-level helicity and surface-based instability. Slightly cooler and drier weather expected late Thursday night into Friday. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Late this week, surface high pressure will build back into the region behind departing TC Michael. Precipitation potential is looking rather low Friday and Saturday as a dry column sits overhead, then rain chances will increase with increasing moisture levels ahead of an approaching cold front Sunday into the first part of next week. Temperatures look to remain above normal. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... There will be periods of moderate to perhaps heavy SHRA at both sites overnight into Wednesday morning as deep moisture continues to arrive from off the Atlantic, with activity becoming more sporadic in nature during Wednesday afternoon. Conditions will lower into the MVFR category at times, maybe even briefly down to IFR if heavy enough rainfall occurs. Steadier rains associated with TC Michael will move into the KSAV area late in the valid 06Z TAF period, and will likely hold off until after that time at KCHS. Winds will be gusty much of the time, increasing to it's highest levels around 20 or 25 kt Wednesday afternoon, and even stronger late in the TAF period as the TC draws closer to the area. Although not explicitly shown in the TAFs, wind gusts of 30 or 40 mph can occur from time to time in the heavier bands of showers through the period. Extended Aviation Outlook: MVFR or lower conditions likely at both terminals Wednesday night through Thursday night as Hurricane Michael moves west of the area as a Tropical Storm. IFR ceilings and/or vsbys will be possible late Wednesday night through Thursday afternoon due to moderate to heavy rain. && .MARINE... We scaled back any t-storm activity until after 4 am, as there has yet to be any occurring and instability is limited. The forecast of winds and seas is verifying nicely and only minor tweaks were necessary with the latest update. Previous discussion... Tonight: Nasty marine conditions will continue across all waters tonight with winds 20-25 kt with gusts to 30 kt. Shower activity will be capable of producing localized wind gusts to 40-45 kt. Seas will build through the night, reaching 5-8 ft nearshore waters and 9-11 ft offshore waters. Wednesday through Saturday: The impacts of Hurricane Michael are obviously the main concern with this package. Marine conditions will become increasingly treacherous during the day Wednesday with the strongest winds and largest seas Wednesday night into Thursday. Improving conditions Thursday night into the weekend as high pressure builds in. Rip Currents: A high risk for rip currents continues into Wednesday due to persistent, strong onshore wind, some swell and astronomical influences. The rip current risk will remain elevated through the week. && .TIDES/COASTAL FLOODING... Coastal Flooding: The decision was made locally to issue a long-duration Coastal Flood Advisory for all coastal zones, excluding Tidal Berkeley, to cover all high tides through the duration of Michael. Minor to locally moderate coastal flooding is expected through the period. At this time, levels are not expected to reach Coastal Flood Warning criteria for either Fort Pulaski or Charleston Harbor with average inundations above ground level expected to stay 2 feet or less. This will be watched carefully and warnings will be issued if needed. High Surf: Expect breakers of 5 to 8 feet to impact the surf zone before winds turn offshore in the wake of Michael. A High Surf Advisory has been posted for all beaches. && .CLIMATE... Record high minimums for 9 October: KCXM: 77/2017. Record high minimums for 10 October: KCHS: 75/2017. KCXM: 78/2017 and previous. KSAV: 75/2017. Rainfall record for 10 October: KCHS: 1.82/1990. KCXM: 2.13/1990. KSAV: 5.68/1990. Rainfall record for 11 October: KCHS: 4.48/1990. KCXM: 5.46/1990. KSAV: 4.43/1885. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Tropical Storm Warning for GAZ087-088-099>101-114>119-137>141. High Rip Current Risk through this evening for GAZ117-119-139- 141. High Surf Advisory until 10 PM EDT Thursday for GAZ117-119-139- 141. Coastal Flood Advisory until 2 PM EDT Thursday for GAZ117-119- 139-141. SC...Tropical Storm Warning for SCZ040-042>045-047>052. High Rip Current Risk through this evening for SCZ048>051. High Surf Advisory until 10 PM EDT Thursday for SCZ048>051. Coastal Flood Advisory until 2 PM EDT Thursday for SCZ048>051. MARINE...Tropical Storm Warning for AMZ330-350-352-354-374. && $$ NEAR TERM... SHORT TERM... LONG TERM... AVIATION... MARINE... TIDES/COASTAL FLOODING... CLIMATE...