826 FXUS62 KCHS 102351 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 751 PM EDT Wed Oct 10 2018 .SYNOPSIS... Hurricane Michael made landfall Wednesday afternoon along the Florida Panhandle. Michael will then gradually weaken to a tropical storm as it moves northeast across Georgia and South Carolina tonight and Thursday. Cooler and drier high pressure will then build in through the weekend before a coastal trough and cold front affect the area Tuesday into Wednesday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Early this evening: Updated rain chances to slow the expansion of increasing chances based on radar trends. Otherwise, the forecast is in good shape and the main threat continues to be tornadoes this evening and overnight. Previous discussion continues below. This evening and tonight: Conditions across southeast Georgia and southeast South Carolina will deteriorate through the night as Hurricane Michael moves northeastward across Georgia and into South Carolina. Based on the current track forecast, the center of Michael is expected to pass just inland of Jenkins County, GA late tonight as it weakens to a tropical storm. Winds will increase through the night as the storm draws closer, bringing bands of heavy showers and thunderstorms and the risk for tornadoes. A Tropical Storm Warning remains in effect for the entire area and the area of strongest winds is expected closer to the center which includes much of interior southeast Georgia and southeast South Carolina. Based on the track, the heaviest corridor of rain is anticipated along and near the center, which will result in 1-3 inches of additional rainfall across areas inland of the coast. While localized flooding will still be possible, it doesn't appear to be a situation that will warrant a Flash Flood Watch since Michael will be moving quickly and limiting the duration of the highest rates. Also, the heaviest rain will be falling in areas that have been dry recently and aren't very flash flood prone to begin with. The biggest concern through the overnight period is the tropical tornado threat as the circulation of Michael encompasses the forecast area. Tornado Watch 407 is already in effect for all of southeast Georgia and the Georgia coastal waters through 2 am. Additional watches are anticipated as the tornado threat spreads north and northeast with time. Wind fields will increase and SRH values are progged to increase into at least the 200-400 m^2/s^2 range through midnight, and could even surge into the 400-600 range. The environment will be quite moist (precipitable water values of 2.2 inches or greater) with low LCL's as well. This is well represented by the Enhanced Risk in the Storm Prediction Center's Day 1 outlook. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... Michael will continue to weaken as it moves through the SC Midlands Thursday morning and toward eastern NC late Thursday afternoon. Based on the latest forecast track, conditions should be improving by late Thursday morning across most of southeast GA while southern SC sees the strongest winds and heaviest rainfall late morning into mid afternoon. Our wind forecast with the 5 pm advisory package is a tad higher though only 1-3 kt higher. In general our forecast for Thursday remains quite similar though our forecast rainfall closer to the coast is lower due to a slightly farther inland track. A significant tornado threat could persist mainly over the Charleston Tri- County area through early Thursday afternoon before the best instability axis shifts to the northeast. Dry high pressure will build over the area Thursday night through Saturday with rain-free weather and highs in the low to mid 80s. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Late this week cooler and drier high pressure will build back into the region behind Michael. A weak coastal trough will then develop early next week ahead of a cold front which could move into the area as early as Monday night. Rain chances are not expected until early next week. Temperatures look to remain near to above normal levels. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Conditions will begin to deteriorate through late evening. Prevailing MVFR ceilings are expected at both sites, beginning around 03z at KSAV and around 09z at KCHS. MVFR ceilings will continue through Thursday morning with a return to VFR by the afternoon. Showers and bands of very heavy rainfall will be possible, with at least TEMPO conditions of IFR visibilities. As the center of Hurricane Michael moves across interior Georgia and South Carolina, winds will pick up significantly, turning from southerly to more southwesterly with time. The TAF's feature wind speeds in the 25g35kt range, with higher gusts possible within any showers or thunderstorms that pass through. Overall conditions will improve by mid morning as the main precipitation shield races off to the northeast. Gusty winds will continue into the afternoon but will turn more southwesterly and then westerly. Extended Aviation Outlook: Flight restrictions and gusty winds possible through early Thursday evening at KCHS due to lingering convection behind Michael. VFR thereafter. && .MARINE... Through tonight: Conditions across the local waters will steadily deteriorate as Hurricane Michael passes inland across Georgia and into South Carolina. Michael is forecast to weaken to a tropical storm through the night, but will still produce solid Tropical Storm conditions. As a result, the Tropical Storm Warnings remain in effect. Winds will especially ramp up beginning around and after midnight tonight, spreading to the northeast with time. Max winds are expected along and closer to the coast with gusts approaching 50 knots through sunrise. The strong winds will support building seas, with up to 10 feet possible in the nearshore waters and up to 12 feet in the outer waters. Another concern is the potential for thunderstorms producing waterspouts. A Tornado Watch is in effect for the Georgia coastal waters through 2 am, and additional watches are expected through the night. Dangerous marine conditions including tropical storm force winds, large seas, and scattered waterspouts expected to continue on Thursday as Tropical Storm Michael moves through the SC Midlands toward eastern NC. Thereafter, rapidly improving conditions as winds become offshore and the gradient weakens. Cooler/drier high pressure will then build in from the north with some increase in winds/seas although likely staying below advisory levels. A weak coastal trough should then develop early next week while a cold front approaches from the west. Rip Currents: A high risk for rip currents continues through Thursday due to strong winds and moderate swells. && .TIDES/COASTAL FLOODING... Coastal Flooding: Over the last several high tide cycles, guidance has been too aggressive with max values and as we head through the night and into Thursday morning, winds will become much less favorable as they veer around from southeast, to south, and eventually southwest. The next high tide will be around 10 pm this evening and is the lower of the diurnal high tides. Values are expected to peak in the 7-7.2 ft MLLW range at Charleston, and around 9.2 feet MLLW at Fort Pulaski. Then by Thursday morning, we could have one more tide around 7.4 ft MLLW at Charleston, while Fort Pulaski should peak well below coastal flood thresholds with the arrival strengthening southwest winds. The Coastal Flood Advisory remains in effect, but we might be able to begin dropping it in Georgia thereafter for the Thursday morning high tide. Areas of erosion are still possible with the period of strong onshore winds this evening and tonight, increased wave action, and elevated tide levels. High Surf: There will continue to be large breaking waves impacting the entire stretch of beaches through Thursday, reaching as large as 5 to 8 ft, highest during Thursday morning with Michael at its closest approach. A High Surf Advisory will therefore remain in effect through Thursday evening. && .CLIMATE... 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 Thursday evening for GAZ117-119- 139-141. High Surf Advisory until 8 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 Thursday evening for SCZ048>051. High Surf Advisory until 8 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...BSH SHORT TERM...JRL LONG TERM...RJB AVIATION...BSH/JRL MARINE...BSH/JRL TIDES/COASTAL FLOODING... CLIMATE...