074 FXUS62 KCHS 110417 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1217 AM EDT Thu Oct 11 2018 .SYNOPSIS... Tropical Storm Michael will move northeast across Georgia overnight and then through South Carolina 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 THIS MORNING/... A solid band of convection running north-south across our southern South Carolina counties to offshore and near Tybee island in Georgia is the main issue through the overnight, and has prompted the issuance of a Tornado Watch for all South Carolina counties through 8 am. We'll maintain the Watch for the Georgia counties through 2 am, just in case some of this skirt Tybee and/or another band developing in proximity to the main convective rain shield with TS Michael. Parameters remain favorable for isolated Tropical Cyclone Induced Tornadoes through the rest of the overnight. Previous discussion... Based on latest radar trends we have scaled back the onset of the majority of the convection, as Michael continues to weaken and moves off to the northeast. It's most recent position as per satellite and radar looks to be about 180 miles west of Savannah. Record high minimum temps for all three Climate sites still seems a good bet for October 10th given latest dew points in the mid and upper 70s and stronger southeast and south winds to persist. There hasn't been much indication of any severe storms in or near the immediate area of Georgia where we have a Tornado Watch until 2 am. But since the shear and helicity remain high, we have maintained mention of tornadoes in the Georgia counties through early tonight. Another Watch for our South Carolina counties is expected later tonight. && .SHORT TERM /6 AM THIS 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 /04Z THURSDAY THROUGH MONDAY/... Conditions will generally hold in the MVFR range overnight and 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 TS 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... Conditions across the local waters will steadily deteriorate as TS Michael passes inland across Georgia. As a result, the Tropical Storm Warnings remain in effect. Winds will especially ramp up overnight, 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, with Tornado watches in effect for all waters. 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: For 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 this evening for GAZ117-119-139- 141. High Surf Advisory until 8 PM EDT this evening for GAZ117-119- 139-141. Coastal Flood Advisory until 2 PM EDT this afternoon 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 8 PM EDT this evening for SCZ048>051. Coastal Flood Advisory until 2 PM EDT this afternoon for SCZ048>051. MARINE...Tropical Storm Warning for AMZ330-350-352-354-374. && $$ NEAR TERM... SHORT TERM...JRL LONG TERM...RJB AVIATION...BSH/JRL MARINE... TIDES/COASTAL FLOODING... CLIMATE...