944 FXUS62 KCHS 091713 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 113 PM EDT Tue Oct 9 2018 ...HIGH SURF AND COASTAL FLOOD ADVISORIES ISSUED FOP THE DURATION OF MICHAEL... .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 Northwest across Georgia and South Carolina Wednesday into Thursday. Cooler high pressure will then build in through early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Grids and text products have been updated to reflect the 11 am NHC Advisory. Made additional minor adjustments to hourly pops based on latest radar data. Shower activity associated with a ribbon of tropical moisture located off the Florida east coast has been slow to move into the area this morning. Activity should gradually move in from the southeast through the afternoon as subtropical high pressure located offshore of the Virginia Tidewater slowly propagates farther offshore. Have lowered pops for much of the day, increasing them back into the likely category across the far southern zones by late afternoon. Extensive cloud cover and some shower activity will help suppress high temperatures compared to previous days. Mid 80s look reasonable for most locations. Breezy conditions will persist at the beaches as the pressure gradient tightens. The risk for gusty winds associated with the approaching shower activity will increase through the day. Could easily see wind gusts 40-45 mph with any robust shower activity that forms. Limited instability will keep any risk for tstm activity into the isolated category. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... Focused/onshore moisture transport pushing PWAT values well over 2 inches into the region justify likely/categorical PoPs tonight. Locally heavy rainfall will be possible. Based on the latest NHC forecast, Hurricane Michael will weaken to a tropical storm as it moves across central GA Wednesday night and through the SC Midlands Thursday. Mainly dry conditions expected Friday as Michael departs off the NC Outer Banks. Heavy Rainfall: Looks like one round of moderate to possibly heavy rain will move through Wednesday, mainly in SC. Then rain chances should increase from the southwest Wednesday night and continue Thursday with increased intensity and this is when the best chance for flash flooding should occur, especially in coastal areas around times of high tide. Rainfall amounts should average 3-6 inches with locally higher amounts possible. Tornadoes: The forecast area is expected to remain in the favorable right hand side of Michael and thus isolated, brief tornadoes are possible. The greatest low-level instability is likely to be closer to the coast while the greatest low-level helicity should be farther inland closer to the core of the storm. The best chance of favorable conditions lining up will be late Wednesday afternoon through Thursday afternoon, with the threat ending earliest in GA on Thursday. Winds: Winds will ramp up Wednesday night in GA and then early Thursday across SC coincident with Michael's closest approach. Sustained tropical storm force winds of 35-40 mph with gusts near 50 mph are generally expected for most areas, mainly highest in the stronger showers and storms. Conditions should improve rapidly Thursday night. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... 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 /18Z TUESDAY THROUGH SUNDAY/... Conditions will deteriorate across the terminals next 24 hours as Hurricane Michael moves across the eastern Gulf of Mexico. Outer bands will move through the KSAV terminal later this afternoon and across KCHS tonight. These bands will bring reductions to vsbys, possibly as low as IFR at times. Timing of these conditions is proving a bit tricky, but generally followed a blend of the latest high resolution guidance to pin down impact times. First, expect steadier rains to move into KSAV by 22z and KCHS by 03-04z. This band will linger for about 2-4 hours before moving north of each site. Showers will linger after these times, but timing is too uncertain to include prevailing or TEMPO groups. Amendments will be issued as needed. Gusty winds will also linger through the entire period, possibly as high as 30 kt at times. Extended Aviation Outlook: Flight restrictions likely through Thursday due to periods of moderate to heavy showers/tstms. Gusty winds expected Wednesday night and Thursday as tropical cyclone Michael moves northeast to the west of the terminals. && .MARINE... Today and tonight: Between strong high pressure to the north and a coastal trough, east winds will gust to 25-30 knots, and seas will average 4-7 ft near shore and 7-10 ft across outer waters. Wednesday through Sunday: Conditions will quickly deteriorate Wednesday night into Thursday from south to north as tropical cyclone Michael shifts northeast across inland GA/SC. Tropical storm force winds are expected during this time with seas building to near 11 feet. Conditions are expected to rapidly improve late Thursday before deteriorating a bit again this weekend as cooler/drier high pressure builds in from the north leading to a tightening pressure gradient. Rip Currents: A high risk for rip currents has been issued for all beaches 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. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Tropical Storm Watch for GAZ087-088-099>101-114>119-137>141. High Risk for Rip Currents until 8 PM EDT this 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 Watch for SCZ040-042>045-047>052. High Risk for Rip Currents until 8 PM EDT this 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 Watch for AMZ330-350-352-354-374. && $$