599 FXUS62 KCHS 010804 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 404 AM EDT Tue Oct 1 2019 .SYNOPSIS... High pressure will prevail through much of the week, before a cold front passes through the area late Friday into early Saturday. High pressure will return over the weekend and persist into early next week. && .NEAR TERM /THROUGH TONIGHT/... Through daybreak: Due to some wet grounds from the rains yesterday and dry air above a somewhat moist boundary layer, plus light winds will lead to patchy fog and stratus, especially far inland. Otherwise, scattered to locally broken cumulus and stratocumulus will advance onshore from the Atlantic. There is just enough low level convergence to produce isolated showers across our coastal Georgia zones. Temps are beginning the day once again far above climo. Today: An abnormally strong and deep layered ridge will remain anchored over the Tennessee Valley aloft, as large surface high pressure exists and covers much of the eastern states, western Atlantic and Gulf of Mexico. A very subtle coastal trough over the nearby waters will combine with adequate low level moisture and an upper jet streak and the sea breeze to produce isolated to scattered showers and maybe a stray t-storm or two, from Hilton Head to Sapelo Island and inland to Savannah, Ludowici and Hinesville. It is these locations where the low level trajectories are more directly onshore than further north. Temps at H85 are still above normal at 16-17C, but lower than recently. That along with a deep northeast flow should prevent temps from getting quite as warm as yesterday. Even so we're still anticipating highs a good 6-10F above normal. Tonight: The surface high will settle almost directly atop the forecast district, as the strong and deep anticyclone aloft holds in place over the Tennessee Valley. Clear to mostly clear skies, winds decoupling and becoming light or calm, and dry air atop a sufficiently moist boundary layer will lead to the formation of patchy fog after midnight. There's decent radiational cooling to allow for min temps to drop to the mid and upper 60s inland from US-17, lower 70s closer to the coast. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... A large mid level ridge will remain over the Southeast through the period, although it will weaken on Friday in response to a strong shortwave moving over the Northeast. High pressure will be the dominant feature at the surface. This synoptic pattern will favor warm temperatures and plenty of sunshine. Large scale subsidence will keep precipitation at bay. A cold front is forecast to approach the area later on Friday, and it looks as though any showers associated with it will stay to our north until Friday night. High temperatures will be solidly in the 90s away from the beaches - much more reminiscent of summer than fall. In fact, highs are expected to be within a few degrees of records at KCHS (KSAV records are a good bit higher). Lows will be in the upper 60s/low 70s. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... A cold front is forecast to drop south through the area Friday night into Saturday. Cooler high pressure will build in its wake and prevail into early next week, although the air mass will modify some as the high shifts into the Atlantic. Rain chances will be in the forecast given shortwave energy, elevated moisture, and enhanced low level convergence within onshore flow. While it will be much cooler than previous days, temperatures are forecast to stay near early October normals. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... VFR conditions will prevail at both KCHS and KSAV much of the time through 06Z Wednesday with the better coverage of fog and stratus to occur inland from both sites in this morning. However, at least occasional MVFR weather (and maybe even IFR) will occur from about 10-14Z with moisture trapped beneath the inversion and drier air aloft. Scattered showers from mid morning to mid afternoon in association with a subtle coastal trough could brush KSAV. This is not enough to warrant mentioning at this time, plus impacts would likely be minimal even it were to occur. Extended Aviation Outlook: Mostly VFR. Low risk for flight restrictions each morning due to low clouds/fog. && .MARINE... Today: High pressure centered to the southeast of New England will extend across the region, with a fairly decent gradient in place locally. This leads to NE-E winds as high as 15 kt and gusty, getting a small boost from the sea breeze influences this afternoon. Seas will be a mix of wind waves and swells from distant Hurricane Lorenzo, resulting in seas building to 4-6 ft on the AMZ350 waters, up to 5-7 ft over the AMZ374 waters, and 3-5 ft elsewhere. The Small Craft Advisory for the outer Georgia waters seems well justified, but we have limited confidence on the advisory for the Charleston County Atlantic waters. Thus we have delayed it from officially beginning, backing off the time until late this morning. Tonight: A portion of the Atlantic high will break off and form closer to the local area, allowing for a slackening of the gradient. The resulting winds will progressively come down, but it'll take longer for seas to subside. We'll likely see the advisory for AMZ350 ending early, but persisting across the outer Georgia waters through the night (and even in Wednesday). Wednesday through Sunday: Lingering 6 foot seas in the outer Georgia waters will subside by Wednesday evening. Otherwise, rather benign marine conditions are expected through late week as a weak pressure pattern remains in place. A cold front will drop south through the area Friday night into Saturday, and Small Craft Advisories could be needed in its wake. Winds and seas will improve late weekend into early next week. Rip Currents: A continued onshore flow, lingering astronomical influences and small swells from Hurricane Lorenzo will produce a Moderate Risk of rip currents at all beaches today. && .TIDES/COASTAL FLOODING... Tidal departures continue to remain far above predicted, and it won'd take much to produce moderate coastal flooding with the late morning high tide. In fact there is even some concern we could approach warning levels. For now we have tides reaching as high as 7.7 to 7.9 ft MLLW at Charleston and 9.4 to 9.6 ft MLLW at Fort Pulaski. Thus a Coastal Flood Advisory is in effect for all coastal sections, outside of tidal Berkeley, from 9 am to 1 pm. Additional Coastal Flood Advisories will be possible through mid week for minor salt water flooding. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Coastal Flood Advisory from 9 AM this morning to 1 PM EDT this afternoon for GAZ117-119-139-141. SC...Coastal Flood Advisory from 9 AM this morning to 1 PM EDT this afternoon for SCZ048>051. MARINE...Small Craft Advisory from 11 AM this morning to 8 PM EDT this evening for AMZ350. Small Craft Advisory until 11 PM EDT Wednesday for AMZ374. && $$ NEAR TERM... SHORT TERM... LONG TERM...ETM AVIATION... MARINE... TIDES/COASTAL FLOODING...