232 FXUS62 KCHS 062101 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 401 PM EST Sun Nov 6 2022 .SYNOPSIS... Strong high pressure will prevail into the early part of the week. Low pressure that develops in the Atlantic could impact the area during the middle and latter portion of this week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... The expanding wind field around developing low pressure north of Puerto Rico will cause low-level winds to back to a more northeast direction across coastal SC/GA tonight. As the deep southeasterly flow subsides, boundary layer moisture will decrease as well. The area of scattered showers and isolated thunderstorms across southeast GA and far western SC will gradually shift inland and diminish through early to mid evening. Overnight we should see dry conditions with skies gradually clearing. Surface winds will go light and variable in many areas away from the coast, allowing for patchy fog to develop. We can't rule out some dense fog across far inland SC/GA locales a few hours before daybreak Monday. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... Monday and Monday night: A strong 591 dm high centered in the Tennessee valley will cover the region resulting in large scale subsidence and a stable environment. Meanwhile deepening low pressure east of the Bahamas will begin to take on tropical or subtropical characteristics as it lifts slowly northward, while at the same time a robust 1040+ mb high builds out of Canada from the northwest. After some morning fog, a good deal of sunshine will transpire, and with above normal heights aloft and low level thickness, we're looking at another warm day. Our latest forecast actually shows max temps within a degree or two of record warmth at KCHS and KSAV (see CLIMATE section below). There is a change in the air mass late Monday night as the Canadian high continues to build in over a decaying cold front. This will lead to some upper 50s northern sections and lower 60s elsewhere for min temps. Tuesday and Tuesday night: As the surface high shifts into southeast Canada and the northeast states, it will set up a wedge pattern along the eastern slopes of the Appalachians into the Southeast. This will be the steering mechanism for the low in the Atlantic that makes a sharp turn toward the west-southwest as it heads toward the northwest Bahamas. The pressure gradient between these two features will tighten, leading to northeast winds that increase, with frequent gusts of 20 mph or greater inland and close to 30 mph at times along the coast. The resulting air mass will be both cooler and drier, with temps a good 8-10F cooler than Monday, and dew point values that plunge into the 40s or even in some cases the 30s. You'll certainly be able to feel the cooler air Tuesday night with the cold advection leading to min temps actually close to climo. We'll need to keep a watch out winds on Lake Moultrie and the possible need for a Lake Wind Advisory. Wednesday: Impressive high pressure covering the area from New England to the Southeast will continue steer the low to the south westward near the northwest Bahamas and the Florida peninsula. the gradient will continue to tighten further, and we're looking at the possibility of Wind Advisories and a lake Wind Advisory for northeast winds of 20-30 mph and gusty. Moisture convergence does increase over the ocean, leading to at least some formation of showers. But there is still too much ridging and subsidence in place over land, plus limited moisture, thus keeping land areas free of any rainfall. Temps will actually be below normal for the first time in more than a week, with latest projections are that we struggle to get out of the 60s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Our main focus will be on the low to the south that will eventually reach near or over the Florida peninsula, still being steered westward by the high to the north. The challenge is when will the ridge break down enough to allow for the low to gain latitude. A faster eroding ridge will cease the westward movement of the system where it has the potential to then take on a more northeastward track as a trough phases with its upper counterpart. This scenario will likely result in a slightly quicker departure of the low; moving out of the area by early weekend. On the other hand, a more substantial ridge could allow the system to reach the Gulf of Mexico before becoming absorbed by the trough and phasing with a surface cold front, shifting it eastward back into the Atlantic as the front sweeps the area. Rain coverage and intensity will likely increase late in the week, with some risk for flash flooding if the low tracks close enough to the local counties. In addition, strong and gusty winds will continue. Even though guidance has trended more consistent with the low of late, since there remain uncertainties about when the ridge breaks down, the exact details of the forecast will likely change through the week. && .AVIATION /21Z SUNDAY THROUGH FRIDAY/... Numerous showers will impact KSAV early this afternoon, along with possible MVFR ceilings. Conditions should improve by 20 or 21Z. For the remainder of the terminals and 18Z TAF period, VFR anticipated. Some shallow ground fog possible late tonight but the best chance for more widespread and/or dense fog will be far inland. Extended Aviation Outlook: Due to strong high pressure to the north and low pressure to the south, gusty NE winds are likely at the terminals Tuesday through Friday. Eventually flight restrictions could occur, especially the latter half of the week due to increasing rain chances. && .MARINE... Winds will turn back to the northeast tonight with speeds at or below 15 kt. Nearshore seas appear to be staying below 6 ft, though just beyond 20 nm we expect 6-7 ft seas to persist through the night so we maintained the Small Craft Advisory for the GA offshore waters. Monday through Friday: Even though winds and seas will be somewhat elevated as we begin the period, enough for a continuation of the Small Craft Advisory for AMZ374 due to 6 or 7 foot seas, this will actually be the "best" conditions of the upcoming week. We're looking at a prolonged period of potentially dangerous marine conditions that will occur, mainly due to the large pressure difference between strong high pressure to the north and tropical or subtropical low pressure to the south. Latest indications are that developing low pressure east of the Bahamas will only go so far north early in the week, before turning rather abruptly toward the W-SW midweek and heading toward the NW Bahamas and eventually the Florida peninsula. late int he week the low will gain some latitude as it starts to get steered by a cold front and upper trough. Conditions over the maritime community will deteriorate Monday night and Tuesday, enough so that Small Craft Advisories will cover all of the waters. During the mid and late week period there is an elevated risk for Gale Watches and Warnings for NE and E winds in excess of 35 or 40 kt. Seas will easily respond and build to as large as 9 to 13 feet on the 0-20 nm waters and 13-17 feet further out. At some point the coverage and intensity of rains will develop, mainly during the second half of the week. High Surf: Low pressure that will to form to the south this week will interact with strong high pressure to the north. Strengthening northeast winds and building seas between these two systems will result in dangerous surf conditions beginning Tuesday. Breakers of 5 feet or larger will impact the beaches, and High Surf Advisories will likely be required. In addition, areas of beach erosion will occur, some of which could potentially be significant. && .TIDES/COASTAL FLOODING... Astronomical high tides will impact the area this week due to the influences of the full moon on November 8th. So tides will already be elevated to begin with, and with strong high pressure to the north and a tropical or subtropical low to the south, the potential for coastal flooding will increase through the week. Initially there is only a minor coastal flooding concern starting with the Monday morning high tide, mainly in the Charleston area. However, with persistent and stronger northeast winds to occur Tuesday through late in the week, even higher tidal anamolies will occur. This could result in moderate or perhaps even eventually major coastal flooding along the entire southern South Carolina and southeast Georgia coasts. A series of Coastal Flood Advisories are almost a certainty, and even Coastal Flood Watches and Warnings could eventually be necessary. && .CLIMATE... Record highs for Monday, Nov 7th: CHS: 84 in 1986 CXM: 82 in 2015 and previous KSAV: 86 in 1986 && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...Small Craft Advisory until 6 AM EST Saturday for AMZ374. && $$ NEAR TERM...JRL SHORT TERM... LONG TERM... AVIATION...JRL MARINE...JRL TIDES/COASTAL FLOODING... CLIMATE...