815 FXUS62 KCHS 050600 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 100 AM EST Thu Mar 5 2020 .SYNOPSIS... A stationary front will linger south of the area through tonight. Low pressure will then pass over south Georgia and eventually lift northeast up the coast on Thursday. High pressure is expected Friday through the weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... On the midnight update, we lowered POPs as much of the overnight should see a break from the steadier and heavier rains but there will still be scattered light rains around the region with an uptick in activity toward dawn. Temps will remain fairly steady with widespread cloud cover and light north to northeast winds. && .SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY/... A stationary front will likely be positioned just south of the area or near the Altamaha at the start of the period. Low pressure will then ride along the boundary across southern Georgia and eventually lift northeast up the coast through the day. Strengthening low level jet will allow for strong moisture transport into the area. PWats are forecast to be near or over climatological maxes. Given this and ample forcing for ascent from shortwave energy, upper divergence and multi-layer isentropic lift, another batch of moderate to potentially heavy rain will overspread the area. Additional rainfall of 1.5-2 inches, with isolated higher amounts, will be possible. Given saturated grounds, ponding on roadways and low lying areas are possible. WPC currently has the entire area within a Slight Risk for excessive rainfall. In addition to heavy rainfall, there will be some severe weather threat in the afternoon with 0-6 km shear values of an impressive 70+ knots. Majority of the forecast area will remain on the cool side of the low, so the best potential lies across our far southeast Georgia zones in closest proximity and south of the track of the low. Instability again is quite limited. The primary threats would be damaging wind gusts and isolated tornadoes with very high 0-1 km helicity values. The surface low will lift northeast and away from the area on Thursday night. As drier air moves in, precipitation should quickly come to an end. An amplified mid level trough over the eastern U.S. will shift off the coast Friday into Friday night. At the surface, high pressure will build into the area from the west. Deep dry air will provide sunny skies and dry weather. The main story for Friday will be the gusty northwest winds with an enhanced pressure gradient in place. Gusts to 25 knots over Lake Moultrie will be possible later in the day into Friday night, and a Lake Wind Advisory could eventually be needed. On Friday night, low temperatures are forecast to drop into the 30s - ranging from mid 30s inland to around 40 at the coast. At this time, conditions appear too dry and winds too elevated to support mention of frost. However, this will need to be monitored. Quiet weather will prevail on Saturday as high pressure continues to expand into the area. Despite sunny skies, ongoing cold advection will limit highs to the upper 50s. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... High pressure slowly moving across the Southeast U.S. will dominate the weather through Monday. Expect dry conditions with moderating high temperatures. A cold front could approach on Tuesday, bringing a chance of showers. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... Overnight, soundings suggest MVFR/IFR cigs should be more common at KSAV overnight with confidence in low clouds at KCHS quite low as models show some drier low level air briefly building in, Today, rains will expand and become heavier from mid to late morning through the afternoon hours. We cannot rule out some thunder at KSAV but at time, it looks elevated with not a lot of severe risk. Low level wind shear is possible but mainly to the south of the terminal this afternoon. Widespread IFR cigs and vsbys will be likely during the day. Tonight, the precip should taper to drizzle with the low offshore pulling away. There will probably also be widespread IFR cigs around prior to midnight as well. Extended Aviation Outlook: Low pressure will bring flight restrictions through late Thursday. Gusty winds are expected on Friday. VFR will prevail Friday through the weekend. && .MARINE... Generally, the sfc pressure gradient should yield strengthening NE winds overnight, with gusts to 20 kts across the offshore waters. Seas are expected to increase, ranging between 3-4 ft. Thursday through Saturday: An enhanced pressure gradient is expected Thursday into Friday as low pressure passes across southern Georgia and eventually up the Southeast coast. The best gradient appears to be across Charleston county waters on Thursday, and we have hoisted a Small Craft Advisory. There is potential it may need to be expanded into the Charleston Harbor. More solid Small Craft Advisory conditions are expected across all waters later Friday into Friday night following passage of the low. There also remains the potential for gale-force gusts across the outer Georgia waters, and a Gale Watch or Warning could eventually be needed. Conditions should subside a bit on Saturday, however it will take a little longer for the outer GA waters as 6 ft seas persist. Sunday: High pressure over the Southeast will bring tranquil conditions. && .HYDROLOGY... A Flash Flood Watch in effect, for most of our Georgia zones, except for the coastal zones. Periods of moderate to heavy rainfall will continue through Thursday. Additional rainfall totals are forecast average up to 2 inches, although isolated higher amounts cannot be ruled out. Reports from emergency management indicate there are several ongoing road closures due to flooding from prior rainfall, primarily across interior Georgia counties. Forecast rainfall will only exacerbate conditions through the duration of this event, and the Flash Flood Watch will continue. River levels are likely to rise again by late this week into the weekend. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Flash Flood Watch through this afternoon for GAZ087-088- 099>101-114>116-118-137-138-140. SC...None. MARINE...Small Craft Advisory from 10 AM this morning to 4 AM EST Friday for AMZ350. && $$ NEAR TERM... SHORT TERM... LONG TERM... AVIATION... MARINE... HYDROLOGY...