textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Rounds of passing showers could bring some rainfall to southeast Georgia and southeast South Carolina through Thursday.

- 2) A disturbance could bring much-needed rain to the region Friday night through Saturday, though no significant impacts are expected at this time.

DISCUSSION

KEY MESSAGE 1: Rounds of passing showers could bring some rainfall to southeast Georgia and southeast South Carolina through Thursday.

Through tonight: Early this morning, a large area of convection associated with an area of low pressure is producing severe weather across a large area that covers the ArkLaTex, the Lower MS Valley, and portions of the Deep South. Through the pre-dawn hours, this upstream convection is expected to steadily shift to the east and should be on the doorstep of the forecast area by around sunrise. The convection will certainly be in a deteriorating state and will likely mostly be an area of showers or remnant light stratiform rainfall. This will work eastward across the forecast area through the morning while continuing to weaken and dissipate. Rainfall amounts should be light, with the highest amounts mostly less than a tenth of an inch and still with many area receiving little to no measurable rainfall. In the wake of this area for the afternoon, the environment should be pretty stable with only a low end threat for an isolated shower to develop. Overnight, the front will push into the area and likely become aligned along the Gulf Coast and into southeast GA late. Model guidance then develops another area of convection along the front and the Gulf Coast and tracks it eastward toward the area in the early morning hours. Model guidance does show some potential for a corridor of instability (along and south of I- 16) that could allow this convection to maintain some strength and potentially even pose a damaging wind gust threat. The severe threat is still considered low, though we will have to watch the evolution of the convective cluster as it arrives in the pre-dawn hours.

Thursday: The aforementioned early morning convection should track to the east quickly and offshore by mid morning. This will likely be on a trajectory to mostly be an issue for southeast GA, but will depend on exactly where the front aligns. This diminishing convection should exit to the east quickly in the morning and leave the rest of the day dry for most of the forecast area. Depending on where the front is exactly, there is some risk of afternoon and evening thunderstorm development along and south of I-16 where destabilization is most likely. But for most of the area, a dry forecast.

KEY MESSAGE 2: A disturbance could bring much-needed rain to the region Friday night through Saturday, though no significant impacts are expected at this time.

A wave of low pressure will traverse the northeastern Gulf coast Friday and then swing along the Carolina coast Saturday before exiting the Southeast. An abundance of Gulf moisture will be ushered into the region, noted by PWATs increasing to around 1.5-1.7 inches. While its too early to pin down the exact axis of heaviest rain, as it stands, models show the general area receiving a healthy dose of rain from this event. NBM mean 24-hr rainfall totals average about 1- 1.5 inches across southeast South Carolina and southeast Georgia. Probabilities for 2 inches or greater range from 10-30% most places with 30-40% far inland. Due to limited instability (SBCAPE less than 500 J/kg), thunderstorm activity will likely remain offshore or south of the Altamaha River. That being said, the risk of significant impacts remains low.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

The 06z TAF period begins with VFR conditions at KCHS, KJZI, and KSAV. The first forecast concern is the potential for MVFR and IFR stratus to develop over the next few hours. Model guidance is quite aggressive in doing so, though there are no signs of any development yet. We have timed in IFR ceilings starting around 09-10z at all 3 sites and allowed this to run through much of the morning. The next forecast challenge concerns an area of showers expected to move across the terminals from around sunrise through midday. This activity should be in the form of either light stratiform rain or passing showers, and IFR ceilings and some MVFR visibilities can be expected. Overall, this should come to an end by around midday and the afternoon should be VFR and rain-free.

Extended Aviation Outlook: Flight restrictions are possible through the rest of the week within showers/thunderstorms, especially Friday into Saturday as a system moves across the region.

MARINE

Today through Thursday night: Southerly flow is expected to strengthen across the local waters today ahead of an approaching cold front. Winds should peak in the afternoon through the early evening, and will be a solid 15-20 knots for most of the waters with the strongest winds across the Charleston County waters. Gusts into the 20-25 knot range are expected here, and could be marginally supportive of a Small Craft Advisory (SCA). The cold front will drop through Wednesday night into Thursday morning, turning winds northerly and then northeasterly through Thursday night. Conditions during this time should be well below SCA criteria.

Extended Marine: A low pressure system affecting the local waters Friday night through Saturday night could bring another period of elevated winds and seas. Small Craft Advisories could be needed for gusts 25-30 kt and seas 5-6 ft.

Rip Currents: Higher-period swell (10-11 seconds) and increasing south to southwest winds along the coast will result in a moderate risk of rip currents at all beaches today.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...None.