textproduct: Charleston

WHAT HAS CHANGED

The Aviation section was updated for 12Z TAFs.

KEY MESSAGES

- 1) Rounds of unsettled weather will linger through Monday.

DISCUSSION

KEY MESSAGE 1: Rounds of unsettled weather will linger through Monday.

Saturday: A stationary front will continue to meander across northern Florida today. Guidance shows an MCS developing over the lower Mississippi Valley this morning before tracking east across the Gulf Coast and into southern Georgia this afternoon. This convection is expected to reach the forecast area during the afternoon hours and move offshore by early evening. However, trends through the morning will need to be monitored closely, as some solutions suggest the convection may remain just south of the area and/or weaken as it heads into the western portions of the forecast area. Deterministic and ensemble guidance continue to indicate a local maximum in SBCAPE along the Southeast Georgia coast, generally around 1000-1500 J/kg, with lower instability extending into coastal southeast South Carolina and inland areas. Deep-layer shear remains fairly uniform across the region at 40-50 kt, while the steepest low- level lapse rates, around 6-7 deg C/km, are forecast across portions of southeastern Georgia. As a result, this area has potential for thunderstorms to become strong to marginally severe. Long, narrow forecast soundings should limit the large hail threat, but the combination of steep low-level lapse rates and inverted-V sounding profiles supports the potential for strong, locally damaging wind gusts within any stronger storms.

Sunday: The mid-levels will consist of mainly zonal flow overhead. Though, models indicate there should be some vorticity passing to our south during the morning and into the afternoon. At the surface, a stationary front may be located just to our south in the morning. It'll try to slowly lift north during the day, probably dissipating as it moves through our area. There will be a deep plume of moisture around the front, with PWATs peaking around 1.8" across our area. These values are well above normal for this time of year. High temperatures near or slightly above normal will generate some instability. All of these factors along with the inland moving sea breeze will help to generate showers and thunderstorms during the day and into the night. SPC has portions of our area, mainly south of I-16, under a Marginal Risk of severe thunderstorms, with the main threat being damaging winds due to precipitation loading. This will be highly dependent on several factors coming together simultaneously.

Monday: A mid-level shortwave over the Lower MS Valley in the morning will shift eastward, moving over the Southeast U.S. overnight. A cold front will also be moving eastward with it, possibly making it to our area by the late afternoon or early evening. Deep moisture originating from the Gulf will be ushered into our area in the afternoon. There are signs that PWATs could make a run for 2", which is well above normal. But the combination of lift and moisture will probably generate a round of showers and thunderstorms just ahead of the front. Temperatures may rise into the lower 80s ahead of the front, which will generate a small window of decent instability and shear. There is the potential for severe thunderstorms with damaging winds. We'll have to see what the SPC forecast for our area shows. After the convection, conditions should improve overnight.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

12Z TAFs: A lull in precipitation is expected through the late morning before attention turns to a potential round of showers and thunderstorms associated with an approaching MCS this afternoon into early evening. Confidence in direct terminal impacts remains somewhat uncertain, as some guidance suggests convection could weaken upon arrival or remain just south of the area. The environment across southeast Georgia could support a strong to marginally severe thunderstorm capable of producing strong wind gusts. As a result, KSAV has the highest likelihood of seeing impacts from stronger storms should convection directly affect the terminal. However, at this time mention of direct impacts have been left out, considering our low confidence. Late morning, ceilings are expected to lower and hover around MVFR levels, likely persisting through much of the daylight hours. Any direct impacts from storms would likely result in brief IFR restrictions. Conditions are then expected to improve to VFR this evening as any convection moves offshore. Another round of lowering ceilings and MVFR/IFR cigs look likely just before sunrise Sunday.

Extended Aviation Outlook: A stationary front and then a cold front will bring occasional flight restrictions due to showers and thunderstorms through Monday. Then, winds may be gusty late Monday night into Tuesday.

MARINE

Today and tonight: Southerly winds will remain light through tonight along with relatively calm seas, accompanied by periods of isolated to scattered showers and thunderstorms.

Extended Marine: A front is forecasted to lift north through our area on Sunday, and possibly dissipate. Then, a cold front will quickly move through on Monday, bringing near gale conditions that should last into Tuesday. Small Craft Advisories will be needed for portions of our waters during this time period. Likewise, we'll also need to monitor the potential for gale conditions in the outer waters. Conditions improve later Tuesday into Wednesday as High pressure quickly passes to our north.

CHS WATCHES/WARNINGS/ADVISORIES

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