textproduct: Charleston

SYNOPSIS

A storm system will move through our region on Saturday, yielding widespread showers and some thunderstorms. High pressure and drier conditions return next week, with gradually warming temperatures.

NEAR TERM /UNTIL 6 AM SATURDAY MORNING/

Virga continues this evening as dry air below 560 mb, and VERY dry air below 750 mb, keep precip from reach the ground. Latest expectation is still that it will be early morning hours before low level moistening occurring, and a dry evening is still expected.

Tonight: A southern stream h5 shortwave will dig across the South Central United States and into the lower Mississippi River Valley, helping develop/sharpen low pressure over the Deep South while the subtropical jet remains across the northern Gulf Coast. Sfc winds will turn more southerly in advance of the system, resulting in much of the local area becoming warm- sectored during overnight hours along and south of a warm front positioned across South Carolina. Overnight temps will remain mild as a result, only dipping into the upper 40s inland to lower-middle 50s near the coast. Southerly winds will eventually advect deeper moisture across the region overnight, but it will take some time for precip to arrive with more favorable forcing across far western zones after midnight. The latest forecast continues to support 50-70% pops across far interior Southeast South Carolina and Southeast Georgia starting a few hours prior to daybreak, although few to scattered showers are possible across the Tri-County Area late, in the vicinity of the warm front.

SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/

Saturday: The mid-levels will consist of a shortwave over the Lower MS Valley in the morning. It'll shift over the Southeast during the day, traversing our area during the evening hours, then shifting offshore overnight. Additional, there will be a jet streak following this shortwave. At the surface, in the morning a front should stretch from the Lower MS Valley eastward, being located just west and north of our area. This front will slowly shift eastward during the day, with weak Low pressure trying to develop over south central GA, which will somewhat aid in defining the front. There will be a plume of moisture ahead of the front, with PWATs easily exceeding 1", and values possibly peaking around 1.5" across our southern tier of counties late in the afternoon. These values are above normal for this time of year. Models are in good agreement having light to moderate showers ongoing across most of our area at daybreak, followed by some letup later in the morning, before another possibly more potent round moves through late in the afternoon and early evening. There is a threat of severe thunderstorms in the afternoon, with the SPC highlighting areas south of the Charleston Tri- County under a Marginal Risk. As is typical this time of year, it's a high shear low CAPE event. 0-6 km bulk shear could be 40-50 kt in the afternoon. But both surface and MLCAPEs stay below 1,000 J/kg, with the highest values across southeast GA after peak heating. This is partly because there is a wide range in temperatures, with highs across our extreme northern tier maybe hitting the mid 50s and temperatures across our southern tier of counties approaching the lower 70s. So while stronger to marginally severe thunderstorms with damaging winds can't be ruled out, it appears the highest probabilities will be south of I-16 later in the afternoon. Luckily, the system will be moving fast enough to limit the rainfall potential. Storm total amounts should mostly be in the 0.5-0.75" range, with locally higher amounts expected in thunderstorms. This will put a dent in our drought, but the dry ground should do a good job at absorbing the rainfall, thus limiting the flood potential. Any rainfall and storms will end from west to east during the evening hours, with it expected to be dry after midnight. Lows should be in the mid 30s across our extreme northern tier, to the mid 40s across our southernmost tier of counties.

Sunday and Monday: Mid-level troughing located off the Southeast Sunday morning will shift further away while ridging builds from the Central U.S. This will lead to northwest flow overhead. Surface High pressure to our northwest Sunday morning will pass to our north Sunday night, then move off the Delmarva peninsula on Monday. The periphery of this High will bring our area drier conditions with a mix of sun and clouds. Northerly flow and some cold air advection will keep high temperatures at or slightly below normal on Sunday. Temperatures rise a few degrees warmer on Monday.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Expect dry weather to prevail as High pressure continues to dominate the forecast through the end of next week. Temperatures will be well above normal, especially for the second half of next week.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

VFR prevails into the very early morning hours with dry air in the low levels and light winds. Moisture advection strengthens as we approach daybreak, with gradually lowering ceilings filling in from the west. CHS/SAV/JZI will likely begin to see some MVFR ceilings around or shortly after daybreak as an initial wave passes north and west of the terminals. There is some uncertainty as we approach late morning, as IFR probs become very high (70+%) despite the area being in the warm sector in the afternoon. Nonetheless, have IFR cigs prevailing by late morning into the afternoon, with scattered downpours and thunderstorms possible Saturday afternoon.

Extended Aviation Outlook:Showers and storms could hang around into Saturday evening, with clearing conditions arriving from the west late evening into Saturday overnight. VFR then prevails Sunday into next week.

MARINE

Overnight, sfc winds should become more south as the region becomes warm-sectored in advance of a low pressure system tracking across the Deep South. The pressure gradient could weaken slightly, but wind gusts up to 15-20 kt will still remain common. Seas should build about a foot by daybreak, largest across outer Georgia waters.

Saturday: A storm system will move through our area, bringing some impacts to the coastal waters. Expect elevated SW winds and seas ahead of the system during the day, quickly veering to the NNW behind it overnight. The Small Craft Advisory remains out for the GA waters from 20-60 nm. Also, expect widespread showers and some thunderstorms with locally higher wind gusts.

Next Week: Sunday morning winds will ease and seas will subside. High pressure will then prevail north of our area, bringing tranquil marine conditions.

TIDES/COASTAL FLOODING

Astronomical tides will be elevated this weekend due to the full moon (on Saturday). Saturday, wind directions will not be favorable for high tidal departures, so the Charleston high tide is forecasted to be below 7 ft MLLW with the morning high tide. However, light rainfall associated with a passing storm system could be ongoing. Sunday, surface winds turn more towards the north-northeast during the morning, likely leading to greater tidal departures. Even though the rainfall is expected to end before the morning high tide cycle, minor coastal flooding is currently forecasted. A Coastal Flood Advisory could eventually be needed Sunday morning.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory from 10 AM Saturday to 3 AM EST Sunday for AMZ374.