textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Unsettled weather returns tonight and lingers through early next week.

DISCUSSION

KEY MESSAGE 1: Unsettled weather returns tonight and lingers through early next week.

Dry surface high pressure will continue to traverse the region from west to east before moving offshore this evening, with a stationary front draped across northern Florida. While some weak echo's are observed on radar across across our far south near Darien, GA, a dry layer between 850-700mb is preventing those raindrops from reaching the surface. Low-level moisture off the gulf surges precipitable water values towards 1.5-1.75 inches across the southeast region tonight, and combined with shortwaves in the mid-levels and low- level isentropic lift, chances for a couple rounds of more focused rainfall return. The first round arrives late tonight and departs Saturday morning, with the next arriving early afternoon Saturday (~1-2 PM) pushing offshore in the evening hours.

The afternoon round will need to be monitored for strong to severe thunderstorms, but will be largely dependent on how quickly the earlier activity dissipates which will influence how much instability will be able to build. Deterministic and ensemble guidance suggest 1000-1500 J/kg of CAPE builds across southeast Georgia, with lesser amounts moving northwards into southeast South Carolina. 0-6 km bulk shear is fairly uniform across the region between 40 to 50 knots, though the highest low-level lapse rates of 6-7.5 deg C/km are expected across portions of southeastern Georgia. This matches well with SPC's Day 2 convective outlook, showing a marginal risk (level 1 out of 5) for portions of southeast Georgia, which also agrees well with the various AI/ML output. Given the long and skinny sounding profiles large hail is not expected, but with the aforementioned low-level lapse rates and inverted v sounding signatures, strong winds appear to be the greatest risk.

We may see a brief break in rain coverage between rounds of shortwaves aloft, though precipitation coverage rises again Sunday morning into Monday as stronger shortwaves move in aloft. This will bring widespread precip activity, further enforced by an approaching cold front and additional shortwaves that move in Monday before exiting on Tuesday. Total precipitation Friday night through Monday is continues to range from 0.75 to 1.75 inches, though a few locations could exceed these amounts should showers and/or thunderstorms become focused near the boundary/nearly stationary front for longer durations late weekend. However, given the prolonged event to reach these rainfall totals, precip rates are not currently expected to result in a significant flooding threat.

Surface high pressure builds in behind the cold front, bringing back dry conditions for a few days.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Prevailing VFR conditions continue at CHS/JZI/SAV terminals through 12Z Saturday. Showers should develop and move into/across the local area tonight, starting across southeast Georgia and impacting the SAV terminal in the 06-12Z timeframe possibly lingering longer into the afternoon, then spreading into Southeast South Carolina and impacting the CHS/JZI terminals starting around 10Z Saturday. PROB30 groups have been added with MVFR flight restrictions during these noted times. Scattered thunderstorm coverage looks to increase Saturday afternoon, but have left mention out as PROB30 group would have started at 18Z.

Extended Aviation Outlook: Occasional flight restrictions Saturday through Monday as a stalled front brings showers and thunderstorms.

MARINE

Today - Tuesday: Winds remain on the weaker side with calm seas through the weekend, accompanied by periods of isolated to scattered showers and thunderstorms. Ahead of an approaching cold front on Monday, the pressure gradient along the coast does get pinched into Tuesday, leading to some marginally breezy south-southeasterly winds. Strongest winds are expected behind the cold front as a surface high pressure moves in overnight into Tuesday morning, likely necessitating a Small Craft Advisory for waters outside of the Charleston Harbor.

CHS WATCHES/WARNINGS/ADVISORIES

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