Marine Weather and Tide Forecast for Charleston, SC

NEAR TERM /THROUGH TONIGHT/
Rest of the afternoon: A couple shortwaves are moving southeastwards towards the area out ahead of the ridge axis aloft, bringing chances for a couple rain showers into the evening hours. The highest chances (40-50%) for thunderstorms will arrive during the early evening hours as the remnants of the ongoing group of thunderstorms (or MCS) moves down towards the area along and south of a stalled frontal boundary. With CAPE values of up to 2000 J/kg, and 40 to 50 knots of effective bulk shear there is a low end potential (level 1 out of 5) for an isolated strong to severe thunderstorm. Chances for hail look to be minimal/near- zero given long and skinny CAPE profiles and thus weak mid-level lapse rates, while 400-800 J/kg of DCAPE does lead to a low risk for strong to severe winds. Overall, most guidance shows the thunderstorms decaying as they move into the Low Country,

Given the increase in cloud coverage, in addition to the aforementioned rain, did lower highs a touch for today while still expecting afternoon highs in the upper 80s to lower 90s, highest across southeastern Georgia where cloud coverage and rain chances will be lowest. Beaches still expected to reach up into the mid to upper 80s.

Tonight: Upper level ridging tonight and into the overnight hours will lead to quiet conditions returning, with the stalled surface boundary remaining just to the north of the forecast area. Winds will weaken and remain variable overnight, with cloud coverage remaining high enough to keep chances for fog low.

SHORT TERM /TUESDAY THROUGH THURSDAY/
Tuesday: Weak frontal remnants over the Midlands and Pee Dee will meander farther to the north through the day as subtropical ridging builds aloft. Model soundings show a considerable amount of dry air will be in place through peak heating with little in the way of meaningful instability noted. K-indices are progged to drop into the teens as mid-level dry air deepens with time. This will essentially eliminate any convective potential south of the Santee River even if some weak mixed-layer instability is able to develop. Gridded pops were held below mentionable thresholds. Highs will reaching the lower-mid 90s away from the beaches. Overnight lows will bottom out in the lower 70s except mid 70s at the beaches and Downtown Charleston.

Wednesday: The upper flow across the Southeast U.S. will become more zonal as a shortwave dampens across the Central/Northern Plains. A weak shortwave is progged to pass by to the north during the afternoon hours which will help push a cold front with a band of showers/tstms into the region during the afternoon/evening hours. Model cross sections suggest the ribbon of strongest forcing will pass by to the north with the shortwave itself with only meager UVVs noted this far the south. Modest stability will be place ahead of the front, but the coverage of showers/tstms should diminish with time as the front encounters less net available moisture over Southeast South Carolina and Southeast Georgia. The greatest juxtaposition of instability and 850 hPa theta-e looks to occur across Southeast Georgia, so this should be where the greatest coverage of convection occurs. Pops 20-40% looks reasonable, highest south of the I-16 corridor. Rain chances will end during the evening hours as the front pushes offshore. Highs will warm into the lower 90s away from the beaches with lows ranging from the lower 60s well inland to the lower 70s at the beaches and Downtown Charleston Wednesday night.

Thursday: Weak high pressure will build into the area Thursday as the flow aloft becomes slightly more cyclonic. Dry, stable conditions will keep the area rain-fre. It will be a bit cooler behind the front with highs reaching into the mid-upper 80s.

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
High pressure will extend over the area through the weekend. A weak warm front will develop and lift near/north of the area Sunday into Monday. A few showers/tstms could develop near/south of the front, mainly Monday. Temperatures will be at to slightly below normal.

AVIATION /19Z MONDAY THROUGH SATURDAY/
19.18Z: After a brief lull, afternoon showers and eventually thunderstorms will expand in coverage for the rest of this afternoon and into the evening hours. Lowest confidence is for southeastern Georgia, as dry air in the mid-levels may hinder rain formation, so have left mention out of the KSAV TAF. For KJZI and KCHS, started shower activity at 22/21Z respectively, and included a PROB30 group at 20.00/19.23 for thunderstorm mention.
Thunderstorms may bring brief MVFR cigs and visbys, along with some breezy winds out of the west. After that, quiet conditions return with VFR conditions for the rest of the period.

Extended Aviation Outlook: Isolated to scattered showers/tstms are possible Wednesday afternoon.

MARINE
Today and tonight: 5 to 10 knot winds will remain out of the south- southeast for the rest of today, perhaps a touch closer to 15 knots for areas directly along the coast. Chances for scattered showers increase into the evening hours, perhaps even a thunderstorm or two.
Can't entirely rule out a SMW being necessary as thunderstorms will be capable of producing strong winds over 30 knots. Wave heights of 2 feet will continue into the overnight period, with the wind direction becoming southwesterly into the overnight period and past daybreak.

Monday through Friday: There are no major concerns through the period. Afternoon sea breeze surges along the land/sea interface and Charleston Harbor are possible Tuesday and Wednesday afternoons.
Offshore winds will develop Wednesday night as a cold front pushes off the coast, but will return southerly by Thursday as high pressure builds back in. Both winds and seas will remain below Small Craft Advisory levels.

CHS WATCHES/WARNINGS/ADVISORIES
GA...None.
SC...None.
MARINE...None.