textproduct: Charleston

WHAT HAS CHANGED

The Aviation section was updated for the 18/12z TAFs.

KEY MESSAGES

- 1) Minor coastal flooding is possible along coastal areas of Charleston and Colleton Counties with high tide this evening and possibly Tuesday evening.

- 2) Mostly dry conditions expected through midweek with increasing rain chances to occur late week.

DISCUSSION

KEY MESSAGE 1: Minor coastal flooding is possible along coastal areas of Charleston and Colleton Counties with high tide this evening and possibly Tuesday evening.

Astronomical influences associated with the recent new moon and lunar perigee along with a modest onshore flow will continue to drive elevated tide levels, leading to minor coastal flooding along parts of the lower South Carolina coast this evening. The latest forecast advertises a peak high tide 7.0-7.2 ft MLLW in the Charleston Harbor this evening and 6.9-7.1 ft MLLW Tuesday evening. A Coastal Flood Advisory for Coastal Colleton and Charleston Counties could be for this evening's high tide and possibly again Tuesday evening although confidence in reaching the 7.0 ft MLLW minor flood stage is much more uncertain by then. Astronomical tide levels then begin to fall and the potential for minor coastal flooding will diminish.

KEY MESSAGE 2: Mostly dry conditions expected through midweek with increasing rain chances to occur late week.

Sfc high pressure and upper level ridging holds tight across the region through mid-week, allowing largely dry conditions to prevail. Model soundings also remain quite capped, so in the off chance that precipitation does develop, expect overall accumulations and severe potential to remain low. Otherwise, look for afternoon highs to warm into the upper 80s to lower 90s under mostly sunny skies, with lows only dipping into the mid to upper 60s.

Upper level pattern shifts heading into the latter half of the forecast period, resulting in chances for unsettled weather. As noted in the previous discussion, a decent amount of model uncertainty still exists, making it hard to put too much confidence in any one solution just yet. While details still need to be ironed out, most guidance does showcase a shortwave trough digging across the central/northern Plains by Thursday. Meanwhile, at the sfc, will see a cold front dive southeastward across the Ohio/Tennessee River Valley, sending the aforementioned high pressure into the Atlantic. There are some indications that this boundary could stall across our area through Saturday, which would support increasing moisture and higher rain chances. However, if the ridge remains stronger, the front and better forcing could remain farther to the west and north, resulting in lower rain chances than currently forecast. Do think it is worth noting though, that latest ensemble probabilities for accumulated rainfall > 1" now showcase a 20-60% chance (highest inland). Certainly something to keep an eye on in the coming days.

AVIATION /09Z MONDAY THROUGH FRIDAY/

18/12z TAF Discussion: KCHS/KJZI/KSAV: Shallow ground fog at all three terminals will quickly dissipate at sunrise. VFR for the period. Gusty winds will occur with the passage of the sea breeze this afternoon. Shallow ground fog will be possible again at all terminals early Tuesday morning.

Extended Aviation Outlook: There are no high confidence concerns.

MARINE

Through Tonight: The synoptic flow regime will change little through tonight as Atlantic high pressure remains centered well offshore. A easterly flow regime will prevail with east to southeast winds 15 kt or less prevailing. Some local enhancement could occur along the land/sea interface and Charleston Harbor this afternoon with sea breeze. Seas will average 2-4 ft.

Monday through Friday: No marine concerns are expected. High pressure to the east will drive onshore east-southeasterly flow each day, with wind speeds mostly topping out in the 10-15 knot range. Each afternoon and evening there could be some local enhancement along the land/sea interface with the diurnal sea breeze. Seas should average 2-4 feet through the period.

Rip Currents: Influences from the new moon cycle combined with persistent onshore flow will produce an elevated risk of rip currents through midweek. A moderate risk for rip currents is in place for all beaches through Tuesday.

CHS WATCHES/WARNINGS/ADVISORIES

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