textproduct: Charleston

WHAT HAS CHANGED

Aviation section has been updated to reflect the 12z Aviation forecast.

KEY MESSAGES

- 1) Rain chances will then gradually increase this weekend and especially by early next week. Cooler temperatures return by the end of the week.

DISCUSSION

KEY MESSAGE 1: Rain chances will then gradually increase this weekend and especially by early next week. Cooler temperatures return by the end of the week.

Saturday and Sunday: Increasingly unsettled weather will begin to setup this weekend as an upper level low slowly drifts across Florida and into the northern Gulf. At the surface a weak backdoor front will slip into the area from the north late Saturday evening into the day on Sunday. Moisture will increase throughout the weekend as we move to the eastern side of the upper low and the surface front sags into the area. PWATS should approach the 2 inch range by Saturday afternoon and increased chances for showers and thunderstorms will be expected Saturday and Sunday. The best chances this afternoon look to be mainly around the Tri-county area where the influences of the backdoor front will be and along a slow moving seabreeze this afternoon. By Sunday, rain chances look to be more confined to the seabreeze. Given PWATS near 2 inches, a localized heavy rainfall threat cannot be ruled out; however, rather poor instability and no real focus for continued redevelopment would likely not support a more widespread heavy rain issue. Poor instability and little to no deep layer flow will also likely limit the severe potential.

Monday Onward: An upper-level low over the Florida Peninsula will weaken as it gets swept northeast by an approaching longwave trough. The combination of the upper low and an incoming surface cold front will yield an increase in shower and thunderstorm coverage through midweek. The highest storm coverage, along with a localized threat for heavy rainfall and minor flooding (given PWATs 2+ inches), will align with the arrival of the front Tuesday into Wednesday. During peak afternoon heating, a few strong thunderstorms will also be possible, but the overall severe threat looks to be limited.

A noticeable cool-down will take hold on Thursday behind the passage of the cold front as high pressure wedges south, ushering in cold air advection. Cooler, drier conditions will persist through the end of the week with highs currently forecast to top out in the upper 70s to lower 80s across southeast South Carolina and the mid 80s in southeast Georgia. Overnight low temperatures will fall into the lower 60s away from the immediate coast.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

19/12z TAFs:VFR conditions should prevail throughout the forecast with winds becoming light and easterly during the afternoon. A few showers could be possible around CHS/JZI during the late afternoon before clearing during the early evening. MVFR ceilings should spread south after midnight as a weak front slowly moves through the area.

Extended Aviation Outlook: Shower/thunderstorm chances are expected to peak Tuesday into Wednesday with the approach of a cold front. Periodic flight restrictions are possible.

MARINE

Today: Very quiet conditions will prevail across the local waters. Winds will be strongest this afternoon and through the evening along the land/sea interface with the sea breeze, though winds should peak in the 10-15 knot range. Then overnight, winds will diminish to be 5 knots or less. Seas will average 1-2 ft, except 2-3 ft early for the Georgia offshore leg.

Sunday through Thursday: There are no marine concerns through early next week as winds/seas are expected to remain well below Small Craft Advisory levels. However, a cold front is anticipated to reach the area by the middle of next week, which is expected to produce an uptick in winds with gusts nearing 25 kt, along with building seas (3-6 ft). Trends will need to be monitored for potential Small Craft Advisory level conditions. Additionally, shower/thunderstorm coverage is expected to increase during the middle of next week ahead/along the approaching front.

CHS WATCHES/WARNINGS/ADVISORIES

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