textproduct: Charleston

WHAT HAS CHANGED

The Aviation section has been updated for the 12Z TAF issuance.

KEY MESSAGES

- 1) A passing cold front will result in widespread rainfall today.

DISCUSSION

KEY MESSAGE 1: A passing cold front will result in widespread rainfall today.

A shortwave aloft tracking across the Deep South will advance into the Southeast U.S. today, bringing multiple rounds of vorticity energy. A weak cold front, currently draped across the Upstate, will gradually sink southward across the forecast area through the day before pushing offshore this evening. Relatively deep moisture, with precipitable water values around 1.3-1.4 inches, will remain in place during the passage of the front and support widespread shower development. The heaviest rainfall is expected this morning through the afternoon, with some lingering showers continuing into the evening. Once the front pushes offshore this evening, most of the rainfall will diminish as drier air filters in behind it and high pressure builds.

Showers will generally be light to moderate, producing enough to drop a healthy amount of much needed rain. Rainfall totals are forecast to range from one-quarter to three-quarters of an inch. The lowest totals are expected along the coast, with higher amounts inland, particularly across the CSRA and the South Carolina Midlands. Locations across northern Berkeley, Dorchester, and Colleton counties could receive close to one inch of rainfall.

While showers will be the primary precipitation type, weak instability (CAPE values around 100-300 J/kg) across extreme southeast Georgia could produce an isolated thunderstorm in the late morning/early afternoon, mainly south of Savannah and near the Altamaha River.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

Light to moderate shower activity is expected to spread across the area today, producing prevailing MVFR conditions at CHS/JZI through at least 15Z Friday, and TEMPO MVFR conditions at SAV until 16Z Friday. Expect conditions to gradually deteriorate to IFR late morning into afternoon hours at all terminals, although trends could lead to delaying the arrival of IFR a few hours into the afternoon. Shower activity should end with cold fropa early-mid evening, but IFR cigs are likely to persist following the front through 12Z Saturday. There are also hints that vsbys could lower post fropa overnight, generally in the 3-6SM range, but confidence is too low to include prevailing groups with vsbys below 6SM at this time.

Extended Aviation Outlook: Periods of MVFR/IFR cigs are likely at all terminals through around daybreak Saturday, until dry high pressure takes over with improving cigs to VFR by late Saturday morning. VFR conditions should then prevail Sunday into Monday. The next chance of flight restrictions arrive late Monday and Tuesday with a passing cold front next week.

MARINE

Today through Sunday: No marine concerns are expected through the period. A cold front will approach the area late today and likely shift offshore this evening, helping produce northerly winds around 15 kt while seas range between 2-3 ft. High pressure will then spread across the region through the weekend with conditions that remain below Small Craft Advisory levels into early next week.

Monday and Tuesday: A cold front should shift south across the Carolinas early next week with high pressure wedging into the area and creating a strong pressure gradient across coastal waters. Northerly winds could surge to around 25 kt with seas building up to 6-8 ft. Small Craft Advisories could eventually be needed across a majority of local waters.

CHS WATCHES/WARNINGS/ADVISORIES

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