textproduct: Charleston

WHAT HAS CHANGED

Aviation section was updated for the 18z TAFs. A Small Craft Advisory has been issued for AMZ374 from Thursday afternoon into Thursday night.

KEY MESSAGES

- 1) Some much needed rain will fall across the area today through early Thursday as a cold front pushes through.

DISCUSSION

KEY MESSAGE 1: Some much needed rain will fall across the area today through early Thursday as a cold front pushes through.

A surface cold front is approaching the region from the west this afternoon. Aloft, a positively tilted trough positioned just west of the Ohio River Valley at 250 hPa will swing eastward through this afternoon and tonight. Rainfall will continue to spread eastward this afternoon, with most locations receiving generally 0.25-0.5" of rain. While the surface cold front is expected to clear the region late tonight/early Thursday morning, this upper trough will still be situated over the Eastern CONUS Thursday morning. This will likely yield very light rain or even drizzle over portions of the forecast area, especially the Charleston Tri-County. While the cold front will usher in a colder airmass, temperatures are expected to remain above freezing while precipitation lingers. There is a very low chance (<10%) that very northern Berkeley County could see temperatures briefly drop below freezing early Thursday morning while some precipitation is ongoing. Given that this scenario is such a low probability it is not reflected in the forecast, but worth mentioning there could be a little freezing rain in this location.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Flight restrictions are expected this afternoon as rainfall overtakes the region associated with a cold front pushing through the region. As of 18Z KCHS/KJZI/KSAV are all VFR, however MVFR cigs are likely to arrive at KCHS/KJZI within the next hour so have initialized the 18Z TAFs with MVFR cigs. Conditions tonight will deteriorate at all terminals, with IFR cigs expected overnight. Restrictive cigs are expected to linger at KCHS/KJZI Thursday morning, with some drizzle possible as well.

Extended Aviation Outlook: MVFR cigs could persist into mid-late afternoon Thursday at CHS/JZI/SAV terminals. VFR conditions should then return Thursday night and prevail during the weekend.

MARINE

A cold front will approach the region today, favoring a southwest wind in the 10-15 kt range with occasional gusts to 20 kt away from the coast. Seas should range between 2-4 ft. The front is expected to shift across the region tonight, tightening the pressure gradient across local waters prior to arrival this evening, then followed by strong cold air advection within a north-northwest flow in its wake during the second half of the night. As a result, winds/seas will trend stronger/larger heading into the day Thursday and are anticipated to reach Small Craft Advisory levels across outer Georgia waters Thursday afternoon and evening (northwest winds gusting to around 25 kt and seas 4-6 ft), before improvement begins with high pressure becoming more centered nearby during the second half of the night. A Small Craft Advisory has been therefore been issued for offshore Georgia waters Thursday afternoon into early Friday morning.

Conditions should remain below Small Craft Advisory levels for all waters for much of the daytime Friday, but are anticipated to deteriorate again with another passing cold front late day and overnight. Small Craft Advisories should be needed for all local waters with west winds gusting upwards to 25-30 kt across most areas. There is even a low-end threat for gale force wind gusts across outer Georgia waters Friday night. Seas should also build largest away from the coast, generally up to 5-8 ft during the peak of the event Friday night. Conditions then improve during the weekend, falling below Small Craft Advisory levels across all waters late morning Saturday, then remain below advisory levels while high pressure dominates the pattern into early next week.

EQUIPMENT

The KCLX radar is operational, but could go down at any time. Additional repairs are planned for Wednesday or Thursday.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory from 1 PM Thursday to 1 AM EST Friday for AMZ374.