textproduct: Charleston

WHAT HAS CHANGED

The Aviation section was updated for the 12Z TAFs.

KEY MESSAGES

- 1) Periods of unsettled weather could continue into Tuesday. A few thunderstorms on Monday could become severe.

DISCUSSION

KEY MESSAGE 1: Periods of unsettled weather could continue into Tuesday. A few thunderstorms on Monday could become severe.

Weak isentropic lift will produce light showers across the area through the morning. Rain will focus across southeast Georgia and spread north into southeast South Carolina, moving offshore a few hours after daybreak. Rainfall totals will be minimal today, with only a few hundredths of inch likely. A lull in precipitation is expected before an isolated shower or thunderstorm possibly develops along the sea breeze later this afternoon. Instability is mainly limited to southeast Georgia and meager at best, thus no hazardous weather is expected today.

On Monday the mid-levels will consist of broad troughing over the eastern half of the U.S. Embedded in this trough will be a shortwave over the Lower Plains in the morning. It'll slowly shift eastward, with models indicating it may not pass over the Southeast U.S. until later Tuesday. At the surface, a cold front will be located to our west and northwest in the morning, and approaching our area. It should make it to our area by the late afternoon or evening, then shift offshore overnight. Deep moisture originating from the Gulf will be ushered into our area ahead of the front. PWATs should peak ~1.8", which is 2 standard deviations above normal per NAEFs and above the 90% mark for CHS per SPC Sounding Climatology. The combination of this deep moisture along with lift from the approaching front and the sea breeze will generate convection starting late in the morning. Models indicate there should be enough breaks in the clouds during the morning to cause temperatures to rise into the lower to middle 80s. This will generate decent instability and shear, as indicated by the longer range CAMs. SPC has our entire area under a Marginal Risk for severe thunderstorms, with damaging winds being the primary concern. This seems reasonable given the setup. Convection should initiate along the sea breeze in the late morning and then further inland as we get into the afternoon. Colliding and interacting boundaries could generate some stronger storms with locally heavy rainfall and maybe even some hail. Though, the storms should have enough speed to limit flooding concerns. The risk of severe storms will lower during the evening. Though, scattered to numerous showers will persist well into the night.

The models differ on whether the showers will continue across most of our area into Tuesday or if High pressure building in from the north will dry things out quickly. We have slight chance to chance POPs in the forecast Tuesday morning, but this portion of the forecast will need another look.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

10/12z TAF Discussion: Weak isentropic lift will produce spotty light rain through the morning. However, this will have little impact in terms of reduced visibilities. We anticipate prevailing VFR, although there is a low chance of brief MVFR cigs developing from low stratus between now (10/11z) and 10/14z. Otherwise, conditions should clear within the next couple of hours. An isolated shower (or less likely, a thunderstorm) could develop this afternoon, but due to the low probability and overall lack in coverage there is no mention of direct impacts at KCHS/KJZI/KSAV.

Extended Aviation Outlook: A cold front will bring occasional flight restrictions due to showers and thunderstorms through Monday night, and possibly Tuesday morning. VFR returns later Tuesday and will prevail afterwards.

MARINE

Winds will gradually increase ahead of an approaching cold front on Monday. The front will move through the waters Monday evening, then quickly shift offshore Monday night. There will be a surge of winds and building seas behind the front, leading to Small Craft Advisories for at least the inner waters. Gale conditions cannot be ruled out for the outer waters Monday night. Conditions will quickly improve late Tuesday through the remainder of the week as High pressure becomes the dominant synoptic feature.

CHS WATCHES/WARNINGS/ADVISORIES

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