textproduct: Charleston

WHAT HAS CHANGED

The Aviation Section has been updated to reflect the 12Z TAFs. Small Craft Advisory issued for the outer GA waters from 1 PM Sunday until 1 PM Monday.

KEY MESSAGES

- 1) An impactful system arrives on Sunday, resulting in renewed precipitation chances and perhaps a few thunderstorms.

DISCUSSION

KEY MESSAGE 1: An impactful system arrives on Sunday, resulting in renewed precipitation chances and perhaps a few thunderstorms.

Overnight into Sunday, guidance continues to depict an upper level shortwave moving across the northeast CONUS, with another upper level shortwave moving in from the west towards the area. A surface low pressure is accompanying the shortwave moving in from the west. As these features shift eastwards throughout the day, southeast South Carolina and southeast Georgia remain in the developing warm sector, with precipitable water values rising throughout the morning hours. As upward vertical motion rises from the plethora of forcing mechanisms, scattered showers and isolated thunderstorms will be expanding in coverage and intensity throughout the morning and into the afternoon hours. While precipitable water values look to rise to above the 90th percentile of climatology for this time of year near 1.25", per the ensemble situational awareness tables, rainfall totals look to remain in the 0.5-1 inch range before rain ends Monday morning. Global physical and AI ensembles have trended down the probabilities for an inch, with most keeping chances below 10%, while the time-lagged NBM 5.0 keeps probabilities for an inch in the 20-40% range, which to be fair does have some support from a few of the CAMs that go out that far.

While we'll see a couple hundred Joules of CAPE build in during the afternoon hours, enough to result in some isolated thunderstorms, the chances for strong/severe thunderstorms looks to remain off to our south where the shear and instability are both greater. Aside from rainfall chances, temperatures will remain on the warmer side with overnight lows in the upper 40s to mid 50s and afternoon highs in the 60s and 70s. Southerly winds will be on the breezier side on Sunday, sustained in the teens with gusts into the upper teens to lower 20s, becoming breezy out of the north-northeast on Monday.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

VFR will prevail at KCHS/KJZI/KSAV through the 12Z TAF period.

Extended Aviation Outlook: The potential for flight restrictions will increase Sunday through Sunday night as an area of low pressure moves into the region.

MARINE

High pressure will remain across the marine zones today, then gradually fading tonight. An area of low pressure will approach from the west on Sunday, resulting in a pinched gradient by Sunday afternoon. Winds gusts are forecast to strengthen to around 25 kts across the outer GA waters, with wave heights building to 6 to 8 ft Sunday evening. A band of showers and thunderstorms should develop along and ahead of a cold front late Sunday afternoon and evening. It is possible that some storm segments will require Special Marine Warnings due to gusty winds.

The NBM probability of wind gusts >25 kts outside the outer GA waters is 20% or less late Sunday. Conditions across the marine zones should begin to improve as the low departs on Monday. The gusty winds and elevated seas will be highlighted with a Small Craft Advisory across the outer GA waters from 1 PM Sunday until 1 PM Monday. High pressure will build over the region late Monday and remain through mid- week.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory from 1 PM Sunday to 1 PM EST Monday for AMZ374.