textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Frost/freeze conditions tonight through Sunday night.

DISCUSSION

KEY MESSAGE 1: Frost/freeze conditions tonight through Sunday night.

The center of a large 1030 mb will settle just north of the Ohio River Valley by 12Z Sunday. As dry high pressure builds over the forecast area, the pressure gradient across SE GA/SC will decrease tonight. Winds could completely decouple across inland counties tonight, with light and variable winds across the coastal counties. Shallow cumulus clouds across the region this afternoon should dissipate early this evening. REFS indicates that sky is expected to remain clear through late tonight, then thin high clouds sourced from the Southern Plains may reach SE GA around daybreak Sunday. Given nearly optimal radiational cooling condition, the cooler temperature guidance will be favored. Using a blend of cooler guidance, low temperatures are forecast to range from the upper 20s inland to mid 30s across the coastal counties away from the beaches. A Freeze Warning has been posted for inland SE GA/SC. A Frost Advisory will be issued for coastal SC counties and the I-95 corridor of SE GA. Hours of frost supporting temperatures should favor widespread to areas of frost tonight.

If widespread freezing temperatures occur tonight into Sunday morning, then this will end the local growing season and Frost/Freeze products will not be issued for Sunday night into Monday morning. However, if only some areas observe freezing temperatures, then the growing season continues and we will likely need Frost/Freeze products on Sunday night into Monday morning. Regardless of the outcome, overnight temperatures will be below normal for this time of year.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

18Z TAFs: VFR. Steady north winds this afternoon will become light and variable tonight. North winds should return to 5 to 10 kts after sunrise Sunday. Patchy to areas of frost may develop on untreated aircraft during the pre-dawn hours on Sunday.

Extended Aviation Outlook: VFR.

MARINE

High pressure centered over the mid to upper Mississippi Valley tonight will gradually move eastward, becoming located over the Mid- Atlantic states by the middle of next week. A light to fresh breeze along with low seas should prevail through Monday. As the High gets closer to our region late Monday, the surface pressure gradient will become elevated, leading to increasing winds and building seas. Gusts to >=25 kts and seas >=6 ft (Small Craft Advisory) will develop across our GA waters Monday night, then spread into our SC waters on Tuesday. If this forecast holds, we may need Small Craft Advisories for most of our marine zones by the middle of next week.

CHS WATCHES/WARNINGS/ADVISORIES

GA...Freeze Warning from 1 AM to 9 AM EST Sunday for GAZ087-088- 099>101-114-115. Frost Advisory from 1 AM to 9 AM EST Sunday for GAZ137-216-218- 238-240. SC...Freeze Warning from 1 AM to 9 AM EST Sunday for SCZ040-042>045- 147. Frost Advisory from 1 AM to 9 AM EST Sunday for SCZ148>150-152. MARINE...None.