textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Dry conditions with gusty winds this afternoon.

- 2) Frost/freeze conditions are possible tonight through Sunday night.

DISCUSSION

KEY MESSAGE 1: Dry conditions with gusty winds this afternoon.

Temperatures should peak this afternoon in the low to mid 60s over dewpoints in the 30s. RH values this afternoon have already fallen into the low to mid 30s, and could fall into the upper 20s during the heat of the afternoon. The dry conditions combined with gusty west winds could pose a limited fire weather risk for a few hours this afternoon given continued drought/dry fuels. Winds will decrease and RH will recover quickly early this evening.

KEY MESSAGE 2: Frost/freeze conditions are possible Friday night through Sunday night.

The center of an 1025 mb high will push south over the Mid West tonight. As the high builds south, steady H85 CAA is forecast to occur until 12Z Saturday, with values between 0 to -2C. Using a blend of guidance, low temperatures Saturday morning are forecast to range from the mid 30s inland to the low to mid 40s across the coastal counties. Northwest winds should range between 5 to 8 mph through much of tonight, but could decouple during the pre-dawn hours. Given temperatures in the mid 30s, light to calm winds, and RH in the 90s, areas to patchy frost is expected along and west of the I-95 corridor. The area has been highlighted with a Frost Advisory from 2-8 AM Saturday.

Saturday and Saturday Night: High pressure will be spread along the mid and upper MS Valley, with it's periphery stretching into the Southeast U.S. Northerly winds will continue to usher cold air into our area. Thickness values and 850 mb temperatures point towards colder temperatures than what some of the MOS has, and we leaned this way with the forecast. Despite full sunshine, high temperatures may struggle to reach the 60 degree mark, which is about 10 degrees below normal for this time of year. The combination of clear skies and calm or very light north to northeasterly winds will lead to plenty of radiational cooling. Lows should range from the upper 20s in the coldest spots far inland to around freezing closer to the coast, with coastal counties generally in the mid to upper 30s, and the beaches generally in the 40s. Since there is still some uncertainty with the temperatures, we maintained the Freeze Watch. Plus, this matches our surrounding offices. Though, adjustments may be needed with the areal coverage when it's upgraded to a warning. Additionally, there will be frost within the current watch and closer to the coast (where there are no watches).

Sunday and Sunday Night: High pressure along the mid and upper MS Valley in the morning will slowly shift eastward towards the OH Valley, with it's periphery continuing to stretch into the Southeast U.S. Winds may shift a bit to the northeast during the day, and continue to usher cold air into our area. Once again, we leaned towards the colder end of guidance. Once again, with plenty of sunshine, high temperatures may struggle to reach the 60 degree mark. Calm winds and clear skies will lead to plenty of radiational cooling the first half of the night. Though, increasing high clouds and light winds may limit the full cooling potential the second half of the night. As a result, lows should be around freezing very far inland, the mid to upper 30s closer to the coast, with locations at and near the beaches reaching well into the 40s.

If we have widespread freezing temperatures Saturday night into Sunday morning, then that will end our local growing season, and no Frost/Freeze products will be needed Sunday night into Monday morning. But if only some areas reach freezing, then the growing season and Frost/Freeze products will continue Sunday night into Monday morning. Either way, temperatures will be colder than normal.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

18Z TAFs: VFR. Gusty WNW winds will continue across the terminals through the rest of this afternoon. Winds will decrease to 5-8 kts this evening and turn from the northwest tonight, then from the north after sunrise on Saturday.

Extended Aviation Outlook: VFR.

MARINE

Tonight: A period of cold air advection and tightening of the pressure gradient is likely across coastal waters this evening and overnight. Conditions across the outer GA waters will feature gusty west-northwest winds up to 25-30 kt and building seas up to 3-6 ft. A Small Craft Advisory (SCA) has been issued for offshore Georgia waters from this evening through sunrise Saturday. Conditions across the nearshore waters may near SCA conditions this evening into late tonight, but are expected to remain just below criteria.

Extended Marine: High pressure over the mid and upper MS Valley Saturday will slowly shift towards the Mid-Atlantic States by the middle of next week. While there should be modest winds and seas through Monday, no Small Craft Advisories are expected. Though, as the High gets closer on Tuesday, winds and seas are expected to increase, leading to Small Craft Advisories.

CHS WATCHES/WARNINGS/ADVISORIES

GA...Frost Advisory from 1 AM to 8 AM EST Saturday for GAZ087-088- 099>101-114-115-137-216-238. Freeze Watch from late Saturday night through Sunday morning for GAZ087-088-099>101-114-115. SC...Frost Advisory from 1 AM to 8 AM EST Saturday for SCZ040- 042>045-147. Freeze Watch from late Saturday night through Sunday morning for SCZ040-042>045-147. MARINE...Small Craft Advisory from 6 PM this evening to 2 AM EST Saturday for AMZ384.