textproduct: Charleston

WHAT HAS CHANGED

Key Message 1 has been updated for fog trends this morning. The Aviation Section has been updated for the 12Z TAF issuance.

KEY MESSAGES

- 1) Dry conditions and seasonable temperatures expected through Thursday. Colder conditions this weekend.

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

DISCUSSION

KEY MESSAGE 1: Dry conditions and seasonable temperatures expected through Thursday. Colder conditions this weekend.

Early Morning: High pressure prevails with light sfc winds in place under clear skies. Latest satellite imagery and sfc obs indicate shallow fog reducing vsbys to 1 mile spots in northern Charleston and Berkeley Counties, mainly in the Francis Marion Forest. Conditions are expected to improve quickly this morning as fog lifts/mixes out during the next hour or two.

Today and Wednesday: High pressure will continue to dominate the weather pattern across the Southeast United States, supporting dry conditions and above normal temperatures, despite an increase in mid- high clouds through mid-week. Highs should generally peak in the mid- upper 70s each afternoon, although should remain a few degrees cooler along the beaches. Low temps will be dependent on how much mid-high cloud remains across the local area during overnight periods. However, latest guidance suggests lows to trend slightly warmer tonight (upper 40s inland to mid-upper 50s near the coast) and Wednesday night (low 50s inland to upper 50s/around 60 near the coast) as a light southwesterly wind develops along the edge of high pressure becoming more centered offshore across the western Atlantic.

Thursday: Aloft, a mid-upper trough over the Midwest will advance east across the Appalachians early, helping push a cold front toward the local area late day into the early overnight period. Ahead of the front, a breezy southwesterly wind is anticipated with gusts near 25-30 mph during peak heating hours. Afternoon highs will remain above normal for one last day this week, generally peaking in the mid-upper 70s. The front is anticipated to shift through the local area late day, then offshore during the evening, remaining mostly dry for all areas. However, h5 shortwave energy traversing across minimal low-lvl moisture could result in a few light showers as the front progresses across the region. At this time, a dry forecast is advertised. Strong cold air advection begins post fropa, leading to noticeably cooler lows in the low-mid 40s inland to around 50 at the beaches during predawn hours Friday.

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

Friday: Cold air advection (CAA) behind the front begins, starting the trend of cooler temperatures into and throughout the weekend. After a cooler start to the day (lower 40s inland up into the lower 50s along the coast) temperatures look to max out in the lower to mid 60s across the region. In addition, breezy west-northwesterly winds gusting 20 to 25 mph will certainly make it feel like fall outside, so be sure to at least grab a jacket heading out on Friday.

With the cold air continuing to funnel down into the region, Friday night into Saturday will be our first night where concerns for frost formation return to the area, though wind speeds continue to remain high enough to keep concerns on the lower end for now. A renewed push of cooler air on the leading edge of a surface high pressure, combined with light overnight winds and clear skies, will likely lead to strong radiational cooling setup into Sunday morning. This is expected to bring the highest chances for frost/freeze. Another chance for frost/freeze returns into Monday morning as cold temperatures linger.

Nov 10 01z NBM 10km neighborhood probabilities for emergency management warming shelter planning:

Friday Night/Saturday Morning: Inland Areas Coastal Corridor Temps 35 degrees or colder: 20-50% 5% Temps 32 degrees or colder: 5-20% <5% Temps 30 degrees or colder: <5% <5%

Saturday Night/Sunday Morning: Inland Areas Coastal Corridor Temps 35 degrees or colder: 60-80% 10-40% Temps 32 degrees or colder: 30-50% <5% Temps 30 degrees or colder: 10-20% <5%

Sunday Night/Monday Morning: Inland Areas Coastal Corridor Temps 35 degrees or colder: 20-40% 5-10% Temps 32 degrees or colder: 10-20% 5-10% Temps 30 degrees or colder: 5-20% <5%

Frost Advisories, Freeze Watches and Freeze Warnings may eventually be needed, especially for areas roughly inland of US-17 in the Lowcountry and I-95 in Southeast Georgia.

Detailed information on first freeze dates for the area can be found online at: https://www.weather.gov/media/chs/climate/AverageFirstLastFreezeDates.pdf

AVIATION /12Z TUESDAY THROUGH SATURDAY/

VFR conditions are expected to prevail at CHS/JZI/SAV terminals through 12Z Wednesday.

Extended Aviation Outlook: VFR during the daytime, with isolated to scattered visibility restrictions possible during the late overnight into early morning hours on both Tuesday and Wednesday.

MARINE

Today and Tonight: High pressure will dominate the weather pattern leading to rather quiet marine conditions. South/southwest winds up to 10-15 kt today should become more west tonight as high pressure is centered more offshore. Seas will range between 2-3 ft.

Surface high pressure will continue across the Southeast U.S. through Wednesday, bringing a light to perhaps gentle breeze. Seas will be 2-3 ft within 20 nm and 3-4 ft for the 20-60 nm waters. Winds increase out of the southwest Thursday ahead of an approaching cold front, becoming gusty to near 30 knots. Likewise, wind-driven seas will build. Small Craft Advisories will likely be needed for our waters starting Thursday afternoon. Winds shift to become out of the west-northwest overnight into Friday, with a brief period of weakening winds during the morning/afternoon before wind speeds pick up again. Winds decrease below Small Craft Thresholds Saturday morning/afternoon, with the northwesterly winds ushering out the 6 feet waves around the same time.

CHS WATCHES/WARNINGS/ADVISORIES

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