textproduct: Charleston

WHAT HAS CHANGED

The Aviation section was updated for the 12z TAF issuance.

KEY MESSAGES

- 1) Another day of above normal temperatures and dry conditions is expected today.

- 2) Expect gusty winds and temperatures well below normal this weekend behind a strong cold front.

DISCUSSION

KEY MESSAGE 1: Another day of above normal temperatures and dry conditions is expected today.

Aloft, the day will begin with the forecast area situated between a ridge centered over the southwest Atlantic and a sharp trough stretching from the western Great Lakes into the Central Plains. The trough will make steady progress today and tonight, and should be situated near the spine of the Appalachians by sunrise Saturday. The trough aloft will push a strong cold front to the east-southeast today, with the front likely entering the interior of the forecast area by the early morning hours on Saturday. So for today, the forecast area will sit solidly within the warm sector ahead of the front. The result will be one more day with well above normal temperatures. Highs are forecast to reach the mid to upper 80s everywhere yet again which is on the order of 7-9 degrees above normal. Daily record highs are at or above 90 at both CHS and SAV (see Climate section), so it is unlikely we will set any records. But regardless, quite warm for mid October.

Today will also bring breezier conditions than the last several days. The combination of gradually increasing wind fields aloft ahead of the front, as well as deep diurnal mixing associated with temperatures in the mid to upper 80s will yield frequent gusts into the 15-20 mph range this afternoon and into the early evening.

KEY MESSAGE 2: Expect gusty winds and temperatures well below normal this weekend behind a strong cold front.

Saturday: A strong cold front will be located off our coast in the morning, and quickly shifting away. Meanwhile, strong High pressure across the Central U.S. will be building towards the east. Models hint at perhaps isolated to maybe scattered light showers across our area in the morning and early afternoon. Though, QPF will be minimal. Drier conditions build in by late afternoon. But the big change will be the temperatures. Cold air advection behind the front will only allow highs to reach into the mid to upper 60s across most of our area, and perhaps the lower 70s along our GA coast. Lows will generally be in the 40s. It'll also be very breezy, especially closer to the coast.

Sunday: Temperatures will be even colder despite abundant sunshine. Highs should only top out in the lower to middle 60s across most of our area, and maybe the upper 60s along/near our GA coast. The breezy winds will continues, especially closer to the coast.

Lake Wind: A Lake Wind Advisory will probably be needed for Moultrie Saturday into Sunday.

Monday through Midweek: High pressure should persist across the region, but start to show signs of weakening across the Southeast heading into the middle of next week. Temperatures should gradually warm by the middle of next week, but could remain a few degrees below normal.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

The 12z TAF period begins with some shallow ground fog but overall VFR conditions at KCHS, KJZI, and KSAV. VFR will prevail through the period. Southwest winds could produce a few modest gusts into the 15-18 knot range this afternoon. The main change will come very late in the TAF period when a strong cold front moves through. Winds will turn out of the northwest and begin to strengthen the last few hours. There will also likely be a few showers associated with the front, but that activity will mostly be after 12z Saturday. Extended Aviation Outlook: VFR. Breezy winds are expected through Monday.

MARINE

Today through tonight: A cold front will approach from the northwest today and will be in the process of crossing the local waters late tonight up to sunrise Saturday. For today, southwest flow will increase into the 10-15 knot range this afternoon with a few gusts up to around 20 knots primarily in the SC waters. Overnight, the southwest flow will gradually increase into the early morning hours. The front will move through late, turning winds to northwesterly and bringing the beginning of a significant surge of flow. By sunrise Saturday, sustained winds of 20 knots are expected with frequent gusts into the 25+ knot range. Seas will gradually increase today and into the early morning hours, with the greatest increase beginning with the passage of the front close to sunrise Saturday. By that time, seas are expected to be 2-4 feet and increasing.

Extended Marine: Gale to Strong Gale conditions are expected this weekend through Monday.

A strong cold front will be located off our coast Saturday morning, and quickly shifting away. Meanwhile, strong High pressure across the Central U.S. will be building towards the east. The interaction between these two synoptic features will lead to strong cold air advection and pressure differences across our coastal waters, leading to rapidly deteriorating marine conditions on Saturday. We'll start off with a few hours of Small Craft Advisories Saturday morning, followed by Gale conditions in our Atlantic zones by the afternoon. We now have Gale Watches up for our Atlantic zones, but it's safe to say they'll be upgraded to warnings. The synoptic pattern should support gale to strong gale conditions through Monday, with the highest winds and steepest/largest seas further offshore. Winds should ease Monday night into Tuesday. However, seas may remain elevated through the middle of next week.

High Surf: Elevated seas and strong/persistent north-northeast winds will support breakers in excess of 5 ft along our beaches, with the largest waves across our GA beaches. High Surf Advisories are likely for our entire coast Sunday into Monday, and possibly along our GA coast into Tuesday.

Rip Currents: The combination of strong/persistent gales and elevated seas will generate a Moderate Risk of rip currents at all of our beaches on Saturday, followed by an elevated risk continuing well into next week.

CLIMATE

Record High Temperatures:

October 16: KCHS: 90/2018 KCXM: 88/2018 KSAV: 91/2018

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory from 5 AM to 2 PM EDT Saturday for AMZ360- 362-364. Gale Watch from Saturday afternoon through late Monday night for AMZ360-362-364. Gale Watch from Saturday morning through Tuesday morning for AMZ380-382-384. Small Craft Advisory from 5 AM to 11 AM EDT Saturday for AMZ384.