textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

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

- 2) Freezing temperatures are possible across far inland areas Friday night, followed by a potential widespread freeze Saturday night.

DISCUSSION

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

Through daybreak: Dry high pressure prevails with a decoupled boundary layer favoring light/calm winds across most areas until sunrise. These winds under clear skies will support strong radiational cooling for the rest of the night with lows dipping into the low-mid 40s inland to upper 50s near the beaches. The setup could also pose a risk for some fog to develop during predawn hours, particularly across Southeast Georgia where some guidance continues to pin 30-50% probabilities for vsbys less than 1 mile, with the greatest potential along the I-95 corridor south of Chatham County and mostly across areas closer to the Altamaha River (McIntosh to Tattnall Counties). Most fog that develops should remain shallow, except near the Altamaha River, where condensation pressure deficits and low-lvl moisture are more favorable for locally dense fog prior to and around daybreak. Latest satellite imagery does depict a thin layer of cirrus traversing Southeast Georgia, which appears to be limiting fog potential and could continue to pose this limitation through daybreak based on the trajectory of additional cirrus upstream. Conditions will continue to be monitored for this key factor in relation to fog development late.

Today through Wednesday: High pressure will continue to dominate the weather pattern across the Southeast United States, supporting dry conditions and modifying temperatures under ample sunshine. High temperatures will remain above normal, generally peaking in the mid- upper 70s each afternoon although will be slightly cooler along the beaches. Overnight periods should continue to display a strong case for radiational cooling with a decoupled boundary layer leading to calm winds under mostly clear skies. However, increasing cloud cover should limit the setup starting Tuesday night. Overnight lows in the low-mid 40s inland to mid-upper 50s closer to the coast will be common, but will trend warmer each night as cloud cover increases and a light return flow returns along the western edge of high pressure become more centered across the western Atlantic.

KEY MESSAGE 2: Freezing temperatures are possible across far inland areas Friday night, followed by a potential widespread freeze Saturday night.

Ahead of an approaching cold front, southwesterly winds are expected to become breezy throughout the day as the pressure gradient increases, while afternoon high temperatures will remain in the mid to upper 70s. Peak wind gusts of 20 to 30 mph are expected during the afternoon hours, likely remaining breezy into the overnight hours as the front pushes through. Rainfall chances continue to look bleak with the latest forecast coming in mostly dry, though that may still change as new data flows in.

The front pushes through quickly overnight into Friday, bringing overnight lows back down into the lower 40s for inland areas, and into the upper 40s to lower 50s along the coast. Combined with the breezy west-northwesterly winds, wind chills will likely dip down into the upper 30s to lower 40s for inland areas, so be sure to dress appropriately Friday morning. As cold-air advection (CAA) commences, temperatures on Friday will struggle to reach up into the upper 50s to lower 60s, accompanied by breezy westerly winds gusting 25 to 35 mph.

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 look to remain high enough to keep concerns on the lower end for now. Overnight lows in the mid 30s for inland areas are expected, with probabilities for reaching 32 degrees largely in the 10 to 20% range. Combined with the breezy westerly winds, wind chills in the upper 20s to mid 30s are expected across the area into early Saturday morning. With the CAA continuing, temperatures on Saturday will be a few degrees cooler than Friday, with max temperatures at or below 60 degrees.

As a surface high pressure moves in late Saturday into Sunday, clear skies and light winds will allow for radiational cooling to further decrease temperatures. Probabilities for reaching freezing temperatures for inland areas rise into the 20 to 45% range, indicating a Freeze Watch may be needed as we get closer to the event. In addition to the freezing temperatures, given the light winds, frost formation appears likely.

AVIATION /06Z MONDAY THROUGH FRIDAY/

At CHS/JZI, VFR conditions are expected through 06Z Tuesday. Shallow ground fog could develop prior to daybreak this morning, but does not appear to pose a more substantial concern in reducing vsbys. MIFG remains at the terminals for a few hours prior to daybreak.

At SAV, VFR conditions should generally prevail, but there is a greater risk for shallow ground fog and/or fog reducing vsbys to MVFR levels. MIFG and TEMPO MVFR vsbys remain in the latest TAF between 10-12Z this morning.

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 tranquil marine conditions. North/northwest winds should remain around 10 kt or less today, then turn more west-southwest overnight as high pressure becomes more centered offshore late. Seas will range between 2-4 ft.

Tuesday through Friday: 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. Winds shift to become out of the west-northwest overnight into Friday, with gusts to near 30 knots continuing throughout the day.

CHS WATCHES/WARNINGS/ADVISORIES

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