textproduct: Charleston

WHAT HAS CHANGED

The Aviation Section has been updated to reflect the 12Z TAF issuance.

KEY MESSAGES

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

DISCUSSION

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

A high pressure system of 1025 mb will continue to shift southward over the Mid-west through daybreak. This will yield steady H85 CAA through this early morning, therefore expect low temperatures in the morning to drop into the mid 30s across inland counties with low to mid 40s across the coastal counties. Also, calm to light northwesterly winds around 5 mph will preserve through daybreak. Thus, the combination of the low temperatures, the light to calm winds, and RH values ranging in the mid to upper 90s will result in areas to patchy frost along and west of the I-95 corridor. A Frost Advisory has been issued for this area from 2AM to 8AM this morning as a result.

Continuing on through the rest of today, the high pressure will expand into the mid and upper MS Valley, with it's periphery stretching into the Southeastern CONUS. Expect northerly winds to continue to usher cold air into the region throughout tonight. Despite an ample amount of sunshine, afternoon highs will only reach into the upper 50s to low 60s. The combination of clear skies with calm to light winds will lead to a good amount of radiational cooling. As a result, expect overnight lows to drop into upper 20s to low 30s across the inland counties and mid 30s to low 40s across the coastal counties. Therefore, there was a good amount of confidence to upgrade the Freeze Watch to a Freeze Warning for early Sunday morning across the interior southeast Georgia and southeast South Carolina counties. The forecast notes widespread to areas of frost to account for this. It's possible we might need to issue a Frost Advisory with the next forecast update for a couple counties east of the Freeze Warning.

If widespread freezing temperatures occur on Saturday night 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 /12Z SATURDAY THROUGH WEDNESDAY/

VFR through the 12Z TAF period at KCHS/KJZI/KSAV with NW/NNW winds 5 to 10 knots today. Winds are forecast to go light to calm tonight.

Extended Aviation Outlook: VFR.

MARINE

Given current observations of gusts 25 knots in the Charleston County nearshore waters, have issued a Small Craft Advisory through 8 AM this morning.

Today and Tonight: In the wake of a departing cold front and building high pressure, a pinched pressure gradient is present over the marine waters early this morning. This is resulting in NW gusts upwards of 25 knots across the 20 to 60 nm offshore GA waters. The Small Craft Advisory for these waters has been extended until 8 AM this morning. As the day progresses and high pressure begins to dominate the synoptic pattern winds will decline over the waters, with gusts upwards of 15 knots this afternoon. Similarly, seas will relax as well, with 2 to 3 ft by this afternoon.

Extended Marine: Surface high pressure over the mid to upper Mississippi Valley this weekend will shift to the Mid-Atlantic states early next week. No Small Craft Advisories are anticipated through Monday. However, a pinched pressure gradient will develop off the coast Tuesday into midweek as the high pressure shifts to the Mid-Atlantic states. Gusts to 25 knots and seas building to 6 ft are in the forecast and Small Craft Advisories will likely be needed for portions of the marine zones.

CHS WATCHES/WARNINGS/ADVISORIES

GA...Frost Advisory until 8 AM EST this morning for GAZ087-088- 099>101-114-115-137-216-238. Freeze Warning from 1 AM to 9 AM EST Sunday for GAZ087-088- 099>101-114-115. SC...Frost Advisory until 8 AM EST this morning for SCZ040-042>045- 147. Freeze Warning from 1 AM to 9 AM EST Sunday for SCZ040-042>045- 147. MARINE...Small Craft Advisory until 8 AM EST this morning for AMZ360- 384.