Marine Weather and Tide Forecast for Kiawah Island, SC

KEY MESSAGES
- 1) Cold temperatures in the low to mid 20s (upper 20s to lower 30s along the coast) possible Tuesday and Wednesday morning.

- 2) Widespread precipitation is expected to occur this weekend, bringing increasing potential for a winter weather event to impact the region.

DISCUSSION
KEY MESSAGE 1: Cold temperatures in the low to mid 20s (upper 20s to lower 30s along the coast) possible Tuesday, and Wednesday morning.

Surface High pressure will build in from the northwest today, then pass to our north Tuesday night. The High will continue to bring colder than normal temperatures to our region. Tonight, expect lows in the low to mid 20s for most locations, except the upper 20s to lower 30s along the immediate coast. Winds will be rather light, perhaps going calm. This will lead to very little, if any, wind chill. Expect similar low temperatures Wednesday morning. Though, temperatures will be several degrees warmer along the immediate coast (the mid to upper 30s). Winds will again be light to calm, yielding little to no wind chill.
So Cold Weather Advisories are not expected either night.
Otherwise, expect afternoon highs in the upper 40s to lower 50s Tuesday, trending warmer on Wednesday.

KEY MESSAGE 2: Widespread precipitation is expected to occur this weekend, bringing increasing potential for a winter weather event to impact the region.

Aloft, deep zonal flow will persist across the region through the weekend on the southern periphery of a rather impressive 150+ kt upper level jet. At the surface, cold high pressure centered across the Upper Midwest will build southward into the Southeast beginning early Saturday. Increasing isentropic ascent is expected to yield an expanding shield of precipitation that will impact the forecast area Saturday through Sunday as an area of low pressure develops off the Southeast coast and moves off to the east. The overall result is what looks to be a cold and wet weekend, with the forecast advertising increasing precipitation chances.

Most impactful is that there is growing concern for a winter weather event to affect much, if not all, of southeast GA and southeast SC this weekend. As the aforementioned cold high pressure builds in, there is increasing likelihood for temperatures to fall below freezing Saturday night and Sunday morning (potentially mid to upper 20s in some areas) across nearly all of the forecast area in the presence of ongoing precipitation. Such a setup would set the stage for a winter weather event, which could be rather significant depending on how the critical details work out. There is increasing support for winter weather among both ensembles, deterministic model runs, as well as in probabilistic guidance. While it is too early to nail down specific precipitation types and any potential transitions, model soundings seem to suggest primarily a freezing rain threat with a shallow sub-freezing layer at the surface and a prominent warm nose centered around 800-850 mb. As such, the forecast grids will introduce freezing rain across most of the area starting Saturday night and continuing through Sunday morning.

It cannot be stressed enough that while the chance of a potentially significant winter weather event is increasing, there remains substantial uncertainty regarding the details including timing, impacted areas, precipitation types, and precipitation amounts. All of southeast GA and southeast SC should begin to prepare to experience at least minor winter weather impacts this weekend.

AVIATION /00Z TUESDAY THROUGH SATURDAY/
00Z TAFs: VFR. SW winds around 5 knots tonight will shift to the NW Tuesday, increasing to around 10 knots.

Extended Aviation Forecast: VFR.

MARINE
Today and Tonight: High pressure will build into our region, which will keep conditions below Small Craft Advisory criteria.

Tuesday through Saturday: Overall, conditions are expected to remain below Small Craft Advisory thresholds this week. Winds will be strongest on Tuesday with up to 15-20 knots of northwest flow possible. Thereafter, winds will turn more northeasterly. However, as we move into the weekend northeast flow is expected to increase as high pressure builds inland and an area of low pressure develops just off the Southeast coast. This setup could produce an enhanced gradient across the local waters with an increasingly likelihood of Small Craft Advisory conditions for all zones by Saturday.

CHS WATCHES/WARNINGS/ADVISORIES
GA...None.
SC...None.
MARINE...None.