textproduct: Charleston

WHAT HAS CHANGED

All precipitation has moved offshore and skies are now clear across the region and therefore the Key Message regarding mixed precipitation chances has been removed. There is a threat of patchy black ice across the area tonight into Monday morning, mainly in wind sheltered areas. The aviation section has been updated to reflect the 00Z TAFs.

KEY MESSAGES

- 1) Patchy black ice is possible tonight into Monday morning. - 2) Cold temperatures in the low to mid 20s (upper 20s to lower 30s along the coast) possible Monday, Tuesday, and Wednesday morning.

DISCUSSION

KEY MESSAGE 1: Patchy black ice is possible tonight into Monday morning.

All precipitation has ended across the region and skies have gone clear, with dew points dropping into the mid to upper 20s far inland. These lower dew points will make their way towards the coastline through the overnight hours. In addition to the lower dew points, winds will remain slightly elevated tonight, generally 5 to 10 mph. These conditions will allow for most of the lingering puddles from the rain today to evaporate, however some spots in wind sheltered locations could see patchy black ice form as temperatures tonight drop below freezing away from the immediate coastline. Care should be taken Monday morning on roads and sidewalks that appear wet, as it is likely ice.

KEY MESSAGE 2: Cold temperatures in the low to mid 20s (upper 20s to lower 30s along the coast) possible Monday, Tuesday, and Wednesday morning.

Behind the departing surface low and exiting shortwave aloft, cooler air is ushered in tonight into Monday morning. Weak cold air advection (CAA) from a surface high pressure moving into the Gulf, combined with some radiational cooling, will bring overnight lows down into the mid 20s for inland areas rising up to the lower 30s along the coast. Probabilities for temperatures at or below 20 deg F have become fairly low (<10% for majority of the area), though a small footprint of 30% probabilities remain across portions of inland southeast Georgia. Winds will remain fairly weak overall, and don't look to be able to produce wind chills below 20 degrees across portions of inland southeast Georgia and up towards the mid 20s elsewhere. LREF probabilities for wind chills at or below 20 deg F remain near 40% range for the aforementioned portions of inland southeast Georgia, while the high res HREF and REFS both keep chances below 10%. Given the lack of clear signal and the general trend for winds to remain weak, have opted to forgo a Cold Weather Advisory at this time, though this will continue to be monitored.

Ahead of our next cold front, highs on Monday are only expected to reach into the upper 40s to lower 50s. The cold front pushes through during the late evening hours, with a surface high pressure moving into the southeast region from the central CONUS. This will bring another round of overnight lows in the mid 20s inland to lower 30s along the coast, with wind chills in the upper teens to upper 20s. Probabilities for wind chills at or below 20 degrees F are highest for areas west of the I-95 corridor, though they have decreased slightly with the latest LREF and HREF data ranging from 30 to 40%, while the REFS has probabilities < 10%. A cold weather advisory appears unlikely at this time, though the area to watch will continue to be portions of inland southeast Georgia.

Highs on Tuesday are again expected to be in the mid 40s to lower 50s. Our final cold overnight period from this event will occur as the previously mentioned surface high pressure slides by just to the north of the local area. We could see Cold Weather Advisory criteria (20 degrees F or lower) across inland areas from either temperatures alone if there is no wind (20-40% chance), or from wind chills if winds are a touch stronger (30-40% chance).

The later half of the week will see a return to near-normal highs and lows, though near-freezing temperatures may return for inland areas Friday morning behind a cold front.

AVIATION /00Z MONDAY THROUGH FRIDAY/

VFR conditions will prevail through the 00Z TAF period for KCHS/KJZI/KSAV. Scattered skies will go clear prior to midnight, remaining SKC through the remainder of the TAF period.

Extended Aviation Forecast: There are no concerns.

MARINE

Through Tonight: Rain will be ending from west to east throughout the afternoon hours. As cold air advection continue out of the northwest, wind gusts into the lower to mid 20s will remain over the waters throughout the afternoon hours, strongest from 15NM out to 60NM. 6 foot waves look to remain confined close to the 60NM boundary, decreasing to 3 foot waves along the coast. While conditions will slowly improve and may dip below Small Craft Advisory criteria this evening, a resurgence in winds speeds above criteria is noted on high res guidance during the late evening/early overnight hours as a push of cold air moves onto the waters. Have thus extended the expiration time for all zones through 9Z. The Charleston Harbor looks to remain just below criteria, but that will need to be closely monitored this evening. Rain exits the area Sunday afternoon/evening, with winds subsiding into the overnight hours.

Monday to Thursday: No high confidence marine concerns in the extended. Northwesterly winds become breezy on Tuesday, with gusts up into the upper teens throughout the afternoon hours. Wave heights begin to trend upwards on Wednesday, continuing into Thursday as swell moves in from the Atlantic, though wave heights look to remain below 6 ft.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory until 4 AM EST Monday for AMZ350-352-354- 374.