textproduct: Charleston

WHAT HAS CHANGED

A Lake Wind Advisory has been issued for Lake Moultrie in Berkeley County.

KEY MESSAGES

- 1) Warm and breezy today ahead of an afternoon/early evening cold front.

- 2) Frost/freeze conditions are possible Friday night through Sunday night.

DISCUSSION

KEY MESSAGE 1: Warm and breezy today ahead of an afternoon/early evening cold front.

Breezy westerly winds will continue as a cold front pushes off the coast later this afternoon. Gusts 25-30 mph will be common through the late afternoon while surface temps warm into the mid-upper 70s one last day this week. Strong cold air advection will occur in the wake of the front overnight with a west-northwest flow bringing noticeably cooler air into the local area. This could maintain gusty conditions into the mid evening hours, but a notable decrease in low- lvl wind fields is expected through the night post fropa.

Lake Winds: Breezy west-southwesterly winds across Lake Moultrie will peak around 25-30 kt through late afternoon. Low- lvl wind fields will support favorable mixing with the passage of the cold front, trending weaker by sunset. A brief Lake Wind Advisory has been issued for Lake Moultrie until this evening.

KEY MESSAGE 2: Frost/freeze conditions are possible Friday night through Sunday night.

A dry cold front will sweep across the region today. Following the cold front, steady H85 CAA is forecast to occur until 12Z Saturday, with values between -1 to -2C. Using a blend of guidance, low temperatures Saturday morning are forecast to range from the mid 30s inland to the low to mid 40s across the coastal counties. Northwest winds Friday night into Saturday morning should range between 5 to 8 mph with RH below 95 percent. Given marginal temperatures, winds, and RH frost may only form in sheltered locations or rooftops across inland counties Saturday morning. The forecast will mention areas to patchy frost in the most favorable locations.

Chilly llvl thicknesses will remain on Saturday, with highs ranging around 60 degrees. The center of 1030 mb high over the Mid West will ridge SE across GA and SC Saturday night into Sunday morning. The weakening pressure gradient should yield light to calm winds through much of Saturday night. Given a clear sky, light to calm winds, and deep dry air, radiational cooling conditions should provide the lowest temperatures so far this season. Favoring values near the 10th percentile of the guidance, low temperatures are forecast to fall below freezing inland, generally west of I-95. Frost supporting temperatures are possible into portions of the coastal counties. A Freeze Watch may be needed for a portion of the inland forecast area. If temperature exceed the currently forecasted values, then the low temperatures on Sunday morning could end the growing season for the region. The forecast will indicate widespread to areas of frost Sunday morning.

The cool air mass will linger into early next week. Frost supporting temperature are possible inland again Monday morning. By Tuesday into Wednesday morning, temperatures should remain in the upper 30s for the coolest locations.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

VFR conditions prevail throughout the forecast. Gusty westerly winds should slowly diminish tonight becoming light out of the west-northwest around midnight. Gusts to 15 to 20 knots will be possible across all TAF sites tomorrow afternoon before finally diminishing during the early evening.

Extended Aviation Outlook: VFR.

MARINE

Tonight: Gusty west-southwest winds between 25-30 kt will continue across the local waters due to a pinched pressure gradient as a cold front pushes offshore this evening. A Small Craft Advisory has been issued for the Charleston Harbor, in addition to the current ongoing SCAs, for a brief period of 25 kt gusts through this evening. Seas will continue to build and peak around 4-6 ft this evening, largest across the Charleston County waters (0-20 nm) and offshore Georgia waters (20-60 nm). A notable decrease in low-lvl wind fields will support improving conditions by daybreak Friday, when Small Craft Advisories are set to drop off.

Friday through Monday: Surges of winds are possible across the waters Friday into Saturday, associated with periods of CAA. The combination of a tightening pressure gradient and CAA may push wind gusts high enough for Small Craft Advisory criteria across the outer GA waters Friday night into Saturday. Otherwise, high pressure will continue to build into the region through the weekend into early next week with wind/sea conditions remaining well below Small Craft Advisory level thresholds.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...Lake Wind Advisory until 8 PM EST this evening for SCZ045. MARINE...Small Craft Advisory until 8 PM EST this evening for AMZ340. Small Craft Advisory until 3 AM EST Friday for AMZ360-362-364. Small Craft Advisory until 7 AM EST Friday for AMZ384.