textproduct: Charleston

SYNOPSIS

High pressure will extend across the region for much of the week. A cold front will move through Wednesday evening and push offshore Thursday morning with another cold front possibly moving through very late in the weekend.

NEAR TERM /THROUGH TONIGHT/

This Afternoon: Satellite shows widespread and persistent stratus that has been in place for the past several days is finally showing signs of thinning with distinct breaks noted across parts of the interior. Clouds will continue to scatter out through the remainder of the afternoon hours as low-level moisture thins with time; however, it may very well take until late afternoon for some areas to see considerable breaks to develop.

Tonight: High pressure centered over Eastern North Carolina will slowly propagate south/southeast through the night while maintaining its influence on the area. The boundary layer should decouple quickly around sunset with winds going calm and skies going clear. The combination of clear skies and light/calm winds will support strong radiational cooling. The 09/13z NBM was used for the basis for overnight lows and range from the upper 20s well inland to the lower 40s at the beaches. These may be a bit too warm in some of the more sheltered spots well inland, over the Francis Marion National Forest and parts of the lower South Carolina coastal corridor away from the beaches and I-526 corridor. These areas tend to run colder than guidance, including the NBM, in strong radiational regimes. Unfortunately, no local adjustments were made to account for these cooler conditions given national policy constraints.

SHORT TERM /WEDNESDAY THROUGH FRIDAY/

After a chilly start to the day, a surface low pressure to the north will swing the winds around to become out of the southwest Wednesday morning, out ahead of an approaching cold front. With near normal 850mb temperatures, Wednesday will feel notably warmer with most areas in the lower to mid 60s. Unfortunately mixing down these warmer temperatures does require breezier winds, with gusts into the lower to upper 20s expected, though at least dry conditions will prevail. Overnight lows into Thursday will be warmer as well, upper 30s inland to mid 40s along the coast.

Lake Winds: Wednesday afternoon into the early Thursday morning hours, southeast winds will become sustained in the 18-22 kt range with gusts in the 22-27 kt range. As this is expected to create hazardous conditions, a Lake Wind Advisory has been issued.

Thursday will see a quick moving dry cold front slip through the region during the morning hours, with surface high pressure building in behind it. With cold air advection and the heightened surface pressure gradient, winds will remain on the breezier side. Temperatures behind the front will be a few degrees cooler than Wednesday, largely in the mid to upper 50s. As the center of the surface high slides by to our south, radiational cooling will aid in bringing overnight lows into Friday back down into the lower 30s inland and lower 40s along the coast. As the high slides out to sea, southwesterly winds will again bring near-normal temperatures back to the region, with highs mostly in the lower to mid 60s.

LONG TERM /FRIDAY NIGHT THROUGH MONDAY/

Friday night through Saturday look to be rather uneventful, as broad troughing aloft moves across the area and surface high pressure remains near the region. Highs on Saturday actually look to be above normal, with temperatures in the mid 60s to lower 70s. It is looking like these warm temperatures continue into Sunday, as models continue to delay a strong cold front heading towards the area, with current consensus being the front moving through overnight into Monday.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

09/18z TAF Discussion: KCHS/KJZI/KSAV: Satellite shows widespread stratus is starting to thin with breaks developing west of the terminals. These breaks will gradually expand to all three sites later this afternoon. Timing is still somewhat uncertain when exactly clouds will scatter out to VFR, but 19-21z,is favored at KCHS and KJZI with 21-23z at KSAV. Once VFR returns it will remain VFR through 18z Wednesday.

Extended Aviation Outlook: VFR conditions expected. Breezy southwest winds are expected Wednesday afternoon, gusting up to 25 knots.

MARINE

Through Tonight: There are no concerns. North winds will gradually diminish through the afternoon and evening, becoming north to northwest 5-10 kt overnight. Seas will subside to 2-3 ft nearshore waters and 3-4 ft over the Georgia offshore waters.

Wednesday through Thursday: Out ahead of an approaching cold front, Small Craft Advisory (SCA) conditions expected to develop across all nearshore and offshore waters late Wednesday afternoon into Thursday morning, not including the Charleston Harbor. Winds will be westerly in the morning and fairly light before swinging around to the southeast and becoming sustained in the 20-30 kt range with gusts of 25-34 kt starting Wednesday afternoon. Seas of 4-7 ft are also expected, lowest along the coast and increasing heading out to sea. As the cold front passes through Thursday morning, SCA conditions improve though gusts into the teens continue with winds out of the west- northwest.

Friday through Sunday: With surface high pressure across the region, no marine concerns are expected.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...Lake Wind Advisory from 1 PM Wednesday to 4 AM EST Thursday for SCZ045. MARINE...Small Craft Advisory from 1 PM Wednesday to 7 AM EST Thursday for AMZ350-352. Small Craft Advisory from 4 PM Wednesday to 4 AM EST Thursday for AMZ354. Small Craft Advisory from 4 PM Wednesday to 7 AM EST Thursday for AMZ374.