textproduct: Charleston

SYNOPSIS

A cold front will shift across the area early today, resulting in an influx of drier air and breezy winds. High pressure will then prevail over the weekend, with another cold front forecast to impact the area Monday.

NEAR TERM /THROUGH TONIGHT/

A cold front at the surface has pushed offshore the southeast coast as of this morning, with high pressure quickly building in behind the front. At the upper levels, a potent trough will continue to dig across the eastern CONUS this afternoon and into tonight. The downstream 250hPa jet streak as of 12Z this morning was positioned across the southeast coastline into the Mid-Atlantic states. The 12Z KCHS RAOB sounding depicted the upper level winds perfectly, with nearly 50 knots at 2k ft. This has resulted in NW wind gusts 20 to 30 mph across the region this morning as mixing occurs. Across Lake Moultrie gusts up to 25 knots will be possible into the early afternoon, but given the short duration a Lake Wind Advisory is not anticipated. Gusts will gradually wane this afternoon, dropping off to near calm by midnight.

Tonight the upper level trough will push off the Eastern Seaboard with high pressure dominating at the surface. As the winds go calm, combined with the clear skies, a very good radiational cooling regime will set up tonight. Low temperatures are forecast to dip into the low 30s inland with upper 30s to near 40 along the coastal counties.

SHORT TERM /SATURDAY THROUGH MONDAY/

Sfc high pressure builds across the region Saturday in the wake of FROPA, allowing dry conditions to prevail. Winds look to remain light during this time, with direction shifting more southeasterly through the afternoon as the aforementioned high drifts into the Mid- Atlantic. Outside of this, expect dewpoints to rise a bit as a sea- breeze pushes inland, with highs rising into the lower 60s under sunny skies.

Upper level flow remains quasi-zonal heading into Sunday as a shortwave strengthens south of the James Bay area. Meanwhile, at the sfc, high pressure building into into the Mid-Atlantic will force a cold front through our area Sunday, with CAD building down the coast late Sunday through the early part of next week. That being said, overall moisture remains quite meager, keeping the forecast dry. In regard to temperatures, have afternoon highs warming into the mid to upper 60s Sunday prior to FROPA, with temperatures then dipping back into the 50s to lower 60s Monday in its wake.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Quiet conditions continue throughout the extended period as sfc high pressure strengthens overhead. Both deterministic and ensemble guidance also remain in good agreement that strong upper level ridging will develop across the central CONUS during this time, allowing unseasonably warm temperatures to prevail. Currently have highs in the 60s Tuesday warming into the 70s by Christmas Eve/Christmas Day. Lows will also remain quite mild, as temperatures only fall into the mid to upper 40s.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Prevailing VFR through the 18Z TAF period. Gusty W/NW winds this afternoon will go light and variable overnight.

Extended Aviation Outlook: VFR expected to prevail over the weekend, with periods of MVFR possible Monday morning in the wake of FROPA.

MARINE

Today and Tonight: Gusty winds will prevail over the marine waters as high pressure builds into the region behind a departing cold front. Gusts will remain in the 25-30 knot range into this afternoon, with Small Craft Advisories in effect for all waters. The SCAs will drop at various times this afternoon as gusts wane. Higher seas will linger in the Charleston County nearshore waters and the 20 to 60 nm offshore GA waters into this evening. Conditions will continue to improve through the overnight period.

Saturday and Sunday: Seas 2 to 4 ft with winds gusting up to 15 kt at times. No advisories or warnings are expected.

Early next week: High pressure building over the Mid-Atlantic will force a reinforcing backdoor cold front down the coast later Sunday into Monday. Small Craft Advisories will likely be needed for all zones (the one exception being the harbor), with winds peaking around daybreak Monday. Gale probs remain less than 10% at this point. Winds will gradually subside into midweek as ridging moves more directly overhead.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory until 4 PM EST this afternoon for AMZ330. Small Craft Advisory until 7 PM EST this evening for AMZ350- 374. Small Craft Advisory until 1 PM EST this afternoon for AMZ352- 354.