textproduct: Charleston

SYNOPSIS

A warm front will lift north later today, then a cold front will move through Monday afternoon. High pressure will build in through late week, then a cold front could affect the area next weekend.

NEAR TERM /THROUGH TONIGHT/

This Afternoon: Aloft, a broad ridge with axis placed directly across the Southeast will gradually shift east and offshore. At the sfc, a weak front stalled just south of the Savannah River should gradually lift north, but is anticipated to remain dry across land areas throughout the day. Cloud cover has been rather expansive through early afternoon hours, especially north of the front, and will be slow to erode and/or result in some sunshine across much of Southeast South Carolina during peak diurnal heating hours. Given this trend, afternoon temps have been lowered a few degrees across South Carolina, resulting in highs in the upper 60s across the Charleston Tri-County and lower 70s approaching the Savannah River. South of the front, breaks in cloud cover along with a southwest wind will help warm temps into the mid 70s.

Tonight: Aloft, the ridge axis continues to shift east well offshore while the flow becomes more zonal across the local area well ahead of a trough advancing across the Midwest overnight. At the sfc, the weak front in the vicinity during the day will likely have departed the local area by early evening, placing a warm sector firmly across the region in advance of a cold front approaching from the west. Southwest flow will help keep temps mild during overnight hours with lows only in the upper 50s to around 60 degrees for most areas.

Conditions still remain somewhat favorable for sea fog to develop just offshore this evening, with highest probabilities for dense fog occurring across Georgia nearshore coastal waters and perhaps southern nearshore South Carolina waters along and South of Edisto Island, SC off the beaches. However, there remains a window of opportunity for some patchy sea fog to drift onshore during evening hours while winds are more southerly, before winds turn more offshore and increase in speed after midnight, substantially decreasing fog chances during the second half of the night.

SHORT TERM /MONDAY THROUGH WEDNESDAY/

A strong cold front will sweep through the area Monday afternoon. Strong warm advection ahead of the front, along with adiabatic compression, should allow surface temps to quickly climb Monday morning. Warming could be somewhat moderated by fairly extensive cloud cover. Far inland areas may not rise above the mid 60s before the cold advection takes over, but the rest of the area should easily hit 70 degrees by early afternoon. Moisture will be quite limited with the front, so only isolated showers are expected, mainly in southeast GA. 40 kt geostrophic winds with fairly deep mixing will result in breezy conditions with some gusts to 30 mph at times. Winds on Lake Moultrie could be close to Lake Wind Advisory Monday afternoon and evening. However with water temperatures in the mid 50s, mixing profiles should be relatively poor and the strongest winds will be at the lake shore. We capped wind gusts at about 23 kt with this forecast package.

Cool, dry weather expected Tuesday through Wednesday with lows in the 20s/30s and highs in the low 50s

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/

Gradual warming late week into the weekend. Rain chances increase Friday into Saturday as low pressure moves in from the southwest.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

VFR conditions should prevail at CHS/JZI/SAV terminals this afternoon. The spread in guidance is quite large overnight, with some solutions suggesting a return of MVFR cigs at all terminals and even reduced vsbys at JZI due to sea fog drifting onshore. However, southwesterly flow is expected to increase after midnight, limiting the potential for reduced vsbys at all terminals during the second half of the night. Conditions become quite breezy at all terminals by mid-late morning Monday (starting around 14Z) with southwest winds gusting to around 20-25 kt through the afternoon as a cold front passes through the area. The front looks to be dry, but low clouds are expected as it nears, leading to prevailing MVFR cigs between the 14-18Z Monday time frame at all terminals. It's possible IFR cigs could need to be introduced ahead of and near fropa Monday morning, but confidence is too low to include in the 18Z Sunday TAF issuance.

Extended Aviation Outlook: Gusty winds are possible on Monday, along with a brief period where MVFR cigs are expected as weak rain showers move in along a cold front. Conditions improve shortly thereafter, with VFR conditions expected into the extended period.

MARINE

This Afternoon and Tonight: A weak front stalled across Georgia waters will gradually lift north through the day and eventually depart the local area by the evening, resulting in northeasterly winds north of it to turn southerly across all waters. Warm air advecting over cooler waters could result in sea fog development across local waters late day and even more likely this evening, with the potential of dense sea fog along a stretch of nearshore waters off the Georgia coast and southern South Carolina coast (Edisto Island, SC and south). The window for sea fog development is limited to evening hours due to increasing low-lvl wind fields and sfc winds turning more offshore in advance of a cold front approaching from the west. However, if sea fog is able to develop during this time, Marine Dense Fog Advisories could eventually be needed. After midnight, expect southwest winds to approach 15-20 across most waters and sea fog to erode/dissipate. Seas should also build from 1-3 ft this afternoon to 3-5 ft overnight, largest across outer Georgia waters late.

Monday through Thursday: Gusty SW to W winds expected Monday, with seas gradually building over the outer waters. We now have Small Craft Advisories for all waters including Charleston Harbor for varying times Monday through Monday night. Conditions drastically improve Tuesday as high pressure builds in.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory from 10 AM to 11 PM EST Monday for AMZ330. Small Craft Advisory from 7 AM Monday to 7 AM EST Tuesday for AMZ350. Small Craft Advisory from 1 PM Monday to 4 AM EST Tuesday for AMZ352. Small Craft Advisory from 4 PM Monday to 4 AM EST Tuesday for AMZ354. Small Craft Advisory from 7 AM Monday to 1 PM EST Tuesday for AMZ374.