textproduct: Charleston

WHAT HAS CHANGED

A Dense Fog Advisory has been issued for the entire SC Lowcountry and SE Georgia through 9 AM Sunday morning. The Aviation Section was updated to reflect the 06Z TAF issuance. A Small Craft Advisory was issued for all waters Monday into Tuesday.

KEY MESSAGES

- 1) Dense fog is expected tonight and into early Sunday morning across the SC Lowcountry and SE Georgia. A Dense Fog Advisory is in effect until 9 AM.

- 2) Notable temperature swings through Wednesday.

- 3) Warm temperatures and chances of rain for late next week into the weekend.

DISCUSSION

KEY MESSAGE 1: Dense fog is expected tonight and into early Sunday morning across the SC Lowcountry and SE Georgia. A Dense Fog Advisory is in effect until 9 AM.

Observations and webcams show that dense fog is developing across the forecast area, with several sites reporting vsbys of 1/4 mi along and west of I-95. While the most favorable conditions for dense fog remain west of I-95, the Dense Fog Advisory in effect covers the whole forecast area. GOES Satellite shows that there is still a stubborn pocket of low stratus clouds lingering over the Charleston Tri- County region, but as the stratus erodes fog is expected to develop. Guidance continues to indicate that the fog will become dense across the region and linger into the morning hours.

KEY MESSAGE 2: Notable temperature swings through Wednesday.

A dry cold front will move south through our area tonight, followed by high pressure wedging in from the north. A building ridge aloft Tuesday into Wednesday will then make for a drastic warm up. This will cause quite a swing in temperatures over the coming days. Temperatures are progged to rise well above normal today, into the mid 70s for most locations (except cooler at the beaches), then remaining a few degrees above normal tonight. The wedge pattern will lead to a drastic temperature gradient across the forecast area on Monday, becoming much cooler for most locations. Highs will range from the mid 50s near the Santee River, to the low 70s near the Altamaha River. Low temperatures on Monday night should be within a few degrees of normal. High temperatures will then rise back above normal on Tuesday, ranging from the lower to middle 70s away from the beaches. The warming trend continues on Wednesday with highs ranging from the mid to upper 70s across most of our area (except cooler at the beaches), and possibly the lower 80s across portions of inland GA south of I-16.

KEY MESSAGE 3: Warm temperatures and chances of rain for late next week into the weekend.

The region will be under the influence of high pressure, both at the surface and aloft, centered offshore late next week into the weekend. This will set the stage for warming temperatures to continue. There is a fairly small spread in max temperature guidance, with upper 70s to even low 80s likely in most locations away from the immediate coast. Early March normals are in the upper 60s, so these values would be around 10 degrees above normal. Lows will also trend on the mild side, in the upper 50s to around 60 degrees.

Deeper moisture will return to the area with ensemble means indicating PWats climbing to around 1.2", which falls in the 85-90th percentile of climo. While larger scale forcing is lacking, moisture and some instability could lead to isolated to scattered diurnally driven showers developing, especially in the afternoons and into the early evening. NBM indicates only a 10-20% chance for >0.25" of rain in any 24 hour period during this time frame. Severe and flooding risk looks minimal at this time.

AVIATION /06Z SUNDAY THROUGH THURSDAY/

The 06Z TAF period will initialize with IFR at KCHS/KJZI and MVFR at KSAV. Dense fog is expected to impact the KSAV terminal tonight, with lower confidence on any impacts to KCHS/KJZI given the lingering low cigs. Both vsby and cig restrictions will linger into the early morning hours, with VFR returning by noontime Sunday at all terminals.

Extended Aviation Outlook: Gusty northeast winds are possible at the terminals Monday.

MARINE

Dense fog may make a run for the Charleston Harbor early Sunday and a Marine Dense Fog Advisory may eventually be needed.

High pressure will wedge in from the northeast early Monday, pinching the gradient across the waters. Small Craft Advisories have been introduced for all marine zones, including the Charleston Harbor, for gusts 25 to 30 kt and building seas of 6 ft or greater. Wind speeds will begin to weaken late Monday night, though seas will be slower to subside. Small Craft Advisories will expire for the nearshore waters within 20 nm first on Tuesday, and then the GA waters beyond 20 nm on Wednesday.

CHS WATCHES/WARNINGS/ADVISORIES

GA...Dense Fog Advisory until 9 AM EST this morning for GAZ087-088- 099>101-114>119-137>141. SC...Dense Fog Advisory until 9 AM EST this morning for SCZ040- 042>045-047>052. MARINE...Small Craft Advisory from 10 AM Monday to 1 AM EST Tuesday for AMZ330-354. Small Craft Advisory from 5 AM Monday to 1 PM EST Tuesday for AMZ350. Small Craft Advisory from 5 AM Monday to 7 AM EST Tuesday for AMZ352. Small Craft Advisory from 10 AM Monday to 4 PM EST Wednesday for AMZ374.