textproduct: Charleston

SYNOPSIS

A coastal trough will reside offshore today, before lifting north and into the area this evening and tonight. High pressure will return Tuesday and prevail thereafter.

NEAR TERM /THROUGH MONDAY/

Tonight: The mid-level low will be moving east across Georgia and then South Carolina. This cutoff low actually originated from the northern jet stream, with the 1.5 PV surface actually being forecast at a height of around 500/ 600 mb. This tropopause depression has been well forecast for several days now, and usually in this type of setup/ tropospheric folding the fractured frontal zone causes a slight decrease in static stability with increased winds (especially on the back side of the associated cold front). The latest forecast soundings show the tropopause depressed to around 600 mb with most of the profile below 600 mb saturated, but still pockets of dry air in place. Further south towards Savannah, even more dry air is present. As such, the general idea is for low ceilings to be present out ahead of the upper level low and approaching cold front (greatest risk towards South Carolina). Since the low is moving overhead at night, a rather impressive low level inversion is forecast so not much in the way of winds are forecast. Given the pockets of dry air in the forecast soundings, precipitation will likely be in the form of a weak shower or even drizzle (further supported by low level warm air advection). The associated cold front will then cross the zones Monday morning with a weak line of showers possible along the front. Behind the cold front, winds turn from the northwest and will increase in speed with gusts 15 to 20 kt possible.

SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/

Monday will begin with a closed mid-level low situated over the southeastern states, while surface low pressure develops off the NC coastline. Some isolated showers may be ongoing at daybreak, but will quickly wane as the better forcing/moisture is located to the northeast of the region. High pressure will begin to build into the the region behind the departing surface low, with NW winds gusting to around 15 mph. Given the NW flow and some cloud cover temperatures will be cooler, with highs in the mid to upper 60s. Overnight lows on Monday will dip into the low to mid 40s inland with upper 40s to low 50s along the coastal counties.

Zonal flow will develop aloft Tuesday and Wednesday, while surface high pressure builds in from the west. A dry forecast has been maintained, with highs warming from the upper 60s/low 70s on Tuesday to mid/upper 70s on Wednesday. Tuesday night will feature favorable radiational cooling conditions, with lows forecast to dip into the upper 30s inland and 40s elsewhere.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/

A shortwave trough will ripple across the zonal flow aloft late this week, while at the surface a weak front will push through the region. Moisture is not impressive with the front and the forecast has remained rain-free. High pressure will then prevail into the weekend. Temperatures will be slightly above normal through the period.

AVIATION /00Z MONDAY THROUGH FRIDAY/

CHS/JZI: Tempo MVFR cigs are possible between 00-02Z Monday, followed by prevailing MVFR cigs between 02-06Z Monday, then IFR cigs between 06-14Z Monday while a cold front shifts across the region tonight. Drier air arrives post fropa, likely supporting VFR conditions at both terminals by 14Z Monday. Gusty northwest winds develop at both terminals Monday afternoon, generally up to the 15- 20 kt range, before ending in the 22-24Z timeframe late day.

SAV: Latest trends suggest drier air to impact the terminal, thus have limited cigs to MVFR levels only between 07-13Z Monday. VFR conditions will likely follow behind a cold front shifting offshore. Gusty northwest winds are likely Monday afternoon, generally up to the 15-20 kt range, before ending in the 22-24Z timeframe late day.

Extended Aviation Outlook: Flight restrictions could linger into Monday morning, with prevailing VFR thereafter.

MARINE

Tonight: Winds and seas will remain below Small Craft Advisory criteria through the period. Northeast winds around 10 kt will slowly back to the north and then from the northwest. Wind gusts 10 to 15 kt with seas 2 to 4 ft.

Monday through Friday: High pressure will build into the local waters from the west Monday and into Tuesday as a surface low pressure system develops off the NC coastline and pushes towards the NE. This pattern will yield a pinched pressure gradient, with the local waters located between the building high pressure and surface low pressure. Gusty NE winds are in the forecast, possibly approaching 25 knots, especially over the nearshore Charleston County waters and the 20 to 60 nm offshore GA waters. Additionally, seas could reach 5 to maybe 6 ft across these waters. A Small Craft Advisory may be required. The center of high pressure will slowly progress towards the local waters through the week, resulting in winds and seas remaining well below advisory criteria through the end of the week.

TIDES/COASTAL FLOODING

Elevated tide cycles are expected this week due to the upcoming full moon and perigee. Coastal flooding will be possible with the morning high tides along the entire southeast South Carolina and Georgia coast, especially as we head towards the middle of the week when base astronomical levels are already at or near minor flooding thresholds. Coastal Flood Advisories will be likely. However, there is still considerable uncertainty with how high the tides will reach since levels will greatly depend on the wind direction. Most models, including the national blended solution, are largely showing more northerly, even somewhat north- northwest/offshore winds, through at least Thursday. These wind directions would be less conducive to pushing tide levels much higher than the base astronomical levels. We will continue to monitor the latest model trends.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...None.