Marine Weather and Tide Forecast for Whitemarsh Island, GA

NEAR TERM /UNTIL 6 AM THIS MORNING/
Overnight composite analysis reveals large scale northern/southern stream phasing/amplification beginning to take shape with short- wave energy lifting into the Ohio Valley/lower Great Lakes while a second strong wave is diving through the Northern Plains.
Occluded and elongated surface low is advancing into the western Great Lakes region while deep layer southwesterly flow has established from the Gulf into the Deep South and southeastern U.S. Strong isentropic ascent, coincident with upper level jet support is producing a wide area of precip extending from the southern states into the lower Great Lakes. Across our area, "warm advection wing" is brushing by this morning. However, a nice wedge of dry low level air (below 700 mb on last evenings sounding) is keeping things dry with no more than sprinkles moving through the inland counties.

Larger scale flow amplification will proceed through tonight with a fairly deep trough developing through the central CONUS by Tuesday. As this occurs, axis of deep moisture will be shifting/folding into the southeast region later today and tonight bringing increasing rain chances to southeast Georgia and southeast South Carolina.

Outside of a few sprinkles grazing the inland areas this morning, wedge of dry air below 700 mb will maintain dry weather through at least midday/early afternoon. But shower chances will increase through the afternoon hours and continue into tonight as the aforementioned moisture axis (PWAT values in excess of 1.5 inches) shifts into the region, along with some increase in upper jet support by late day into tonight. Still appears the higher precip chances/QPF will reside across the inland areas where the best combination of ingredients is anticipated. But overall rainfall amounts through tonight will remain under one quarter of an inch...with highest amounts inland.

Temperatures today will warm into the upper 60s to lower 70s, although given the cloud cover, forecast max temperatures have been lowered a degree or two. Lows tonight will range from the middle 50s to near 60.

SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY/
Tuesday and Wednesday: SW flow will be present in the mid-levels as a trough progresses eastward from the Midwest towards the east coast. At the surface high pressure will retreat eastward off the southeastern coast into the adjacent Atlantic waters while a cold front approaches from the west. The most recent model runs show a slow down of FROPA, with the front now forecast to push through the region late Wednesday. This has yielded a shift in timing with regards to the highest PoPs, with PoPs highest now on Wednesday.
PWATs are forecast to increase to around 1.3", above normal for this time of year according to SPC Climatology. In addition to the rainfall, breezy conditions are expected Tuesday night into Wednesday, with gusts in the 20-30 mph range possible. Conditions across Lake Moultrie could approach Lake Wind Advisory criteria.
Very mild temperatures are forecast on Tuesday as the SW flow aloft ushers in a warm, moist airmass. Temperatures are forecast to reach into the 70s, highest furthest south along the Altamaha River in GA.
Overnight temperatures on Tuesday will also remain rather mild, only dipping into the 50s with low 60s along the beaches. The temperature for Wednesday is rather challenging, as it all hinges on the timing of FROPA. The forecast as of this juncture depicts an abnormal diurnal trend, with highest temperatures occurring in the morning and a cooling trend into the afternoon with FROPA. Temperatures Wednesday night will likely dip below freezing across most interior locations, with mid to upper 30s elsewhere.

Thursday: High pressure will build in behind the departing cold front at the surface while zonal flow develops aloft. Skies are forecast to quickly clear out by Thursday morning post-FROPA.
Despite the plentiful sunshine, temperatures are forecast to only reach into the low 50s across the region as northerly winds usher in a cooler airmass.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
Surface high pressure will build into the region from the north through the weekend. Aloft zonal flow will prevail into Saturday, with a mid-level trough forecast to ripple across the southeastern states on Sunday. Generally quiet conditions are forecast through the period, with temperatures remaining slightly below normal. A slight chance of showers is possible along the coastline Saturday afternoon into Sunday associated with the upper level disturbance and a developing coastal trough.

AVIATION /08Z MONDAY THROUGH FRIDAY/
Overall VFR conditions will prevail through TAF period.
However, mid and high level cloud cover will persist across the region overnight and through the day Monday. Cloud cover continues to lower to 4-6K feet Monday evening along with some increasing rain chances. Meanwhile, south/southwest winds could occasionally gust to around 15 kt at all terminals between 18Z Monday to 00Z Tuesday.

Extended Aviation Outlook: Flight restrictions are possible Tuesday and Wednesday as a cold front pushes through the region. Gusty W/NW winds are also possible on Wednesday.



MARINE
Southwest to south flow will prevail through tonight ahead of an approaching cold front. No marine concerns are anticipated, with speeds generally 15 knots or less and seas averaging 2-3 feet.

Tuesday through Saturday: Surface high pressure will shift further eastward into the Atlantic Ocean as a cold front approaches from the west. This cold front is progged to push through the region Wednesday, with high pressure returning post-FROPA. Winds are forecast to surge Tuesday night ahead of the cold front, with SW gusts around 25 knots. Additionally, seas are forecast to build to 4 to 6 ft. Small Craft Advisories will likely be required for all marine zones, including the Charleston Harbor. Additionally, there is a low-end chance for some gale force gusts on Wednesday, especially across the Charleston County nearshore waters and the 20 to 60 nm offshore GA waters. Wind gusts are forecast to diminish slightly on Thursday, however with the development of a coastal trough through the weekend NE gusts will again approach 25 knots Friday and into Saturday. Additional Small Craft Advisories may be required into the weekend.

CHS WATCHES/WARNINGS/ADVISORIES
GA...None.
SC...None.
MARINE...None.