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Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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983 FXUS62 KCHS 151430 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1030 AM EDT Thu Aug 15 2024 .SYNOPSIS... High pressure will build in from the north through late week. Another cold front may approach the area early next week, then remain nearby through late week. && .NEAR TERM /THROUGH TONIGHT/... Hurricane Ernesto was located well east of the Bahamas and heading north, caught in a deep trough over the western Atlantic. Our area is strongly under the influence of high pressure, and with a dry northwest flow aloft, PWat is down to just 70-80% of normal for many places. The KCHS sounding shows PWat 2/3 inches less than yesterday morning, with a tremendous dry layer between about 650 mb and 450 mb, where RH is down less than 5% through that layer. Rain chances are limited to just slight chance through the day, mainly over southeast Georgia over McIntosh and Long County where there is some higher theta-E air. There could be a stray shower along the sea breeze along the coastal corridor where there is an axis of better moisture convergence. But the vast majority of the forecast area will stay dry with a strong inversion around 10K-12K feet. We maintain d a forecast free of t-storms with the HREF with their 1-hour thunder probabilities less than 10% and MLCAPE only about 100-200 J/kg. Being the time of year it`s possible that an isolated t-storm could form, but odds are strongly against such an occurrence. Dew points for most locations will be in the 60s through the day, making for more tolerable humidity levels than we`re accustomed to in summer. Max temperatures will be similar to Wednesday, and mainly in the 80s to around 90F degrees. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... Friday: Aloft the region will remain along the eastern periphery of high pressure centered over Texas. A mid-level low pressure center will be positioned just to the west of the Great Lakes, while to the east Tropical Cyclone Ernesto remains well off of the SE coastline. Surface high pressure will be directly overhead on Friday, yielding a dry forecast with highs in the upper 80s to around 90. Overnight temperatures will be a little cooler, with upper 60s in many locations and around 70 at the beaches. Saturday and Sunday: Slight ridging aloft will develop along the southeastern coastline through the weekend as the region becomes pinched between the low pressure over the Great Lakes and Tropical Cyclone Ernesto. High pressure will remain the dominant synoptic feature at the surface, however a weak cold front will approach from the west on Sunday. Dry conditions are forecast on Saturday, however rain chances increase into Sunday as the weak cold front approaches. High temperatures both days are forecast to reach into the low 90s, with overnight lows in the low to mid 70s. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... Broad troughing aloft will develop late Sunday and into early next week along the Eastern Seaboard as the aforementioned area of low pressure over the Great Lakes pushes towards the NE. At the surface a weak cold front is progged to impact the region early in the work week. Even with the weak cold front, PoPs are limited to around 30- 40% each afternoon. Temperatures are forecast to remain right around normal through the period. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... VFR conditions are expected to prevail at KCHS, KJZI, and KSAV through 12z Friday. Extended Aviation Outlook: Surface high pressure will yield VFR conditions through Saturday. A cold front is forecast to impact the region late this weekend/early next week, bringing the risk of brief flight restrictions. && .MARINE... Today: Surface high pressure will center across the coastal plain of SC/NC with winds out of the E/NE up near 15 or 15-20 kt. Seas will average 3-4 feet, with some 5 footers on the outer Georgia waters. Friday through Tuesday: Surface high pressure will begin to shift away from the local marine waters on Friday, with winds shifting from the NE in the morning to the E/SE by the evening hours. Swell from Hurricane Ernesto will begin to impact the region on Friday, with seas reaching 5 to 6 ft out to 20 nm, and 6 to 7 ft out to 60 nm in SE GA. Small Craft Advisories will likely be required for all marine zones outside of the Charleston Harbor. These Small Craft Advisories may linger into Saturday as swell continues to impact the region. By Sunday the region should be clear of all advisory conditions, with winds generally around 10 to 15 knots, increasing in speed along the coastline in the afternoon hours with the sea breeze circulation. Rip Currents: Although the beaches are still not feeling impacts o Hurricane Ernesto`s swells, based on numerous reports of rip currents from Tybee Beach yesterday, the Rip Current MOS showing a solid Moderate Risk, and WFO JAX with a High Risk at their Georgia beaches, we opted to go with Moderate Risk from Tybee to Sapelo today. Low Risk is maintained elsewhere. Long period swell (13 to 15 seconds) from Hurricane Ernesto is forecast to reach the forecast area on Friday. This in combination with onshore winds will produce a high risk of rip currents at all area beaches on Friday. The threat for rip currents could persist into Saturday as well. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM...CPM LONG TERM...CPM AVIATION...Adam/CPM MARINE...