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Area Forecast Discussion
090 FXUS62 KCHS 241949 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 349 PM EDT TUE MAY 24 2016 .SYNOPSIS... Atlantic high pressure will prevail through Friday. A wave of low pressure could develop offshore over the weekend before dissipating or moving away early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... A warm late afternoon/early evening featuring scattered diurnal cumulus, an inland progressing sea breeze and temps in the 80s inland/70s on the beaches will give way to a mostly clear/tranquil night. With light southerly flow, temperatures are expected to bottom out in the lower/mid 60s at most locations late tonight, except in the lower 70s on the beaches. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... Wednesday and Thursday: Quiet, dry and warm conditions will prevail during this period as the area remains positioned between building subtropical ridge to the west and the formation of a weakness near the Bahamas. Point soundings off the various global models all depict a dry, subsident pattern holding for much of the week with a pronounced mid-level capping inversion remaining in tact, despite temperatures warming into the mid-upper 80s away from the beaches. A rain-free forecast will be maintained both days with only a shallow, diurnally driven cumulus field forming during the afternoon ahead of the sea breeze. Lows both Wednesday and Thursday Nights will range from the mid 60s inland to around 70 at the beaches. Friday: Subsidence is poised to intensify further Friday as a large tropical wave moves north of the Greater Antilles to a position near the Bahamas Friday Night. Although an isolated shower could certainly occur along/ahead of the sea breeze during peak heating, the development of deep, moist convection should be curtailed by increasing mid-level subsidence. Pops will be kept below mentionable thresholds. Highs will be tempered somewhat by the deepening onshore flow ahead of the approaching tropical wave. Highs should only top out in the mid 80s for most locations away from the beaches with a few upper 80s possible across far interior Southeast Georgia. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... There is considerable uncertainty this weekend and into early next week as much will depend on the timing and strength of an approaching tropical wave. There are signs that a weak surface low could form somewhere off the Southeast U.S. coast as an upper low over the Bahamas becomes a bit better defined, but there is a lot of uncertainty on exactly how this scenario will play out. The only clear signal right now is that the area could see a modest increase in moisture and shower activity as the holiday weekend unfolds. A conservative approach to this portion of the forecast remains the best option this far out. Pops will be limited to 20-40% through the period with the highest rain chances confined to the coastal regions. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... VFR through 18Z Wed. Very low probability for localized ground fog around daybreak Wednesday. Extended Aviation Outlook: There are no concerns with a >30% probability of occurrence at this time. && .MARINE... Tonight...the sea breeze circulation will give way to synoptic scale southerly flow as high pressure consolidates offshore. Winds should remain below 15 kt, accompanied by seas 1-2 feet within near shore waters and 2-3 feet beyond 20 nm. Wednesday through Friday: A typical summer wind regime will dominate through the period with a general South to Southeast wind regime prevailing. Sea breeze influences are likely each afternoon, especially near the land-sea interface, but the wind fields do not look especially strong during any one period. Some tightening of the pressure is likely by Friday as influences from an approaching tropical wave intensify, but speeds look to go no higher than 15 kt at this time. Seas will average 1-2 ft nearshore with 2-3 ft offshore...building to 2-3 ft nearshore and 3-4 ft offshore by Friday. Saturday through Monday: A retreating Atlantic ridge and the approach of a tropical wave/very weak low will produce more of an east/northeast flow into the weekend. The gradient doesn`t appear to be too strong at this time, with winds to remain below 15 kt or so. However, seas will build some in response to the wave of low pressure and some 6 footers might make it at least into the outer Georgia waters at some point. Small Craft Advisory conditions may occur at some point over the weekend. Rip Currents: There could be increased risk of rip currents at area beaches over the holiday weekend as an onshore flow strengthens a bit ahead of a tropical wave coincident with a slight uptick in swell energy. && .EQUIPMENT... Grays Reef Buoy 41008 has returned to service. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...SPR SHORT TERM...ST LONG TERM... AVIATION...SPR/ST MARINE...SPR/ST EQUIPMENT...