984 FXUS62 KCHS 141144 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 644 AM EST Mon Nov 14 2022 .SYNOPSIS... Cool high pressure will prevail today. A coastal trough will develop tonight, and low pressure will advance across the region Tuesday. High pressure should then prevail through late week. Another cold front could cross the region during the weekend. && .NEAR TERM /THROUGH TONIGHT/... Today: Aloft, progressive southwest flow will prevail as a shortwave moves out of the Four Corners region and into the Central Plains. At the surface, high pressure will remain in control across the region while an inverted trough develops and sharpens just off the coast of the forecast area. The day will begin with clear skies across the forecast area, though cloud cover will steadily increase through out the day. Most of the cloud cover will come this afternoon in the form of stratocumulus spreading onshore based in the 4-6 kft range. Even with a good amount of sunshine early on, the day will be quite cool with highs struggling to reach 60 for most of the forecast area. Such values would be around 10 degrees below normal for mid November, and more typical of normal highs for late December and early January. Making it feel even cooler will be a persistent northeast wind that will be solid in the 10-15 mph range with occasional gusts up to around 20 mph, especially closer to the coast. Tonight: Within the progressive southwest flow aloft, subtle embedded shortwave energy is progged to approach and pass through the region late in the period. Meanwhile at the surface, the inland high will weaken and allow the coastal trough to draw closer to shore and potentially even begin to move inland. Such a scenario would bring the convergence within the trough and improving low-level moisture profiles onshore, with increasing chances of shower activity. The model consensus generally favors the South Carolina coast for the best shower coverage, especially along the Charleston County coast. The forecast features rain chances increasing into the 20-40 percent chance range in this area late tonight. As cloud cover increases and the coastal trough moves inland, it sets up a scenario for temperatures to reach their lows early in the tonight period then rise slowly towards daybreak Tuesday. Forecast lows range from the mid to upper 40s inland to the low to mid 50s along the coast. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... Tuesday: A coastal trough will impact the local area early, lifting north through mid day with few to scattered showers ahead of a low pressure system quickly advancing toward the region from the west. The main issue will be how much high pressure holds across inland areas as the system approaches, resulting in a rather large temperature gradient across southeast South Carolina and southeast Georgia. Given the extent of cloud cover and likelihood of north- northeast sfc winds within high pressure across the Midlands, max temps could struggle to reach the upper 50s well inland, but should peak in the lower 70s near the beaches. There is even a risk for a few thunderstorms across coastal Georgia where instability is highest during afternoon hours before the onset of scattered to numerous showers entering the area from the west. Showers could continue into evening hours, but weather conditions will trend drier from west to east through midnight as high pressure begins to spread into the region behind a departing cold front. Overnight lows should range in the mid-upper 40s inland to mid 50s near the coast. Wednesday and Thursday: Sfc high pressure will spread across the region in advance of a large mid-lvl trough pivoting across the Midwest. Expect dry conditions with a west-northwest wind across the region and perhaps some cirrus associated with a right entrance region of a strong h25 jet aloft. Temps will trend noticeably cooler during the period, peaking in the lower 60s Wednesday, then struggling to reach the low-mid 50s Thursday. Overnight lows will also be considerably colder, dipping into mid-upper 30s inland to mid-upper 40s near the coast Wednesday night. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... Dry and cool high pressure will prevail across the area through late week. The main issue will be how cold temps reach during overnight periods, especially Thursday night and Friday night. Latest guidance suggests a hard freeze along and west of the I-95 corridor Thursday night with lows dipping into the upper 20s. A Freeze Watch/Warning could eventually be needed should trends persist. Friday night will also be cold, with temps dipping into the low-mid 30s across inland counties. These temps could also promote frost for areas away from the coast during the night. Friday and Saturday highs will struggle to reach the mid-upper 50s. The next chance of precip could arrive this weekend with a coastal trough attempting to develop along the Southeast Coast and/or a low pressure system approaching the region from the east-southeast, but forecast uncertainty increases in regards to the track of these two features. At this time, a few showers have been included in the forecast Saturday and Sunday with highest precip chances starting early next week. Temps will continue to remain well below normal, ranging in the mid-upper 50s for most areas to perhaps 60 degrees near the coast for highs and dipping into the mid-upper 30s away from the coast for lows. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... VFR conditions will prevail at KCHS, KJZI, and KSAV through most of the 12z TAF period. Clear skies this morning will give way to increasing cloud cover in the 4-6 kft range this afternoon and especially this afternoon and evening. We could even see VFR ceilings by the late afternoon. Northeast winds will remain elevated, especially this morning, and we could see occasional gusts into the 15-18 knot range especially at KJZI. Late tonight, the chances for ceilings to lower into the MVFR range increase. Also, we could start to see some light rain showers try to push onshore, especially around KCHS and KJZI. Extended Aviation Outlook: Periods of flight restrictions are possible Tuesday into early Wednesday due to low clouds and showers associated with a coastal trough shifting onshore and a low pressure system arriving from the west. VFR conditions should then prevail at all terminals Wednesday afternoon through Friday. && .MARINE... Today through tonight: A tightly pinched gradient will prevail across the local waters today, driving strong and gusty northeast flow. Winds are expected to hold in the 20-25 knot range with frequent gusts to around 30 knots across all zones. Small Craft Advisories remain in effect through the day. In Charleston Harbor, it appears increasingly likely that winds will be 15-20 knots with gusts to 25 knots. Therefore, the Small Craft Advisory has been expanded there until the early evening. Overnight, the gradient should slowly relax as a nearby coastal trough draws closer to shore. Winds will decrease gradually late and conditions should improve to sub-advisory thresholds in the southern South Carolina waters and the nearshore Georgia waters. Seas will increase in response to the northeast flow, with 4-6 ft across the nearshore waters and 5-7 ft near the 20 nm line and beyond. Overnight, seas will diminish a bit, becoming 3-5 ft across the nearshore waters and 5-6 ft for the outer waters late. Tuesday through Saturday: A coastal trough is expected to shift north across local waters Tuesday, decreasing the pressure gradient and favoring conditions that remain below Small Craft Advisory levels. A cold front is then expected to shift offshore Tuesday night with high pressure building in its wake through the remainder of the week. Post fropa, the pattern supports elevated winds/seas, generally ranging between 15-20 kt and 3-5 ft (highest across offshore Georgia waters), but conditions are expected to remain below Small Craft Advisory level conditions through late week. Another surge of winds and building seas is possible this weekend as the pressure gradient increases across local waters in advance of another low pressure system approaching the region. Small Craft Advisories could eventually be needed during the weekend. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...Small Craft Advisory until 7 PM EST this evening for AMZ330. Small Craft Advisory until 8 AM EST Tuesday for AMZ350-374. Small Craft Advisory until 5 AM EST Tuesday for AMZ352-354. && $$ NEAR TERM...BSH SHORT TERM...DPB LONG TERM...DPB AVIATION...BSH/DPB MARINE...BSH/DPB