133 FXUS62 KCHS 082042 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 342 PM EST Fri Jan 8 2021 .SYNOPSIS... A storm system will move away from the area tonight. High pressure will then bring dry and seasonal weather into early next week before another weak storm system impacts the area Monday into Tuesday. High pressure will then likely return for Wednesday and Thursday. && .NEAR TERM /THROUGH TONIGHT/... A mid-level low will be over the Southeast this evening, becoming located near the Outer Banks of NC around midnight, then quickly moving offshore and to the northeast after midnight. At the surface, low pressure off the Outer Banks of NC this evening will continue to move away overnight, while broad high pressure centered over the Northern Plains slowly approaches our region. There isn't much moisture across our area, with PWATs peaking ~0.6" this evening, then declining overnight. Though, there will be enough lift with the mid-level low to generate showers into this evening. Both the synoptic models and the CAMs are very aggressive, having scattered to numerous light showers spreading from west to east into this evening, then pivoting to the northeast and rapidly moving away. Our entire area is expected to be rain-free by midnight. Total QPF will generally be 0.05" or less, owing to the low PWATs and fast movement of the showers. Though, areas around the Altamaha River probably won't receive any measurable rain. Even with the dry air moving in overnight, skies will be slow to clear, with the clearing increasing around daybreak Saturday. Lows will range from the mid 30s far inland to around 40 degrees near the beaches. && .SHORT TERM /SATURDAY THROUGH MONDAY/... Moderate to high confidence this period. A weak trough will move through Saturday and Saturday night keeping some clouds in place but no rain is expected. Temperatures will be a bit tricky as much depends on the extent of cloud cover but leaned toward the cooler MOS guidance based on persistence from today. Inland areas should see a light freeze Saturday night. Dry high pressure will then build in and continue through Sunday night with slightly milder temperatures, although some of the normally colder inland rural areas could see another light freeze Sunday night. An offshore trough will then likely strengthen Monday, possibly into a weak low, while moisture deepens and upper shortwave energy moves through. This could lead to a few showers but no significant rainfall is expected. Temperatures will likely be a bit above normal Monday. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Monday night and Tuesday: A weakening upper low is expected to move across the mid Atlantic states as a weak coastal low moves northeastward over the Atlantic waters. Have chance PoPs for light showers through the first part of Tuesday, then trending lower by afternoon as the upper low and associated surface coastal low move northeast of the region. Lows Monday night a bit milder than previous nights, lower to mid 40s most areas, except upper 40s to around 50 near the coast. Highs Tuesday in the upper 50s to lower 60s. Tuesday night through Wednesday night: Weak surface high pressure, dry conditions and temperatures near seasonal normals are expected. Global models indicate another weak upper low to move across the region within the southwest flow. However, the strength and timing of this feature is different between models. For now, have gone with consensus solution to keep PoPs to 10% of less as deep layer moisture and any upper forcing remain south of the region. Thursday and Friday: The upper pattern begins to dramatically amplify, as a strong upper trough develops and extends from the Great Lakes, southward into the southeast U.S.. The low level flow will turn to southwest and increase ahead of a strong arctic front on Thursday, then veer to west-northwest behind the front on Friday. There is still a lot of uncertainty with the timing of this next strong cold front, but all models seem to indicate that the front will come through relatively dry. Temperatures are expected to be near to slightly above normal on Thursday, then possibly much colder/below normal behind the arctic front Friday. It is too far out to get a good feel for how cold temperatures will eventually be behind this front, and have therefore kept high temperatures near to slightly below normal on Friday. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... 18Z TAFs: IFR ceilings will prevail for much of the TAF time period. Light showers could impact both TAF sites for a few hours this afternoon. Ceilings within/around these showers should be slightly higher, and this is covered within TEMPO groups. Otherwise, it won't be until late in the TAF time periods where ceilings finally rise to a prevailing MVFR and then VFR. Extended Aviation Outlook: High confidence in VFR conditions Saturday night through Sunday night with MVFR or worse conditions possible starting Monday as moisture increases in association with an approaching storm system. && .MARINE... Tonight: Surface low pressure off the Outer Banks of NC will continue to move away, while high pressure centered over the Plains gradually approaches. The synoptic flow will lead to prevailing northwest winds. Winds are expected to increase this evening as a mid-level trough passes over the region. As the trough moves away after midnight, winds are then expected to ease. Small Craft Advisories remain in effect for all of the ocean waters. They're anticipated to drop from south to north for the waters within 20 nm, followed by the GA waters beyond 20 nm. Some changes to the end times may be needed with each zone. But we'll leave those refinements to future updates. Finally, wind gusts should exceed 20 kt for Charleston Harbor this evening. It's possible they could hit 25 kt for a short period as well. But the time window doesn't appear large enough to warrant an Advisory. Saturday through Wednesday: Moderate to high confidence this period. Tranquil conditions expected into early next week before they go downhill at least slightly starting late Monday as a storm system moves through the area through Tuesday. Small Craft Advisories will be possible during this period but aren't likely at this point. && .TIDES/COASTAL FLOODING... Increasing astronomical tides and onshore winds could lead to minor coastal flooding near Charleston during the morning high tides early to mid next week, especially on Monday. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...Small Craft Advisory until 9 PM EST this evening for AMZ352- 354. Small Craft Advisory until 5 AM EST Saturday for AMZ374. Small Craft Advisory until 1 AM EST Saturday for AMZ350. && $$ NEAR TERM... SHORT TERM... LONG TERM... AVIATION... MARINE... TIDES/COASTAL FLOODING...