925 FXUS62 KCHS 162326 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 726 PM EDT Sun Oct 16 2022 .SYNOPSIS... High pressure over the area will move offshore tonight. A strong cold front will move through the region Monday night, followed by cool high pressure into next weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Early this evening: All is quiet as weak high pressure prevails ahead of an approaching cold front. Aloft, the flow will remain nearly zonal with a bit of cyclonic curvature thanks to the deep upper low centered across the Great Lakes. The upstream front will draw closer overnight, moving just into the lee of the Southern Appalachians around or just after sunrise Monday. This setup will drive southwesterly flow across the forecast area, and there could be just enough low-level convergence to kick off an isolated shower or two. However, model soundings are quite dry through the mid-levels, so no measurable rainfall is expected across land areas. More bonafide showers will be possible across the coastal waters, but whatever develops will be weak at best. We will see a steady stream of mostly high clouds in the westerly flow aloft, which will help lows from getting too low. Upper 50s to low 60s should be common. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... Synopsis/Forecast: Highly amplified Omega blocking pattern persists across the CONUS with sharp N-S ridging through the Rockies, anchored by troughing over the eastern Pacific and anomalously deep troughing/cold air across eastern NOAM. Prominent short-wave energy and reinforcing shot of cold air is diving down through the upper Midwest today and will close off another deep upper low over the Great Lakes through at least the first half of this week. This will drive a cold front down through the coastal Carolinas and SE Georgia Monday afternoon/Monday night while anomalously cold H8 air (10-15 C below normal) overspreads most the the eastern CONUS...all the way into northern Florida. Details: Aforementioned surface cold front will be advancing down through the western Carolinas/northern Georgia region Monday morning with quiet weather hanging on here...although with increasing cloud cover out ahead of the boundary. Boundary continues to slip into and through our area later Monday afternoon through Monday evening and out into the Atlantic by Tuesday morning. Interestingly, guidance remains quite stingy with precip chances/QPF across the CWA as the front presses through, possibly the result of some drier low level air seen in forecast soundings. But given moisture advection ahead of and along the boundary, some potential destabilization (500-1000 J/Kg MLCAPE Monday afternoon per HRRR guidance) and low level convergence with the front...will hang on to at least isolated to scattered pops Monday afternoon through Monday evening. Given strong mid- level westerly flow developing across the region and 0-6 Km bulk shear values in excess of 40 knots, if we can get some convection to develop, some stronger storms still cannot be ruled out, and the SPC Day 2 outlook maintains a thin marginal risk across the coastal counties. Behind the boundary, much cooler and drier air overspreads the region starting Tuesday, setting up a quieter/cooler stretch of weather. Clearing skies by Tuesday night might allow for decent radiational cooling conditions, although we do hang on to some boundary layer wind throughout the night that may curtail the temperature drop and frost possibilities. Will continue to advertise patchy frost across our cold spots (well inland west of the I-95 corridor) with lows in the middle to upper 30s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Surface high pressure will reassert itself through the long- term period and bring another stretch of quiet weather. Large expanse of anomalously cold air will continue rotate through most of the eastern CONUS through at least early Thursday before gradually undergoing modification and retreating to the north/east. Temperatures will continue to run below normal through the latter half of the week, particularly overnight lows. And with weakening winds/clear skies, the coldest overnight/early morning temps (and best candidate for frost headlines) will likely occur Wednesday night/Thursday morning with solid middle to upper 30s anticipated inland. Will maintain patchy to areas of frost across those inland areas at this juncture and continue to highlight the frost potential in the Hazardous Weather Outlook. Temperatures rebound to around seasonal norms through next weekend. Quiet weather overall. But with that said, longer term model guidance hint at the development of some troughiness in the coastal waters next weekend...which might eventually present some forecast challenges. 12Z Euro has turned very bullish with the development of a stronger coastal system pressing into our area next weekend, which is most certainly an outlier within the envelope of guidance. But something to keep an eye on. && .AVIATION /23Z SUNDAY THROUGH FRIDAY/... VFR conditions will prevail at KCHS, KJZI, and KSAV through 00z Tuesday. Southwesterly winds could get a little gusty on Monday, with gusts into the 15-20 knot range mostly in the afternoon. Also, isolated showers and thunderstorms could develop in the late afternoon and early evening. As of now confidence is low in any direct impacts to the terminals. Extended Aviation Outlook: Isolated showers and thunderstorms are possible late Monday afternoon and Monday evening as a cold front moves through the region. Some brief flight restrictions are possible with any precip that moves over a terminal. After FROPA, high pressure builds across the region for the rest of the week and will bring solid VFR conditions. && .MARINE... Tonight: South winds this evening will veer to the southwest and increase to 10-15 kt overnight, with 15-20 kt possible at times. Seas 1-2 ft will build to 2-3 ft by daybreak Monday. Monday through Friday: Southwest winds will increase in the coastal waters on Monday...ahead of a cold front that will move across the waters Monday night. Some gusts on Monday may touch Small Craft Advisory criteria although seas will remain well below criteria. Small Craft Advisory headlines may eventually be needed, but no headlines are planned at this juncture. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...BSH SHORT TERM...TBA LONG TERM...TBA AVIATION...BSH/TBA MARINE...TBA