056 FXUS62 KCHS 121343 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 943 AM EDT Tue Jul 12 2022 .SYNOPSIS... A stationary front will remain over or near the area today while dissipating. High pressure will then build in briefly before another front moves in late this week and lingers into early next week. && .NEAR TERM /THROUGH TONIGHT/... Update: Radar indicates light showers across portions of our inland GA counties. While this is a bit earlier than anticipated, we raised POPs here, continuing the trend into the afternoon. Temperatures across the area a few degrees lower than what the hourly forecast has, likely due to the abundant cloud cover. We expect the clouds to scatter out and for temperatures to quickly rise into this afternoon. Rest of Today: A weakness will be found in the mid level pattern as it stretches from the Gulf of Mexico to the Carolina's. this feature will move little through the day, nestled between the sub-tropical Atlantic ridge that extends across Florida, and a 5930-5940 meter "heat ridge" in the Rockies. At the surface, the stationary front will waver across the area, before dissipating. There is yet again an abundance of moisture, with a plume of 2.25 to 2.50 inch PWat in place, which is well above normal for the time of year per the SPC sounding climatology. Not only is there this deep moisture, but we actually have a little 0-6 km bulk shear of 20-25 kt, along with MUCAPE of 2000-2500 J/kg. These conditions favor conditions that are favorable for convection to develop on and near the sea breeze this afternoon. Coverage will increase east of I-95, and will likely combine with additional activity moving in from the west by late day. This supports PoPs as great as 50-70%, and with DCAPE as high as 800 to maybe 1000 J/kg, a few wet microbursts might occur, producing strong to marginally severe wind gusts. There is also another day with a potential for at least minor flooding concerns, due to the combination of the elevated CAPE values, limited storm motion and the high moisture content with deep, warm cloud layers. The soils are thoroughly saturated with 3-day rain totals of as much as 5-8 inches, and the HREF 3 hour PMM depicts a 10% chance of greater than 3 inches. This is mainly near and east of I-95 where we find the greatest MUCAPE, and does include the Charleston and Savannah metro regions. A few Flood Advisories might again be required. We'll also need to maintain a close weather watch on Church Creek in the West Ashley/Charleston area for possible flood concerns, since it is still running quite high. Due to the erosion of the wedge, there will be at least some sunshine through the day. The low level thickness will expand and with 850 mb temps close to the 90th percentile, we do expect hotter temps today compared to yesterday. While we do have max temps mainly around 90F, rain-cooled conditions within t-storms will drop readings into the 70s during the mid and late afternoon. Tonight: there is little change in the pattern aloft, while at the surface the stationary front will have dissipated and the Atlantic ridge will strengthen a tad. Diurnal convection will quickly wane this evening, and any additional activity would come from lingering outflows and coastal convergence. At the present time the fog potential looks low given too much boundary layer mixing and unfavorable condensation pressure deficits. But due to the wet soils, at least ground fog form late. Temps will average in the lower and middle 70s, with a few upper 70s right along the coast. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... Forecast confidence: Moderate. Main forecast concern: Localized flooding, especially Thursday/Friday. Should see a return to more typical summertime weather Wednesday with high pressure to the east and an inland trough to the west. Best rain chances should be inland as the sea breeze pushes west during the afternoon, possibly combining with some convection over the CSRA/Midlands where deeper moisture/forcing will reside. Rain chances should then increase over the entire Lowcountry/Coastal Empire Thursday and remain higher than normal Friday as the aforementioned deeper moisture/forcing to the west shifts east over the local area. Don't anticipate significant severe storm chances through the period given that instability/deep layer shear should mostly remain fairly marginal. The best chance, albeit low, could come Wednesday afternoon/evening for inland areas. Minor flooding from heavy rain seems to be the greatest threat however. Expect high temperatures to be near normal until Friday when they should be below normal with lows mostly staying above normal. Max heat indices could be near our Heat Advisory criteria of 110 degrees inland from the coast to around the I-95 corridor Wednesday/Thursday afternoons but don't suspect we'll need Heat Advisories at this time. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... Forecast confidence: Low to moderate. A stalling cold front, upper troughing and deep moisture should lead to a fairly unsettled period, especially given the potential for a tropical low to develop along the central/eastern Gulf Coast and move northeast across the Deep South. High temperatures should mostly stay below normal while low temps mostly stay near normal. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... Conditions are expected to improve at KSAV as ceilings lift/SCT. KCHS and KJZI shouldn't have any flight restrictions this morning. However, due to the nearby front and developing sea breeze there will be a few light showers around. The sea breeze boundary will become quite active this afternoon, with greater instability compared to recent days, and there is even a little shear. Thus we expect TSRA to impact all terminals after around 18-19Z until close to sunset. Gusty winds, heavy rains and at least MVFR conditions will occur. VFR returns tonight. Extended Aviation Outlook: Confidence is moderate to high for periodic flight restrictions at KCHS/KSAV/KJZI due to mainly daytime/evening showers and storms Wednesday through the weekend. && .MARINE... Today and tonight: A stationary front will gradually dissipate across the local waters today, which then allows for Atlantic high pressure to build across the region tonight. Until the front dissipates the winds will be somewhat erratic, but all will become S or SW this afternoon, mainly 15 kt or less. The exception will be in Charleston harbor where some gusts will reach around 20 kt at times. Winds will clock around at similar speeds from the S-SW early on to the W-SW by late. Seas both today and tonight will average no higher than 3 or 4 feet. T-storms could again pose a hazard to mariners, with strong wind gusts, heavy rains and lightning strikes to occur, mainly this afternoon and evening. The SPC Non-supercell Tornado Parameter is up to 6 units this morning. Should any well defined boundary form, then the potential for waterspouts will increase. Wednesday through Sunday: Moderate confidence. The pressure gradient increases through mid week ahead of another approaching cold front but should stay below Small Craft Advisory levels. The cold front should stall out over or near the area late in the week and through the weekend with no significant wind/sea concerns. Conditions could become at least marginally favorable for non-supercell waterspouts depending on where the front ends up as that will impact wind speeds/land breeze development. Rip Currents: The combination of gusty winds associated with the afternoon sea breeze and an onshore swell near 2 ft around 9 seconds will lead to a Moderate Risk of rip currents at all of our beaches Tuesday and again on Wednesday. && .TIDES/COASTAL FLOODING... The full moon and perigee occur Wednesday, and the perigee is the closest of the year. This is known as a Proxigee. Tides continue to run high not only due to these astronomical influences, but also getting a boost from winds, rainfall, and swell energy. This will be enough to cause moderate coastal flooding with the evening high tide across tidal portions of Charleston and Colleton Counties. Even at Fort Pulaski/Savannah minor coastal flooding might occur. Coastal Flood Advisories will be required later today for the evening high tide. Tides will continue to be a concern through the week. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM...RJB LONG TERM...RJB AVIATION... MARINE... TIDES/COASTAL FLOODING...