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Show Area Forecast Discussion - Charleston, SC (Charleston, SC Area) Selection: |
| #1238068 (Received by flhurricane at: 2:03 PM 14.Jul.2025) AFDCHS Area Forecast Discussion National Weather Service Charleston SC 159 PM EDT Mon Jul 14 2025 .SYNOPSIS... Atlantic high pressure will prevail into the upcoming weekend. && .NEAR TERM /THROUGH TONIGHT/... This Afternoon: Aloft, a weak upper-lvl ridge will remain across the Southeast as a surface low offshore of the Florida coastline continues to track westward. These features will yield east- northeastward flow throughout the day, which is uncommon for this time of the year. At the surface, this low developing off the Florida coastline will dominate the flow across the region and might cause for a more progressive seabreeze this afternoon. From KCHS 12Z sounding, moderate instability and a K index value of ~35 suggests isolated to numerous thunderstorms will develop in the afternoon (mainly along and west of I-95 corridor). Recent hi- res guidance has been indicating that drier air will be located along the immediate coastline and just inland of the South Carolina coastline with PWAT values from 1.4 to 1.8 inches with the deeper moisture (PWAT values > 2.0 inches) west of I-95. Thus, the current idea remains that showers and thunderstorms will initiate along and west of the I-95 corridor. DCAPE values will be ~800 J/kg, but nothing looks particularly noteworthy in terms of the severe threat. However, there is still a possibility of strong to marginally severe storms where boundary interactions occur. Locally heavy rainfall will be possible along and west of I-95 where the ample moisture and storm coverage is expected. As far as rainfall amounts .. 1-2 inches with higher amounts possible with these storms. Heat index values as of 2PM are generally between 100-106 across the forecast area, just shy of Heat Advisory criteria. As convection begins this afternoon some relief in the heat is expected. Tonight: Showers and thunderstorms should shift further inland and off to the southwest throughout the evening. Temperatures will drop into the mid to upper 70s (with warmer temperatures closer to the beaches). As the developing low offshore of the Florida coastline travels westward, showers and thunderstorms could develop over the coastal waters overnight. Coverage should increase overnight and could draw closer to the coast by daybreak. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... Tuesday: A weakening TUTT will be approaching Florida with dry air located on the northwest flank. PWATs drop to less than 1.5", with 2"+ PWATs on either side. Surface convergence from Monday will have moved further inland over GA on Tuesday with a sea breeze forecast to move inland during the afternoon. The lower PWAT air will likely limit convection slightly, but the overall extent of coverage should still be at least chance. High temperatures will also be lower on Tuesday as 1000/ 850 mb thicknesses fall to 1415 m (or about 10 m cooler than Monday) due to the undercutting TUTT. Wednesday - Thursday: Another TUTT will break off and approach the region Wednesday allowing thunderstorms to continue both days. Storm motions Wednesday are forecast to be around 10 kt, but increase to near 20 kt by Thursday as the TUTT moves overhead and elongates the wind field slightly. This means the greatest chance for locally heavy rainfall will be on Wednesday, with slightly lower chances on Thursday due to increased storm motion. High temperatures will be near climo or in the lower 90s. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... The TUTT that was near the area on Thursday will cross Florida Saturday keeping afternoon thunderstorm chances in the forecast through the weekend. High temperatures will also remain near climo/ slightly above climo as low level thicknesses slowly recover. Max heat index values each afternoon will be near or just below advisory criteria (108 F). && .AVIATION /18Z MONDAY THROUGH SATURDAY/... 00Z TAFs: Expect VFR conditions to persist at KCHS/KJZI/KSAV. Showers and thunderstorms are expected to develop along and west of I-95 this afternoon and maintained VCTS starting at 21Z. Most of the thunderstorm activity should remain inland of KCHS and KJZI. There is a chance of fog developing at KSAV before daybreak (~09Z), however left the mention out of the TAFs at this moment as confidence is low with this. Extended Aviation Outlook (Tuesday through Saturday): VFR will mainly prevail throughout the period, however brief flight restrictions are possible within showers and thunderstorms that develop in the afternoon and/or evening hours. && .MARINE... This Afternoon and Tonight: Expect generally northeast to east- northeast flow at 5 to 10 kt to prevail through tonight. This flow pattern will generally be driven by the circulation around the developing low pressure off the Florida coastline. It could become a bit gusty in the afternoon with gusts up to 15 to 20 kt as the seabreeze pushes inland (gusts strongest across the immediate coastline and the Charleston Harbor). Southeasterly swell will continue to mix into the local waters and seas will be 1 to 2 ft. Showers and thunderstorms will develop over the coastal waters tonight and increase in coverage closer to daybreak. Otherwise, no marine concerns expected. Tuesday through Saturday: A TUTT will be located just off of the SC coast through the extended while at the surface Bermuda high pressure will be in control. For the marine zones, this will translate to each afternoon featuring wind gusts peaking 15 to 20 kt due to an inland advancing sea breeze. Seas through the period will be 2-4 ft. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ |
| #1238037 (Received by flhurricane at: 7:12 AM 14.Jul.2025) AFDCHS Area Forecast Discussion National Weather Service Charleston SC 708 AM EDT Mon Jul 14 2025 .SYNOPSIS... Atlantic high pressure will prevail into the upcoming weekend. && .NEAR TERM /THROUGH TONIGHT/... Today: Aloft, the upper ridge will be centered near the FL panhandle and will extend into northern and western portions of GA and the Carolinas. Also of note is the upper low just north of the Bahamas and off the east coast of Florida. The forecast area will sit between these features which will yield deep layer north to northeast flow which is certainly not common. At the surface, the developing lows off the east coast of FL will drive the flow across the forecast area. Current thinking is that the result of this northeast to easterly flow will result in a more progressive sea breeze than we have seen the past few days with the primary convergence zone setting up along and west of the I-95 corridor. There is general agreement in the hi-res model solutions that the best convective coverage will set up this afternoon in this area. Also of note, this zone along and west of I-95 will be where the deepest moisture will reside with precipitable water values of 2 inches or higher. Coincident with this, some relatively drier air will work in from the east with precipitable water values approximately 1.7-1.9 inches along and just inland of the southeast SC coast. Once again, the severe threat does not look particularly noteworthy with middling DCAPE values and certainly no support for anything organized. But, the standard summertime disclaimer applies in that where boundary interactions occur and enhance updrafts there could be an isolated strong to marginally severe storm. Locally heavy rain will be possible in this area along and west of I-95 where the best moisture and storm coverage is expected. A quick 1-2 inches will be possible in areas directly impacted by storms but we do not anticipate any significant flooding threat at this time. Highs are forecast to mostly reach the low 90s along and east of I-95, with mid to upper 90s west of I-95. We have again lowered dewpoints a bit from the raw NBM by blending in the NBM10, which seems to have worked out well yesterday and yielded some more realistic heat index values. So for today we expect to see heat indices max out around 105, and we should stay below Heat Advisory criteria. Tonight: Afternoon convection should gradually shift further inland and off to the southwest through the evening. The rest of the overnight should be dry for land areas, though we will likely see increasing coverage over the coastal waters which could draw close to the coast by daybreak. Look for lows in the low to mid 70s inland and upper 70s along the coast. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... On Tuesday, the area will remain sandwiched between a weak upper ridge over the northern Gulf Coast states and an expansive upper ridge across the central and western Atlantic. Wednesday into Thursday, the Atlantic ridge will expand into the Southeast. And increase in mid-level subsidence during this period should reduce the coverage of diurnal convection, though with ample moisture and instability plus an active sea breeze, we should still see scattered showers and tstms each day. Temps will be near normal and heat indices are currently forecast to fall short of Heat Advisory criteria. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... Deep layered ridging will persist into the upcoming weekend. Fairly typical July weather will continue with mainly scattered diurnal convection each day. && .AVIATION /11Z MONDAY THROUGH FRIDAY/... The 12z TAF period begins with VFR conditions at KCHS, KJZI, and KSAV. For afternoon and evening thunderstorm potential, the focus for storms is expected to be further inland today. This means that thunderstorm activity should remain inland of KCHS and KJZI. KSAV will have a better chance of at least seeing a storm in the vicinity and we have maintained VCTS starting at 21z. Extended Aviation Outlook: VFR will mainly prevail throughout the period, however brief flight restrictions are possible within showers and thunderstorms that develop in the afternoon and/or evening hours. && .MARINE... Today and tonight: The flow pattern across the local waters will largely be driven by circulation around the developing area of low pressure off the east coast of FL. This setup will drive northeast to east-northeast flow, which could turn more east or east-southeast for portions of the waters at times. Wind speeds will remain on the weaker side, perhaps as high as 10-15 knot at times. Seas should average around 2 feet through the period. Thunderstorms do not appear to be as big of a threat this afternoon and evening as most of the activity is expected to remain inland of the coast. Moderate southerly winds will continue Tuesday through Friday. Speeds will generally be no higher than 15 kt and seas will run 2-4 ft. A decent sea breeze should occur each afternoon along the coast, with a few gusts in Charleston Harbor approaching 20 kt. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ |
| #1238018 (Received by flhurricane at: 1:42 AM 14.Jul.2025) AFDCHS Area Forecast Discussion National Weather Service Charleston SC 138 AM EDT Mon Jul 14 2025 .SYNOPSIS... Atlantic high pressure will prevail into the upcoming weekend. && .NEAR TERM /THROUGH TONIGHT/... Today: Aloft, the upper ridge will be centered near the FL panhandle and will extend into northern and western portions of GA and the Carolinas. Also of note is the upper low just north of the Bahamas and off the east coast of Florida. The forecast area will sit between these features which will yield deep layer north to northeast flow which is certainly not common. At the surface, the developing lows off the east coast of FL will drive the flow across the forecast area. Current thinking is that the result of this northeast to easterly flow will result in a more progressive sea breeze than we have seen the past few days with the primary convergence zone setting up along and west of the I-95 corridor. There is general agreement in the hi-res model solutions that the best convective coverage will set up this afternoon in this area. Also of note, this zone along and west of I-95 will be where the deepest moisture will reside with precipitable water values of 2 inches or higher. Coincident with this, some relatively drier air will work in from the east with precipitable water values approximately 1.7-1.9 inches along and just inland of the southeast SC coast. Once again, the severe threat does not look particularly noteworthy with middling DCAPE values and certainly no support for anything organized. But, the standard summertime disclaimer applies in that where boundary interactions occur and enhance updrafts there could be an isolated strong to marginally severe storm. Locally heavy rain will be possible in this area along and west of I-95 where the best moisture and storm coverage is expected. A quick 1-2 inches will be possible in areas directly impacted by storms but we do not anticipate any significant flooding threat at this time. Highs are forecast to mostly reach the low 90s along and east of I-95, with mid to upper 90s west of I-95. We have again lowered dewpoints a bit from the raw NBM by blending in the NBM10, which seems to have worked out well yesterday and yielded some more realistic heat index values. So for today we expect to see heat indices max out around 105, and we should stay below Heat Advisory criteria. Tonight: Afternoon convection should gradually shift further inland and off to the southwest through the evening. The rest of the overnight should be dry for land areas, though we will likely see increasing coverage over the coastal waters which could draw close to the coast by daybreak. Look for lows in the low to mid 70s inland and upper 70s along the coast. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... On Tuesday, the area will remain sandwiched between a weak upper ridge over the northern Gulf Coast states and an expansive upper ridge across the central and western Atlantic. Wednesday into Thursday, the Atlantic ridge will expand into the Southeast. And increase in mid-level subsidence during this period should reduce the coverage of diurnal convection, though with ample moisture and instability plus an active sea breeze, we should still see scattered showers and tstms each day. Temps will be near normal and heat indices are currently forecast to fall short of Heat Advisory criteria. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... Deep layered ridging will persist into the upcoming weekend. Fairly typical July weather will continue with mainly scattered diurnal convection each day. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... The 06z TAF period begins with VFR conditions at KCHS, KJZI, and KSAV. Overall, it does not appear that there are any significant concerns for fog and stratus through day break. Then for afternoon and evening thunderstorm potential, the focus for storms is expected to be further inland today. This means that thunderstorm activity should remain inland of KCHS and KJZI. KSAV will have a better chance of at least seeing a storm in the vicinity and we have maintained VCTS starting at 21z. Extended Aviation Outlook: VFR will mainly prevail throughout the period, however brief flight restrictions are possible within showers and thunderstorms that develop in the afternoon and/or evening hours. && .MARINE... Today and tonight: The flow pattern across the local waters will largely be driven by circulation around the developing area of low pressure off the east coast of FL. This setup will drive northeast to east-northeast flow, which could turn more east or east-southeast for portions of the waters at times. Wind speeds will remain on the weaker side, perhaps as high as 10-15 knot at times. Seas should average around 2 feet through the period. Thunderstorms do not appear to be as big of a threat this afternoon and evening as most of the activity is expected to remain inland of the coast. Moderate southerly winds will continue Tuesday through Friday. Speeds will generally be no higher than 15 kt and seas will run 2-4 ft. A decent sea breeze should occur each afternoon along the coast, with a few gusts in Charleston Harbor approaching 20 kt. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ |
