Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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571 FXUS62 KCHS 290839 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 439 AM EDT Sat Jun 29 2024 .SYNOPSIS... Atlantic high pressure will prevail this weekend, while a trough of low pressure resides inland. A cold front is expected to impact the area Monday into Tuesday. High pressure will return for the latter half of next week. && .NEAR TERM /THROUGH TONIGHT/... Today: Aloft, a ridge will extend across the Southeast United States along with dry air noted on water vapor imagery. At the sfc, high pressure will extend across the region from the Atlantic, resulting in a light southerly/onshore wind. There will be very little in the way of mid-upper level features to promote afternoon convection, but ample low-lvl moisture driven onshore and a sea breeze circulation will likely contribute to afternoon showers and thunderstorms away from the coast during peak diurnal heating. Expect convection to be typical of summertime, being pulse type in nature within an environment displaying PWATs near 2.0 inches, SBCAPE between 2000- 2500 J/kg and weak 0-6 km bulk shear. Gusty winds and brief downpours will be the main result, although a stronger thunderstorm or two can not be ruled out during peak heating. High temps should peak in the low-mid 90s, warmest well inland. The combination of warm temps and sfc dewpts in the low-mid 70s should support heat indices in the 100-105 range for most areas away from the beaches. There could be a brief window where heat indices reach 105-108 where highest dewpts and warmest temps overlap near an inland moving sea breeze (around the I-95 corridor), but the duration of the event should fall just short for the issuance of a Heat Advisory. Tonight: Similar to the previous night, mild and humid conditions will be in place for the night. A few showers and/or thunderstorm can not be ruled out with boundary interactions early evening well inland, but activity will likely be waning with diurnal heat loss. Late night, a continued onshore wind could drive a few showers onshore. Patchy fog is also possible late, mainly for locations that see rain during the day. In general, low temps will range between the mid 70s inland to upper 70s/around 80 near the beaches. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... High pressure will be situated offshore on Sunday, while a trough of low pressure resides inland ahead of an approaching cold front. Main drivers of convection will be daytime heating and the sea breeze and then along the inland trough which could eventually move into the local area later in the day and into Sunday night. Ample instability near or over 2000 J/kg will be present but shear doesn`t look particularly impressive. Widespread organized severe weather is not expected, but a few strong to severe thunderstorms with gusty winds are possible, in addition to locally heavy rainfall with PWats well over 2 inches. Also of note is the heat. High temps largely in the mid 90s will combine with elevated dew points to make it feel even hotter. Heat indices are forecast to top out in the 105-109F range. Heat Advisories will be possible for some areas, but worth noting that convection could disrupt temperature trends and heat indices may not reach the 2 hour duration requirement. Lows only fall to the mid/upper 70s. The aforementioned front will sink into the area late Sunday night into Monday. It looks to be a fairly active day with numerous to widespread showers and thunderstorms expected. Activity generally looks to shift south and east through the day as drier air tries to work in behind the front. A couple strong to severe storms will be possible along and ahead of the front in the afternoon/evening with slightly better wind fields and sufficient instability. Damaging wind gusts would be the primary hazard. It will not be quite as hot, with highs ranging from the upper 80s near the Santee River to low 90s south near the Altamaha. The front will stall nearby into Tuesday before eventually dissipating. Additional showers and thunderstorms will be possible, with best coverage in the south in proximity to better moisture, but the trend overall has been drier. It will be notably cooler than previous days, with highs mainly in the mid to upper 80s. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... Mid level ridge builds over the Southeast for mid to late week. Atlantic high pressure will largely prevail at the surface, with a trough of low pressure eventually developing inland. Large scale subsidence under the ridge will help limit convection, but isolated to scattered diurnally-driven showers and thunderstorms will still be possible. Main concern looks to be the return of the heat. Still several days out, but the set-up does appear to bring the potential for excessive heat headlines. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... KCHS/KJZI/KSAV: VFR conditions will prevail through much of valid 06Z TAF cycle. However, tempo MVFR cigs/vsbys are possible at JZI/CHS terminals between 06-09Z Saturday due to showers and/or potentially thunderstorms that shift onshore during the next few hours. Additionally, there could be some light fog/stratus a few hours on either side of daybreak at any terminal resulting in sub-VFR weather. There is then the potential for some SHRA/TSRA activity along the sea breeze Saturday as it moves inland. At this time, VCSH remains in the JZI TAF late morning and early afternoon while VCTS is in place at CHS/SAV terminals Saturday afternoon. Any direct impacts from showers or thunderstorms will likely result in brief flight restrictions and gusty winds. Extended Aviation Outlook: Prevailing VFR. Brief flight restrictions are possible in showers and thunderstorms, mainly in the afternoon and evenings. && .MARINE... Today and Tonight: A weak pressure gradient will remain in place across local waters along the western periphery of high pressure extending across the Atlantic and south of a stationary front positioned across the Mid-Atlantic states. In general, winds/seas will remain well below Small Craft Advisory levels, remaining south- southwest around 10-15 kt or less with seas no higher than 2-3 ft. Peak winds should occur near the coast, when a sea breeze circulation develops and shifts inland early afternoon. Sunday through Thursday: Southerly flow will persist Sunday into Monday with speeds 15 knots or less. Winds turn to the northeast/east Monday night into Tuesday as a cold front sinks through the waters and high pressure ridges in from the north. The high will eventually shift offshore and remain the primary feature through late week. No marine headlines are expected. Seas average 2- 3 feet. Waterspouts: We`re well into the local "Waterspout Season", and an in-house Waterspout Index provides us with a Moderate Risk this morning with light winds, weak shear, and ample low-lvl moisture in place. Much will depend if a land breeze lingers and/or a line of cumulus develops along a boundary after daybreak. For now it is just something to be aware of. Rip Currents: Latest guidance indicates a Moderate Risk for rip currents along all beaches today. Given the weekend is here, have opted to maintain the Moderate Risk for today. A Low Risk is in place for all beaches Sunday. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...DPB SHORT TERM...ETM LONG TERM...ETM AVIATION...DPB/ETM MARINE...DPB/ETM