Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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086 FXUS62 KCHS 061026 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 626 AM EDT Sat Jul 6 2024 .SYNOPSIS... A weak front will remain stalled near the area through much of next week. && .NEAR TERM /THROUGH TONIGHT/... Latest 500 MB hand analysis revealed a 592 dam ridge centered near the Panhandle of FL with a broad trough axis centered across the central United States. On water vapor, an area of low pressure in the mid-levels was noted in the western Atlantic retrograding to the west. During the day today, the trough axis will slightly nudge to the east with the mid-level low over the Atlantic making progress to the west. As this occurs, the mid- level ridge that was over the FL Panhandle will start to re- center across central FL. Low level thicknesses today (1000/ 850 mb) reflect the new position of the ridge with a slight decrease to 1430 m (compared to 1435 m on Friday). Given this, have kept high temperatures mostly in the mid 90s today with upper 80s forecast at area beaches. However, dewpoints will remain in the mid to upper 70s with heat index values up to 110 degrees in places. As such, a heat advisory remains in effect for portions of southeast GA and SC. The main change for today compared to Friday will be the dramatic increase in coverage of showers and thunderstorms. PWATs will rise to above 2.5" across the western zones with drier air remaining entrenched across Charleston and Berkeley counties (PWATs around 1.7"). This makes sense as the dry air from Friday is getting squeezed between and approaching disturbance from the west and east. A very weak cold front will also approach the Upstate of SC this afternoon with a lee side trough again developing across the Midlands of SC. This setup usually favors CI occurring across the Upstate first followed by the Midlands. Along the coast of SC not much in the way of coverage is expected with a tight gradient to likely PoPs in Allendale county. West of I-95 in GA also should observe fairly robust coverage with the weak trough and approaching front. Isolated totals up to 3" will be possible as storm motion is less than 5 kt (estimated by the mean cloud-bearing wind). However, most locations that measure precipitation today will be in the 1" to 2" range. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... A weak upper ridge will remain over the Southeast during the period, though weak disturbances will continuously move through. Meanwhile, a weak front will remain stalled just inland. The airmass will be particularly moist during the period with PWATs generally at or above 2.1". Prevailing S to SE surface flow will support a robust inland-moving sea breeze each afternoon. There will be plenty of forcing and moisture to support numerous showers and thunderstorms, particularly during the afternoon and evening hours. The greatest coverage is expected to be across the inland areas. Instability does not look to be strong enough to warrant a significant severe thunderstorm risk, though localized flooding is possible due to heavy rainfall. The weakening upper ridge will bring some slight relief from the heat, though mid to upper 70s dewpoints will still push heat indices above 100F each day. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... A relatively wet pattern is likely to persist into late next week. Deep tropical moisture will remain in place while a series of shortwaves ripple through. Meanwhile, a weak lee trough will remain across the Midlands and a robust sea breeze will occur each afternoon. Numerous showers and thunderstorms expected each day, with potentially scattered coverage extending well into the overnight hours. High temps will briefly rise into the mid 90s by Wednesday, then back to the lower 90s late in the week. We could flirt with Heat Advisory criteria just about any day, though our forecast right now keeps most areas below 108 heat index. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... KSAV: Terminal will remain VFR through most of the issuance. Mid-level high pressure will begin to breakdown this morning with upper level disturbances to the west and east. A weak lee side trough (or convergence of surface winds) is again forecast to take shape across the Midlands of South Carolina. The best chance of showers and thunderstorms will likely be just west of KSAV, but KSAV does have a high enough chance to at least maintain the mention of vicinity thunder. KCHS/ KJZI: VFR through the issuance expected. Mid-level high pressure will begin to breakdown this morning with upper level disturbances to the west and east. A weak lee side trough (or convergence of surface winds) is again forecast to take shape across the Midlands of South Carolina. The Charleston terminals will be to close to the coast (and far enough east) of the inland forming showers and thunderstorms to preclude the mention of vicinity thunder. Extended Aviation Outlook: Brief flight restrictions possible in showers and thunderstorms, particularly during the afternoon and early evening. && .MARINE... Saturday: Expect seas around 3 ft with southerly winds backing from the southeast in the afternoon with a daytime sea breeze developing. Winds will mainly be 15 kt or less. Sunday through Thursday, a typical summertime pattern will prevail. Southerly winds will typically be less than 15 knots and seas no higher than 4 ft. Rip Currents: A swell of 2 feet every 9 to 10 seconds and proximity to the new moon will maintain a Moderate Risk for rip currents for today (Saturday). && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for GAZ087-088-099>101-114>119-137>141. SC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for SCZ040-042>045-047>052. MARINE...None. && $$ NEAR TERM...Haines SHORT TERM...JRL LONG TERM...JRL AVIATION...Haines/JRL MARINE...Haines/JRL